* io.c (rb_open_file): encoding in mode string was ignored if perm is

[ruby-svn.git] / string.c

/**********************************************************************

  string.c -

  $Author$
  created at: Mon Aug  9 17:12:58 JST 1993

  Copyright (C) 1993-2007 Yukihiro Matsumoto
  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
  Copyright (C) 2000  Information-technology Promotion Agency, Japan

**********************************************************************/

#include "ruby/ruby.h"
#include "ruby/re.h"
#include "ruby/encoding.h"

#define BEG(no) regs->beg[no]
#define END(no) regs->end[no]

#include <math.h>
#include <ctype.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#undef rb_str_new_cstr
#undef rb_tainted_str_new_cstr
#undef rb_usascii_str_new_cstr
#undef rb_str_new2
#undef rb_str_new3
#undef rb_str_new4
#undef rb_str_new5
#undef rb_tainted_str_new2
#undef rb_usascii_str_new2
#undef rb_str_dup_frozen
#undef rb_str_buf_new_cstr
#undef rb_str_buf_new2
#undef rb_str_buf_cat2
#undef rb_str_cat2

VALUE rb_cString;
VALUE rb_cSymbol;

#define STR_TMPLOCK FL_USER7
#define STR_NOEMBED FL_USER1
#define STR_SHARED  FL_USER2 /* = ELTS_SHARED */
#define STR_ASSOC   FL_USER3
#define STR_SHARED_P(s) FL_ALL(s, STR_NOEMBED|ELTS_SHARED)
#define STR_ASSOC_P(s)  FL_ALL(s, STR_NOEMBED|STR_ASSOC)
#define STR_NOCAPA  (STR_NOEMBED|ELTS_SHARED|STR_ASSOC)
#define STR_NOCAPA_P(s) (FL_TEST(s,STR_NOEMBED) && FL_ANY(s,ELTS_SHARED|STR_ASSOC))
#define STR_UNSET_NOCAPA(s) do {\
    if (FL_TEST(s,STR_NOEMBED)) FL_UNSET(s,(ELTS_SHARED|STR_ASSOC));\
} while (0)
                                    

#define STR_SET_NOEMBED(str) do {\
    FL_SET(str, STR_NOEMBED);\
    STR_SET_EMBED_LEN(str, 0);\
} while (0)
#define STR_SET_EMBED(str) FL_UNSET(str, STR_NOEMBED)
#define STR_EMBED_P(str) (!FL_TEST(str, STR_NOEMBED))
#define STR_SET_EMBED_LEN(str, n) do { \
    long tmp_n = (n);\
    RBASIC(str)->flags &= ~RSTRING_EMBED_LEN_MASK;\
    RBASIC(str)->flags |= (tmp_n) << RSTRING_EMBED_LEN_SHIFT;\
} while (0)

#define STR_SET_LEN(str, n) do { \
    if (STR_EMBED_P(str)) {\
        STR_SET_EMBED_LEN(str, n);\
    }\
    else {\
        RSTRING(str)->as.heap.len = (n);\
    }\
} while (0) 

#define STR_DEC_LEN(str) do {\
    if (STR_EMBED_P(str)) {\
        long n = RSTRING_LEN(str);\
        n--;\
        STR_SET_EMBED_LEN(str, n);\
    }\
    else {\
        RSTRING(str)->as.heap.len--;\
    }\
} while (0)

#define RESIZE_CAPA(str,capacity) do {\
    if (STR_EMBED_P(str)) {\
        if ((capacity) > RSTRING_EMBED_LEN_MAX) {\
            char *tmp = ALLOC_N(char, capacity+1);\
            memcpy(tmp, RSTRING_PTR(str), RSTRING_LEN(str));\
            RSTRING(str)->as.heap.ptr = tmp;\
            RSTRING(str)->as.heap.len = RSTRING_LEN(str);\
            STR_SET_NOEMBED(str);\
            RSTRING(str)->as.heap.aux.capa = (capacity);\
        }\
    }\
    else {\
        REALLOC_N(RSTRING(str)->as.heap.ptr, char, (capacity)+1);\
        if (!STR_NOCAPA_P(str))\
            RSTRING(str)->as.heap.aux.capa = (capacity);\
    }\
} while (0)

#define is_ascii_string(str) (rb_enc_str_coderange(str) == ENC_CODERANGE_7BIT)
#define is_broken_string(str) (rb_enc_str_coderange(str) == ENC_CODERANGE_BROKEN)

#define STR_ENC_GET(str) rb_enc_from_index(ENCODING_GET(str))

static int
single_byte_optimizable(VALUE str)
{
    rb_encoding *enc = STR_ENC_GET(str);

    if (rb_enc_mbmaxlen(enc) == 1)
        return 1;

    /* Conservative.  It may be ENC_CODERANGE_UNKNOWN. */
    if (ENC_CODERANGE(str) == ENC_CODERANGE_7BIT)
        return 1;

    /* Conservative.  Possibly single byte.
     * "\xa1" in Shift_JIS for example. */
    return 0;
}

VALUE rb_fs;

static inline const char *
search_nonascii(const char *p, const char *e)
{
#if SIZEOF_VALUE == 8
# define NONASCII_MASK 0x8080808080808080LL
#elif SIZEOF_VALUE == 4
# define NONASCII_MASK 0x80808080UL
#endif
#ifdef NONASCII_MASK
    if (sizeof(VALUE) * 2 < e - p) {
        const VALUE *s, *t;
        const VALUE lowbits = sizeof(VALUE) - 1;
        s = (const VALUE*)(~lowbits & ((VALUE)p + lowbits));
        while (p < (const char *)s) {
            if (!ISASCII(*p))
                return p;
            p++;
        }
        t = (const VALUE*)(~lowbits & (VALUE)e);
        while (s < t) {
            if (*s & NONASCII_MASK) {
                t = s;
                break;
            }
            s++;
        }
        p = (const char *)t;
    }
#endif
    while (p < e) {
        if (!ISASCII(*p))
            return p;
        p++;
    }
    return NULL;
}

static int
coderange_scan(const char *p, long len, rb_encoding *enc)
{
    const char *e = p + len;

    if (rb_enc_to_index(enc) == 0) {
        /* enc is ASCII-8BIT.  ASCII-8BIT string never be broken. */
        p = search_nonascii(p, e);
        return p ? ENC_CODERANGE_VALID : ENC_CODERANGE_7BIT;
    }

    if (rb_enc_asciicompat(enc)) {
        p = search_nonascii(p, e);
        if (!p) {
            return ENC_CODERANGE_7BIT;
        }
        while (p < e) {
            int ret = rb_enc_precise_mbclen(p, e, enc);
            if (!MBCLEN_CHARFOUND_P(ret)) {
                return ENC_CODERANGE_BROKEN;
            }
            p += MBCLEN_CHARFOUND_LEN(ret);
            if (p < e) {
                p = search_nonascii(p, e);
                if (!p) {
                    return ENC_CODERANGE_VALID;
                }
            }
        }
        if (e < p) {
            return ENC_CODERANGE_BROKEN;
        }
        return ENC_CODERANGE_VALID;
    }

    while (p < e) {
        int ret = rb_enc_precise_mbclen(p, e, enc);

        if (!MBCLEN_CHARFOUND_P(ret)) {
            return ENC_CODERANGE_BROKEN;
        }
        p += MBCLEN_CHARFOUND_LEN(ret);
    }
    if (e < p) {
        return ENC_CODERANGE_BROKEN;
    }
    return ENC_CODERANGE_VALID;
}

long
rb_str_coderange_scan_restartable(const char *s, const char *e, rb_encoding *enc, int *cr)
{
    const char *p = s;

    if (*cr == ENC_CODERANGE_BROKEN)
        return e - s;

    if (rb_enc_to_index(enc) == 0) {
        /* enc is ASCII-8BIT.  ASCII-8BIT string never be broken. */
        p = search_nonascii(p, e);
        *cr = (!p && *cr != ENC_CODERANGE_VALID) ? ENC_CODERANGE_7BIT : ENC_CODERANGE_VALID;
        return e - s;
    }
    else if (rb_enc_asciicompat(enc)) {
        p = search_nonascii(p, e);
        if (!p) {
            if (*cr != ENC_CODERANGE_VALID) *cr = ENC_CODERANGE_7BIT;
            return e - s;
        }
        while (p < e) {
            int ret = rb_enc_precise_mbclen(p, e, enc);
            if (!MBCLEN_CHARFOUND_P(ret)) {
                *cr = MBCLEN_INVALID_P(ret) ? ENC_CODERANGE_BROKEN: ENC_CODERANGE_UNKNOWN;
                return p - s;
            }
            p += MBCLEN_CHARFOUND_LEN(ret);
            if (p < e) {
                p = search_nonascii(p, e);
                if (!p) {
                    *cr = ENC_CODERANGE_VALID;
                    return e - s;
                }
            }
        }
        *cr = e < p ? ENC_CODERANGE_BROKEN: ENC_CODERANGE_VALID;
        return p - s;
    }
    else {
        while (p < e) {
            int ret = rb_enc_precise_mbclen(p, e, enc);
            if (!MBCLEN_CHARFOUND_P(ret)) {
                *cr = MBCLEN_INVALID_P(ret) ? ENC_CODERANGE_BROKEN: ENC_CODERANGE_UNKNOWN;
                return p - s;
            }
            p += MBCLEN_CHARFOUND_LEN(ret);
        }
        *cr = e < p ? ENC_CODERANGE_BROKEN: ENC_CODERANGE_VALID;
        return p - s;
    }
}

static inline void
str_enc_copy(VALUE str1, VALUE str2)
{
    rb_enc_set_index(str1, ENCODING_GET(str2));
}

static void
rb_enc_cr_str_copy_for_substr(VALUE dest, VALUE src)
{
    /* this function is designed for copying encoding and coderange
     * from src to new string "dest" which is made from the part of src.
     */
    str_enc_copy(dest, src);
    switch (ENC_CODERANGE(src)) {
      case ENC_CODERANGE_7BIT:
        ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
        break;
      case ENC_CODERANGE_VALID:
        if (!rb_enc_asciicompat(STR_ENC_GET(src)) ||
            search_nonascii(RSTRING_PTR(dest), RSTRING_END(dest)))
            ENC_CODERANGE_SET(dest, ENC_CODERANGE_VALID);
        else
            ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
        break;
      default:
        if (RSTRING_LEN(dest) == 0) {
            if (!rb_enc_asciicompat(STR_ENC_GET(src)))
                ENC_CODERANGE_SET(dest, ENC_CODERANGE_VALID);
            else
                ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
        }
        break;
    }
}

static void
rb_enc_cr_str_exact_copy(VALUE dest, VALUE src)
{
    str_enc_copy(dest, src);
    ENC_CODERANGE_SET(dest, ENC_CODERANGE(src));
}

int
rb_enc_str_coderange(VALUE str)
{
    int cr = ENC_CODERANGE(str);

    if (cr == ENC_CODERANGE_UNKNOWN) {
        rb_encoding *enc = STR_ENC_GET(str);
        cr = coderange_scan(RSTRING_PTR(str), RSTRING_LEN(str), enc);
        ENC_CODERANGE_SET(str, cr);
    }
    return cr;
}

int
rb_enc_str_asciionly_p(VALUE str)
{
    rb_encoding *enc = STR_ENC_GET(str);

    if (!rb_enc_asciicompat(enc))
        return Qfalse;
    else if (rb_enc_str_coderange(str) == ENC_CODERANGE_7BIT)
        return Qtrue;
    return Qfalse;
}

static inline void
str_mod_check(VALUE s, const char *p, long len)
{
    if (RSTRING_PTR(s) != p || RSTRING_LEN(s) != len){
        rb_raise(rb_eRuntimeError, "string modified");
    }
}

static inline void
str_frozen_check(VALUE s)
{
    if (OBJ_FROZEN(s)) {
        rb_raise(rb_eRuntimeError, "string frozen");
    }
}

size_t
rb_str_capacity(VALUE str)
{
    if (STR_EMBED_P(str)) {
        return RSTRING_EMBED_LEN_MAX;
    }
    else if (STR_NOCAPA_P(str)) {
        return RSTRING(str)->as.heap.len;
    }
    else {
        return RSTRING(str)->as.heap.aux.capa;
    }
}

static inline VALUE
str_alloc(VALUE klass)
{
    NEWOBJ(str, struct RString);
    OBJSETUP(str, klass, T_STRING);

    str->as.heap.ptr = 0;
    str->as.heap.len = 0;
    str->as.heap.aux.capa = 0;

    return (VALUE)str;
}

static VALUE
str_new(VALUE klass, const char *ptr, long len)
{
    VALUE str;

    if (len < 0) {
        rb_raise(rb_eArgError, "negative string size (or size too big)");
    }

    str = str_alloc(klass);
    if (len > RSTRING_EMBED_LEN_MAX) {
        RSTRING(str)->as.heap.aux.capa = len;
        RSTRING(str)->as.heap.ptr = ALLOC_N(char,len+1);
        STR_SET_NOEMBED(str);
    }
    if (ptr) {
        memcpy(RSTRING_PTR(str), ptr, len);
    }
    STR_SET_LEN(str, len);
    RSTRING_PTR(str)[len] = '\0';
    return str;
}

VALUE
rb_str_new(const char *ptr, long len)
{
    return str_new(rb_cString, ptr, len);
}

VALUE
rb_usascii_str_new(const char *ptr, long len)
{
    VALUE str = rb_str_new(ptr, len);
    ENCODING_CODERANGE_SET(str, rb_usascii_encindex(), ENC_CODERANGE_7BIT);
    return str;
}

VALUE
rb_enc_str_new(const char *ptr, long len, rb_encoding *enc)
{
    VALUE str = rb_str_new(ptr, len);
    rb_enc_associate(str, enc);
    return str;
}

VALUE
rb_str_new_cstr(const char *ptr)
{
    if (!ptr) {
        rb_raise(rb_eArgError, "NULL pointer given");
    }
    return rb_str_new(ptr, strlen(ptr));
}

RUBY_ALIAS_FUNCTION(rb_str_new2(const char *ptr), rb_str_new_cstr, (ptr))
#define rb_str_new2 rb_str_new_cstr

VALUE
rb_usascii_str_new_cstr(const char *ptr)
{
    VALUE str = rb_str_new2(ptr);
    ENCODING_CODERANGE_SET(str, rb_usascii_encindex(), ENC_CODERANGE_7BIT);
    return str;
}

RUBY_ALIAS_FUNCTION(rb_usascii_str_new2(const char *ptr), rb_usascii_str_new_cstr, (ptr))
#define rb_usascii_str_new2 rb_usascii_str_new_cstr

VALUE
rb_tainted_str_new(const char *ptr, long len)
{
    VALUE str = rb_str_new(ptr, len);

    OBJ_TAINT(str);
    return str;
}

VALUE
rb_tainted_str_new_cstr(const char *ptr)
{
    VALUE str = rb_str_new2(ptr);

    OBJ_TAINT(str);
    return str;
}

RUBY_ALIAS_FUNCTION(rb_tainted_str_new2(const char *ptr), rb_tainted_str_new_cstr, (ptr))
#define rb_tainted_str_new2 rb_tainted_str_new_cstr

static VALUE
str_replace_shared(VALUE str2, VALUE str)
{
    if (RSTRING_LEN(str) <= RSTRING_EMBED_LEN_MAX) {
        STR_SET_EMBED(str2);
        memcpy(RSTRING_PTR(str2), RSTRING_PTR(str), RSTRING_LEN(str)+1);
        STR_SET_EMBED_LEN(str2, RSTRING_LEN(str));
    }
    else {
        FL_SET(str2, STR_NOEMBED);
        RSTRING(str2)->as.heap.len = RSTRING_LEN(str);
        RSTRING(str2)->as.heap.ptr = RSTRING_PTR(str);
        RSTRING(str2)->as.heap.aux.shared = str;
        FL_SET(str2, ELTS_SHARED);
    }
    rb_enc_cr_str_exact_copy(str2, str);

    return str2;
}

static VALUE
str_new_shared(VALUE klass, VALUE str)
{
    return str_replace_shared(str_alloc(klass), str);
}

static VALUE
str_new3(VALUE klass, VALUE str)
{
    return str_new_shared(klass, str);
}

VALUE
rb_str_new_shared(VALUE str)
{
    VALUE str2 = str_new3(rb_obj_class(str), str);

    OBJ_INFECT(str2, str);
    return str2;
}

RUBY_ALIAS_FUNCTION(rb_str_new3(VALUE str), rb_str_new_shared, (str))
#define rb_str_new3 rb_str_new_shared

static VALUE
str_new4(VALUE klass, VALUE str)
{
    VALUE str2;

    str2 = str_alloc(klass);
    STR_SET_NOEMBED(str2);
    RSTRING(str2)->as.heap.len = RSTRING_LEN(str);
    RSTRING(str2)->as.heap.ptr = RSTRING_PTR(str);
    if (STR_SHARED_P(str)) {
        FL_SET(str2, ELTS_SHARED);
        RSTRING(str2)->as.heap.aux.shared = RSTRING(str)->as.heap.aux.shared;
    }
    else {
        FL_SET(str, ELTS_SHARED);
        RSTRING(str)->as.heap.aux.shared = str2;
    }
    rb_enc_cr_str_exact_copy(str2, str);
    OBJ_INFECT(str2, str);
    return str2;
}

VALUE
rb_str_new_frozen(VALUE orig)
{
    VALUE klass, str;

    if (OBJ_FROZEN(orig)) return orig;
    klass = rb_obj_class(orig);
    if (STR_SHARED_P(orig) && (str = RSTRING(orig)->as.heap.aux.shared)) {
        long ofs;
        ofs = RSTRING_LEN(str) - RSTRING_LEN(orig);
        if ((ofs > 0) || (klass != RBASIC(str)->klass) ||
            (!OBJ_TAINTED(str) && OBJ_TAINTED(orig))) {
            str = str_new3(klass, str);
            RSTRING(str)->as.heap.ptr += ofs;
            RSTRING(str)->as.heap.len -= ofs;
        }
        rb_enc_cr_str_exact_copy(str, orig);
        OBJ_INFECT(str, orig);
    }
    else if (STR_EMBED_P(orig)) {
        str = str_new(klass, RSTRING_PTR(orig), RSTRING_LEN(orig));
        rb_enc_cr_str_exact_copy(str, orig);
        OBJ_INFECT(str, orig);
    }
    else if (STR_ASSOC_P(orig)) {
        VALUE assoc = RSTRING(orig)->as.heap.aux.shared;
        FL_UNSET(orig, STR_ASSOC);
        str = str_new4(klass, orig);
        FL_SET(str, STR_ASSOC);
        RSTRING(str)->as.heap.aux.shared = assoc;
    }
    else {
        str = str_new4(klass, orig);
    }
    OBJ_FREEZE(str);
    return str;
}

RUBY_ALIAS_FUNCTION(rb_str_new4(VALUE orig), rb_str_new_frozen, (orig))
#define rb_str_new4 rb_str_new_frozen

VALUE
rb_str_new_with_class(VALUE obj, const char *ptr, long len)
{
    return str_new(rb_obj_class(obj), ptr, len);
}

RUBY_ALIAS_FUNCTION(rb_str_new5(VALUE obj, const char *ptr, long len),
           rb_str_new_with_class, (obj, ptr, len))
#define rb_str_new5 rb_str_new_with_class

#define STR_BUF_MIN_SIZE 128

VALUE
rb_str_buf_new(long capa)
{
    VALUE str = str_alloc(rb_cString);

    if (capa < STR_BUF_MIN_SIZE) {
        capa = STR_BUF_MIN_SIZE;
    }
    FL_SET(str, STR_NOEMBED);
    RSTRING(str)->as.heap.aux.capa = capa;
    RSTRING(str)->as.heap.ptr = ALLOC_N(char, capa+1);
    RSTRING(str)->as.heap.ptr[0] = '\0';

    return str;
}

VALUE
rb_str_buf_new_cstr(const char *ptr)
{
    VALUE str;
    long len = strlen(ptr);

    str = rb_str_buf_new(len);
    rb_str_buf_cat(str, ptr, len);

    return str;
}

RUBY_ALIAS_FUNCTION(rb_str_buf_new2(const char *ptr), rb_str_buf_new_cstr, (ptr))
#define rb_str_buf_new2 rb_str_buf_new_cstr

VALUE
rb_str_tmp_new(long len)
{
    return str_new(0, 0, len);
}

void
rb_str_free(VALUE str)
{
    if (!STR_EMBED_P(str) && !STR_SHARED_P(str)) {
        xfree(RSTRING(str)->as.heap.ptr);
    }
}

VALUE
rb_str_to_str(VALUE str)
{
    return rb_convert_type(str, T_STRING, "String", "to_str");
}

void
rb_str_shared_replace(VALUE str, VALUE str2)
{
    rb_encoding *enc;
    int cr;
    if (str == str2) return;
    enc = STR_ENC_GET(str2);
    cr = ENC_CODERANGE(str2);
    rb_str_modify(str);
    OBJ_INFECT(str, str2);
    if (!STR_SHARED_P(str) && !STR_EMBED_P(str)) {
        xfree(RSTRING_PTR(str));
    }
    if (RSTRING_LEN(str2) <= RSTRING_EMBED_LEN_MAX) {
        STR_SET_EMBED(str);
        memcpy(RSTRING_PTR(str), RSTRING_PTR(str2), RSTRING_LEN(str2)+1);
        STR_SET_EMBED_LEN(str, RSTRING_LEN(str2));
        rb_enc_associate(str, enc);
        ENC_CODERANGE_SET(str, cr);
        return;
    }
    STR_SET_NOEMBED(str);
    STR_UNSET_NOCAPA(str);
    RSTRING(str)->as.heap.ptr = RSTRING_PTR(str2);
    RSTRING(str)->as.heap.len = RSTRING_LEN(str2);
    if (STR_NOCAPA_P(str2)) {
        FL_SET(str, RBASIC(str2)->flags & STR_NOCAPA);
        RSTRING(str)->as.heap.aux.shared = RSTRING(str2)->as.heap.aux.shared;
    }
    else {
        RSTRING(str)->as.heap.aux.capa = RSTRING(str2)->as.heap.aux.capa;
    }
    RSTRING(str2)->as.heap.ptr = 0;     /* abandon str2 */
    RSTRING(str2)->as.heap.len = 0;
    RSTRING(str2)->as.heap.aux.capa = 0;
    STR_UNSET_NOCAPA(str2);
    rb_enc_associate(str, enc);
    ENC_CODERANGE_SET(str, cr);
}

static ID id_to_s;

VALUE
rb_obj_as_string(VALUE obj)
{
    VALUE str;

    if (TYPE(obj) == T_STRING) {
        return obj;
    }
    str = rb_funcall(obj, id_to_s, 0);
    if (TYPE(str) != T_STRING)
        return rb_any_to_s(obj);
    if (OBJ_TAINTED(obj)) OBJ_TAINT(str);
    return str;
}

static VALUE rb_str_replace(VALUE, VALUE);

VALUE
rb_str_dup(VALUE str)
{
    VALUE dup = str_alloc(rb_obj_class(str));
    rb_str_replace(dup, str);
    return dup;
}


/*
 *  call-seq:
 *     String.new(str="")   => new_str
 *  
 *  Returns a new string object containing a copy of <i>str</i>.
 */

static VALUE
rb_str_init(int argc, VALUE *argv, VALUE str)
{
    VALUE orig;

    if (argc > 0 && rb_scan_args(argc, argv, "01", &orig) == 1)
        rb_str_replace(str, orig);
    return str;
}

long
rb_enc_strlen(const char *p, const char *e, rb_encoding *enc)
{
    long c;
    const char *q;

    if (rb_enc_mbmaxlen(enc) == rb_enc_mbminlen(enc)) {
        return (e - p + rb_enc_mbminlen(enc) - 1) / rb_enc_mbminlen(enc);
    }
    else if (rb_enc_asciicompat(enc)) {
        c = 0;
        while (p < e) {
            if (ISASCII(*p)) {
                q = search_nonascii(p, e);
                if (!q)
                    return c + (e - p);
                c += q - p;
                p = q;
            }
            p += rb_enc_mbclen(p, e, enc);
            c++;
        }
        return c;
    }

    for (c=0; p<e; c++) {
        p += rb_enc_mbclen(p, e, enc);
    }
    return c;
}

long
rb_enc_strlen_cr(const char *p, const char *e, rb_encoding *enc, int *cr)
{
    long c;
    const char *q;
    int ret;

    *cr = 0;
    if (rb_enc_mbmaxlen(enc) == rb_enc_mbminlen(enc)) {
        return (e - p + rb_enc_mbminlen(enc) - 1) / rb_enc_mbminlen(enc);
    }
    else if (rb_enc_asciicompat(enc)) {
        c = 0;
        while (p < e) {
            if (ISASCII(*p)) {
                q = search_nonascii(p, e);
                if (!q) {
                    if (!*cr) *cr = ENC_CODERANGE_7BIT;
                    return c + (e - p);
                }
                c += q - p;
                p = q;
            }
            ret = rb_enc_precise_mbclen(p, e, enc);
            if (MBCLEN_CHARFOUND_P(ret)) {
                *cr |= ENC_CODERANGE_VALID;
                p += MBCLEN_CHARFOUND_LEN(ret);
            }
            else {
                *cr = ENC_CODERANGE_BROKEN;
                p++;
            }
            c++;
        }
        if (!*cr) *cr = ENC_CODERANGE_7BIT;
        return c;
    }

    for (c=0; p<e; c++) {
        ret = rb_enc_precise_mbclen(p, e, enc);
        if (MBCLEN_CHARFOUND_P(ret)) {
            *cr |= ENC_CODERANGE_VALID;
            p += MBCLEN_CHARFOUND_LEN(ret);
        }
        else {
            *cr = ENC_CODERANGE_BROKEN;
            p++;
        }
    }
    if (!*cr) *cr = ENC_CODERANGE_7BIT;
    return c;
}

#ifdef NONASCII_MASK
#define is_utf8_lead_byte(c) (((c)&0xC0) != 0x80)
static inline VALUE
count_utf8_lead_bytes_with_word(const VALUE *s)
{
    VALUE d = *s;
    d |= ~(d>>1);
    d >>= 6;
    d &= NONASCII_MASK >> 7;
    d += (d>>8);
    d += (d>>16);
#if SIZEOF_VALUE == 8
    d += (d>>32);
#endif
    return (d&0xF);
}
#endif

static long
str_strlen(VALUE str, rb_encoding *enc)
{
    const char *p, *e;
    int n, cr;

    if (single_byte_optimizable(str)) return RSTRING_LEN(str);
    if (!enc) enc = STR_ENC_GET(str);
    p = RSTRING_PTR(str);
    e = RSTRING_END(str);
#ifdef NONASCII_MASK
    if (ENC_CODERANGE(str) == ENC_CODERANGE_VALID &&
        enc == rb_utf8_encoding()) {
        VALUE len = 0;
        if (sizeof(VALUE) * 2 < e - p) {
            const VALUE *s, *t;
            const VALUE lowbits = sizeof(VALUE) - 1;
            s = (const VALUE*)(~lowbits & ((VALUE)p + lowbits));
            t = (const VALUE*)(~lowbits & (VALUE)e);
            while (p < (const char *)s) {
                if (is_utf8_lead_byte(*p)) len++;
                p++;
            }
            while (s < t) {
                len += count_utf8_lead_bytes_with_word(s);
                s++;
            }
            p = (const char *)s;
        }
        while (p < e) {
            if (is_utf8_lead_byte(*p)) len++;
            p++;
        }
        return (long)len;
    }
#endif
    n = rb_enc_strlen_cr(p, e, enc, &cr);
    if (cr) {
        ENC_CODERANGE_SET(str, cr);
    }
    return n;
}

/*
 *  call-seq:
 *     str.length   => integer
 *     str.size     => integer
 *  
 *  Returns the character length of <i>str</i>.
 */

VALUE
rb_str_length(VALUE str)
{
    int len;

    len = str_strlen(str, STR_ENC_GET(str));
    return INT2NUM(len);
}

/*
 *  call-seq:
 *     str.bytesize  => integer
 *  
 *  Returns the length of <i>str</i> in bytes.
 */

static VALUE
rb_str_bytesize(VALUE str)
{
    return INT2NUM(RSTRING_LEN(str));
}

/*
 *  call-seq:
 *     str.empty?   => true or false
 *  
 *  Returns <code>true</code> if <i>str</i> has a length of zero.
 *     
 *     "hello".empty?   #=> false
 *     "".empty?        #=> true
 */

static VALUE
rb_str_empty(VALUE str)
{
    if (RSTRING_LEN(str) == 0)
        return Qtrue;
    return Qfalse;
}

/*
 *  call-seq:
 *     str + other_str   => new_str
 *  
 *  Concatenation---Returns a new <code>String</code> containing
 *  <i>other_str</i> concatenated to <i>str</i>.
 *     
 *     "Hello from " + self.to_s   #=> "Hello from main"
 */

VALUE
rb_str_plus(VALUE str1, VALUE str2)
{
    VALUE str3;
    rb_encoding *enc;

    StringValue(str2);
    enc = rb_enc_check(str1, str2);
    str3 = rb_str_new(0, RSTRING_LEN(str1)+RSTRING_LEN(str2));
    memcpy(RSTRING_PTR(str3), RSTRING_PTR(str1), RSTRING_LEN(str1));
    memcpy(RSTRING_PTR(str3) + RSTRING_LEN(str1),
           RSTRING_PTR(str2), RSTRING_LEN(str2));
    RSTRING_PTR(str3)[RSTRING_LEN(str3)] = '\0';

    if (OBJ_TAINTED(str1) || OBJ_TAINTED(str2))
        OBJ_TAINT(str3);
    ENCODING_CODERANGE_SET(str3, rb_enc_to_index(enc),
                           ENC_CODERANGE_AND(ENC_CODERANGE(str1), ENC_CODERANGE(str2)));
    return str3;
}

/*
 *  call-seq:
 *     str * integer   => new_str
 *  
 *  Copy---Returns a new <code>String</code> containing <i>integer</i> copies of
 *  the receiver.
 *     
 *     "Ho! " * 3   #=> "Ho! Ho! Ho! "
 */

VALUE
rb_str_times(VALUE str, VALUE times)
{
    VALUE str2;
    long n, len;

    len = NUM2LONG(times);
    if (len < 0) {
        rb_raise(rb_eArgError, "negative argument");
    }
    if (len && LONG_MAX/len <  RSTRING_LEN(str)) {
        rb_raise(rb_eArgError, "argument too big");
    }

    str2 = rb_str_new5(str, 0, len *= RSTRING_LEN(str));
    if (len) {
        n = RSTRING_LEN(str);
        memcpy(RSTRING_PTR(str2), RSTRING_PTR(str), n);
        while (n <= len/2) {
            memcpy(RSTRING_PTR(str2) + n, RSTRING_PTR(str2), n);
            n *= 2;
        }
        memcpy(RSTRING_PTR(str2) + n, RSTRING_PTR(str2), len-n);
    }
    RSTRING_PTR(str2)[RSTRING_LEN(str2)] = '\0';
    OBJ_INFECT(str2, str);
    rb_enc_cr_str_copy_for_substr(str2, str);

    return str2;
}

/*
 *  call-seq:
 *     str % arg   => new_str
 *  
 *  Format---Uses <i>str</i> as a format specification, and returns the result
 *  of applying it to <i>arg</i>. If the format specification contains more than
 *  one substitution, then <i>arg</i> must be an <code>Array</code> containing
 *  the values to be substituted. See <code>Kernel::sprintf</code> for details
 *  of the format string.
 *     
 *     "%05d" % 123                              #=> "00123"
 *     "%-5s: %08x" % [ "ID", self.object_id ]   #=> "ID   : 200e14d6"
 */

static VALUE
rb_str_format_m(VALUE str, VALUE arg)
{
    volatile VALUE tmp = rb_check_array_type(arg);

    if (!NIL_P(tmp)) {
        return rb_str_format(RARRAY_LEN(tmp), RARRAY_PTR(tmp), str);
    }
    return rb_str_format(1, &arg, str);
}

static inline void
str_modifiable(VALUE str)
{
    if (FL_TEST(str, STR_TMPLOCK)) {
        rb_raise(rb_eRuntimeError, "can't modify string; temporarily locked");
    }
    if (OBJ_FROZEN(str)) rb_error_frozen("string");
    if (!OBJ_UNTRUSTED(str) && rb_safe_level() >= 4)
        rb_raise(rb_eSecurityError, "Insecure: can't modify string");
}

static inline int
str_independent(VALUE str)
{
    str_modifiable(str);
    if (!STR_SHARED_P(str)) return 1;
    if (STR_EMBED_P(str)) return 1;
    return 0;
}

static void
str_make_independent(VALUE str)
{
    char *ptr;
    long len = RSTRING_LEN(str);

    ptr = ALLOC_N(char, len+1);
    if (RSTRING_PTR(str)) {
        memcpy(ptr, RSTRING_PTR(str), len);
    }
    STR_SET_NOEMBED(str);
    ptr[len] = 0;
    RSTRING(str)->as.heap.ptr = ptr;
    RSTRING(str)->as.heap.len = len;
    RSTRING(str)->as.heap.aux.capa = len;
    STR_UNSET_NOCAPA(str);
}

void
rb_str_modify(VALUE str)
{
    if (!str_independent(str))
        str_make_independent(str);
    ENC_CODERANGE_CLEAR(str);
}

void
rb_str_associate(VALUE str, VALUE add)
{
    /* sanity check */
    if (OBJ_FROZEN(str)) rb_error_frozen("string");
    if (STR_ASSOC_P(str)) {
        /* already associated */
        rb_ary_concat(RSTRING(str)->as.heap.aux.shared, add);
    }
    else {
        if (STR_SHARED_P(str)) {
            VALUE assoc = RSTRING(str)->as.heap.aux.shared;
            str_make_independent(str);
            if (STR_ASSOC_P(assoc)) {
                assoc = RSTRING(assoc)->as.heap.aux.shared;
                rb_ary_concat(assoc, add);
                add = assoc;
            }
        }
        else if (STR_EMBED_P(str)) {
            str_make_independent(str);
        }
        else if (RSTRING(str)->as.heap.aux.capa != RSTRING_LEN(str)) {
            RESIZE_CAPA(str, RSTRING_LEN(str));
        }
        FL_SET(str, STR_ASSOC);
        RBASIC(add)->klass = 0;
        RSTRING(str)->as.heap.aux.shared = add;
    }
}

VALUE
rb_str_associated(VALUE str)
{
    if (STR_SHARED_P(str)) str = RSTRING(str)->as.heap.aux.shared;
    if (STR_ASSOC_P(str)) {
        return RSTRING(str)->as.heap.aux.shared;
    }
    return Qfalse;
}

VALUE
rb_string_value(volatile VALUE *ptr)
{
    VALUE s = *ptr;
    if (TYPE(s) != T_STRING) {
        s = rb_str_to_str(s);
        *ptr = s;
    }
    return s;
}

char *
rb_string_value_ptr(volatile VALUE *ptr)
{
    return RSTRING_PTR(rb_string_value(ptr));
}

char *
rb_string_value_cstr(volatile VALUE *ptr)
{
    VALUE str = rb_string_value(ptr);
    char *s = RSTRING_PTR(str);

    if (!s || RSTRING_LEN(str) != strlen(s)) {
        rb_raise(rb_eArgError, "string contains null byte");
    }
    return s;
}

VALUE
rb_check_string_type(VALUE str)
{
    str = rb_check_convert_type(str, T_STRING, "String", "to_str");
    return str;
}

/*
 *  call-seq:
 *     String.try_convert(obj) -> string or nil
 *
 *  Try to convert <i>obj</i> into a String, using to_str method.
 *  Returns converted regexp or nil if <i>obj</i> cannot be converted
 *  for any reason.
 *
 *     String.try_convert("str")     # => str
 *     String.try_convert(/re/)      # => nil
 */
static VALUE
rb_str_s_try_convert(VALUE dummy, VALUE str)
{
    return rb_check_string_type(str);
}

char*
rb_enc_nth(const char *p, const char *e, int nth, rb_encoding *enc)
{
    if (rb_enc_mbmaxlen(enc) == 1) {
        p += nth;
    }
    else if (rb_enc_mbmaxlen(enc) == rb_enc_mbminlen(enc)) {
        p += nth * rb_enc_mbmaxlen(enc);
    }
    else if (rb_enc_asciicompat(enc)) {
        const char *p2, *e2;
        int n;

        while (p < e && 0 < nth) {
            e2 = p + nth;
            if (e < e2)
                return (char *)e;
            if (ISASCII(*p)) {
                p2 = search_nonascii(p, e2);
                if (!p2)
                    return (char *)e2;
                nth -= p2 - p;
                p = p2;
            }
            n = rb_enc_mbclen(p, e, enc);
            p += n;
            nth--;
        }
        if (nth != 0)
            return (char *)e;
        return (char *)p;
    }
    else {
        while (p<e && nth--) {
            p += rb_enc_mbclen(p, e, enc);
        }
    }
    if (p > e) p = e;
    return (char*)p;
}

static char*
str_nth(const char *p, const char *e, int nth, rb_encoding *enc, int singlebyte)
{
    if (singlebyte)
        p += nth;
    else {
        p = rb_enc_nth(p, e, nth, enc);
    }
    if (!p) return 0;
    if (p > e) p = e;
    return (char *)p;
}

/* char offset to byte offset */
static int
str_offset(const char *p, const char *e, int nth, rb_encoding *enc, int singlebyte)
{
    const char *pp = str_nth(p, e, nth, enc, singlebyte);
    if (!pp) return e - p;
    return pp - p;
}

#ifdef NONASCII_MASK
static char *
str_utf8_nth(const char *p, const char *e, int nth)
{
    if (sizeof(VALUE) * 2 < nth) {
        const VALUE *s, *t;
        const VALUE lowbits = sizeof(VALUE) - 1;
        s = (const VALUE*)(~lowbits & ((VALUE)p + lowbits));
        t = (const VALUE*)(~lowbits & (VALUE)e);
        while (p < (const char *)s) {
            if (is_utf8_lead_byte(*p)) nth--;
            p++;
        }
        do {
            nth -= count_utf8_lead_bytes_with_word(s);
            s++;
        } while (s < t && sizeof(VALUE) <= nth);
        p = (char *)s;
    }
    while (p < e) {
        if (is_utf8_lead_byte(*p)) {
            if (nth == 0) break;
            nth--;
        }
        p++;
    }
    return (char *)p;
}

static int
str_utf8_offset(const char *p, const char *e, int nth)
{
    const char *pp = str_utf8_nth(p, e, nth);
    if (!pp) return e - p;
    return pp - p;
}
#endif

/* byte offset to char offset */
long
rb_str_sublen(VALUE str, long pos)
{
    if (single_byte_optimizable(str) || pos < 0)
        return pos;
    else {
        char *p = RSTRING_PTR(str);
        return rb_enc_strlen(p, p + pos, STR_ENC_GET(str));
    }
}

VALUE
rb_str_subseq(VALUE str, long beg, long len)
{
    VALUE str2 = rb_str_new5(str, RSTRING_PTR(str)+beg, len);

    rb_enc_cr_str_copy_for_substr(str2, str);
    OBJ_INFECT(str2, str);

    return str2;
}

VALUE
rb_str_substr(VALUE str, long beg, long len)
{
    rb_encoding *enc = STR_ENC_GET(str);
    VALUE str2;
    char *p, *s = RSTRING_PTR(str), *e = s + RSTRING_LEN(str);
    int singlebyte;

    if (len < 0) return Qnil;
    if (!RSTRING_LEN(str)) {
        len = 0;
    }
    if (beg < 0) {
        if (len > -beg) len = -beg;
        if (-beg * rb_enc_mbmaxlen(enc) < RSTRING_LEN(str) / 8) {
            beg = -beg;
            while (beg-- > len && (e = rb_enc_prev_char(s, e, enc)) != 0);
            p = e;
            if (!p) return Qnil;
            while (len-- > 0 && (p = rb_enc_prev_char(s, p, enc)) != 0);
            if (!p) return Qnil;
            len = e - p;
            goto sub;
        }
        else {
            beg += str_strlen(str, enc);
            if (beg < 0) return Qnil;
        }
    }
    else if (beg > 0 && beg > str_strlen(str, enc)) {
        return Qnil;
    }
    singlebyte = single_byte_optimizable(str);
    if (len == 0) {
        p = 0;
    }
#ifdef NONASCII_MASK
    else if (ENC_CODERANGE(str) == ENC_CODERANGE_VALID &&
        enc == rb_utf8_encoding()) {
        p = str_utf8_nth(s, e, beg);
        len = str_utf8_offset(p, e, len);
    }
#endif
    else if ((p = str_nth(s, e, beg, enc, singlebyte)) == e) {
        len = 0;
    }
    else if (rb_enc_mbmaxlen(enc) == rb_enc_mbminlen(enc)) {
        if (len * rb_enc_mbmaxlen(enc) > e - p)
            len = e - p;
        else
            len *= rb_enc_mbmaxlen(enc);
    }
    else {
        len = str_offset(p, e, len, enc, singlebyte);
    }
  sub:
    if (len > RSTRING_EMBED_LEN_MAX && beg + len == RSTRING_LEN(str)) {
        str2 = rb_str_new4(str);
        str2 = str_new3(rb_obj_class(str2), str2);
        RSTRING(str2)->as.heap.ptr += RSTRING(str2)->as.heap.len - len;
        RSTRING(str2)->as.heap.len = len;
    }
    else {
        str2 = rb_str_new5(str, p, len);
        rb_enc_cr_str_copy_for_substr(str2, str);
        OBJ_INFECT(str2, str);
    }

    return str2;
}

VALUE
rb_str_freeze(VALUE str)
{
    if (STR_ASSOC_P(str)) {
        VALUE ary = RSTRING(str)->as.heap.aux.shared;
        OBJ_FREEZE(ary);
    }
    return rb_obj_freeze(str);
}

RUBY_ALIAS_FUNCTION(rb_str_dup_frozen(VALUE str), rb_str_new_frozen, (str))
#define rb_str_dup_frozen rb_str_new_frozen

VALUE
rb_str_locktmp(VALUE str)
{
    if (FL_TEST(str, STR_TMPLOCK)) {
        rb_raise(rb_eRuntimeError, "temporal locking already locked string");
    }
    FL_SET(str, STR_TMPLOCK);
    return str;
}

VALUE
rb_str_unlocktmp(VALUE str)
{
    if (!FL_TEST(str, STR_TMPLOCK)) {
        rb_raise(rb_eRuntimeError, "temporal unlocking already unlocked string");
    }
    FL_UNSET(str, STR_TMPLOCK);
    return str;
}

void
rb_str_set_len(VALUE str, long len)
{
    STR_SET_LEN(str, len);
    RSTRING_PTR(str)[len] = '\0';
}

VALUE
rb_str_resize(VALUE str, long len)
{
    long slen;

    if (len < 0) {
        rb_raise(rb_eArgError, "negative string size (or size too big)");
    }

    rb_str_modify(str);
    slen = RSTRING_LEN(str);
    if (len != slen) {
        if (STR_EMBED_P(str)) {
            char *ptr;
            if (len <= RSTRING_EMBED_LEN_MAX) {
                STR_SET_EMBED_LEN(str, len);
                RSTRING(str)->as.ary[len] = '\0';
                return str;
            }
            ptr = ALLOC_N(char,len+1);
            MEMCPY(ptr, RSTRING(str)->as.ary, char, slen);
            RSTRING(str)->as.heap.ptr = ptr;
            STR_SET_NOEMBED(str);
        }
        else if (len <= RSTRING_EMBED_LEN_MAX) {
            char *ptr = RSTRING(str)->as.heap.ptr;
            STR_SET_EMBED(str);
            if (slen > 0) MEMCPY(RSTRING(str)->as.ary, ptr, char, len);
            RSTRING(str)->as.ary[len] = '\0';
            STR_SET_EMBED_LEN(str, len);
            xfree(ptr);
            return str;
        }
        else if (slen < len || slen - len > 1024) {
            REALLOC_N(RSTRING(str)->as.heap.ptr, char, len+1);
        }
        if (!STR_NOCAPA_P(str)) {
            RSTRING(str)->as.heap.aux.capa = len;
        }
        RSTRING(str)->as.heap.len = len;
        RSTRING(str)->as.heap.ptr[len] = '\0';  /* sentinel */
    }
    return str;
}

static VALUE
str_buf_cat(VALUE str, const char *ptr, long len)
{
    long capa, total, off = -1;

    if (ptr >= RSTRING_PTR(str) && ptr <= RSTRING_END(str)) {
        off = ptr - RSTRING_PTR(str);
    }
    rb_str_modify(str);
    if (len == 0) return 0;
    if (STR_ASSOC_P(str)) {
        FL_UNSET(str, STR_ASSOC);
        capa = RSTRING(str)->as.heap.aux.capa = RSTRING_LEN(str);
    }
    else if (STR_EMBED_P(str)) {
        capa = RSTRING_EMBED_LEN_MAX;
    }
    else {
        capa = RSTRING(str)->as.heap.aux.capa;
    }
    if (RSTRING_LEN(str) >= LONG_MAX - len) {
        rb_raise(rb_eArgError, "string sizes too big");
    }
    total = RSTRING_LEN(str)+len;
    if (capa <= total) {
        while (total > capa) {
            if (capa + 1 >= LONG_MAX / 2) {
                capa = (total + 4095) / 4096;
                break;
            }
            capa = (capa + 1) * 2;
        }
        RESIZE_CAPA(str, capa);
    }
    if (off != -1) {
        ptr = RSTRING_PTR(str) + off;
    }
    memcpy(RSTRING_PTR(str) + RSTRING_LEN(str), ptr, len);
    STR_SET_LEN(str, total);
    RSTRING_PTR(str)[total] = '\0'; /* sentinel */

    return str;
}

VALUE
rb_str_buf_cat(VALUE str, const char *ptr, long len)
{
    if (len == 0) return str;
    if (len < 0) {
        rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    return str_buf_cat(str, ptr, len);
}

VALUE
rb_str_buf_cat2(VALUE str, const char *ptr)
{
    return rb_str_buf_cat(str, ptr, strlen(ptr));
}

VALUE
rb_str_cat(VALUE str, const char *ptr, long len)
{
    if (len < 0) {
        rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    if (STR_ASSOC_P(str)) {
        rb_str_modify(str);
        if (STR_EMBED_P(str)) str_make_independent(str);
        REALLOC_N(RSTRING(str)->as.heap.ptr, char, RSTRING(str)->as.heap.len+len+1);
        memcpy(RSTRING(str)->as.heap.ptr + RSTRING(str)->as.heap.len, ptr, len);
        RSTRING(str)->as.heap.len += len;
        RSTRING(str)->as.heap.ptr[RSTRING(str)->as.heap.len] = '\0'; /* sentinel */
        return str;
    }

    return rb_str_buf_cat(str, ptr, len);
}

VALUE
rb_str_cat2(VALUE str, const char *ptr)
{
    return rb_str_cat(str, ptr, strlen(ptr));
}

static VALUE
rb_enc_cr_str_buf_cat(VALUE str, const char *ptr, long len,
    int ptr_encindex, int ptr_cr, int *ptr_cr_ret)
{
    int str_encindex = ENCODING_GET(str);
    int res_encindex;
    int str_cr, res_cr;
    int str_a8 = ENCODING_IS_ASCII8BIT(str);
    int ptr_a8 = ptr_encindex == 0;

    str_cr = ENC_CODERANGE(str);

    if (str_encindex == ptr_encindex) {
        if (str_cr == ENC_CODERANGE_UNKNOWN ||
            (ptr_a8 && str_cr != ENC_CODERANGE_7BIT)) {
            ptr_cr = ENC_CODERANGE_UNKNOWN;
        }
        else if (ptr_cr == ENC_CODERANGE_UNKNOWN) {
            ptr_cr = coderange_scan(ptr, len, rb_enc_from_index(ptr_encindex));
        }
    }
    else {
        rb_encoding *str_enc = rb_enc_from_index(str_encindex);
        rb_encoding *ptr_enc = rb_enc_from_index(ptr_encindex);
        if (!rb_enc_asciicompat(str_enc) || !rb_enc_asciicompat(ptr_enc)) {
            if (len == 0)
                return str;
            if (RSTRING_LEN(str) == 0) {
                rb_str_buf_cat(str, ptr, len);
                ENCODING_CODERANGE_SET(str, ptr_encindex, ptr_cr);
                return str;
            }
            goto incompatible;
        }
        if (ptr_cr == ENC_CODERANGE_UNKNOWN) {
            ptr_cr = coderange_scan(ptr, len, ptr_enc);
        }
        if (str_cr == ENC_CODERANGE_UNKNOWN) {
            if (str_a8 || ptr_cr != ENC_CODERANGE_7BIT) {
                str_cr = rb_enc_str_coderange(str);
            }
        }
    }
    if (ptr_cr_ret)
        *ptr_cr_ret = ptr_cr;

    if (str_encindex != ptr_encindex &&
        str_cr != ENC_CODERANGE_7BIT &&
        ptr_cr != ENC_CODERANGE_7BIT) {
      incompatible:
        rb_raise(rb_eEncCompatError, "incompatible character encodings: %s and %s",
            rb_enc_name(rb_enc_from_index(str_encindex)),
            rb_enc_name(rb_enc_from_index(ptr_encindex)));
    }

    if (str_cr == ENC_CODERANGE_UNKNOWN) {
        res_encindex = str_encindex;
        res_cr = ENC_CODERANGE_UNKNOWN;
    }
    else if (str_cr == ENC_CODERANGE_7BIT) {
        if (ptr_cr == ENC_CODERANGE_7BIT) {
            res_encindex = !str_a8 ? str_encindex : ptr_encindex;
            res_cr = ENC_CODERANGE_7BIT;
        }
        else {
            res_encindex = ptr_encindex;
            res_cr = ptr_cr;
        }
    }
    else if (str_cr == ENC_CODERANGE_VALID) {
        res_encindex = str_encindex;
        res_cr = str_cr;
    }
    else { /* str_cr == ENC_CODERANGE_BROKEN */
        res_encindex = str_encindex;
        res_cr = str_cr;
        if (0 < len) res_cr = ENC_CODERANGE_UNKNOWN;
    }

    if (len < 0) {
        rb_raise(rb_eArgError, "negative string size (or size too big)");
    }
    str_buf_cat(str, ptr, len);
    ENCODING_CODERANGE_SET(str, res_encindex, res_cr);
    return str;
}

VALUE
rb_enc_str_buf_cat(VALUE str, const char *ptr, long len, rb_encoding *ptr_enc)
{
    return rb_enc_cr_str_buf_cat(str, ptr, len,
        rb_enc_to_index(ptr_enc), ENC_CODERANGE_UNKNOWN, NULL);
}

VALUE
rb_str_buf_cat_ascii(VALUE str, const char *ptr)
{
    /* ptr must reference NUL terminated ASCII string. */
    int encindex = ENCODING_GET(str);
    rb_encoding *enc = rb_enc_from_index(encindex);
    if (rb_enc_asciicompat(enc)) {
        return rb_enc_cr_str_buf_cat(str, ptr, strlen(ptr),
            encindex, ENC_CODERANGE_7BIT, 0);
    }
    else {
        char *buf = ALLOCA_N(char, rb_enc_mbmaxlen(enc));
        while (*ptr) {
            int c = (unsigned char)*ptr;
            int len = rb_enc_codelen(c, enc);
            rb_enc_mbcput(c, buf, enc);
            rb_enc_cr_str_buf_cat(str, buf, len,
                encindex, ENC_CODERANGE_VALID, 0);
            ptr++;
        }
        return str;
    }
}

VALUE
rb_str_buf_append(VALUE str, VALUE str2)
{
    int str2_cr;

    str2_cr = ENC_CODERANGE(str2);

    rb_enc_cr_str_buf_cat(str, RSTRING_PTR(str2), RSTRING_LEN(str2),
        ENCODING_GET(str2), str2_cr, &str2_cr);

    OBJ_INFECT(str, str2);
    ENC_CODERANGE_SET(str2, str2_cr);

    return str;
}

VALUE
rb_str_append(VALUE str, VALUE str2)
{
    rb_encoding *enc;
    int cr, cr2;

    StringValue(str2);
    if (RSTRING_LEN(str2) > 0 && STR_ASSOC_P(str)) {
        long len = RSTRING_LEN(str)+RSTRING_LEN(str2);
        enc = rb_enc_check(str, str2);
        cr = ENC_CODERANGE(str);
        if ((cr2 = ENC_CODERANGE(str2)) > cr) cr = cr2;
        rb_str_modify(str);
        REALLOC_N(RSTRING(str)->as.heap.ptr, char, len+1);
        memcpy(RSTRING(str)->as.heap.ptr + RSTRING(str)->as.heap.len,
               RSTRING_PTR(str2), RSTRING_LEN(str2)+1);
        RSTRING(str)->as.heap.len = len;
        rb_enc_associate(str, enc);
        ENC_CODERANGE_SET(str, cr);
        OBJ_INFECT(str, str2);
        return str;
    }
    return rb_str_buf_append(str, str2);
}


/*
 *  call-seq:
 *     str << fixnum        => str
 *     str.concat(fixnum)   => str
 *     str << obj           => str
 *     str.concat(obj)      => str
 *  
 *  Append---Concatenates the given object to <i>str</i>. If the object is a
 *  <code>Fixnum</code>, it is considered as a codepoint, and is converted
 *  to a character before concatenation.
 *     
 *     a = "hello "
 *     a << "world"   #=> "hello world"
 *     a.concat(33)   #=> "hello world!"
 */

VALUE
rb_str_concat(VALUE str1, VALUE str2)
{
    if (FIXNUM_P(str2)) {
        rb_encoding *enc = STR_ENC_GET(str1);
        int c = FIX2INT(str2);
        int pos = RSTRING_LEN(str1);
        int len = rb_enc_codelen(c, enc);
        int cr = ENC_CODERANGE(str1);

        rb_str_resize(str1, pos+len);
        rb_enc_mbcput(c, RSTRING_PTR(str1)+pos, enc);
        ENC_CODERANGE_SET(str1, cr);
        return str1;
    }
    return rb_str_append(str1, str2);
}

#if defined __i386__ || defined _M_IX86
#define UNALIGNED_WORD_ACCESS 1
#endif
#ifndef UNALIGNED_WORD_ACCESS
#define UNALIGNED_WORD_ACCESS 0
#endif

/* MurmurHash described in http://murmurhash.googlepages.com/ */
static unsigned int
hash(const unsigned char * data, int len, unsigned int h)
{
    const unsigned int m = 0x7fd652ad;
    const int r = 16;

    h += 0xdeadbeef;

    if (len >= 4) {
#if !UNALIGNED_WORD_ACCESS
        int align = (VALUE)data & 3;
        if (align) {
            uint32_t t = 0, d = 0;
            int sl, sr, pack;

            switch (align) {
#ifdef WORDS_BIGENDIAN
              case 1: t |= data[2];
              case 2: t |= data[1] << 8;
              case 3: t |= data[0] << 16;
#else
              case 1: t |= data[2] << 16;
              case 2: t |= data[1] << 8;
              case 3: t |= data[0];
#endif
            }

#ifdef WORDS_BIGENDIAN
            t >>= (8 * align) - 8;
#else
            t <<= (8 * align);
#endif

            data += 4-align;
            len -= 4-align;

            sl = 8 * (4-align);
            sr = 8 * align;

            while (len >= 4) {
                d = *(uint32_t *)data;
#ifdef WORDS_BIGENDIAN
                t = (t << sr) | (d >> sl);
#else
                t = (t >> sr) | (d << sl);
#endif
                h += t;
                h *= m;
                h ^= h >> r;
                t = d;

                data += 4;
                len -= 4;
            }

            pack = len < align ? len : align;
            d = 0;
            switch (pack) {
#ifdef WORDS_BIGENDIAN
              case 3: d |= data[2] << 8;
              case 2: d |= data[1] << 16;
              case 1: d |= data[0] << 24;
              case 0:
                h += (t << sr) | (d >> sl);
#else
              case 3: d |= data[2] << 16;
              case 2: d |= data[1] << 8;
              case 1: d |= data[0];
              case 0:
                h += (t >> sr) | (d << sl);
#endif
                h *= m;
                h ^= h >> r;
            }

            data += pack;
            len -= pack;
        }
        else
#endif
        {
            do {
                h += *(uint32_t *)data;
                h *= m;
                h ^= h >> r;

                data += 4;
                len -= 4;
            } while (len >= 4);
        }
    }

    switch(len) {
#ifdef WORDS_BIGENDIAN
      case 3:
        h += data[2] << 8;
      case 2:
        h += data[1] << 16;
      case 1:
        h += data[0] << 24;
#else
      case 3:
        h += data[2] << 16;
      case 2:
        h += data[1] << 8;
      case 1:
        h += data[0];
#endif
        h *= m;
        h ^= h >> r;
    }

    h *= m;
    h ^= h >> 10;
    h *= m;
    h ^= h >> 17;

    return h;
}

int
rb_memhash(const void *ptr, long len)
{
    static int hashseed_init = 0;
    static unsigned int hashseed;

    if (!hashseed_init) {
        hashseed = rb_genrand_int32();
        hashseed_init = 1;
    }

    return hash(ptr, len, hashseed);
}

int
rb_str_hash(VALUE str)
{
    return rb_memhash((const void *)RSTRING_PTR(str), RSTRING_LEN(str));
}

int
rb_str_hash_cmp(VALUE str1, VALUE str2)
{
    int len;

    if (!rb_str_comparable(str1, str2)) return 1;
    if (RSTRING_LEN(str1) == (len = RSTRING_LEN(str2)) &&
        memcmp(RSTRING_PTR(str1), RSTRING_PTR(str2), len) == 0) {
        return 0;
    }
    return 1;
}

/*
 * call-seq:
 *    str.hash   => fixnum
 *
 * Return a hash based on the string's length and content.
 */

static VALUE
rb_str_hash_m(VALUE str)
{
    int hval = rb_str_hash(str);
    return INT2FIX(hval);
}

#define lesser(a,b) (((a)>(b))?(b):(a))

int
rb_str_comparable(VALUE str1, VALUE str2)
{
    int idx1, idx2;
    int rc1, rc2;

    if (RSTRING_LEN(str1) == 0) return Qtrue;
    if (RSTRING_LEN(str2) == 0) return Qtrue;
    idx1 = ENCODING_GET(str1);
    idx2 = ENCODING_GET(str2);
    if (idx1 == idx2) return Qtrue;
    rc1 = rb_enc_str_coderange(str1);
    rc2 = rb_enc_str_coderange(str2);
    if (rc1 == ENC_CODERANGE_7BIT) {
        if (rc2 == ENC_CODERANGE_7BIT) return Qtrue;
        if (rb_enc_asciicompat(rb_enc_from_index(idx2)))
            return Qtrue;
    }
    if (rc2 == ENC_CODERANGE_7BIT) {
        if (rb_enc_asciicompat(rb_enc_from_index(idx1)))
            return Qtrue;
    }
    return Qfalse;
}

int
rb_str_cmp(VALUE str1, VALUE str2)
{
    long len;
    int retval;

    len = lesser(RSTRING_LEN(str1), RSTRING_LEN(str2));
    retval = memcmp(RSTRING_PTR(str1), RSTRING_PTR(str2), len);
    if (retval == 0) {
        if (RSTRING_LEN(str1) == RSTRING_LEN(str2)) {
            if (!rb_enc_compatible(str1, str2)) {
                if (ENCODING_GET(str1) - ENCODING_GET(str2) > 0)
                    return 1;
                return -1;
            }
            return 0;
        }
        if (RSTRING_LEN(str1) > RSTRING_LEN(str2)) return 1;
        return -1;
    }
    if (retval > 0) return 1;
    return -1;
}


/*
 *  call-seq:
 *     str == obj   => true or false
 *  
 *  Equality---If <i>obj</i> is not a <code>String</code>, returns
 *  <code>false</code>. Otherwise, returns <code>true</code> if <i>str</i>
 *  <code><=></code> <i>obj</i> returns zero.
 */

VALUE
rb_str_equal(VALUE str1, VALUE str2)
{
    int len;

    if (str1 == str2) return Qtrue;
    if (TYPE(str2) != T_STRING) {
        if (!rb_respond_to(str2, rb_intern("to_str"))) {
            return Qfalse;
        }
        return rb_equal(str2, str1);
    }
    if (!rb_str_comparable(str1, str2)) return Qfalse;
    if (RSTRING_LEN(str1) == (len = RSTRING_LEN(str2)) &&
        memcmp(RSTRING_PTR(str1), RSTRING_PTR(str2), len) == 0) {
        return Qtrue;
    }
    return Qfalse;
}

/*
 * call-seq:
 *   str.eql?(other)   => true or false
 *
 * Two strings are equal if the have the same length and content.
 */

static VALUE
rb_str_eql(VALUE str1, VALUE str2)
{
    if (TYPE(str2) != T_STRING || RSTRING_LEN(str1) != RSTRING_LEN(str2))
        return Qfalse;

    if (!rb_str_comparable(str1, str2)) return Qfalse;
    if (memcmp(RSTRING_PTR(str1), RSTRING_PTR(str2),
               lesser(RSTRING_LEN(str1), RSTRING_LEN(str2))) == 0)
        return Qtrue;

    return Qfalse;
}

/*
 *  call-seq:
 *     str <=> other_str   => -1, 0, +1
 *  
 *  Comparison---Returns -1 if <i>other_str</i> is less than, 0 if
 *  <i>other_str</i> is equal to, and +1 if <i>other_str</i> is greater than
 *  <i>str</i>. If the strings are of different lengths, and the strings are
 *  equal when compared up to the shortest length, then the longer string is
 *  considered greater than the shorter one. In older versions of Ruby, setting
 *  <code>$=</code> allowed case-insensitive comparisons; this is now deprecated
 *  in favor of using <code>String#casecmp</code>.
 *
 *  <code><=></code> is the basis for the methods <code><</code>,
 *  <code><=</code>, <code>></code>, <code>>=</code>, and <code>between?</code>,
 *  included from module <code>Comparable</code>.  The method
 *  <code>String#==</code> does not use <code>Comparable#==</code>.
 *     
 *     "abcdef" <=> "abcde"     #=> 1
 *     "abcdef" <=> "abcdef"    #=> 0
 *     "abcdef" <=> "abcdefg"   #=> -1
 *     "abcdef" <=> "ABCDEF"    #=> 1
 */

static VALUE
rb_str_cmp_m(VALUE str1, VALUE str2)
{
    long result;

    if (TYPE(str2) != T_STRING) {
        if (!rb_respond_to(str2, rb_intern("to_str"))) {
            return Qnil;
        }
        else if (!rb_respond_to(str2, rb_intern("<=>"))) {
            return Qnil;
        }
        else {
            VALUE tmp = rb_funcall(str2, rb_intern("<=>"), 1, str1);

            if (NIL_P(tmp)) return Qnil;
            if (!FIXNUM_P(tmp)) {
                return rb_funcall(LONG2FIX(0), '-', 1, tmp);
            }
            result = -FIX2LONG(tmp);
        }
    }
    else {
        result = rb_str_cmp(str1, str2);
    }
    return LONG2NUM(result);
}

/*
 *  call-seq:
 *     str.casecmp(other_str)   => -1, 0, +1
 *  
 *  Case-insensitive version of <code>String#<=></code>.
 *     
 *     "abcdef".casecmp("abcde")     #=> 1
 *     "aBcDeF".casecmp("abcdef")    #=> 0
 *     "abcdef".casecmp("abcdefg")   #=> -1
 *     "abcdef".casecmp("ABCDEF")    #=> 0
 */

static VALUE
rb_str_casecmp(VALUE str1, VALUE str2)
{
    long len;
    rb_encoding *enc;
    char *p1, *p1end, *p2, *p2end;

    StringValue(str2);
    enc = rb_enc_compatible(str1, str2);
    if (!enc) {
        return Qnil;
    }

    p1 = RSTRING_PTR(str1); p1end = RSTRING_END(str1);
    p2 = RSTRING_PTR(str2); p2end = RSTRING_END(str2);
    while (p1 < p1end && p2 < p2end) {
        int c1 = rb_enc_codepoint(p1, p1end, enc);
        int c2 = rb_enc_codepoint(p2, p2end, enc);

        if (c1 != c2) {
            c1 = rb_enc_toupper(c1, enc);
            c2 = rb_enc_toupper(c2, enc);
            if (c1 > c2) return INT2FIX(1);
            if (c1 < c2) return INT2FIX(-1);
        }
        len = rb_enc_codelen(c1, enc);
        p1 += len;
        p2 += len;
    }
    if (RSTRING_LEN(str1) == RSTRING_LEN(str2)) return INT2FIX(0);
    if (RSTRING_LEN(str1) > RSTRING_LEN(str2)) return INT2FIX(1);
    return INT2FIX(-1);
}

static long
rb_str_index(VALUE str, VALUE sub, long offset)
{
    long pos;
    char *s, *sptr;
    long len, slen;
    rb_encoding *enc;

    enc = rb_enc_check(str, sub);
    if (is_broken_string(sub)) {
        return -1;
    }
    len = str_strlen(str, enc);
    slen = str_strlen(sub, enc);
    if (offset < 0) {
        offset += len;
        if (offset < 0) return -1;
    }
    if (len - offset < slen) return -1;
    s = RSTRING_PTR(str);
    if (offset) {
        offset = str_offset(s, RSTRING_END(str), offset, enc, single_byte_optimizable(str));
        s += offset;
    }
    if (slen == 0) return offset;
    /* need proceed one character at a time */
    sptr = RSTRING_PTR(sub);
    slen = RSTRING_LEN(sub);
    len = RSTRING_LEN(str) - offset;
    for (;;) {
        char *t;
        pos = rb_memsearch(sptr, slen, s, len, enc);
        if (pos < 0) return pos;
        t = rb_enc_right_char_head(s, s+pos, enc);
        if (t == s + pos) break;
        if ((len -= t - s) <= 0) return -1;
        offset += t - s;
        s = t;
    }
    return pos + offset;
}


/*
 *  call-seq:
 *     str.index(substring [, offset])   => fixnum or nil
 *     str.index(regexp [, offset])      => fixnum or nil
 *  
 *  Returns the index of the first occurrence of the given <i>substring</i> or
 *  pattern (<i>regexp</i>) in <i>str</i>. Returns <code>nil</code> if not
 *  found. If the second parameter is present, it specifies the position in the
 *  string to begin the search.
 *     
 *     "hello".index('e')             #=> 1
 *     "hello".index('lo')            #=> 3
 *     "hello".index('a')             #=> nil
 *     "hello".index(?e)              #=> 1
 *     "hello".index(/[aeiou]/, -3)   #=> 4
 */

static VALUE
rb_str_index_m(int argc, VALUE *argv, VALUE str)
{
    VALUE sub;
    VALUE initpos;
    long pos;

    if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
        pos = NUM2LONG(initpos);
    }
    else {
        pos = 0;
    }
    if (pos < 0) {
        pos += str_strlen(str, STR_ENC_GET(str));
        if (pos < 0) {
            if (TYPE(sub) == T_REGEXP) {
                rb_backref_set(Qnil);
            }
            return Qnil;
        }
    }

    switch (TYPE(sub)) {
      case T_REGEXP:
        pos = rb_reg_adjust_startpos(sub, str, pos, 0);
        pos = rb_reg_search(sub, str, pos, 0);
        pos = rb_str_sublen(str, pos);
        break;

      default: {
        VALUE tmp;

        tmp = rb_check_string_type(sub);
        if (NIL_P(tmp)) {
            rb_raise(rb_eTypeError, "type mismatch: %s given",
                     rb_obj_classname(sub));
        }
        sub = tmp;
      }
        /* fall through */
      case T_STRING:
        pos = rb_str_index(str, sub, pos);
        pos = rb_str_sublen(str, pos);
        break;
    }

    if (pos == -1) return Qnil;
    return LONG2NUM(pos);
}

static long
rb_str_rindex(VALUE str, VALUE sub, long pos)
{
    long len, slen;
    char *s, *sbeg, *e, *t;
    rb_encoding *enc;
    int singlebyte = single_byte_optimizable(str);

    enc = rb_enc_check(str, sub);
    if (is_broken_string(sub)) {
        return -1;
    }
    len = str_strlen(str, enc);
    slen = str_strlen(sub, enc);
    /* substring longer than string */
    if (len < slen) return -1;
    if (len - pos < slen) {
        pos = len - slen;
    }
    if (len == 0) {
        return pos;
    }
    sbeg = RSTRING_PTR(str);
    e = RSTRING_END(str);
    t = RSTRING_PTR(sub);
    slen = RSTRING_LEN(sub);
    for (;;) {
        s = str_nth(sbeg, e, pos, enc, singlebyte);
        if (!s) return -1;
        if (memcmp(s, t, slen) == 0) {
            return pos;
        }
        if (pos == 0) break;
        pos--;
    }
    return -1;
}


/*
 *  call-seq:
 *     str.rindex(substring [, fixnum])   => fixnum or nil
 *     str.rindex(regexp [, fixnum])   => fixnum or nil
 *  
 *  Returns the index of the last occurrence of the given <i>substring</i> or
 *  pattern (<i>regexp</i>) in <i>str</i>. Returns <code>nil</code> if not
 *  found. If the second parameter is present, it specifies the position in the
 *  string to end the search---characters beyond this point will not be
 *  considered.
 *     
 *     "hello".rindex('e')             #=> 1
 *     "hello".rindex('l')             #=> 3
 *     "hello".rindex('a')             #=> nil
 *     "hello".rindex(?e)              #=> 1
 *     "hello".rindex(/[aeiou]/, -2)   #=> 1
 */

static VALUE
rb_str_rindex_m(int argc, VALUE *argv, VALUE str)
{
    VALUE sub;
    VALUE vpos;
    rb_encoding *enc = STR_ENC_GET(str);
    long pos, len = str_strlen(str, enc);

    if (rb_scan_args(argc, argv, "11", &sub, &vpos) == 2) {
        pos = NUM2LONG(vpos);
        if (pos < 0) {
            pos += len;
            if (pos < 0) {
                if (TYPE(sub) == T_REGEXP) {
                    rb_backref_set(Qnil);
                }
                return Qnil;
            }
        }
        if (pos > len) pos = len;
    }
    else {
        pos = len;
    }

    switch (TYPE(sub)) {
      case T_REGEXP:
        /* enc = rb_get_check(str, sub); */
        if (!RREGEXP(sub)->ptr || RREGEXP_SRC_LEN(sub)) {
            pos = rb_reg_adjust_startpos(sub, str, pos, 1);
            pos = rb_reg_search(sub, str, pos, 1);
            pos = rb_str_sublen(str, pos);
        }
        if (pos >= 0) return LONG2NUM(pos);
        break;

      default: {
        VALUE tmp;

        tmp = rb_check_string_type(sub);
        if (NIL_P(tmp)) {
            rb_raise(rb_eTypeError, "type mismatch: %s given",
                     rb_obj_classname(sub));
        }
        sub = tmp;
      }
        /* fall through */
      case T_STRING:
        pos = rb_str_rindex(str, sub, pos);
        if (pos >= 0) return LONG2NUM(pos);
        break;
    }
    return Qnil;
}

/*
 *  call-seq:
 *     str =~ obj   => fixnum or nil
 *  
 *  Match---If <i>obj</i> is a <code>Regexp</code>, use it as a pattern to match
 *  against <i>str</i>,and returns the position the match starts, or 
 *  <code>nil</code> if there is no match. Otherwise, invokes
 *  <i>obj.=~</i>, passing <i>str</i> as an argument. The default
 *  <code>=~</code> in <code>Object</code> returns <code>false</code>.
 *     
 *     "cat o' 9 tails" =~ /\d/   #=> 7
 *     "cat o' 9 tails" =~ 9      #=> nil
 */

static VALUE
rb_str_match(VALUE x, VALUE y)
{
    switch (TYPE(y)) {
      case T_STRING:
        rb_raise(rb_eTypeError, "type mismatch: String given");

      case T_REGEXP:
        return rb_reg_match(y, x);

      default:
        return rb_funcall(y, rb_intern("=~"), 1, x);
    }
}


static VALUE get_pat(VALUE, int);


/*
 *  call-seq:
 *     str.match(pattern)   => matchdata or nil
 *  
 *  Converts <i>pattern</i> to a <code>Regexp</code> (if it isn't already one),
 *  then invokes its <code>match</code> method on <i>str</i>.  If the second
 *  parameter is present, it specifies the position in the string to begin the
 *  search.
 *     
 *     'hello'.match('(.)\1')      #=> #<MatchData "ll" 1:"l">
 *     'hello'.match('(.)\1')[0]   #=> "ll"
 *     'hello'.match(/(.)\1/)[0]   #=> "ll"
 *     'hello'.match('xx')         #=> nil
 *     
 *  If a block is given, invoke the block with MatchData if match succeed, so
 *  that you can write
 *     
 *     str.match(pat) {|m| ...}
 *     
 *  instead of
 *      
 *     if m = str.match(pat)
 *       ...
 *     end
 *      
 *  The return value is a value from block execution in this case.
 */

static VALUE
rb_str_match_m(int argc, VALUE *argv, VALUE str)
{
    VALUE re, result;
    if (argc < 1)
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    re = argv[0];
    argv[0] = str;
    result = rb_funcall2(get_pat(re, 0), rb_intern("match"), argc, argv);
    if (!NIL_P(result) && rb_block_given_p()) {
        return rb_yield(result);
    }
    return result;
}

enum neighbor_char {
    NEIGHBOR_NOT_CHAR,
    NEIGHBOR_FOUND,
    NEIGHBOR_WRAPPED
};

static enum neighbor_char
enc_succ_char(char *p, int len, rb_encoding *enc)
{
    int i, l;
    while (1) {
        for (i = len-1; 0 <= i && (unsigned char)p[i] == 0xff; i--)
            p[i] = '\0';
        if (i < 0)
            return NEIGHBOR_WRAPPED;
        ++((unsigned char*)p)[i];
        l = rb_enc_precise_mbclen(p, p+len, enc);
        if (MBCLEN_CHARFOUND_P(l)) {
            l = MBCLEN_CHARFOUND_LEN(l);
            if (l == len) {
                return NEIGHBOR_FOUND;
            }
            else {
                memset(p+l, 0xff, len-l);
            }
        }
        if (MBCLEN_INVALID_P(l) && i < len-1) {
            int len2, l2;
            for (len2 = len-1; 0 < len2; len2--) {
                l2 = rb_enc_precise_mbclen(p, p+len2, enc);
                if (!MBCLEN_INVALID_P(l2))
                    break;
            }
            memset(p+len2+1, 0xff, len-(len2+1));
        }
    }
}

static enum neighbor_char
enc_pred_char(char *p, int len, rb_encoding *enc)
{
    int i, l;
    while (1) {
        for (i = len-1; 0 <= i && (unsigned char)p[i] == 0; i--)
            p[i] = '\xff';
        if (i < 0)
            return NEIGHBOR_WRAPPED;
        --((unsigned char*)p)[i];
        l = rb_enc_precise_mbclen(p, p+len, enc);
        if (MBCLEN_CHARFOUND_P(l)) {
            l = MBCLEN_CHARFOUND_LEN(l);
            if (l == len) {
                return NEIGHBOR_FOUND;
            }
            else {
                memset(p+l, 0, len-l);
            }
        }
        if (MBCLEN_INVALID_P(l) && i < len-1) {
            int len2, l2;
            for (len2 = len-1; 0 < len2; len2--) {
                l2 = rb_enc_precise_mbclen(p, p+len2, enc);
                if (!MBCLEN_INVALID_P(l2))
                    break;
            }
            memset(p+len2+1, 0, len-(len2+1));
        }
    }
}

/*
  overwrite +p+ by succeeding letter in +enc+ and returns
  NEIGHBOR_FOUND or NEIGHBOR_WRAPPED.
  When NEIGHBOR_WRAPPED, carried-out letter is stored into carry.
  assuming each ranges are successive, and mbclen
  never change in each ranges.
  NEIGHBOR_NOT_CHAR is returned if invalid character or the range has only one
  character.
 */
static enum neighbor_char
enc_succ_alnum_char(char *p, int len, rb_encoding *enc, char *carry)
{
    enum neighbor_char ret;
    int c;
    int ctype;
    int range;
    char save[ONIGENC_CODE_TO_MBC_MAXLEN];

    c = rb_enc_mbc_to_codepoint(p, p+len, enc);
    if (rb_enc_isctype(c, ONIGENC_CTYPE_DIGIT, enc))
        ctype = ONIGENC_CTYPE_DIGIT;
    else if (rb_enc_isctype(c, ONIGENC_CTYPE_ALPHA, enc))
        ctype = ONIGENC_CTYPE_ALPHA;
    else
        return NEIGHBOR_NOT_CHAR;

    MEMCPY(save, p, char, len);
    ret = enc_succ_char(p, len, enc);
    if (ret == NEIGHBOR_FOUND) {
        c = rb_enc_mbc_to_codepoint(p, p+len, enc);
        if (rb_enc_isctype(c, ctype, enc))
            return NEIGHBOR_FOUND;
    }
    MEMCPY(p, save, char, len);
    range = 1;
    while (1) {
        MEMCPY(save, p, char, len);
        ret = enc_pred_char(p, len, enc);
        if (ret == NEIGHBOR_FOUND) {
            c = rb_enc_mbc_to_codepoint(p, p+len, enc);
            if (!rb_enc_isctype(c, ctype, enc)) {
                MEMCPY(p, save, char, len);
                break;
            }
        }
        else {
            MEMCPY(p, save, char, len);
            break;
        }
        range++;
    }
    if (range == 1) {
        return NEIGHBOR_NOT_CHAR;
    }

    if (ctype != ONIGENC_CTYPE_DIGIT) {
        MEMCPY(carry, p, char, len);
        return NEIGHBOR_WRAPPED;
    }

    MEMCPY(carry, p, char, len);
    enc_succ_char(carry, len, enc);
    return NEIGHBOR_WRAPPED;
}


/*
 *  call-seq:
 *     str.succ   => new_str
 *     str.next   => new_str
 *  
 *  Returns the successor to <i>str</i>. The successor is calculated by
 *  incrementing characters starting from the rightmost alphanumeric (or
 *  the rightmost character if there are no alphanumerics) in the
 *  string. Incrementing a digit always results in another digit, and
 *  incrementing a letter results in another letter of the same case.
 *  Incrementing nonalphanumerics uses the underlying character set's
 *  collating sequence.
 *     
 *  If the increment generates a ``carry,'' the character to the left of
 *  it is incremented. This process repeats until there is no carry,
 *  adding an additional character if necessary.
 *     
 *     "abcd".succ        #=> "abce"
 *     "THX1138".succ     #=> "THX1139"
 *     "<<koala>>".succ   #=> "<<koalb>>"
 *     "1999zzz".succ     #=> "2000aaa"
 *     "ZZZ9999".succ     #=> "AAAA0000"
 *     "***".succ         #=> "**+"
 */

VALUE
rb_str_succ(VALUE orig)
{
    rb_encoding *enc;
    VALUE str;
    char *sbeg, *s, *e, *last_alnum = 0;
    int c = -1;
    long l;
    char carry[ONIGENC_CODE_TO_MBC_MAXLEN] = "\1";
    int carry_pos = 0, carry_len = 1;
    enum neighbor_char neighbor = NEIGHBOR_FOUND;

    str = rb_str_new5(orig, RSTRING_PTR(orig), RSTRING_LEN(orig));
    rb_enc_cr_str_copy_for_substr(str, orig);
    OBJ_INFECT(str, orig);
    if (RSTRING_LEN(str) == 0) return str;

    enc = STR_ENC_GET(orig);
    sbeg = RSTRING_PTR(str);
    s = e = sbeg + RSTRING_LEN(str);

    while ((s = rb_enc_prev_char(sbeg, s, enc)) != 0) {
        if (neighbor == NEIGHBOR_NOT_CHAR && last_alnum) {
            if (ISALPHA(*last_alnum) ? ISDIGIT(*s) :
                ISDIGIT(*last_alnum) ? ISALPHA(*s) : 0) {
                s = last_alnum;
                break;
            }
        }
        if ((l = rb_enc_precise_mbclen(s, e, enc)) <= 0) continue;
        neighbor = enc_succ_alnum_char(s, l, enc, carry);
        switch (neighbor) {
          case NEIGHBOR_NOT_CHAR:
            continue;
          case NEIGHBOR_FOUND:
            return str;
          case NEIGHBOR_WRAPPED:
            last_alnum = s;
            break;
        }
        c = 1;
        carry_pos = s - sbeg;
        carry_len = l;
    }
    if (c == -1) {              /* str contains no alnum */
        s = e;
        while ((s = rb_enc_prev_char(sbeg, s, enc)) != 0) {
            enum neighbor_char neighbor;
            if ((l = rb_enc_precise_mbclen(s, e, enc)) <= 0) continue;
            neighbor = enc_succ_char(s, l, enc);
            if (neighbor == NEIGHBOR_FOUND)
                return str;
            if (rb_enc_precise_mbclen(s, s+l, enc) != l) {
                /* wrapped to \0...\0.  search next valid char. */
                enc_succ_char(s, l, enc);
            }
            if (!rb_enc_asciicompat(enc)) {
                MEMCPY(carry, s, char, l);
                carry_len = l;
            }
            carry_pos = s - sbeg;
        }
    }
    RESIZE_CAPA(str, RSTRING_LEN(str) + carry_len);
    s = RSTRING_PTR(str) + carry_pos;
    memmove(s + carry_len, s, RSTRING_LEN(str) - carry_pos);
    memmove(s, carry, carry_len);
    STR_SET_LEN(str, RSTRING_LEN(str) + carry_len);
    RSTRING_PTR(str)[RSTRING_LEN(str)] = '\0';
    rb_enc_str_coderange(str);
    return str;
}


/*
 *  call-seq:
 *     str.succ!   => str
 *     str.next!   => str
 *  
 *  Equivalent to <code>String#succ</code>, but modifies the receiver in
 *  place.
 */

static VALUE
rb_str_succ_bang(VALUE str)
{
    rb_str_shared_replace(str, rb_str_succ(str));

    return str;
}


/*
 *  call-seq:
 *     str.upto(other_str, exclusive=false) {|s| block }   => str
 *  
 *  Iterates through successive values, starting at <i>str</i> and
 *  ending at <i>other_str</i> inclusive, passing each value in turn to
 *  the block. The <code>String#succ</code> method is used to generate
 *  each value.  If optional second argument exclusive is omitted or is <code>false</code>,
 *  the last value will be included; otherwise it will be excluded.
 *     
 *     "a8".upto("b6") {|s| print s, ' ' }
 *     for s in "a8".."b6"
 *       print s, ' '
 *     end
 *     
 *  <em>produces:</em>
 *     
 *     a8 a9 b0 b1 b2 b3 b4 b5 b6
 *     a8 a9 b0 b1 b2 b3 b4 b5 b6
 */

static VALUE
rb_str_upto(int argc, VALUE *argv, VALUE beg)
{
    VALUE end, exclusive;
    VALUE current, after_end;
    ID succ;
    int n, excl;
    rb_encoding *enc;

    rb_scan_args(argc, argv, "11", &end, &exclusive);
    excl = RTEST(exclusive);
    CONST_ID(succ, "succ");
    StringValue(end);
    enc = rb_enc_check(beg, end);
    if (RSTRING_LEN(beg) == 1 && RSTRING_LEN(end) == 1 &&
        is_ascii_string(beg) && is_ascii_string(end)) {
        char c = RSTRING_PTR(beg)[0];
        char e = RSTRING_PTR(end)[0];

        if (c > e || (excl && c == e)) return beg;
        for (;;) {
            rb_yield(rb_enc_str_new(&c, 1, enc));
            if (!excl && c == e) break;
            c++;
            if (excl && c == e) break;
        }
        return beg;
    }
    n = rb_str_cmp(beg, end);
    if (n > 0 || (excl && n == 0)) return beg;
        
    after_end = rb_funcall(end, succ, 0, 0);
    current = beg;
    while (!rb_str_equal(current, after_end)) {
        rb_yield(current);
        if (!excl && rb_str_equal(current, end)) break;
        current = rb_funcall(current, succ, 0, 0);
        StringValue(current);
        if (excl && rb_str_equal(current, end)) break;
        if (RSTRING_LEN(current) > RSTRING_LEN(end) || RSTRING_LEN(current) == 0)
            break;
    }

    return beg;
}

static VALUE
rb_str_subpat(VALUE str, VALUE re, int nth)
{
    if (rb_reg_search(re, str, 0, 0) >= 0) {
        return rb_reg_nth_match(nth, rb_backref_get());
    }
    return Qnil;
}

static VALUE
rb_str_aref(VALUE str, VALUE indx)
{
    long idx;

    switch (TYPE(indx)) {
      case T_FIXNUM:
        idx = FIX2LONG(indx);

      num_index:
        str = rb_str_substr(str, idx, 1);
        if (!NIL_P(str) && RSTRING_LEN(str) == 0) return Qnil;
        return str;

      case T_REGEXP:
        return rb_str_subpat(str, indx, 0);

      case T_STRING:
        if (rb_str_index(str, indx, 0) != -1)
            return rb_str_dup(indx);
        return Qnil;

      default:
        /* check if indx is Range */
        {
            long beg, len;
            VALUE tmp;

            len = str_strlen(str, STR_ENC_GET(str));
            switch (rb_range_beg_len(indx, &beg, &len, len, 0)) {
              case Qfalse:
                break;
              case Qnil:
                return Qnil;
              default:
                tmp = rb_str_substr(str, beg, len);
                return tmp;
            }
        }
        idx = NUM2LONG(indx);
        goto num_index;
    }
    return Qnil;                /* not reached */
}


/*
 *  call-seq:
 *     str[fixnum]                 => new_str or nil
 *     str[fixnum, fixnum]         => new_str or nil
 *     str[range]                  => new_str or nil
 *     str[regexp]                 => new_str or nil
 *     str[regexp, fixnum]         => new_str or nil
 *     str[other_str]              => new_str or nil
 *     str.slice(fixnum)           => new_str or nil
 *     str.slice(fixnum, fixnum)   => new_str or nil
 *     str.slice(range)            => new_str or nil
 *     str.slice(regexp)           => new_str or nil
 *     str.slice(regexp, fixnum)   => new_str or nil
 *     str.slice(other_str)        => new_str or nil
 *  
 *  Element Reference---If passed a single <code>Fixnum</code>, returns a
 *  substring of one character at that position. If passed two <code>Fixnum</code>
 *  objects, returns a substring starting at the offset given by the first, and
 *  a length given by the second. If given a range, a substring containing
 *  characters at offsets given by the range is returned. In all three cases, if
 *  an offset is negative, it is counted from the end of <i>str</i>. Returns
 *  <code>nil</code> if the initial offset falls outside the string, the length
 *  is negative, or the beginning of the range is greater than the end.
 *     
 *  If a <code>Regexp</code> is supplied, the matching portion of <i>str</i> is
 *  returned. If a numeric parameter follows the regular expression, that
 *  component of the <code>MatchData</code> is returned instead. If a
 *  <code>String</code> is given, that string is returned if it occurs in
 *  <i>str</i>. In both cases, <code>nil</code> is returned if there is no
 *  match.
 *     
 *     a = "hello there"
 *     a[1]                   #=> "e"
 *     a[1,3]                 #=> "ell"
 *     a[1..3]                #=> "ell"
 *     a[-3,2]                #=> "er"
 *     a[-4..-2]              #=> "her"
 *     a[12..-1]              #=> nil
 *     a[-2..-4]              #=> ""
 *     a[/[aeiou](.)\1/]      #=> "ell"
 *     a[/[aeiou](.)\1/, 0]   #=> "ell"
 *     a[/[aeiou](.)\1/, 1]   #=> "l"
 *     a[/[aeiou](.)\1/, 2]   #=> nil
 *     a["lo"]                #=> "lo"
 *     a["bye"]               #=> nil
 */

static VALUE
rb_str_aref_m(int argc, VALUE *argv, VALUE str)
{
    if (argc == 2) {
        if (TYPE(argv[0]) == T_REGEXP) {
            return rb_str_subpat(str, argv[0], NUM2INT(argv[1]));
        }
        return rb_str_substr(str, NUM2LONG(argv[0]), NUM2LONG(argv[1]));
    }
    if (argc != 1) {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }
    return rb_str_aref(str, argv[0]);
}

VALUE
rb_str_drop_bytes(VALUE str, long len)
{
    char *ptr = RSTRING_PTR(str);
    long olen = RSTRING_LEN(str), nlen;

    str_modifiable(str);
    if (len > olen) len = olen;
    nlen = olen - len;
    if (nlen <= RSTRING_EMBED_LEN_MAX) {
        char *oldptr = ptr;
        int fl = (RBASIC(str)->flags & (STR_NOEMBED|ELTS_SHARED));
        STR_SET_EMBED(str);
        STR_SET_EMBED_LEN(str, nlen);
        ptr = RSTRING(str)->as.ary;
        memmove(ptr, oldptr + len, nlen);
        if (fl == STR_NOEMBED) xfree(oldptr);
    }
    else {
        if (!STR_SHARED_P(str)) rb_str_new4(str);
        ptr = RSTRING(str)->as.heap.ptr += len;
        RSTRING(str)->as.heap.len = nlen;
    }
    ptr[nlen] = 0;
    ENC_CODERANGE_CLEAR(str);
    return str;
}

static void
rb_str_splice_0(VALUE str, long beg, long len, VALUE val)
{
    if (beg == 0 && RSTRING_LEN(val) == 0) {
        rb_str_drop_bytes(str, len);
        OBJ_INFECT(str, val);
        return;
    }

    rb_str_modify(str);
    if (len < RSTRING_LEN(val)) {
        /* expand string */
        RESIZE_CAPA(str, RSTRING_LEN(str) + RSTRING_LEN(val) - len + 1);
    }

    if (RSTRING_LEN(val) != len) {
        memmove(RSTRING_PTR(str) + beg + RSTRING_LEN(val),
                RSTRING_PTR(str) + beg + len,
                RSTRING_LEN(str) - (beg + len));
    }
    if (RSTRING_LEN(val) < beg && len < 0) {
        MEMZERO(RSTRING_PTR(str) + RSTRING_LEN(str), char, -len);
    }
    if (RSTRING_LEN(val) > 0) {
        memmove(RSTRING_PTR(str)+beg, RSTRING_PTR(val), RSTRING_LEN(val));
    }
    STR_SET_LEN(str, RSTRING_LEN(str) + RSTRING_LEN(val) - len);
    if (RSTRING_PTR(str)) {
        RSTRING_PTR(str)[RSTRING_LEN(str)] = '\0';
    }
    OBJ_INFECT(str, val);
}

static void
rb_str_splice(VALUE str, long beg, long len, VALUE val)
{
    long slen;
    char *p, *e;
    rb_encoding *enc;
    int singlebyte = single_byte_optimizable(str);

    if (len < 0) rb_raise(rb_eIndexError, "negative length %ld", len);

    StringValue(val);
    rb_str_modify(str);
    enc = rb_enc_check(str, val);
    slen = str_strlen(str, enc);

    if (slen < beg) {
      out_of_range:
        rb_raise(rb_eIndexError, "index %ld out of string", beg);
    }
    if (beg < 0) {
        if (-beg > slen) {
            goto out_of_range;
        }
        beg += slen;
    }
    if (slen < len || slen < beg + len) {
        len = slen - beg;
    }
    p = str_nth(RSTRING_PTR(str), RSTRING_END(str), beg, enc, singlebyte);
    if (!p) p = RSTRING_END(str);
    e = str_nth(p, RSTRING_END(str), len, enc, singlebyte);
    if (!e) e = RSTRING_END(str);
    /* error check */
    beg = p - RSTRING_PTR(str); /* physical position */
    len = e - p;                /* physical length */
    rb_str_splice_0(str, beg, len, val);
    rb_enc_associate(str, enc);
}

void
rb_str_update(VALUE str, long beg, long len, VALUE val)
{
    rb_str_splice(str, beg, len, val);
}

static void
rb_str_subpat_set(VALUE str, VALUE re, int nth, VALUE val)
{
    VALUE match;
    long start, end, len;
    rb_encoding *enc;
    struct re_registers *regs;

    if (rb_reg_search(re, str, 0, 0) < 0) {
        rb_raise(rb_eIndexError, "regexp not matched");
    }
    match = rb_backref_get();
    regs = RMATCH_REGS(match);
    if (nth >= regs->num_regs) {
      out_of_range:
        rb_raise(rb_eIndexError, "index %d out of regexp", nth);
    }
    if (nth < 0) {
        if (-nth >= regs->num_regs) {
            goto out_of_range;
        }
        nth += regs->num_regs;
    }

    start = BEG(nth);
    if (start == -1) {
        rb_raise(rb_eIndexError, "regexp group %d not matched", nth);
    }
    end = END(nth);
    len = end - start;
    StringValue(val);
    enc = rb_enc_check(str, val);
    rb_str_splice_0(str, start, len, val);
    rb_enc_associate(str, enc);
}

static VALUE
rb_str_aset(VALUE str, VALUE indx, VALUE val)
{
    long idx, beg;

    switch (TYPE(indx)) {
      case T_FIXNUM:
        idx = FIX2LONG(indx);
      num_index:
        rb_str_splice(str, idx, 1, val);
        return val;

      case T_REGEXP:
        rb_str_subpat_set(str, indx, 0, val);
        return val;

      case T_STRING:
        beg = rb_str_index(str, indx, 0);
        if (beg < 0) {
            rb_raise(rb_eIndexError, "string not matched");
        }
        beg = rb_str_sublen(str, beg);
        rb_str_splice(str, beg, str_strlen(indx, 0), val);
        return val;

      default:
        /* check if indx is Range */
        {
            long beg, len;
            if (rb_range_beg_len(indx, &beg, &len, str_strlen(str, 0), 2)) {
                rb_str_splice(str, beg, len, val);
                return val;
            }
        }
        idx = NUM2LONG(indx);
        goto num_index;
    }
}

/*
 *  call-seq:
 *     str[fixnum] = new_str
 *     str[fixnum, fixnum] = new_str
 *     str[range] = aString
 *     str[regexp] = new_str
 *     str[regexp, fixnum] = new_str
 *     str[other_str] = new_str
 *  
 *  Element Assignment---Replaces some or all of the content of <i>str</i>. The
 *  portion of the string affected is determined using the same criteria as
 *  <code>String#[]</code>. If the replacement string is not the same length as
 *  the text it is replacing, the string will be adjusted accordingly. If the
 *  regular expression or string is used as the index doesn't match a position
 *  in the string, <code>IndexError</code> is raised. If the regular expression
 *  form is used, the optional second <code>Fixnum</code> allows you to specify
 *  which portion of the match to replace (effectively using the
 *  <code>MatchData</code> indexing rules. The forms that take a
 *  <code>Fixnum</code> will raise an <code>IndexError</code> if the value is
 *  out of range; the <code>Range</code> form will raise a
 *  <code>RangeError</code>, and the <code>Regexp</code> and <code>String</code>
 *  forms will silently ignore the assignment.
 */

static VALUE
rb_str_aset_m(int argc, VALUE *argv, VALUE str)
{
    if (argc == 3) {
        if (TYPE(argv[0]) == T_REGEXP) {
            rb_str_subpat_set(str, argv[0], NUM2INT(argv[1]), argv[2]);
        }
        else {
            rb_str_splice(str, NUM2LONG(argv[0]), NUM2LONG(argv[1]), argv[2]);
        }
        return argv[2];
    }
    if (argc != 2) {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 2)", argc);
    }
    return rb_str_aset(str, argv[0], argv[1]);
}

/*
 *  call-seq:
 *     str.insert(index, other_str)   => str
 *  
 *  Inserts <i>other_str</i> before the character at the given
 *  <i>index</i>, modifying <i>str</i>. Negative indices count from the
 *  end of the string, and insert <em>after</em> the given character.
 *  The intent is insert <i>aString</i> so that it starts at the given
 *  <i>index</i>.
 *     
 *     "abcd".insert(0, 'X')    #=> "Xabcd"
 *     "abcd".insert(3, 'X')    #=> "abcXd"
 *     "abcd".insert(4, 'X')    #=> "abcdX"
 *     "abcd".insert(-3, 'X')   #=> "abXcd"
 *     "abcd".insert(-1, 'X')   #=> "abcdX"
 */

static VALUE
rb_str_insert(VALUE str, VALUE idx, VALUE str2)
{
    long pos = NUM2LONG(idx);

    if (pos == -1) {
        return rb_str_append(str, str2);
    }
    else if (pos < 0) {
        pos++;
    }
    rb_str_splice(str, pos, 0, str2);
    return str;
}


/*
 *  call-seq:
 *     str.slice!(fixnum)           => fixnum or nil
 *     str.slice!(fixnum, fixnum)   => new_str or nil
 *     str.slice!(range)            => new_str or nil
 *     str.slice!(regexp)           => new_str or nil
 *     str.slice!(other_str)        => new_str or nil
 *  
 *  Deletes the specified portion from <i>str</i>, and returns the portion
 *  deleted.
 *     
 *     string = "this is a string"
 *     string.slice!(2)        #=> "i"
 *     string.slice!(3..6)     #=> " is "
 *     string.slice!(/s.*t/)   #=> "sa st"
 *     string.slice!("r")      #=> "r"
 *     string                  #=> "thing"
 */

static VALUE
rb_str_slice_bang(int argc, VALUE *argv, VALUE str)
{
    VALUE result;
    VALUE buf[3];
    int i;

    if (argc < 1 || 2 < argc) {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 1)", argc);
    }
    for (i=0; i<argc; i++) {
        buf[i] = argv[i];
    }
    rb_str_modify(str);
    buf[i] = rb_str_new(0,0);
    result = rb_str_aref_m(argc, buf, str);
    if (!NIL_P(result)) {
        rb_str_aset_m(argc+1, buf, str);
    }
    return result;
}

static VALUE
get_pat(VALUE pat, int quote)
{
    VALUE val;

    switch (TYPE(pat)) {
      case T_REGEXP:
        return pat;

      case T_STRING:
        break;

      default:
        val = rb_check_string_type(pat);
        if (NIL_P(val)) {
            Check_Type(pat, T_REGEXP);
        }
        pat = val;
    }

    if (quote) {
        pat = rb_reg_quote(pat);
    }

    return rb_reg_regcomp(pat);
}


/*
 *  call-seq:
 *     str.sub!(pattern, replacement)          => str or nil
 *     str.sub!(pattern) {|match| block }      => str or nil
 *  
 *  Performs the substitutions of <code>String#sub</code> in place,
 *  returning <i>str</i>, or <code>nil</code> if no substitutions were
 *  performed.
 */

static VALUE
rb_str_sub_bang(int argc, VALUE *argv, VALUE str)
{
    VALUE pat, repl, hash = Qnil;
    int iter = 0;
    int tainted = 0;
    int untrusted = 0;
    long plen;

    if (argc == 1 && rb_block_given_p()) {
        iter = 1;
    }
    else if (argc == 2) {
        repl = argv[1];
        hash = rb_check_convert_type(argv[1], T_HASH, "Hash", "to_hash");
        if (NIL_P(hash)) {
            StringValue(repl);
        }
        if (OBJ_TAINTED(repl)) tainted = 1;
        if (OBJ_UNTRUSTED(repl)) untrusted = 1;
    }
    else {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 2)", argc);
    }

    pat = get_pat(argv[0], 1);
    if (rb_reg_search(pat, str, 0, 0) >= 0) {
        rb_encoding *enc;
        int cr = ENC_CODERANGE(str);
        VALUE match = rb_backref_get();
        struct re_registers *regs = RMATCH_REGS(match);
        long beg0 = BEG(0);
        long end0 = END(0);

        if (iter || !NIL_P(hash)) {
            char *p = RSTRING_PTR(str); long len = RSTRING_LEN(str);

            if (iter) {
                repl = rb_obj_as_string(rb_yield(rb_reg_nth_match(0, match)));
            }
            else {
                repl = rb_hash_aref(hash, rb_str_subseq(str, beg0, end0 - beg0));
                repl = rb_obj_as_string(repl);
            }
            str_mod_check(str, p, len);
            str_frozen_check(str);
        }
        else {
            repl = rb_reg_regsub(repl, str, regs, pat);
        }
        enc = rb_enc_compatible(str, repl);
        if (!enc) {
            rb_encoding *str_enc = STR_ENC_GET(str);
            if (coderange_scan(RSTRING_PTR(str), beg0, str_enc) != ENC_CODERANGE_7BIT ||
                coderange_scan(RSTRING_PTR(str)+end0,
                               RSTRING_LEN(str)-end0, str_enc) != ENC_CODERANGE_7BIT) {
                rb_raise(rb_eEncCompatError, "incompatible character encodings: %s and %s",
                         rb_enc_name(str_enc),
                         rb_enc_name(STR_ENC_GET(repl)));
            }
            enc = STR_ENC_GET(repl);
        }
        rb_str_modify(str);
        rb_enc_associate(str, enc);
        if (OBJ_TAINTED(repl)) tainted = 1;
        if (OBJ_UNTRUSTED(repl)) untrusted = 1;
        if (ENC_CODERANGE_UNKNOWN < cr && cr < ENC_CODERANGE_BROKEN) {
            int cr2 = ENC_CODERANGE(repl);
            if (cr2 == ENC_CODERANGE_UNKNOWN || cr2 > cr) cr = cr2;
        }
        plen = end0 - beg0;
        if (RSTRING_LEN(repl) > plen) {
            RESIZE_CAPA(str, RSTRING_LEN(str) + RSTRING_LEN(repl) - plen);
        }
        if (RSTRING_LEN(repl) != plen) {
            memmove(RSTRING_PTR(str) + beg0 + RSTRING_LEN(repl),
                    RSTRING_PTR(str) + beg0 + plen,
                    RSTRING_LEN(str) - beg0 - plen);
        }
        memcpy(RSTRING_PTR(str) + beg0,
               RSTRING_PTR(repl), RSTRING_LEN(repl));
        STR_SET_LEN(str, RSTRING_LEN(str) + RSTRING_LEN(repl) - plen);
        RSTRING_PTR(str)[RSTRING_LEN(str)] = '\0';
        ENC_CODERANGE_SET(str, cr);
        if (tainted) OBJ_TAINT(str);
        if (untrusted) OBJ_UNTRUST(str);

        return str;
    }
    return Qnil;
}


/*
 *  call-seq:
 *     str.sub(pattern, replacement)         => new_str
 *     str.sub(pattern) {|match| block }     => new_str
 *  
 *  Returns a copy of <i>str</i> with the <em>first</em> occurrence of
 *  <i>pattern</i> replaced with either <i>replacement</i> or the value of the
 *  block. The <i>pattern</i> will typically be a <code>Regexp</code>; if it is
 *  a <code>String</code> then no regular expression metacharacters will be
 *  interpreted (that is <code>/\d/</code> will match a digit, but
 *  <code>'\d'</code> will match a backslash followed by a 'd').
 *     
 *  If the method call specifies <i>replacement</i>, special variables such as
 *  <code>$&</code> will not be useful, as substitution into the string occurs
 *  before the pattern match starts. However, the sequences <code>\1</code>,
 *  <code>\2</code>, <code>\k<group_name></code>, etc., may be used.
 *     
 *  In the block form, the current match string is passed in as a parameter, and
 *  variables such as <code>$1</code>, <code>$2</code>, <code>$`</code>,
 *  <code>$&</code>, and <code>$'</code> will be set appropriately. The value
 *  returned by the block will be substituted for the match on each call.
 *     
 *  The result inherits any tainting in the original string or any supplied
 *  replacement string.
 *     
 *     "hello".sub(/[aeiou]/, '*')                  #=> "h*llo"
 *     "hello".sub(/([aeiou])/, '<\1>')             #=> "h<e>llo"
 *     "hello".sub(/./) {|s| s[0].ord.to_s + ' ' }  #=> "104 ello"
 *     "hello".sub(/(?<foo>[aeiou])/, '*\k<foo>*')  #=> "h*e*llo"
 */

static VALUE
rb_str_sub(int argc, VALUE *argv, VALUE str)
{
    str = rb_str_dup(str);
    rb_str_sub_bang(argc, argv, str);
    return str;
}

static VALUE
str_gsub(int argc, VALUE *argv, VALUE str, int bang)
{
    VALUE pat, val, repl, match, dest, hash = Qnil;
    struct re_registers *regs;
    long beg, n;
    long beg0, end0;
    long offset, blen, slen, len, last;
    int iter = 0;
    char *sp, *cp;
    int tainted = 0;
    rb_encoding *str_enc;
    
    switch (argc) {
      case 1:
        RETURN_ENUMERATOR(str, argc, argv);
        iter = 1;
        break;
      case 2:
        repl = argv[1];
        hash = rb_check_convert_type(argv[1], T_HASH, "Hash", "to_hash");
        if (NIL_P(hash)) {
            StringValue(repl);
        }
        if (OBJ_TAINTED(repl)) tainted = 1;
        break;
      default:
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 2)", argc);
    }

    pat = get_pat(argv[0], 1);
    beg = rb_reg_search(pat, str, 0, 0);
    if (beg < 0) {
        if (bang) return Qnil;  /* no match, no substitution */
        return rb_str_dup(str);
    }

    offset = 0;
    n = 0;
    blen = RSTRING_LEN(str) + 30; /* len + margin */
    dest = rb_str_buf_new(blen);
    sp = RSTRING_PTR(str);
    slen = RSTRING_LEN(str);
    cp = sp;
    str_enc = STR_ENC_GET(str);

    do {
        n++;
        match = rb_backref_get();
        regs = RMATCH_REGS(match);
        beg0 = BEG(0);
        end0 = END(0);
        if (iter || !NIL_P(hash)) {
            if (iter) {
                val = rb_obj_as_string(rb_yield(rb_reg_nth_match(0, match)));
            }
            else {
                val = rb_hash_aref(hash, rb_str_subseq(str, BEG(0), END(0) - BEG(0)));
                val = rb_obj_as_string(val);
            }
            str_mod_check(str, sp, slen);
            if (bang) str_frozen_check(str);
            if (val == dest) {  /* paranoid check [ruby-dev:24827] */
                rb_raise(rb_eRuntimeError, "block should not cheat");
            }
        }
        else {
            val = rb_reg_regsub(repl, str, regs, pat);
        }

        if (OBJ_TAINTED(val)) tainted = 1;

        len = beg - offset;     /* copy pre-match substr */
        if (len) {
            rb_enc_str_buf_cat(dest, cp, len, str_enc);
        }

        rb_str_buf_append(dest, val);

        last = offset;
        offset = end0;
        if (beg0 == end0) {
            /*
             * Always consume at least one character of the input string
             * in order to prevent infinite loops.
             */
            if (RSTRING_LEN(str) <= end0) break;
            len = rb_enc_mbclen(RSTRING_PTR(str)+end0, RSTRING_END(str), str_enc);
            rb_enc_str_buf_cat(dest, RSTRING_PTR(str)+end0, len, str_enc);
            offset = end0 + len;
        }
        cp = RSTRING_PTR(str) + offset;
        if (offset > RSTRING_LEN(str)) break;
        beg = rb_reg_search(pat, str, offset, 0);
    } while (beg >= 0);
    if (RSTRING_LEN(str) > offset) {
        rb_enc_str_buf_cat(dest, cp, RSTRING_LEN(str) - offset, str_enc);
    }
    rb_reg_search(pat, str, last, 0);
    if (bang) {
        rb_str_shared_replace(str, dest);
    }
    else {
        RBASIC(dest)->klass = rb_obj_class(str);
        OBJ_INFECT(dest, str);
        str = dest;
    }

    if (tainted) OBJ_TAINT(str);
    return str;
}


/*
 *  call-seq:
 *     str.gsub!(pattern, replacement)        => str or nil
 *     str.gsub!(pattern) {|match| block }    => str or nil
 *  
 *  Performs the substitutions of <code>String#gsub</code> in place, returning
 *  <i>str</i>, or <code>nil</code> if no substitutions were performed.
 */

static VALUE
rb_str_gsub_bang(int argc, VALUE *argv, VALUE str)
{
    return str_gsub(argc, argv, str, 1);
}


/*
 *  call-seq:
 *     str.gsub(pattern, replacement)       => new_str
 *     str.gsub(pattern) {|match| block }   => new_str
 *  
 *  Returns a copy of <i>str</i> with <em>all</em> occurrences of <i>pattern</i>
 *  replaced with either <i>replacement</i> or the value of the block. The
 *  <i>pattern</i> will typically be a <code>Regexp</code>; if it is a
 *  <code>String</code> then no regular expression metacharacters will be
 *  interpreted (that is <code>/\d/</code> will match a digit, but
 *  <code>'\d'</code> will match a backslash followed by a 'd').
 *     
 *  If a string is used as the replacement, special variables from the match
 *  (such as <code>$&</code> and <code>$1</code>) cannot be substituted into it,
 *  as substitution into the string occurs before the pattern match
 *  starts. However, the sequences <code>\1</code>, <code>\2</code>,
 *  <code>\k<group_name></code>, and so on may be used to interpolate
 *  successive groups in the match.
 *     
 *  In the block form, the current match string is passed in as a parameter, and
 *  variables such as <code>$1</code>, <code>$2</code>, <code>$`</code>,
 *  <code>$&</code>, and <code>$'</code> will be set appropriately. The value
 *  returned by the block will be substituted for the match on each call.
 *     
 *  The result inherits any tainting in the original string or any supplied
 *  replacement string.
 *     
 *     "hello".gsub(/[aeiou]/, '*')                  #=> "h*ll*"
 *     "hello".gsub(/([aeiou])/, '<\1>')             #=> "h<e>ll<o>"
 *     "hello".gsub(/./) {|s| s[0].ord.to_s + ' '}   #=> "104 101 108 108 111 "
 *     "hello".gsub(/(?<foo>[aeiou])/, '{\k<foo>}')  #=> "h{e}ll{o}"
 */

static VALUE
rb_str_gsub(int argc, VALUE *argv, VALUE str)
{
    return str_gsub(argc, argv, str, 0);
}


/*
 *  call-seq:
 *     str.replace(other_str)   => str
 *  
 *  Replaces the contents and taintedness of <i>str</i> with the corresponding
 *  values in <i>other_str</i>.
 *     
 *     s = "hello"         #=> "hello"
 *     s.replace "world"   #=> "world"
 */

static VALUE
rb_str_replace(VALUE str, VALUE str2)
{
    long len;
    if (str == str2) return str;

    StringValue(str2);
    len = RSTRING_LEN(str2);
    if (STR_ASSOC_P(str2)) {
        str2 = rb_str_new4(str2);
    }
    if (str_independent(str) && !STR_EMBED_P(str)) {
        xfree(RSTRING_PTR(str));
    }
    if (STR_SHARED_P(str2)) {
        STR_SET_NOEMBED(str);
        RSTRING(str)->as.heap.len = len;
        RSTRING(str)->as.heap.ptr = RSTRING_PTR(str2);
        FL_SET(str, ELTS_SHARED);
        FL_UNSET(str, STR_ASSOC);
        RSTRING(str)->as.heap.aux.shared = RSTRING(str2)->as.heap.aux.shared;
    }
    else {
        str_replace_shared(str, rb_str_new4(str2));
    }

    OBJ_INFECT(str, str2);
    rb_enc_cr_str_exact_copy(str, str2);
    return str;
}

/*
 *  call-seq:
 *     string.clear    ->  string
 *
 *  Makes string empty.
 *
 *     a = "abcde"
 *     a.clear    #=> ""
 */

static VALUE
rb_str_clear(VALUE str)
{
    /* rb_str_modify() */       /* no need for str_make_independent */
    if (str_independent(str) && !STR_EMBED_P(str)) {
        xfree(RSTRING_PTR(str));
    }
    STR_SET_EMBED(str);
    STR_SET_EMBED_LEN(str, 0);
    RSTRING_PTR(str)[0] = 0;
    ENC_CODERANGE_CLEAR(str);
    return str;
}

/*
 *  call-seq:
 *     string.chr    ->  string
 *
 *  Returns a one-character string at the beginning of the string.
 *
 *     a = "abcde"
 *     a.chr    #=> "a"
 */

static VALUE
rb_str_chr(VALUE str)
{
    return rb_str_substr(str, 0, 1);
}

/*
 *  call-seq:
 *     str.getbyte(index)          => 0 .. 255
 *
 *  returns the <i>index</i>th byte as an integer.
 */
static VALUE
rb_str_getbyte(VALUE str, VALUE index)
{
    long pos = NUM2LONG(index);

    if (pos < 0)
        pos += RSTRING_LEN(str);
    if (pos < 0 ||  RSTRING_LEN(str) <= pos)
        return Qnil;

    return INT2FIX((unsigned char)RSTRING_PTR(str)[pos]);
}

/*
 *  call-seq:
 *     str.setbyte(index, int) => int
 *
 *  modifies the <i>index</i>th byte as <i>int</i>.
 */
static VALUE
rb_str_setbyte(VALUE str, VALUE index, VALUE value)
{
    long pos = NUM2LONG(index);
    int byte = NUM2INT(value);

    rb_str_modify(str);

    if (pos < -RSTRING_LEN(str) || RSTRING_LEN(str) <= pos)
        rb_raise(rb_eIndexError, "index %ld out of string", pos);
    if (pos < 0)
        pos += RSTRING_LEN(str);

    RSTRING_PTR(str)[pos] = byte;

    return value;
}

/*
 *  call-seq:
 *     str.reverse   => new_str
 *  
 *  Returns a new string with the characters from <i>str</i> in reverse order.
 *     
 *     "stressed".reverse   #=> "desserts"
 */

static VALUE
rb_str_reverse(VALUE str)
{
    rb_encoding *enc;
    VALUE rev;
    char *s, *e, *p;
    int single = 1;

    if (RSTRING_LEN(str) <= 1) return rb_str_dup(str);
    enc = STR_ENC_GET(str);
    rev = rb_str_new5(str, 0, RSTRING_LEN(str));
    s = RSTRING_PTR(str); e = RSTRING_END(str);
    p = RSTRING_END(rev);

    if (RSTRING_LEN(str) > 1) {
        if (single_byte_optimizable(str)) {
            while (s < e) {
                *--p = *s++;
            }
        }
        else {
            while (s < e) {
                int clen = rb_enc_mbclen(s, e, enc);

                if (clen > 1 || (*s & 0x80)) single = 0;
                p -= clen;
                memcpy(p, s, clen);
                s += clen;
            }
        }
    }
    STR_SET_LEN(rev, RSTRING_LEN(str));
    OBJ_INFECT(rev, str);
    if (ENC_CODERANGE(str) == ENC_CODERANGE_UNKNOWN) {
        if (single) {
            ENC_CODERANGE_SET(str, ENC_CODERANGE_7BIT);
        }
        else {
            ENC_CODERANGE_SET(str, ENC_CODERANGE_VALID);
        }
    }
    rb_enc_cr_str_copy_for_substr(rev, str);

    return rev;
}


/*
 *  call-seq:
 *     str.reverse!   => str
 *  
 *  Reverses <i>str</i> in place.
 */

static VALUE
rb_str_reverse_bang(VALUE str)
{
    if (RSTRING_LEN(str) > 1) {
        if (single_byte_optimizable(str)) {
            char *s, *e, c;
            int cr = ENC_CODERANGE(str);
            int single = 1;

            rb_str_modify(str);
            s = RSTRING_PTR(str);
            e = RSTRING_END(str) - 1;
            while (s < e) {
                c = *s;
                if (*s & 0x80) single = 0;
                *s++ = *e;
                *e-- = c;
            }
            if (cr == ENC_CODERANGE_UNKNOWN && single) {
                cr = ENC_CODERANGE_7BIT;
            }
            ENC_CODERANGE_SET(str, cr);
        }
        else {
            rb_str_shared_replace(str, rb_str_reverse(str));
        }
    }
    return str;
}


/*
 *  call-seq:
 *     str.include? other_str   => true or false
 *  
 *  Returns <code>true</code> if <i>str</i> contains the given string or
 *  character.
 *     
 *     "hello".include? "lo"   #=> true
 *     "hello".include? "ol"   #=> false
 *     "hello".include? ?h     #=> true
 */

static VALUE
rb_str_include(VALUE str, VALUE arg)
{
    long i;

    StringValue(arg);
    i = rb_str_index(str, arg, 0);

    if (i == -1) return Qfalse;
    return Qtrue;
}


/*
 *  call-seq:
 *     str.to_i(base=10)   => integer
 *  
 *  Returns the result of interpreting leading characters in <i>str</i> as an
 *  integer base <i>base</i> (between 2 and 36). Extraneous characters past the
 *  end of a valid number are ignored. If there is not a valid number at the
 *  start of <i>str</i>, <code>0</code> is returned. This method never raises an
 *  exception.
 *     
 *     "12345".to_i             #=> 12345
 *     "99 red balloons".to_i   #=> 99
 *     "0a".to_i                #=> 0
 *     "0a".to_i(16)            #=> 10
 *     "hello".to_i             #=> 0
 *     "1100101".to_i(2)        #=> 101
 *     "1100101".to_i(8)        #=> 294977
 *     "1100101".to_i(10)       #=> 1100101
 *     "1100101".to_i(16)       #=> 17826049
 */

static VALUE
rb_str_to_i(int argc, VALUE *argv, VALUE str)
{
    int base;

    if (argc == 0) base = 10;
    else {
        VALUE b;

        rb_scan_args(argc, argv, "01", &b);
        base = NUM2INT(b);
    }
    if (base < 0) {
        rb_raise(rb_eArgError, "invalid radix %d", base);
    }
    return rb_str_to_inum(str, base, Qfalse);
}


/*
 *  call-seq:
 *     str.to_f   => float
 *  
 *  Returns the result of interpreting leading characters in <i>str</i> as a
 *  floating point number. Extraneous characters past the end of a valid number
 *  are ignored. If there is not a valid number at the start of <i>str</i>,
 *  <code>0.0</code> is returned. This method never raises an exception.
 *     
 *     "123.45e1".to_f        #=> 1234.5
 *     "45.67 degrees".to_f   #=> 45.67
 *     "thx1138".to_f         #=> 0.0
 */

static VALUE
rb_str_to_f(VALUE str)
{
    return DOUBLE2NUM(rb_str_to_dbl(str, Qfalse));
}


/*
 *  call-seq:
 *     str.to_s     => str
 *     str.to_str   => str
 *  
 *  Returns the receiver.
 */

static VALUE
rb_str_to_s(VALUE str)
{
    if (rb_obj_class(str) != rb_cString) {
        VALUE dup = str_alloc(rb_cString);
        rb_str_replace(dup, str);
        return dup;
    }
    return str;
}

static void
str_cat_char(VALUE str, int c, rb_encoding *enc)
{
    char s[16];
    int n = rb_enc_codelen(c, enc);

    rb_enc_mbcput(c, s, enc);
    rb_enc_str_buf_cat(str, s, n, enc);
}

static void
prefix_escape(VALUE str, int c, rb_encoding *enc)
{
    str_cat_char(str, '\\', enc);
    str_cat_char(str, c, enc);
}

/*
 * call-seq:
 *   str.inspect   => string
 *
 * Returns a printable version of _str_, surrounded by quote marks,
 * with special characters escaped.
 *
 *    str = "hello"
 *    str[3] = "\b"
 *    str.inspect       #=> "\"hel\\bo\""
 */

VALUE
rb_str_inspect(VALUE str)
{
    rb_encoding *enc = STR_ENC_GET(str);
    char *p, *pend;
    VALUE result = rb_str_buf_new(0);

    if (!rb_enc_asciicompat(enc)) enc = rb_usascii_encoding();
    rb_enc_associate(result, enc);
    str_cat_char(result, '"', enc);
    p = RSTRING_PTR(str); pend = RSTRING_END(str);
    while (p < pend) {
        int c;
        int n;
        int cc;

        n = rb_enc_precise_mbclen(p, pend, enc);
        if (!MBCLEN_CHARFOUND_P(n)) {
            p++;
            n = 1;
            goto escape_codepoint;
        }
        n = MBCLEN_CHARFOUND_LEN(n);

        c = rb_enc_codepoint(p, pend, enc);
        n = rb_enc_codelen(c, enc);

        p += n;
        if (c == '"'|| c == '\\' ||
            (c == '#' &&
             p < pend &&
             MBCLEN_CHARFOUND_P(rb_enc_precise_mbclen(p,pend,enc)) &&
             (cc = rb_enc_codepoint(p,pend,enc),
              (cc == '$' || cc == '@' || cc == '{')))) {
            prefix_escape(result, c, enc);
        }
        else if (c == '\n') {
            prefix_escape(result, 'n', enc);
        }
        else if (c == '\r') {
            prefix_escape(result, 'r', enc);
        }
        else if (c == '\t') {
            prefix_escape(result, 't', enc);
        }
        else if (c == '\f') {
            prefix_escape(result, 'f', enc);
        }
        else if (c == '\013') {
            prefix_escape(result, 'v', enc);
        }
        else if (c == '\010') {
            prefix_escape(result, 'b', enc);
        }
        else if (c == '\007') {
            prefix_escape(result, 'a', enc);
        }
        else if (c == 033) {
            prefix_escape(result, 'e', enc);
        }
        else if (rb_enc_isprint(c, enc)) {
            rb_enc_str_buf_cat(result, p-n, n, enc);
        }
        else {
            char buf[5];
            char *s;
            char *q;

          escape_codepoint:
            for (q = p-n; q < p; q++) {
                s = buf;
                sprintf(buf, "\\x%02X", *q & 0377);
                while (*s) {
                    str_cat_char(result, *s++, enc);
                }
            }
        }
    }
    str_cat_char(result, '"', enc);

    OBJ_INFECT(result, str);
    return result;
}

#define IS_EVSTR(p,e) ((p) < (e) && (*(p) == '$' || *(p) == '@' || *(p) == '{'))

/*
 *  call-seq:
 *     str.dump   => new_str
 *  
 *  Produces a version of <i>str</i> with all nonprinting characters replaced by
 *  <code>\nnn</code> notation and all special characters escaped.
 */

VALUE
rb_str_dump(VALUE str)
{
    rb_encoding *enc0 = rb_enc_get(str);
    long len;
    const char *p, *pend;
    char *q, *qend;
    VALUE result;

    len = 2;                    /* "" */
    p = RSTRING_PTR(str); pend = p + RSTRING_LEN(str);
    while (p < pend) {
        unsigned char c = *p++;
        switch (c) {
          case '"':  case '\\':
          case '\n': case '\r':
          case '\t': case '\f':
          case '\013': case '\010': case '\007': case '\033':
            len += 2;
            break;

          case '#':
            len += IS_EVSTR(p, pend) ? 2 : 1;
            break;

          default:
            if (ISPRINT(c)) {
                len++;
            }
            else {
                len += 4;               /* \xNN */
            }
            break;
        }
    }
    if (!rb_enc_asciicompat(enc0)) {
        len += 19;              /* ".force_encoding('')" */
        len += strlen(enc0->name);
    }

    result = rb_str_new5(str, 0, len);
    p = RSTRING_PTR(str); pend = p + RSTRING_LEN(str);
    q = RSTRING_PTR(result); qend = q + len;

    *q++ = '"';
    while (p < pend) {
        unsigned char c = *p++;

        if (c == '"' || c == '\\') {
            *q++ = '\\';
            *q++ = c;
        }
        else if (c == '#') {
            if (IS_EVSTR(p, pend)) *q++ = '\\';
            *q++ = '#';
        }
        else if (c == '\n') {
            *q++ = '\\';
            *q++ = 'n';
        }
        else if (c == '\r') {
            *q++ = '\\';
            *q++ = 'r';
        }
        else if (c == '\t') {
            *q++ = '\\';
            *q++ = 't';
        }
        else if (c == '\f') {
            *q++ = '\\';
            *q++ = 'f';
        }
        else if (c == '\013') {
            *q++ = '\\';
            *q++ = 'v';
        }
        else if (c == '\010') {
            *q++ = '\\';
            *q++ = 'b';
        }
        else if (c == '\007') {
            *q++ = '\\';
            *q++ = 'a';
        }
        else if (c == '\033') {
            *q++ = '\\';
            *q++ = 'e';
        }
        else if (ISPRINT(c)) {
            *q++ = c;
        }
        else {
            *q++ = '\\';
            sprintf(q, "x%02X", c);
            q += 3;
        }
    }
    *q++ = '"';
    if (!rb_enc_asciicompat(enc0)) {
        sprintf(q, ".force_encoding(\"%s\")", enc0->name);
        enc0 = rb_ascii8bit_encoding();
    }

    OBJ_INFECT(result, str);
    /* result from dump is ASCII */
    rb_enc_associate(result, enc0);
    return result;
}


/*
 *  call-seq:
 *     str.upcase!   => str or nil
 *  
 *  Upcases the contents of <i>str</i>, returning <code>nil</code> if no changes
 *  were made.
 *  Note: case replacement is effective only in ASCII region.
 */

static VALUE
rb_str_upcase_bang(VALUE str)
{
    rb_encoding *enc;
    char *s, *send;
    int modify = 0;
    int cr = ENC_CODERANGE(str);

    rb_str_modify(str);
    enc = STR_ENC_GET(str);
    s = RSTRING_PTR(str); send = RSTRING_END(str);
    while (s < send) {
        int c = rb_enc_codepoint(s, send, enc);

        if (rb_enc_islower(c, enc)) {
            /* assuming toupper returns codepoint with same size */
            rb_enc_mbcput(rb_enc_toupper(c, enc), s, enc);
            modify = 1;
        }
        s += rb_enc_codelen(c, enc);
    }

    ENC_CODERANGE_SET(str, cr);
    if (modify) return str;
    return Qnil;
}


/*
 *  call-seq:
 *     str.upcase   => new_str
 *  
 *  Returns a copy of <i>str</i> with all lowercase letters replaced with their
 *  uppercase counterparts. The operation is locale insensitive---only
 *  characters ``a'' to ``z'' are affected.
 *  Note: case replacement is effective only in ASCII region.
 *     
 *     "hEllO".upcase   #=> "HELLO"
 */

static VALUE
rb_str_upcase(VALUE str)
{
    str = rb_str_dup(str);
    rb_str_upcase_bang(str);
    return str;
}


/*
 *  call-seq:
 *     str.downcase!   => str or nil
 *  
 *  Downcases the contents of <i>str</i>, returning <code>nil</code> if no
 *  changes were made.
 *  Note: case replacement is effective only in ASCII region.
 */

static VALUE
rb_str_downcase_bang(VALUE str)
{
    rb_encoding *enc;
    char *s, *send;
    int modify = 0;
    int cr = ENC_CODERANGE(str);

    rb_str_modify(str);
    enc = STR_ENC_GET(str);
    s = RSTRING_PTR(str); send = RSTRING_END(str);
    while (s < send) {
        int c = rb_enc_codepoint(s, send, enc);

        if (rb_enc_isupper(c, enc)) {
            /* assuming toupper returns codepoint with same size */
            rb_enc_mbcput(rb_enc_tolower(c, enc), s, enc);
            modify = 1;
        }
        s += rb_enc_codelen(c, enc);
    }

    ENC_CODERANGE_SET(str, cr);
    if (modify) return str;
    return Qnil;
}


/*
 *  call-seq:
 *     str.downcase   => new_str
 *  
 *  Returns a copy of <i>str</i> with all uppercase letters replaced with their
 *  lowercase counterparts. The operation is locale insensitive---only
 *  characters ``A'' to ``Z'' are affected.
 *  Note: case replacement is effective only in ASCII region.
 *     
 *     "hEllO".downcase   #=> "hello"
 */

static VALUE
rb_str_downcase(VALUE str)
{
    str = rb_str_dup(str);
    rb_str_downcase_bang(str);
    return str;
}


/*
 *  call-seq:
 *     str.capitalize!   => str or nil
 *  
 *  Modifies <i>str</i> by converting the first character to uppercase and the
 *  remainder to lowercase. Returns <code>nil</code> if no changes are made.
 *  Note: case conversion is effective only in ASCII region.
 *     
 *     a = "hello"
 *     a.capitalize!   #=> "Hello"
 *     a               #=> "Hello"
 *     a.capitalize!   #=> nil
 */

static VALUE
rb_str_capitalize_bang(VALUE str)
{
    rb_encoding *enc;
    char *s, *send;
    int modify = 0;
    int c;
    int cr = ENC_CODERANGE(str);

    rb_str_modify(str);
    enc = STR_ENC_GET(str);
    if (RSTRING_LEN(str) == 0 || !RSTRING_PTR(str)) return Qnil;
    s = RSTRING_PTR(str); send = RSTRING_END(str);

    c = rb_enc_codepoint(s, send, enc);
    if (rb_enc_islower(c, enc)) {
        rb_enc_mbcput(rb_enc_toupper(c, enc), s, enc);
        modify = 1;
    }
    s += rb_enc_codelen(c, enc);
    while (s < send) {
        c = rb_enc_codepoint(s, send, enc);
        if (rb_enc_isupper(c, enc)) {
            rb_enc_mbcput(rb_enc_tolower(c, enc), s, enc);
            modify = 1;
        }
        s += rb_enc_codelen(c, enc);
    }

    ENC_CODERANGE_SET(str, cr);
    if (modify) return str;
    return Qnil;
}


/*
 *  call-seq:
 *     str.capitalize   => new_str
 *  
 *  Returns a copy of <i>str</i> with the first character converted to uppercase
 *  and the remainder to lowercase.
 *  Note: case conversion is effective only in ASCII region.
 *     
 *     "hello".capitalize    #=> "Hello"
 *     "HELLO".capitalize    #=> "Hello"
 *     "123ABC".capitalize   #=> "123abc"
 */

static VALUE
rb_str_capitalize(VALUE str)
{
    str = rb_str_dup(str);
    rb_str_capitalize_bang(str);
    return str;
}


/*
 *  call-seq: 
*     str.swapcase!   => str or nil
 *  
 *  Equivalent to <code>String#swapcase</code>, but modifies the receiver in
 *  place, returning <i>str</i>, or <code>nil</code> if no changes were made.
 *  Note: case conversion is effective only in ASCII region.
 */

static VALUE
rb_str_swapcase_bang(VALUE str)
{
    rb_encoding *enc;
    char *s, *send;
    int modify = 0;
    int cr = ENC_CODERANGE(str);

    rb_str_modify(str);
    enc = STR_ENC_GET(str);
    s = RSTRING_PTR(str); send = RSTRING_END(str);
    while (s < send) {
        int c = rb_enc_codepoint(s, send, enc);

        if (rb_enc_isupper(c, enc)) {
            /* assuming toupper returns codepoint with same size */
            rb_enc_mbcput(rb_enc_tolower(c, enc), s, enc);
            modify = 1;
        }
        else if (rb_enc_islower(c, enc)) {
            /* assuming toupper returns codepoint with same size */
            rb_enc_mbcput(rb_enc_toupper(c, enc), s, enc);
            modify = 1;
        }
        s += rb_enc_codelen(c, enc);
    }

    ENC_CODERANGE_SET(str, cr);
    if (modify) return str;
    return Qnil;
}


/*
 *  call-seq:
 *     str.swapcase   => new_str
 *  
 *  Returns a copy of <i>str</i> with uppercase alphabetic characters converted
 *  to lowercase and lowercase characters converted to uppercase.
 *  Note: case conversion is effective only in ASCII region.
 *     
 *     "Hello".swapcase          #=> "hELLO"
 *     "cYbEr_PuNk11".swapcase   #=> "CyBeR_pUnK11"
 */

static VALUE
rb_str_swapcase(VALUE str)
{
    str = rb_str_dup(str);
    rb_str_swapcase_bang(str);
    return str;
}

typedef unsigned char *USTR;

struct tr {
    int gen, now, max;
    char *p, *pend;
};

static int
trnext(struct tr *t, rb_encoding *enc)
{
    for (;;) {
        if (!t->gen) {
            if (t->p == t->pend) return -1;
            if (t->p < t->pend - 1 && *t->p == '\\') {
                t->p++;
            }
            t->now = rb_enc_codepoint(t->p, t->pend, enc);
            t->p += rb_enc_codelen(t->now, enc);
            if (t->p < t->pend - 1 && *t->p == '-') {
                t->p++;
                if (t->p < t->pend) {
                    int c = rb_enc_codepoint(t->p, t->pend, enc);
                    t->p += rb_enc_codelen(c, enc);
                    if (t->now > c) continue;
                    t->gen = 1;
                    t->max = c;
                }
            }
            return t->now;
        }
        else if (++t->now < t->max) {
            return t->now;
        }
        else {
            t->gen = 0;
            return t->max;
        }
    }
}

static VALUE rb_str_delete_bang(int,VALUE*,VALUE);

static VALUE
tr_trans(VALUE str, VALUE src, VALUE repl, int sflag)
{
    int trans[256];
    rb_encoding *enc, *e1, *e2;
    struct tr trsrc, trrepl;
    int cflag = 0;
    int c, c0, last = 0, modify = 0, i, l;
    char *s, *send;
    VALUE hash = 0;
    int singlebyte = single_byte_optimizable(str);

    StringValue(src);
    StringValue(repl);
    if (RSTRING_LEN(str) == 0 || !RSTRING_PTR(str)) return Qnil;
    if (RSTRING_LEN(repl) == 0) {
        return rb_str_delete_bang(1, &src, str);
    }

    e1 = rb_enc_check(str, src);
    e2 = rb_enc_check(str, repl);
    if (e1 == e2) {
        enc = e1;
    }
    else {
        enc = rb_enc_check(src, repl);
    }
    trsrc.p = RSTRING_PTR(src); trsrc.pend = trsrc.p + RSTRING_LEN(src);
    if (RSTRING_LEN(src) > 1 &&
        rb_enc_ascget(trsrc.p, trsrc.pend, &l, enc) == '^' &&
        trsrc.p + l < trsrc.pend) {
        cflag = 1;
        trsrc.p += l;
    }
    trrepl.p = RSTRING_PTR(repl);
    trrepl.pend = trrepl.p + RSTRING_LEN(repl);
    trsrc.gen = trrepl.gen = 0;
    trsrc.now = trrepl.now = 0;
    trsrc.max = trrepl.max = 0;

    if (cflag) {
        for (i=0; i<256; i++) {
            trans[i] = 1;
        }
        while ((c = trnext(&trsrc, enc)) >= 0) {
            if (c < 256) {
                trans[c] = -1;
            }
            else {
                if (!hash) hash = rb_hash_new();
                rb_hash_aset(hash, INT2NUM(c), Qtrue);
            }
        }
        while ((c = trnext(&trrepl, enc)) >= 0)
            /* retrieve last replacer */;
        last = trrepl.now;
        for (i=0; i<256; i++) {
            if (trans[i] >= 0) {
                trans[i] = last;
            }
        }
    }
    else {
        int r;

        for (i=0; i<256; i++) {
            trans[i] = -1;
        }
        while ((c = trnext(&trsrc, enc)) >= 0) {
            r = trnext(&trrepl, enc);
            if (r == -1) r = trrepl.now;
            if (c < 256) {
                trans[c] = r;
                if (r > 255) singlebyte = 0;
            }
            else {
                if (!hash) hash = rb_hash_new();
                rb_hash_aset(hash, INT2NUM(c), INT2NUM(r));
            }
        }
    }

    rb_str_modify(str);
    s = RSTRING_PTR(str); send = RSTRING_END(str);
    if (sflag) {
        int clen, tlen, max = RSTRING_LEN(str);
        int offset, save = -1;
        char *buf = ALLOC_N(char, max), *t = buf;

        while (s < send) {
            c0 = c = rb_enc_codepoint(s, send, enc);
            tlen = clen = rb_enc_codelen(c, enc);

            s += clen;
            if (c < 256) {
                c = trans[c];
            }
            else if (hash) {
                VALUE tmp = rb_hash_lookup(hash, INT2NUM(c));
                if (NIL_P(tmp)) {
                    if (cflag) c = last;
                    else c = -1;
                }
                else if (cflag) c = -1;
                else c = NUM2INT(tmp);
            }
            else {
                c = -1;
            }
            if (c >= 0) {
                if (save == c) continue;
                save = c;
                tlen = rb_enc_codelen(c, enc);
                modify = 1;
            }
            else {
                save = -1;
                c = c0;
            }
            while (t - buf + tlen >= max) {
                offset = t - buf;
                max *= 2;
                REALLOC_N(buf, char, max);
                t = buf + offset;
            }
            rb_enc_mbcput(c, t, enc);
            t += tlen;
        }
        *t = '\0';
        RSTRING(str)->as.heap.ptr = buf;
        RSTRING(str)->as.heap.len = t - buf;
        STR_SET_NOEMBED(str);
        RSTRING(str)->as.heap.aux.capa = max;
    }
    else if (rb_enc_mbmaxlen(enc) == 1 || (singlebyte && !hash)) {
        while (s < send) {
            c = (unsigned char)*s;
            if (trans[c] >= 0) {
                if (!cflag) {
                    c = trans[c];
                    *s = c;
                    modify = 1;
                }
                else {
                    *s = last;
                    modify = 1;
                }
            }
            s++;
        }
    }
    else {
        int clen, tlen, max = RSTRING_LEN(str) * 1.2;
        int offset;
        char *buf = ALLOC_N(char, max), *t = buf;

        while (s < send) {
            c0 = c = rb_enc_codepoint(s, send, enc);
            tlen = clen = rb_enc_codelen(c, enc);

            if (c < 256) {
                c = trans[c];
            }
            else if (hash) {
                VALUE tmp = rb_hash_lookup(hash, INT2NUM(c));
                if (NIL_P(tmp)) {
                    if (cflag) c = last;
                    else c = -1;
                }
                else if (cflag) c = -1;
                else c = NUM2INT(tmp);
            }
            else {
                c = -1;
            }
            if (c >= 0) {
                tlen = rb_enc_codelen(c, enc);
                modify = 1;
            }
            else {
                modify = 1;
                c = c0;
            }
            while (t - buf + tlen >= max) {
                offset = t - buf;
                max *= 2;
                REALLOC_N(buf, char, max);
                t = buf + offset;
            }
            if (s != t) rb_enc_mbcput(c, t, enc);
            s += clen;
            t += tlen;
        }
        if (!STR_EMBED_P(str)) {
            xfree(RSTRING(str)->as.heap.ptr);
        }
        *t = '\0';
        RSTRING(str)->as.heap.ptr = buf;
        RSTRING(str)->as.heap.len = t - buf;
        STR_SET_NOEMBED(str);
        RSTRING(str)->as.heap.aux.capa = max;
    }
    
    if (modify) {
        rb_enc_associate(str, enc);
        return str;
    }
    return Qnil;
}


/*
 *  call-seq:
 *     str.tr!(from_str, to_str)   => str or nil
 *  
 *  Translates <i>str</i> in place, using the same rules as
 *  <code>String#tr</code>. Returns <i>str</i>, or <code>nil</code> if no
 *  changes were made.
 */

static VALUE
rb_str_tr_bang(VALUE str, VALUE src, VALUE repl)
{
    return tr_trans(str, src, repl, 0);
}


/*
 *  call-seq:
 *     str.tr(from_str, to_str)   => new_str
 *  
 *  Returns a copy of <i>str</i> with the characters in <i>from_str</i> replaced
 *  by the corresponding characters in <i>to_str</i>. If <i>to_str</i> is
 *  shorter than <i>from_str</i>, it is padded with its last character. Both
 *  strings may use the c1--c2 notation to denote ranges of characters, and
 *  <i>from_str</i> may start with a <code>^</code>, which denotes all
 *  characters except those listed.
 *     
 *     "hello".tr('aeiou', '*')    #=> "h*ll*"
 *     "hello".tr('^aeiou', '*')   #=> "*e**o"
 *     "hello".tr('el', 'ip')      #=> "hippo"
 *     "hello".tr('a-y', 'b-z')    #=> "ifmmp"
 */

static VALUE
rb_str_tr(VALUE str, VALUE src, VALUE repl)
{
    str = rb_str_dup(str);
    tr_trans(str, src, repl, 0);
    return str;
}

static void
tr_setup_table(VALUE str, char stable[256], int first, 
               VALUE *tablep, VALUE *ctablep, rb_encoding *enc)
{
    char buf[256];
    struct tr tr;
    int c, l;
    VALUE table = 0, ptable = 0;
    int i, cflag = 0;

    tr.p = RSTRING_PTR(str); tr.pend = tr.p + RSTRING_LEN(str);
    tr.gen = tr.now = tr.max = 0;
    
    if (RSTRING_LEN(str) > 1 && rb_enc_ascget(tr.p, tr.pend, &l, enc) == '^') {
        cflag = 1;
        tr.p += l;
    }
    if (first) {
        for (i=0; i<256; i++) {
            stable[i] = 1;
        }
    }
    for (i=0; i<256; i++) {
        buf[i] = cflag;
    }

    while ((c = trnext(&tr, enc)) >= 0) {
        if (c < 256) {
            buf[c & 0xff] = !cflag;
        }
        else {
            VALUE key = INT2NUM(c);

            if (!table) {
                table = rb_hash_new();
                if (cflag) {
                    ptable = *ctablep;
                    *ctablep = table;
                }
                else {
                    ptable = *tablep;
                    *tablep = table;
                }
            }
            if (!ptable || !NIL_P(rb_hash_aref(ptable, key))) {
                rb_hash_aset(table, key, Qtrue);
            }
        }
    }
    for (i=0; i<256; i++) {
        stable[i] = stable[i] && buf[i];
    }
}


static int
tr_find(int c, char table[256], VALUE del, VALUE nodel)
{
    if (c < 256) {
        return table[c] ? Qtrue : Qfalse;
    }
    else {
        VALUE v = INT2NUM(c);

        if (del && !NIL_P(rb_hash_lookup(del, v))) {
            if (!nodel || NIL_P(rb_hash_lookup(nodel, v))) {
                return Qtrue;
            }
        }
        return Qfalse;
    }
}

/*
 *  call-seq:
 *     str.delete!([other_str]+)   => str or nil
 *  
 *  Performs a <code>delete</code> operation in place, returning <i>str</i>, or
 *  <code>nil</code> if <i>str</i> was not modified.
 */

static VALUE
rb_str_delete_bang(int argc, VALUE *argv, VALUE str)
{
    char squeez[256];
    rb_encoding *enc = 0;
    char *s, *send, *t;
    VALUE del = 0, nodel = 0;
    int modify = 0;
    int i;
    int cr;

    if (RSTRING_LEN(str) == 0 || !RSTRING_PTR(str)) return Qnil;
    cr = ENC_CODERANGE(str);
    if (argc < 1) {
        rb_raise(rb_eArgError, "wrong number of arguments");
    }
    for (i=0; i<argc; i++) {
        VALUE s = argv[i];

        StringValue(s);
        enc = rb_enc_check(str, s);
        tr_setup_table(s, squeez, i==0, &del, &nodel, enc);
    }

    rb_str_modify(str);
    s = t = RSTRING_PTR(str);
    if (!s || RSTRING_LEN(str) == 0) return Qnil;
    send = RSTRING_END(str);
    while (s < send) {
        int c = rb_enc_codepoint(s, send, enc);
        int clen = rb_enc_codelen(c, enc);

        if (tr_find(c, squeez, del, nodel)) {
            modify = 1;
        }
        else {
            if (t != s) rb_enc_mbcput(c, t, enc);
            t += clen;
        }
        s += clen;
    }
    *t = '\0';
    STR_SET_LEN(str, t - RSTRING_PTR(str));

    ENC_CODERANGE_SET(str, cr);
    if (modify) return str;
    return Qnil;
}


/*
 *  call-seq:
 *     str.delete([other_str]+)   => new_str
 *  
 *  Returns a copy of <i>str</i> with all characters in the intersection of its
 *  arguments deleted. Uses the same rules for building the set of characters as
 *  <code>String#count</code>.
 *     
 *     "hello".delete "l","lo"        #=> "heo"
 *     "hello".delete "lo"            #=> "he"
 *     "hello".delete "aeiou", "^e"   #=> "hell"
 *     "hello".delete "ej-m"          #=> "ho"
 */

static VALUE
rb_str_delete(int argc, VALUE *argv, VALUE str)
{
    str = rb_str_dup(str);
    rb_str_delete_bang(argc, argv, str);
    return str;
}


/*
 *  call-seq:
 *     str.squeeze!([other_str]*)   => str or nil
 *  
 *  Squeezes <i>str</i> in place, returning either <i>str</i>, or
 *  <code>nil</code> if no changes were made.
 */

static VALUE
rb_str_squeeze_bang(int argc, VALUE *argv, VALUE str)
{
    char squeez[256];
    rb_encoding *enc = 0;
    VALUE del = 0, nodel = 0;
    char *s, *send, *t;
    int save, modify = 0;
    int i;

    if (argc == 0) {
        enc = STR_ENC_GET(str);
    }
    else {
        for (i=0; i<argc; i++) {
            VALUE s = argv[i];

            StringValue(s);
            enc = rb_enc_check(str, s);
            tr_setup_table(s, squeez, i==0, &del, &nodel, enc);
        }
    }

    rb_str_modify(str);
    s = t = RSTRING_PTR(str);
    if (!s || RSTRING_LEN(str) == 0) return Qnil;
    send = RSTRING_END(str);
    save = -1;
    while (s < send) {
        int c = rb_enc_codepoint(s, send, enc);
        int clen = rb_enc_codelen(c, enc);

        if (c != save || (argc > 0 && !tr_find(c, squeez, del, nodel))) {
            if (t != s) rb_enc_mbcput(c, t, enc);
            save = c;
            t += clen;
        }
        s += clen;
    }
    *t = '\0';
    if (t - RSTRING_PTR(str) != RSTRING_LEN(str)) {
        STR_SET_LEN(str, t - RSTRING_PTR(str));
        modify = 1;
    }

    if (modify) return str;
    return Qnil;
}


/*
 *  call-seq:
 *     str.squeeze([other_str]*)    => new_str
 *  
 *  Builds a set of characters from the <i>other_str</i> parameter(s) using the
 *  procedure described for <code>String#count</code>. Returns a new string
 *  where runs of the same character that occur in this set are replaced by a
 *  single character. If no arguments are given, all runs of identical
 *  characters are replaced by a single character.
 *     
 *     "yellow moon".squeeze                  #=> "yelow mon"
 *     "  now   is  the".squeeze(" ")         #=> " now is the"
 *     "putters shoot balls".squeeze("m-z")   #=> "puters shot balls"
 */

static VALUE
rb_str_squeeze(int argc, VALUE *argv, VALUE str)
{
    str = rb_str_dup(str);
    rb_str_squeeze_bang(argc, argv, str);
    return str;
}


/*
 *  call-seq:
 *     str.tr_s!(from_str, to_str)   => str or nil
 *  
 *  Performs <code>String#tr_s</code> processing on <i>str</i> in place,
 *  returning <i>str</i>, or <code>nil</code> if no changes were made.
 */

static VALUE
rb_str_tr_s_bang(VALUE str, VALUE src, VALUE repl)
{
    return tr_trans(str, src, repl, 1);
}


/*
 *  call-seq:
 *     str.tr_s(from_str, to_str)   => new_str
 *  
 *  Processes a copy of <i>str</i> as described under <code>String#tr</code>,
 *  then removes duplicate characters in regions that were affected by the
 *  translation.
 *     
 *     "hello".tr_s('l', 'r')     #=> "hero"
 *     "hello".tr_s('el', '*')    #=> "h*o"
 *     "hello".tr_s('el', 'hx')   #=> "hhxo"
 */

static VALUE
rb_str_tr_s(VALUE str, VALUE src, VALUE repl)
{
    str = rb_str_dup(str);
    tr_trans(str, src, repl, 1);
    return str;
}


/*
 *  call-seq:
 *     str.count([other_str]+)   => fixnum
 *  
 *  Each <i>other_str</i> parameter defines a set of characters to count.  The
 *  intersection of these sets defines the characters to count in
 *  <i>str</i>. Any <i>other_str</i> that starts with a caret (^) is
 *  negated. The sequence c1--c2 means all characters between c1 and c2.
 *     
 *     a = "hello world"
 *     a.count "lo"            #=> 5
 *     a.count "lo", "o"       #=> 2
 *     a.count "hello", "^l"   #=> 4
 *     a.count "ej-m"          #=> 4
 */

static VALUE
rb_str_count(int argc, VALUE *argv, VALUE str)
{
    char table[256];
    rb_encoding *enc = 0;
    VALUE del = 0, nodel = 0;
    char *s, *send;
    int i;

    if (argc < 1) {
        rb_raise(rb_eArgError, "wrong number of arguments");
    }
    for (i=0; i<argc; i++) {
        VALUE s = argv[i];

        StringValue(s);
        enc = rb_enc_check(str, s);
        tr_setup_table(s, table,i==0, &del, &nodel, enc);
    }

    s = RSTRING_PTR(str);
    if (!s || RSTRING_LEN(str) == 0) return INT2FIX(0);
    send = RSTRING_END(str);
    i = 0;
    while (s < send) {
        int c = rb_enc_codepoint(s, send, enc);
        int clen = rb_enc_codelen(c, enc);

        if (tr_find(c, table, del, nodel)) {
            i++;
        }
        s += clen;
    }
    return INT2NUM(i);
}


/*
 *  call-seq:
 *     str.split(pattern=$;, [limit])   => anArray
 *  
 *  Divides <i>str</i> into substrings based on a delimiter, returning an array
 *  of these substrings.
 *     
 *  If <i>pattern</i> is a <code>String</code>, then its contents are used as
 *  the delimiter when splitting <i>str</i>. If <i>pattern</i> is a single
 *  space, <i>str</i> is split on whitespace, with leading whitespace and runs
 *  of contiguous whitespace characters ignored.
 *     
 *  If <i>pattern</i> is a <code>Regexp</code>, <i>str</i> is divided where the
 *  pattern matches. Whenever the pattern matches a zero-length string,
 *  <i>str</i> is split into individual characters. If <i>pattern</i> contains
 *  groups, the respective matches will be returned in the array as well.
 *     
 *  If <i>pattern</i> is omitted, the value of <code>$;</code> is used.  If
 *  <code>$;</code> is <code>nil</code> (which is the default), <i>str</i> is
 *  split on whitespace as if ` ' were specified.
 *     
 *  If the <i>limit</i> parameter is omitted, trailing null fields are
 *  suppressed. If <i>limit</i> is a positive number, at most that number of
 *  fields will be returned (if <i>limit</i> is <code>1</code>, the entire
 *  string is returned as the only entry in an array). If negative, there is no
 *  limit to the number of fields returned, and trailing null fields are not
 *  suppressed.
 *     
 *     " now's  the time".split        #=> ["now's", "the", "time"]
 *     " now's  the time".split(' ')   #=> ["now's", "the", "time"]
 *     " now's  the time".split(/ /)   #=> ["", "now's", "", "the", "time"]
 *     "1, 2.34,56, 7".split(%r{,\s*}) #=> ["1", "2.34", "56", "7"]
 *     "hello".split(//)               #=> ["h", "e", "l", "l", "o"]
 *     "hello".split(//, 3)            #=> ["h", "e", "llo"]
 *     "hi mom".split(%r{\s*})         #=> ["h", "i", "m", "o", "m"]
 *     
 *     "mellow yellow".split("ello")   #=> ["m", "w y", "w"]
 *     "1,2,,3,4,,".split(',')         #=> ["1", "2", "", "3", "4"]
 *     "1,2,,3,4,,".split(',', 4)      #=> ["1", "2", "", "3,4,,"]
 *     "1,2,,3,4,,".split(',', -4)     #=> ["1", "2", "", "3", "4", "", ""]
 */

static VALUE
rb_str_split_m(int argc, VALUE *argv, VALUE str)
{
    rb_encoding *enc;
    VALUE spat;
    VALUE limit;
    int awk_split = Qfalse;
    long beg, end, i = 0;
    int lim = 0;
    VALUE result, tmp;

    if (rb_scan_args(argc, argv, "02", &spat, &limit) == 2) {
        lim = NUM2INT(limit);
        if (lim <= 0) limit = Qnil;
        else if (lim == 1) {
            if (RSTRING_LEN(str) == 0)
                return rb_ary_new2(0);
            return rb_ary_new3(1, str);
        }
        i = 1;
    }

    enc = STR_ENC_GET(str);
    if (NIL_P(spat)) {
        if (!NIL_P(rb_fs)) {
            spat = rb_fs;
            goto fs_set;
        }
        awk_split = Qtrue;
    }
    else {
      fs_set:
        if (TYPE(spat) == T_STRING) {
            rb_encoding *enc2 = STR_ENC_GET(spat);

            if (rb_enc_mbminlen(enc2) == 1) {
                if (RSTRING_LEN(spat) == 1 && RSTRING_PTR(spat)[0] == ' '){
                    awk_split = Qtrue;
                }
            }
            else {
                int l;
                if (rb_enc_ascget(RSTRING_PTR(spat), RSTRING_END(spat), &l, enc2) == ' ' &&
                    RSTRING_LEN(spat) == l) {
                    awk_split = Qtrue;
                }
            }
            if (!awk_split) {
                spat = rb_reg_regcomp(rb_reg_quote(spat));
            }
        }
        else {
            spat = get_pat(spat, 1);
        }
    }

    result = rb_ary_new();
    beg = 0;
    if (awk_split) {
        char *ptr = RSTRING_PTR(str);
        char *eptr = RSTRING_END(str);
        char *bptr = ptr;
        int skip = 1;
        int c;

        end = beg;
        while (ptr < eptr) {
            c = rb_enc_codepoint(ptr, eptr, enc);
            ptr += rb_enc_mbclen(ptr, eptr, enc);
            if (skip) {
                if (rb_enc_isspace(c, enc)) {
                    beg = ptr - bptr;
                }
                else {
                    end = ptr - bptr;
                    skip = 0;
                    if (!NIL_P(limit) && lim <= i) break;
                }
            }
            else {
                if (rb_enc_isspace(c, enc)) {
                    rb_ary_push(result, rb_str_subseq(str, beg, end-beg));
                    skip = 1;
                    beg = ptr - bptr;
                    if (!NIL_P(limit)) ++i;
                }
                else {
                    end = ptr - bptr;
                }
            }
        }
    }
    else {
        long start = beg;
        long idx;
        int last_null = 0;
        struct re_registers *regs;

        while ((end = rb_reg_search(spat, str, start, 0)) >= 0) {
            regs = RMATCH_REGS(rb_backref_get());
            if (start == end && BEG(0) == END(0)) {
                if (!RSTRING_PTR(str)) {
                    rb_ary_push(result, rb_str_new("", 0));
                    break;
                }
                else if (last_null == 1) {
                    rb_ary_push(result, rb_str_subseq(str, beg,
                                                      rb_enc_mbclen(RSTRING_PTR(str)+beg,
                                                                    RSTRING_END(str),
                                                                    enc)));
                    beg = start;
                }
                else {
                    if (RSTRING_PTR(str)+start == RSTRING_END(str))
                        start++;
                    else
                        start += rb_enc_mbclen(RSTRING_PTR(str)+start,RSTRING_END(str),enc);
                    last_null = 1;
                    continue;
                }
            }
            else {
                rb_ary_push(result, rb_str_subseq(str, beg, end-beg));
                beg = start = END(0);
            }
            last_null = 0;

            for (idx=1; idx < regs->num_regs; idx++) {
                if (BEG(idx) == -1) continue;
                if (BEG(idx) == END(idx))
                    tmp = rb_str_new5(str, 0, 0);
                else
                    tmp = rb_str_subseq(str, BEG(idx), END(idx)-BEG(idx));
                rb_ary_push(result, tmp);
            }
            if (!NIL_P(limit) && lim <= ++i) break;
        }
    }
    if (RSTRING_LEN(str) > 0 && (!NIL_P(limit) || RSTRING_LEN(str) > beg || lim < 0)) {
        if (RSTRING_LEN(str) == beg)
            tmp = rb_str_new5(str, 0, 0);
        else
            tmp = rb_str_subseq(str, beg, RSTRING_LEN(str)-beg);
        rb_ary_push(result, tmp);
    }
    if (NIL_P(limit) && lim == 0) {
        while (RARRAY_LEN(result) > 0 &&
               RSTRING_LEN(RARRAY_PTR(result)[RARRAY_LEN(result)-1]) == 0)
            rb_ary_pop(result);
    }

    return result;
}

VALUE
rb_str_split(VALUE str, const char *sep0)
{
    VALUE sep;

    StringValue(str);
    sep = rb_str_new2(sep0);
    return rb_str_split_m(1, &sep, str);
}


/*
 *  Document-method: lines
 *  call-seq:
 *     str.lines(separator=$/)   => anEnumerator
 *     str.lines(separator=$/) {|substr| block }        => str
 *  
 *  Returns an enumerator that gives each line in the string.  If a block is
 *  given, it iterates over each line in the string.
 *     
 *     "foo\nbar\n".lines.to_a   #=> ["foo\n", "bar\n"]
 *     "foo\nb ar".lines.sort    #=> ["b ar", "foo\n"]
 */

/*
 *  Document-method: each_line
 *  call-seq:
 *     str.each_line(separator=$/) {|substr| block }   => str
 *  
 *  Splits <i>str</i> using the supplied parameter as the record separator
 *  (<code>$/</code> by default), passing each substring in turn to the supplied
 *  block. If a zero-length record separator is supplied, the string is split
 *  into paragraphs delimited by multiple successive newlines.
 *     
 *     print "Example one\n"
 *     "hello\nworld".each {|s| p s}
 *     print "Example two\n"
 *     "hello\nworld".each('l') {|s| p s}
 *     print "Example three\n"
 *     "hello\n\n\nworld".each('') {|s| p s}
 *     
 *  <em>produces:</em>
 *     
 *     Example one
 *     "hello\n"
 *     "world"
 *     Example two
 *     "hel"
 *     "l"
 *     "o\nworl"
 *     "d"
 *     Example three
 *     "hello\n\n\n"
 *     "world"
 */

static VALUE
rb_str_each_line(int argc, VALUE *argv, VALUE str)
{
    rb_encoding *enc;
    VALUE rs;
    int newline;
    char *p, *pend, *s, *ptr;
    long len, rslen; 
    VALUE line;
    int n;
    VALUE orig = str;

    if (argc == 0) {
        rs = rb_rs;
    }
    else {
        rb_scan_args(argc, argv, "01", &rs);
    }
    RETURN_ENUMERATOR(str, argc, argv);
    if (NIL_P(rs)) {
        rb_yield(str);
        return orig;
    }
    str = rb_str_new4(str);
    ptr = p = s = RSTRING_PTR(str);
    pend = p + RSTRING_LEN(str);
    len = RSTRING_LEN(str);
    StringValue(rs);
    if (rs == rb_default_rs) {
        enc = rb_enc_get(str);
        while (p < pend) {
            char *p0;

            p = memchr(p, '\n', pend - p);
            if (!p) break;
            p0 = rb_enc_left_char_head(s, p, enc);
            if (!rb_enc_is_newline(p0, pend, enc)) {
                p++;
                continue;
            }
            p = p0 + rb_enc_mbclen(p0, pend, enc);
            line = rb_str_new5(str, s, p - s);
            OBJ_INFECT(line, str);
            rb_enc_cr_str_copy_for_substr(line, str);
            rb_yield(line);
            str_mod_check(str, ptr, len);
            s = p;
        }
        goto finish;
    }

    enc = rb_enc_check(str, rs);
    rslen = RSTRING_LEN(rs);
    if (rslen == 0) {
        newline = '\n';
    }
    else {
        newline = rb_enc_codepoint(RSTRING_PTR(rs), RSTRING_END(rs), enc);
    }

    while (p < pend) {
        int c = rb_enc_codepoint(p, pend, enc);

      again:
        n = rb_enc_codelen(c, enc);
        if (rslen == 0 && c == newline) {
            p += n;
            if (p < pend && (c = rb_enc_codepoint(p, pend, enc)) != newline) {
                goto again;
            }
            while (p < pend && rb_enc_codepoint(p, pend, enc) == newline) {
                p += n;
            }
            p -= n;
        }
        if (c == newline &&
            (rslen <= 1 || memcmp(RSTRING_PTR(rs), p, rslen) == 0)) {
            line = rb_str_new5(str, s, p - s + (rslen ? rslen : n));
            OBJ_INFECT(line, str);
            rb_enc_cr_str_copy_for_substr(line, str);
            rb_yield(line);
            str_mod_check(str, ptr, len);
            s = p + (rslen ? rslen : n);
        }
        p += n;
    }

  finish:
    if (s != pend) {
        line = rb_str_new5(str, s, pend - s);
        OBJ_INFECT(line, str);
        rb_enc_cr_str_copy_for_substr(line, str);
        rb_yield(line);
    }

    return orig;
}


/*
 *  Document-method: bytes
 *  call-seq:
 *     str.bytes   => anEnumerator
 *     str.bytes {|fixnum| block }    => str
 *  
 *  Returns an enumerator that gives each byte in the string.  If a block is
 *  given, it iterates over each byte in the string.
 *     
 *     "hello".bytes.to_a        #=> [104, 101, 108, 108, 111]
 */

/*
 *  Document-method: each_byte
 *  call-seq:
 *     str.each_byte {|fixnum| block }    => str
 *  
 *  Passes each byte in <i>str</i> to the given block.
 *     
 *     "hello".each_byte {|c| print c, ' ' }
 *     
 *  <em>produces:</em>
 *     
 *     104 101 108 108 111
 */

static VALUE
rb_str_each_byte(VALUE str)
{
    long i;

    RETURN_ENUMERATOR(str, 0, 0);
    for (i=0; i<RSTRING_LEN(str); i++) {
        rb_yield(INT2FIX(RSTRING_PTR(str)[i] & 0xff));
    }
    return str;
}


/*
 *  Document-method: chars
 *  call-seq:
 *     str.chars                   => anEnumerator
 *     str.chars {|substr| block } => str
 *  
 *  Returns an enumerator that gives each character in the string.
 *  If a block is given, it iterates over each character in the string.
 *     
 *     "foo".chars.to_a   #=> ["f","o","o"]
 */

/*
 *  Document-method: each_char
 *  call-seq:
 *     str.each_char {|cstr| block }    => str
 *  
 *  Passes each character in <i>str</i> to the given block.
 *     
 *     "hello".each_char {|c| print c, ' ' }
 *     
 *  <em>produces:</em>
 *     
 *     h e l l o 
 */

static VALUE
rb_str_each_char(VALUE str)
{
    int i, len, n;
    const char *ptr;
    rb_encoding *enc;

    RETURN_ENUMERATOR(str, 0, 0);
    str = rb_str_new4(str);
    ptr = RSTRING_PTR(str);
    len = RSTRING_LEN(str);
    enc = rb_enc_get(str);
    for (i = 0; i < len; i += n) {
        n = rb_enc_mbclen(ptr + i, ptr + len, enc);
        rb_yield(rb_str_subseq(str, i, n));
    }
    return str;
}

static long
chopped_length(VALUE str)
{
    rb_encoding *enc = STR_ENC_GET(str);
    const char *p, *p2, *beg, *end;

    beg = RSTRING_PTR(str);
    end = beg + RSTRING_LEN(str);
    if (beg > end) return 0;
    p = rb_enc_prev_char(beg, end, enc);
    if (!p) return 0;
    if (p > beg && rb_enc_codepoint(p, end, enc) == '\n') {
        p2 = rb_enc_prev_char(beg, p, enc);
        if (p2 && rb_enc_codepoint(p2, end, enc) == '\r') p = p2;
    }
    return p - beg;
}

/*
 *  call-seq:
 *     str.chop!   => str or nil
 *  
 *  Processes <i>str</i> as for <code>String#chop</code>, returning <i>str</i>,
 *  or <code>nil</code> if <i>str</i> is the empty string.  See also
 *  <code>String#chomp!</code>.
 */

static VALUE
rb_str_chop_bang(VALUE str)
{
    if (RSTRING_LEN(str) > 0) {
        long len;
        rb_str_modify(str);
        len = chopped_length(str);
        STR_SET_LEN(str, len);
        RSTRING_PTR(str)[len] = '\0';
        return str;
    }
    return Qnil;
}


/*
 *  call-seq:
 *     str.chop   => new_str
 *  
 *  Returns a new <code>String</code> with the last character removed.  If the
 *  string ends with <code>\r\n</code>, both characters are removed. Applying
 *  <code>chop</code> to an empty string returns an empty
 *  string. <code>String#chomp</code> is often a safer alternative, as it leaves
 *  the string unchanged if it doesn't end in a record separator.
 *     
 *     "string\r\n".chop   #=> "string"
 *     "string\n\r".chop   #=> "string\n"
 *     "string\n".chop     #=> "string"
 *     "string".chop       #=> "strin"
 *     "x".chop.chop       #=> ""
 */

static VALUE
rb_str_chop(VALUE str)
{
    VALUE str2 = rb_str_new5(str, RSTRING_PTR(str), chopped_length(str));
    rb_enc_cr_str_copy_for_substr(str2, str);
    OBJ_INFECT(str2, str);
    return str2;
}


/*
 *  call-seq:
 *     str.chomp!(separator=$/)   => str or nil
 *  
 *  Modifies <i>str</i> in place as described for <code>String#chomp</code>,
 *  returning <i>str</i>, or <code>nil</code> if no modifications were made.
 */

static VALUE
rb_str_chomp_bang(int argc, VALUE *argv, VALUE str)
{
    rb_encoding *enc;
    VALUE rs;
    int newline;
    char *p, *pp, *e;
    long len, rslen;

    len = RSTRING_LEN(str);
    if (len == 0) return Qnil;
    p = RSTRING_PTR(str);
    e = p + len;
    if (argc == 0) {
        rs = rb_rs;
        if (rs == rb_default_rs) {
          smart_chomp:
            rb_str_modify(str);
            enc = rb_enc_get(str);
            if (rb_enc_mbminlen(enc) > 1) {
                pp = rb_enc_left_char_head(p, e-rb_enc_mbminlen(enc), enc);
                if (rb_enc_is_newline(pp, e, enc)) {
                    e = pp;
                }
                pp = e - rb_enc_mbminlen(enc);
                if (pp >= p) {
                    pp = rb_enc_left_char_head(p, pp, enc);
                    if (rb_enc_ascget(pp, e, 0, enc) == '\r') {
                        e = pp;
                    }
                }
                if (e == RSTRING_END(str)) {
                    return Qnil;
                }
                len = e - RSTRING_PTR(str);
                STR_SET_LEN(str, len);
            }
            else {
                if (RSTRING_PTR(str)[len-1] == '\n') {
                    STR_DEC_LEN(str);
                    if (RSTRING_LEN(str) > 0 &&
                        RSTRING_PTR(str)[RSTRING_LEN(str)-1] == '\r') {
                        STR_DEC_LEN(str);
                    }
                }
                else if (RSTRING_PTR(str)[len-1] == '\r') {
                    STR_DEC_LEN(str);
                }
                else {
                    return Qnil;
                }
            }
            RSTRING_PTR(str)[RSTRING_LEN(str)] = '\0';
            return str;
        }
    }
    else {
        rb_scan_args(argc, argv, "01", &rs);
    }
    if (NIL_P(rs)) return Qnil;
    StringValue(rs);
    rslen = RSTRING_LEN(rs);
    if (rslen == 0) {
        while (len>0 && p[len-1] == '\n') {
            len--;
            if (len>0 && p[len-1] == '\r')
                len--;
        }
        if (len < RSTRING_LEN(str)) {
            rb_str_modify(str);
            STR_SET_LEN(str, len);
            RSTRING_PTR(str)[len] = '\0';
            return str;
        }
        return Qnil;
    }
    if (rslen > len) return Qnil;
    newline = RSTRING_PTR(rs)[rslen-1];
    if (rslen == 1 && newline == '\n')
        goto smart_chomp;

    enc = rb_enc_check(str, rs);
    if (is_broken_string(rs)) {
        return Qnil;
    }
    pp = e - rslen;
    if (p[len-1] == newline &&
        (rslen <= 1 ||
         memcmp(RSTRING_PTR(rs), pp, rslen) == 0)) {
        if (rb_enc_left_char_head(p, pp, enc) != pp)
            return Qnil;
        rb_str_modify(str);
        STR_SET_LEN(str, RSTRING_LEN(str) - rslen);
        RSTRING_PTR(str)[RSTRING_LEN(str)] = '\0';
        return str;
    }
    return Qnil;
}


/*
 *  call-seq:
 *     str.chomp(separator=$/)   => new_str
 *  
 *  Returns a new <code>String</code> with the given record separator removed
 *  from the end of <i>str</i> (if present). If <code>$/</code> has not been
 *  changed from the default Ruby record separator, then <code>chomp</code> also
 *  removes carriage return characters (that is it will remove <code>\n</code>,
 *  <code>\r</code>, and <code>\r\n</code>).
 *     
 *     "hello".chomp            #=> "hello"
 *     "hello\n".chomp          #=> "hello"
 *     "hello\r\n".chomp        #=> "hello"
 *     "hello\n\r".chomp        #=> "hello\n"
 *     "hello\r".chomp          #=> "hello"
 *     "hello \n there".chomp   #=> "hello \n there"
 *     "hello".chomp("llo")     #=> "he"
 */

static VALUE
rb_str_chomp(int argc, VALUE *argv, VALUE str)
{
    str = rb_str_dup(str);
    rb_str_chomp_bang(argc, argv, str);
    return str;
}

/*
 *  call-seq:
 *     str.lstrip!   => self or nil
 *  
 *  Removes leading whitespace from <i>str</i>, returning <code>nil</code> if no
 *  change was made. See also <code>String#rstrip!</code> and
 *  <code>String#strip!</code>.
 *     
 *     "  hello  ".lstrip   #=> "hello  "
 *     "hello".lstrip!      #=> nil
 */

static VALUE
rb_str_lstrip_bang(VALUE str)
{
    rb_encoding *enc;
    char *s, *t, *e;

    rb_str_modify(str);
    enc = STR_ENC_GET(str);
    s = RSTRING_PTR(str);
    if (!s || RSTRING_LEN(str) == 0) return Qnil;
    e = t = RSTRING_END(str);
    /* remove spaces at head */
    while (s < e) {
        int cc = rb_enc_codepoint(s, e, enc);
        
        if (!rb_enc_isspace(cc, enc)) break;
        s += rb_enc_codelen(cc, enc);
    }

    if (s > RSTRING_PTR(str)) {
        rb_str_modify(str);
        STR_SET_LEN(str, t-s);
        memmove(RSTRING_PTR(str), s, RSTRING_LEN(str));
        RSTRING_PTR(str)[RSTRING_LEN(str)] = '\0';
        return str;
    }
    return Qnil;
}


/*
 *  call-seq:
 *     str.lstrip   => new_str
 *  
 *  Returns a copy of <i>str</i> with leading whitespace removed. See also
 *  <code>String#rstrip</code> and <code>String#strip</code>.
 *     
 *     "  hello  ".lstrip   #=> "hello  "
 *     "hello".lstrip       #=> "hello"
 */

static VALUE
rb_str_lstrip(VALUE str)
{
    str = rb_str_dup(str);
    rb_str_lstrip_bang(str);
    return str;
}


/*
 *  call-seq:
 *     str.rstrip!   => self or nil
 *  
 *  Removes trailing whitespace from <i>str</i>, returning <code>nil</code> if
 *  no change was made. See also <code>String#lstrip!</code> and
 *  <code>String#strip!</code>.
 *     
 *     "  hello  ".rstrip   #=> "  hello"
 *     "hello".rstrip!      #=> nil
 */

static VALUE
rb_str_rstrip_bang(VALUE str)
{
    rb_encoding *enc;
    char *s, *t, *e;
    int space_seen = Qfalse;

    rb_str_modify(str);
    enc = STR_ENC_GET(str);
    s = RSTRING_PTR(str);
    if (!s || RSTRING_LEN(str) == 0) return Qnil;
    t = e = RSTRING_END(str);
    while (s < e) {
        int cc = rb_enc_codepoint(s, e, enc);

        if (!cc || rb_enc_isspace(cc, enc)) {
            if (!space_seen) t = s;
            space_seen = Qtrue;
        }
        else {
            space_seen = Qfalse;
        }
        s += rb_enc_codelen(cc, enc);
    }
    if (!space_seen) t = s;
    if (t < e) {
        rb_str_modify(str);
        STR_SET_LEN(str, t-RSTRING_PTR(str));
        RSTRING_PTR(str)[RSTRING_LEN(str)] = '\0';
        return str;
    }
    return Qnil;
}


/*
 *  call-seq:
 *     str.rstrip   => new_str
 *  
 *  Returns a copy of <i>str</i> with trailing whitespace removed. See also
 *  <code>String#lstrip</code> and <code>String#strip</code>.
 *     
 *     "  hello  ".rstrip   #=> "  hello"
 *     "hello".rstrip       #=> "hello"
 */

static VALUE
rb_str_rstrip(VALUE str)
{
    str = rb_str_dup(str);
    rb_str_rstrip_bang(str);
    return str;
}


/*
 *  call-seq:
 *     str.strip!   => str or nil
 *  
 *  Removes leading and trailing whitespace from <i>str</i>. Returns
 *  <code>nil</code> if <i>str</i> was not altered.
 */

static VALUE
rb_str_strip_bang(VALUE str)
{
    VALUE l = rb_str_lstrip_bang(str);
    VALUE r = rb_str_rstrip_bang(str);

    if (NIL_P(l) && NIL_P(r)) return Qnil;
    return str;
}


/*
 *  call-seq:
 *     str.strip   => new_str
 *  
 *  Returns a copy of <i>str</i> with leading and trailing whitespace removed.
 *     
 *     "    hello    ".strip   #=> "hello"
 *     "\tgoodbye\r\n".strip   #=> "goodbye"
 */

static VALUE
rb_str_strip(VALUE str)
{
    str = rb_str_dup(str);
    rb_str_strip_bang(str);
    return str;
}

static VALUE
scan_once(VALUE str, VALUE pat, long *start)
{
    VALUE result, match;
    struct re_registers *regs;
    long i;

    if (rb_reg_search(pat, str, *start, 0) >= 0) {
        match = rb_backref_get();
        regs = RMATCH_REGS(match);
        if (BEG(0) == END(0)) {
            rb_encoding *enc = STR_ENC_GET(str);
            /*
             * Always consume at least one character of the input string
             */
            if (RSTRING_LEN(str) > END(0))
                *start = END(0)+rb_enc_mbclen(RSTRING_PTR(str)+END(0),
                                              RSTRING_END(str), enc);
            else
                *start = END(0)+1;
        }
        else {
            *start = END(0);
        }
        if (regs->num_regs == 1) {
            return rb_reg_nth_match(0, match);
        }
        result = rb_ary_new2(regs->num_regs);
        for (i=1; i < regs->num_regs; i++) {
            rb_ary_push(result, rb_reg_nth_match(i, match));
        }

        return result;
    }
    return Qnil;
}


/*
 *  call-seq:
 *     str.scan(pattern)                         => array
 *     str.scan(pattern) {|match, ...| block }   => str
 *  
 *  Both forms iterate through <i>str</i>, matching the pattern (which may be a
 *  <code>Regexp</code> or a <code>String</code>). For each match, a result is
 *  generated and either added to the result array or passed to the block. If
 *  the pattern contains no groups, each individual result consists of the
 *  matched string, <code>$&</code>.  If the pattern contains groups, each
 *  individual result is itself an array containing one entry per group.
 *     
 *     a = "cruel world"
 *     a.scan(/\w+/)        #=> ["cruel", "world"]
 *     a.scan(/.../)        #=> ["cru", "el ", "wor"]
 *     a.scan(/(...)/)      #=> [["cru"], ["el "], ["wor"]]
 *     a.scan(/(..)(..)/)   #=> [["cr", "ue"], ["l ", "wo"]]
 *     
 *  And the block form:
 *     
 *     a.scan(/\w+/) {|w| print "<<#{w}>> " }
 *     print "\n"
 *     a.scan(/(.)(.)/) {|x,y| print y, x }
 *     print "\n"
 *     
 *  <em>produces:</em>
 *     
 *     <<cruel>> <<world>>
 *     rceu lowlr
 */

static VALUE
rb_str_scan(VALUE str, VALUE pat)
{
    VALUE result;
    long start = 0;
    long last = -1, prev = 0;
    char *p = RSTRING_PTR(str); long len = RSTRING_LEN(str);

    pat = get_pat(pat, 1);
    if (!rb_block_given_p()) {
        VALUE ary = rb_ary_new();

        while (!NIL_P(result = scan_once(str, pat, &start))) {
            last = prev;
            prev = start;
            rb_ary_push(ary, result);
        }
        if (last >= 0) rb_reg_search(pat, str, last, 0);
        return ary;
    }

    while (!NIL_P(result = scan_once(str, pat, &start))) {
        last = prev;
        prev = start;
        rb_yield(result);
        str_mod_check(str, p, len);
    }
    if (last >= 0) rb_reg_search(pat, str, last, 0);
    return str;
}


/*
 *  call-seq:
 *     str.hex   => integer
 *  
 *  Treats leading characters from <i>str</i> as a string of hexadecimal digits
 *  (with an optional sign and an optional <code>0x</code>) and returns the
 *  corresponding number. Zero is returned on error.
 *     
 *     "0x0a".hex     #=> 10
 *     "-1234".hex    #=> -4660
 *     "0".hex        #=> 0
 *     "wombat".hex   #=> 0
 */

static VALUE
rb_str_hex(VALUE str)
{
    rb_encoding *enc = rb_enc_get(str);

    if (!rb_enc_asciicompat(enc)) {
        rb_raise(rb_eEncCompatError, "ASCII incompatible encoding: %s", rb_enc_name(enc));
    }
    return rb_str_to_inum(str, 16, Qfalse);
}


/*
 *  call-seq:
 *     str.oct   => integer
 *  
 *  Treats leading characters of <i>str</i> as a string of octal digits (with an
 *  optional sign) and returns the corresponding number.  Returns 0 if the
 *  conversion fails.
 *     
 *     "123".oct       #=> 83
 *     "-377".oct      #=> -255
 *     "bad".oct       #=> 0
 *     "0377bad".oct   #=> 255
 */

static VALUE
rb_str_oct(VALUE str)
{
    rb_encoding *enc = rb_enc_get(str);

    if (!rb_enc_asciicompat(enc)) {
        rb_raise(rb_eEncCompatError, "ASCII incompatible encoding: %s", rb_enc_name(enc));
    }
    return rb_str_to_inum(str, -8, Qfalse);
}


/*
 *  call-seq:
 *     str.crypt(other_str)   => new_str
 *  
 *  Applies a one-way cryptographic hash to <i>str</i> by invoking the standard
 *  library function <code>crypt</code>. The argument is the salt string, which
 *  should be two characters long, each character drawn from
 *  <code>[a-zA-Z0-9./]</code>.
 */

static VALUE
rb_str_crypt(VALUE str, VALUE salt)
{
    extern char *crypt(const char *, const char *);
    VALUE result;
    const char *s;

    StringValue(salt);
    if (RSTRING_LEN(salt) < 2)
        rb_raise(rb_eArgError, "salt too short (need >=2 bytes)");

    if (RSTRING_PTR(str)) s = RSTRING_PTR(str);
    else s = "";
    result = rb_str_new2(crypt(s, RSTRING_PTR(salt)));
    OBJ_INFECT(result, str);
    OBJ_INFECT(result, salt);
    return result;
}


/*
 *  call-seq:
 *     str.intern   => symbol
 *     str.to_sym   => symbol
 *  
 *  Returns the <code>Symbol</code> corresponding to <i>str</i>, creating the
 *  symbol if it did not previously exist. See <code>Symbol#id2name</code>.
 *     
 *     "Koala".intern         #=> :Koala
 *     s = 'cat'.to_sym       #=> :cat
 *     s == :cat              #=> true
 *     s = '@cat'.to_sym      #=> :@cat
 *     s == :@cat             #=> true
 *
 *  This can also be used to create symbols that cannot be represented using the
 *  <code>:xxx</code> notation.
 *     
 *     'cat and dog'.to_sym   #=> :"cat and dog"
 */

VALUE
rb_str_intern(VALUE s)
{
    VALUE str = RB_GC_GUARD(s);
    VALUE sym;
    ID id, id2;

    id = rb_intern_str(str);
    sym = ID2SYM(id);
    id2 = SYM2ID(sym);
    if (id != id2) {
        const char *name = rb_id2name(id2);

        if (name) {
            rb_raise(rb_eRuntimeError, "symbol table overflow (%s given for %s)",
                     name, RSTRING_PTR(str));
        }
        else {
            rb_raise(rb_eRuntimeError, "symbol table overflow (symbol %s)",
                     RSTRING_PTR(str));
        }
    }
    return sym;
}


/*
 *  call-seq:
 *     str.ord   => integer
 *  
 *  Return the <code>Integer</code> ordinal of a one-character string.
 *     
 *     "a".ord         #=> 97
 */

VALUE
rb_str_ord(VALUE s)
{
    int c;

    c = rb_enc_codepoint(RSTRING_PTR(s), RSTRING_END(s), STR_ENC_GET(s));
    return INT2NUM(c);
}
/*
 *  call-seq:
 *     str.sum(n=16)   => integer
 *  
 *  Returns a basic <em>n</em>-bit checksum of the characters in <i>str</i>,
 *  where <em>n</em> is the optional <code>Fixnum</code> parameter, defaulting
 *  to 16. The result is simply the sum of the binary value of each character in
 *  <i>str</i> modulo <code>2n - 1</code>. This is not a particularly good
 *  checksum.
 */

static VALUE
rb_str_sum(int argc, VALUE *argv, VALUE str)
{
    VALUE vbits;
    int bits;
    char *ptr, *p, *pend;
    long len;

    if (argc == 0) {
        bits = 16;
    }
    else {
        rb_scan_args(argc, argv, "01", &vbits);
        bits = NUM2INT(vbits);
    }
    ptr = p = RSTRING_PTR(str);
    len = RSTRING_LEN(str);
    pend = p + len;
    if (bits >= sizeof(long)*CHAR_BIT) {
        VALUE sum = INT2FIX(0);

        while (p < pend) {
            str_mod_check(str, ptr, len);
            sum = rb_funcall(sum, '+', 1, INT2FIX((unsigned char)*p));
            p++;
        }
        if (bits != 0) {
            VALUE mod;

            mod = rb_funcall(INT2FIX(1), rb_intern("<<"), 1, INT2FIX(bits));
            mod = rb_funcall(mod, '-', 1, INT2FIX(1));
            sum = rb_funcall(sum, '&', 1, mod);
        }
        return sum;
    }
    else {
       unsigned long sum = 0;

        while (p < pend) {
            str_mod_check(str, ptr, len);
            sum += (unsigned char)*p;
            p++;
        }
        if (bits != 0) {
           sum &= (((unsigned long)1)<<bits)-1;
        }
        return rb_int2inum(sum);
    }
}

static VALUE
rb_str_justify(int argc, VALUE *argv, VALUE str, char jflag)
{
    rb_encoding *enc;
    VALUE w;
    long width, len, flen = 1, fclen = 1;
    VALUE res;
    char *p;
    const char *f = " ";
    long n, llen, rlen;
    volatile VALUE pad;
    int singlebyte = 1;

    rb_scan_args(argc, argv, "11", &w, &pad);
    enc = STR_ENC_GET(str);
    width = NUM2LONG(w);
    if (argc == 2) {
        StringValue(pad);
        enc = rb_enc_check(str, pad);
        f = RSTRING_PTR(pad);
        flen = RSTRING_LEN(pad);
        fclen = str_strlen(pad, enc);
        singlebyte = single_byte_optimizable(pad);
        if (flen == 0 || fclen == 0) {
            rb_raise(rb_eArgError, "zero width padding");
        }
    }
    len = str_strlen(str, enc);
    if (width < 0 || len >= width) return rb_str_dup(str);
    n = width - len;
    llen = (jflag == 'l') ? 0 : ((jflag == 'r') ? n : n/2);
    rlen = n - llen;
    res = rb_str_new5(str, 0, RSTRING_LEN(str)+n*flen/fclen+2);
    p = RSTRING_PTR(res);
    while (llen) {
        if (flen <= 1) {
            *p++ = *f;
            llen--;
        }
        else if (llen > fclen) {
            memcpy(p,f,flen);
            p += flen;
            llen -= fclen;
        }
        else {
            char *fp = str_nth(f, f+flen, llen, enc, singlebyte);
            n = fp - f;
            memcpy(p,f,n);
            p+=n;
            break;
        }
    }
    memcpy(p, RSTRING_PTR(str), RSTRING_LEN(str));
    p+=RSTRING_LEN(str);
    while (rlen) {
        if (flen <= 1) {
            *p++ = *f;
            rlen--;
        }
        else if (rlen > fclen) {
            memcpy(p,f,flen);
            p += flen;
            rlen -= fclen;
        }
        else {
            char *fp = str_nth(f, f+flen, rlen, enc, singlebyte);
            n = fp - f;
            memcpy(p,f,n);
            p+=n;
            break;
        }
    }
    *p = '\0';
    STR_SET_LEN(res, p-RSTRING_PTR(res));
    OBJ_INFECT(res, str);
    if (!NIL_P(pad)) OBJ_INFECT(res, pad);
    rb_enc_associate(res, enc);
    return res;
}


/*
 *  call-seq:
 *     str.ljust(integer, padstr=' ')   => new_str
 *  
 *  If <i>integer</i> is greater than the length of <i>str</i>, returns a new
 *  <code>String</code> of length <i>integer</i> with <i>str</i> left justified
 *  and padded with <i>padstr</i>; otherwise, returns <i>str</i>.
 *     
 *     "hello".ljust(4)            #=> "hello"
 *     "hello".ljust(20)           #=> "hello               "
 *     "hello".ljust(20, '1234')   #=> "hello123412341234123"
 */

static VALUE
rb_str_ljust(int argc, VALUE *argv, VALUE str)
{
    return rb_str_justify(argc, argv, str, 'l');
}


/*
 *  call-seq:
 *     str.rjust(integer, padstr=' ')   => new_str
 *  
 *  If <i>integer</i> is greater than the length of <i>str</i>, returns a new
 *  <code>String</code> of length <i>integer</i> with <i>str</i> right justified
 *  and padded with <i>padstr</i>; otherwise, returns <i>str</i>.
 *     
 *     "hello".rjust(4)            #=> "hello"
 *     "hello".rjust(20)           #=> "               hello"
 *     "hello".rjust(20, '1234')   #=> "123412341234123hello"
 */

static VALUE
rb_str_rjust(int argc, VALUE *argv, VALUE str)
{
    return rb_str_justify(argc, argv, str, 'r');
}


/*
 *  call-seq:
 *     str.center(integer, padstr)   => new_str
 *  
 *  If <i>integer</i> is greater than the length of <i>str</i>, returns a new
 *  <code>String</code> of length <i>integer</i> with <i>str</i> centered and
 *  padded with <i>padstr</i>; otherwise, returns <i>str</i>.
 *     
 *     "hello".center(4)         #=> "hello"
 *     "hello".center(20)        #=> "       hello        "
 *     "hello".center(20, '123') #=> "1231231hello12312312"
 */

static VALUE
rb_str_center(int argc, VALUE *argv, VALUE str)
{
    return rb_str_justify(argc, argv, str, 'c');
}

/*
 *  call-seq:
 *     str.partition(sep)              => [head, sep, tail]
 *  
 *  Searches the string for <i>sep</i> and returns the part before
 *  it, the <i>sep</i>, and the part after it.  If <i>sep</i> is not found,
 *  returns <i>str</i> and two empty strings.
 *     
 *     "hello".partition("l")         #=> ["he", "l", "lo"]
 *     "hello".partition("x")         #=> ["hello", "", ""]
 */

static VALUE
rb_str_partition(VALUE str, VALUE sep)
{
    long pos;
    int regex = Qfalse;

    if (TYPE(sep) == T_REGEXP) {
        pos = rb_reg_search(sep, str, 0, 0);
        regex = Qtrue;
    }
    else {
        VALUE tmp;

        tmp = rb_check_string_type(sep);
        if (NIL_P(tmp)) {
            rb_raise(rb_eTypeError, "type mismatch: %s given",
                     rb_obj_classname(sep));
        }
        pos = rb_str_index(str, sep, 0);
    }
    if (pos < 0) {
      failed:
        return rb_ary_new3(3, str, rb_str_new(0,0),rb_str_new(0,0));
    }
    if (regex) {
        sep = rb_str_subpat(str, sep, 0);
        if (pos == 0 && RSTRING_LEN(sep) == 0) goto failed;
    }
    return rb_ary_new3(3, rb_str_subseq(str, 0, pos),
                          sep,
                          rb_str_subseq(str, pos+RSTRING_LEN(sep),
                                             RSTRING_LEN(str)-pos-RSTRING_LEN(sep)));
}

/*
 *  call-seq:
 *     str.rpartition(sep)            => [head, sep, tail]
 *  
 *  Searches <i>sep</i> in the string from the end of the string, and
 *  returns the part before it, the <i>sep</i>, and the part after it.
 *  If <i>sep</i> is not found, returns two empty strings and
 *  <i>str</i>.
 *     
 *     "hello".rpartition("l")         #=> ["hel", "l", "o"]
 *     "hello".rpartition("x")         #=> ["", "", "hello"]
 */

static VALUE
rb_str_rpartition(VALUE str, VALUE sep)
{
    long pos = RSTRING_LEN(str);
    int regex = Qfalse;

    if (TYPE(sep) == T_REGEXP) {
        pos = rb_reg_search(sep, str, pos, 1);
        regex = Qtrue;
    }
    else {
        VALUE tmp;

        tmp = rb_check_string_type(sep);
        if (NIL_P(tmp)) {
            rb_raise(rb_eTypeError, "type mismatch: %s given",
                     rb_obj_classname(sep));
        }
        pos = rb_str_sublen(str, pos);
        pos = rb_str_rindex(str, sep, pos);
    }
    if (pos < 0) {
        return rb_ary_new3(3, rb_str_new(0,0),rb_str_new(0,0), str);
    }
    if (regex) {
        sep = rb_reg_nth_match(0, rb_backref_get());
    }
    return rb_ary_new3(3, rb_str_substr(str, 0, pos),
                          sep,
                          rb_str_substr(str,pos+str_strlen(sep,STR_ENC_GET(sep)),RSTRING_LEN(str)));
}

/*
 *  call-seq:
 *     str.start_with?([prefix]+)   => true or false
 *  
 *  Returns true if <i>str</i> starts with the prefix given.
 */

static VALUE
rb_str_start_with(int argc, VALUE *argv, VALUE str)
{
    int i;

    for (i=0; i<argc; i++) {
        VALUE tmp = rb_check_string_type(argv[i]);
        if (NIL_P(tmp)) continue;
        rb_enc_check(str, tmp);
        if (RSTRING_LEN(str) < RSTRING_LEN(tmp)) continue;
        if (memcmp(RSTRING_PTR(str), RSTRING_PTR(tmp), RSTRING_LEN(tmp)) == 0)
            return Qtrue;
    }
    return Qfalse;
}

/*
 *  call-seq:
 *     str.end_with?([suffix]+)   => true or false
 *  
 *  Returns true if <i>str</i> ends with the suffix given.
 */

static VALUE
rb_str_end_with(int argc, VALUE *argv, VALUE str)
{
    int i;
    char *p, *s;
    rb_encoding *enc;

    for (i=0; i<argc; i++) {
        VALUE tmp = rb_check_string_type(argv[i]);
        if (NIL_P(tmp)) continue;
        enc = rb_enc_check(str, tmp);
        if (RSTRING_LEN(str) < RSTRING_LEN(tmp)) continue;
        p = RSTRING_PTR(str);
        s = p + RSTRING_LEN(str) - RSTRING_LEN(tmp);
        if (rb_enc_left_char_head(p, s, enc) != s)
            continue;
        if (memcmp(s, RSTRING_PTR(tmp), RSTRING_LEN(tmp)) == 0)
            return Qtrue;
    }
    return Qfalse;
}

void
rb_str_setter(VALUE val, ID id, VALUE *var)
{
    if (!NIL_P(val) && TYPE(val) != T_STRING) {
        rb_raise(rb_eTypeError, "value of %s must be String", rb_id2name(id));
    }
    *var = val;
}


/*
 *  call-seq:
 *     str.force_encoding(encoding)   => str
 *
 *  Changes the encoding to +encoding+ and returns self.
 */

static VALUE
rb_str_force_encoding(VALUE str, VALUE enc)
{
    str_modifiable(str);
    rb_enc_associate(str, rb_to_encoding(enc));
    return str;
}

/*
 *  call-seq:
 *     str.valid_encoding?  => true or false
 *  
 *  Returns true for a string which encoded correctly.
 *
 *    "\xc2\xa1".force_encoding("UTF-8").valid_encoding? => true
 *    "\xc2".force_encoding("UTF-8").valid_encoding? => false
 *    "\x80".force_encoding("UTF-8").valid_encoding? => false
 */

static VALUE
rb_str_valid_encoding_p(VALUE str)
{
    int cr = rb_enc_str_coderange(str);

    return cr == ENC_CODERANGE_BROKEN ? Qfalse : Qtrue;
}

/*
 *  call-seq:
 *     str.ascii_only?  => true or false
 *  
 *  Returns true for a string which has only ASCII characters.
 *
 *    "abc".force_encoding("UTF-8").ascii_only? => true
 *    "abc\u{6666}".force_encoding("UTF-8").ascii_only? => false
 */

static VALUE
rb_str_is_ascii_only_p(VALUE str)
{
    int cr = rb_enc_str_coderange(str);

    return cr == ENC_CODERANGE_7BIT ? Qtrue : Qfalse;
}

/**********************************************************************
 * Document-class: Symbol
 *
 *  <code>Symbol</code> objects represent names and some strings
 *  inside the Ruby
 *  interpreter. They are generated using the <code>:name</code> and
 *  <code>:"string"</code> literals
 *  syntax, and by the various <code>to_sym</code> methods. The same
 *  <code>Symbol</code> object will be created for a given name or string
 *  for the duration of a program's execution, regardless of the context
 *  or meaning of that name. Thus if <code>Fred</code> is a constant in
 *  one context, a method in another, and a class in a third, the
 *  <code>Symbol</code> <code>:Fred</code> will be the same object in
 *  all three contexts.
 *     
 *     module One
 *       class Fred
 *       end
 *       $f1 = :Fred
 *     end
 *     module Two
 *       Fred = 1
 *       $f2 = :Fred
 *     end
 *     def Fred()
 *     end
 *     $f3 = :Fred
 *     $f1.object_id   #=> 2514190
 *     $f2.object_id   #=> 2514190
 *     $f3.object_id   #=> 2514190
 *     
 */


/*
 *  call-seq:
 *     sym == obj   => true or false
 *  
 *  Equality---If <i>sym</i> and <i>obj</i> are exactly the same
 *  symbol, returns <code>true</code>. Otherwise, compares them
 *  as strings.
 */

static VALUE
sym_equal(VALUE sym1, VALUE sym2)
{
    if (sym1 == sym2) return Qtrue;
    return Qfalse;
}


/*
 *  call-seq:
 *     sym.inspect    => string
 *  
 *  Returns the representation of <i>sym</i> as a symbol literal.
 *     
 *     :fred.inspect   #=> ":fred"
 */

static VALUE
sym_inspect(VALUE sym)
{
    VALUE str;
    ID id = SYM2ID(sym);
    rb_encoding *enc;

    sym = rb_id2str(id);
    enc = STR_ENC_GET(sym);
    str = rb_enc_str_new(0, RSTRING_LEN(sym)+1, enc);
    RSTRING_PTR(str)[0] = ':';
    memcpy(RSTRING_PTR(str)+1, RSTRING_PTR(sym), RSTRING_LEN(sym));
    if (RSTRING_LEN(sym) != strlen(RSTRING_PTR(sym)) ||
        !rb_enc_symname_p(RSTRING_PTR(sym), enc)) {
        str = rb_str_inspect(str);
        strncpy(RSTRING_PTR(str), ":\"", 2);
    }
    return str;
}


/*
 *  call-seq:
 *     sym.id2name   => string
 *     sym.to_s      => string
 *  
 *  Returns the name or string corresponding to <i>sym</i>.
 *     
 *     :fred.id2name   #=> "fred"
 */


VALUE
rb_sym_to_s(VALUE sym)
{
    ID id = SYM2ID(sym);

    return str_new3(rb_cString, rb_id2str(id));
}


/*
 * call-seq:
 *   sym.to_sym   => sym
 *   sym.intern   => sym
 *
 * In general, <code>to_sym</code> returns the <code>Symbol</code> corresponding
 * to an object. As <i>sym</i> is already a symbol, <code>self</code> is returned
 * in this case.
 */

static VALUE
sym_to_sym(VALUE sym)
{
    return sym;
}

static VALUE
sym_call(VALUE args, VALUE sym, int argc, VALUE *argv)
{
    VALUE obj;

    if (argc < 1) {
        rb_raise(rb_eArgError, "no receiver given");
    }
    obj = argv[0];
    return rb_funcall3(obj, (ID)sym, argc - 1, argv + 1);
}

/*
 * call-seq:
 *   sym.to_proc
 *
 * Returns a _Proc_ object which respond to the given method by _sym_.
 *
 *   (1..3).collect(&:to_s)  #=> ["1", "2", "3"]
 */

static VALUE
sym_to_proc(VALUE sym)
{
    return rb_proc_new(sym_call, (VALUE)SYM2ID(sym));
}


static VALUE
sym_succ(VALUE sym)
{
    return rb_str_intern(rb_str_succ(rb_sym_to_s(sym)));
}

static VALUE
sym_cmp(VALUE sym, VALUE other)
{
    if (!SYMBOL_P(other)) {
        return Qnil;
    }
    return rb_str_cmp_m(rb_sym_to_s(sym), rb_sym_to_s(other));
}

static VALUE
sym_casecmp(VALUE sym, VALUE other)
{
    if (!SYMBOL_P(other)) {
        return Qnil;
    }
    return rb_str_casecmp(rb_sym_to_s(sym), rb_sym_to_s(other));
}

static VALUE
sym_match(VALUE sym, VALUE other)
{
    return rb_str_match(rb_sym_to_s(sym), other);
}

static VALUE
sym_eqq(VALUE sym, VALUE other)
{
    if (sym == other) return Qtrue;
    return rb_str_equal(rb_sym_to_s(sym), other);
}

static VALUE
sym_aref(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_aref_m(argc, argv, rb_sym_to_s(sym));
}

static VALUE
sym_length(VALUE sym)
{
    return rb_str_length(rb_id2str(SYM2ID(sym)));
}

static VALUE
sym_empty(VALUE sym)
{
    return rb_str_empty(rb_id2str(SYM2ID(sym)));
}

static VALUE
sym_upcase(VALUE sym)
{
    return rb_str_intern(rb_str_upcase(rb_id2str(SYM2ID(sym))));
}

static VALUE
sym_downcase(VALUE sym)
{
    return rb_str_intern(rb_str_downcase(rb_id2str(SYM2ID(sym))));
}

static VALUE
sym_capitalize(VALUE sym)
{
    return rb_str_intern(rb_str_capitalize(rb_id2str(SYM2ID(sym))));
}

static VALUE
sym_swapcase(VALUE sym)
{
    return rb_str_intern(rb_str_swapcase(rb_id2str(SYM2ID(sym))));
}

static VALUE
sym_encoding(VALUE sym)
{
    return rb_obj_encoding(rb_id2str(SYM2ID(sym)));
}

ID
rb_to_id(VALUE name)
{
    VALUE tmp;
    ID id;

    switch (TYPE(name)) {
      default:
        tmp = rb_check_string_type(name);
        if (NIL_P(tmp)) {
            rb_raise(rb_eTypeError, "%s is not a symbol",
                     RSTRING_PTR(rb_inspect(name)));
        }
        name = tmp;
        /* fall through */
      case T_STRING:
        name = rb_str_intern(name);
        /* fall through */
      case T_SYMBOL:
        return SYM2ID(name);
    }
    return id;
}

/*
 *  A <code>String</code> object holds and manipulates an arbitrary sequence of
 *  bytes, typically representing characters. String objects may be created
 *  using <code>String::new</code> or as literals.
 *     
 *  Because of aliasing issues, users of strings should be aware of the methods
 *  that modify the contents of a <code>String</code> object.  Typically,
 *  methods with names ending in ``!'' modify their receiver, while those
 *  without a ``!'' return a new <code>String</code>.  However, there are
 *  exceptions, such as <code>String#[]=</code>.
 *     
 */

void
Init_String(void)
{
#undef rb_intern
#define rb_intern(str) rb_intern_const(str)

    rb_cString  = rb_define_class("String", rb_cObject);
    rb_include_module(rb_cString, rb_mComparable);
    rb_define_alloc_func(rb_cString, str_alloc);
    rb_define_singleton_method(rb_cString, "try_convert", rb_str_s_try_convert, 1);
    rb_define_method(rb_cString, "initialize", rb_str_init, -1);
    rb_define_method(rb_cString, "initialize_copy", rb_str_replace, 1);
    rb_define_method(rb_cString, "<=>", rb_str_cmp_m, 1);
    rb_define_method(rb_cString, "==", rb_str_equal, 1);
    rb_define_method(rb_cString, "eql?", rb_str_eql, 1);
    rb_define_method(rb_cString, "hash", rb_str_hash_m, 0);
    rb_define_method(rb_cString, "casecmp", rb_str_casecmp, 1);
    rb_define_method(rb_cString, "+", rb_str_plus, 1);
    rb_define_method(rb_cString, "*", rb_str_times, 1);
    rb_define_method(rb_cString, "%", rb_str_format_m, 1);
    rb_define_method(rb_cString, "[]", rb_str_aref_m, -1);
    rb_define_method(rb_cString, "[]=", rb_str_aset_m, -1);
    rb_define_method(rb_cString, "insert", rb_str_insert, 2);
    rb_define_method(rb_cString, "length", rb_str_length, 0);
    rb_define_method(rb_cString, "size", rb_str_length, 0);
    rb_define_method(rb_cString, "bytesize", rb_str_bytesize, 0);
    rb_define_method(rb_cString, "empty?", rb_str_empty, 0);
    rb_define_method(rb_cString, "=~", rb_str_match, 1);
    rb_define_method(rb_cString, "match", rb_str_match_m, -1);
    rb_define_method(rb_cString, "succ", rb_str_succ, 0);
    rb_define_method(rb_cString, "succ!", rb_str_succ_bang, 0);
    rb_define_method(rb_cString, "next", rb_str_succ, 0);
    rb_define_method(rb_cString, "next!", rb_str_succ_bang, 0);
    rb_define_method(rb_cString, "upto", rb_str_upto, -1);
    rb_define_method(rb_cString, "index", rb_str_index_m, -1);
    rb_define_method(rb_cString, "rindex", rb_str_rindex_m, -1);
    rb_define_method(rb_cString, "replace", rb_str_replace, 1);
    rb_define_method(rb_cString, "clear", rb_str_clear, 0);
    rb_define_method(rb_cString, "chr", rb_str_chr, 0);
    rb_define_method(rb_cString, "getbyte", rb_str_getbyte, 1);
    rb_define_method(rb_cString, "setbyte", rb_str_setbyte, 2);

    rb_define_method(rb_cString, "to_i", rb_str_to_i, -1);
    rb_define_method(rb_cString, "to_f", rb_str_to_f, 0);
    rb_define_method(rb_cString, "to_s", rb_str_to_s, 0);
    rb_define_method(rb_cString, "to_str", rb_str_to_s, 0);
    rb_define_method(rb_cString, "inspect", rb_str_inspect, 0);
    rb_define_method(rb_cString, "dump", rb_str_dump, 0);

    rb_define_method(rb_cString, "upcase", rb_str_upcase, 0);
    rb_define_method(rb_cString, "downcase", rb_str_downcase, 0);
    rb_define_method(rb_cString, "capitalize", rb_str_capitalize, 0);
    rb_define_method(rb_cString, "swapcase", rb_str_swapcase, 0);

    rb_define_method(rb_cString, "upcase!", rb_str_upcase_bang, 0);
    rb_define_method(rb_cString, "downcase!", rb_str_downcase_bang, 0);
    rb_define_method(rb_cString, "capitalize!", rb_str_capitalize_bang, 0);
    rb_define_method(rb_cString, "swapcase!", rb_str_swapcase_bang, 0);

    rb_define_method(rb_cString, "hex", rb_str_hex, 0);
    rb_define_method(rb_cString, "oct", rb_str_oct, 0);
    rb_define_method(rb_cString, "split", rb_str_split_m, -1);
    rb_define_method(rb_cString, "lines", rb_str_each_line, -1);
    rb_define_method(rb_cString, "bytes", rb_str_each_byte, 0);
    rb_define_method(rb_cString, "chars", rb_str_each_char, 0);
    rb_define_method(rb_cString, "reverse", rb_str_reverse, 0);
    rb_define_method(rb_cString, "reverse!", rb_str_reverse_bang, 0);
    rb_define_method(rb_cString, "concat", rb_str_concat, 1);
    rb_define_method(rb_cString, "<<", rb_str_concat, 1);
    rb_define_method(rb_cString, "crypt", rb_str_crypt, 1);
    rb_define_method(rb_cString, "intern", rb_str_intern, 0);
    rb_define_method(rb_cString, "to_sym", rb_str_intern, 0);
    rb_define_method(rb_cString, "ord", rb_str_ord, 0);

    rb_define_method(rb_cString, "include?", rb_str_include, 1);
    rb_define_method(rb_cString, "start_with?", rb_str_start_with, -1);
    rb_define_method(rb_cString, "end_with?", rb_str_end_with, -1);

    rb_define_method(rb_cString, "scan", rb_str_scan, 1);

    rb_define_method(rb_cString, "ljust", rb_str_ljust, -1);
    rb_define_method(rb_cString, "rjust", rb_str_rjust, -1);
    rb_define_method(rb_cString, "center", rb_str_center, -1);

    rb_define_method(rb_cString, "sub", rb_str_sub, -1);
    rb_define_method(rb_cString, "gsub", rb_str_gsub, -1);
    rb_define_method(rb_cString, "chop", rb_str_chop, 0);
    rb_define_method(rb_cString, "chomp", rb_str_chomp, -1);
    rb_define_method(rb_cString, "strip", rb_str_strip, 0);
    rb_define_method(rb_cString, "lstrip", rb_str_lstrip, 0);
    rb_define_method(rb_cString, "rstrip", rb_str_rstrip, 0);

    rb_define_method(rb_cString, "sub!", rb_str_sub_bang, -1);
    rb_define_method(rb_cString, "gsub!", rb_str_gsub_bang, -1);
    rb_define_method(rb_cString, "chop!", rb_str_chop_bang, 0);
    rb_define_method(rb_cString, "chomp!", rb_str_chomp_bang, -1);
    rb_define_method(rb_cString, "strip!", rb_str_strip_bang, 0);
    rb_define_method(rb_cString, "lstrip!", rb_str_lstrip_bang, 0);
    rb_define_method(rb_cString, "rstrip!", rb_str_rstrip_bang, 0);

    rb_define_method(rb_cString, "tr", rb_str_tr, 2);
    rb_define_method(rb_cString, "tr_s", rb_str_tr_s, 2);
    rb_define_method(rb_cString, "delete", rb_str_delete, -1);
    rb_define_method(rb_cString, "squeeze", rb_str_squeeze, -1);
    rb_define_method(rb_cString, "count", rb_str_count, -1);

    rb_define_method(rb_cString, "tr!", rb_str_tr_bang, 2);
    rb_define_method(rb_cString, "tr_s!", rb_str_tr_s_bang, 2);
    rb_define_method(rb_cString, "delete!", rb_str_delete_bang, -1);
    rb_define_method(rb_cString, "squeeze!", rb_str_squeeze_bang, -1);

    rb_define_method(rb_cString, "each_line", rb_str_each_line, -1);
    rb_define_method(rb_cString, "each_byte", rb_str_each_byte, 0);
    rb_define_method(rb_cString, "each_char", rb_str_each_char, 0);

    rb_define_method(rb_cString, "sum", rb_str_sum, -1);

    rb_define_method(rb_cString, "slice", rb_str_aref_m, -1);
    rb_define_method(rb_cString, "slice!", rb_str_slice_bang, -1);

    rb_define_method(rb_cString, "partition", rb_str_partition, 1);
    rb_define_method(rb_cString, "rpartition", rb_str_rpartition, 1);

    rb_define_method(rb_cString, "encoding", rb_obj_encoding, 0); /* in encoding.c */
    rb_define_method(rb_cString, "force_encoding", rb_str_force_encoding, 1);
    rb_define_method(rb_cString, "valid_encoding?", rb_str_valid_encoding_p, 0);
    rb_define_method(rb_cString, "ascii_only?", rb_str_is_ascii_only_p, 0);

    id_to_s = rb_intern("to_s");

    rb_fs = Qnil;
    rb_define_variable("$;", &rb_fs);
    rb_define_variable("$-F", &rb_fs);

    rb_cSymbol = rb_define_class("Symbol", rb_cObject);
    rb_include_module(rb_cSymbol, rb_mComparable);
    rb_undef_alloc_func(rb_cSymbol);
    rb_undef_method(CLASS_OF(rb_cSymbol), "new");
    rb_define_singleton_method(rb_cSymbol, "all_symbols", rb_sym_all_symbols, 0); /* in parse.y */

    rb_define_method(rb_cSymbol, "==", sym_equal, 1);
    rb_define_method(rb_cSymbol, "inspect", sym_inspect, 0);
    rb_define_method(rb_cSymbol, "to_s", rb_sym_to_s, 0);
    rb_define_method(rb_cSymbol, "id2name", rb_sym_to_s, 0);
    rb_define_method(rb_cSymbol, "intern", sym_to_sym, 0);
    rb_define_method(rb_cSymbol, "to_sym", sym_to_sym, 0);
    rb_define_method(rb_cSymbol, "to_proc", sym_to_proc, 0);
    rb_define_method(rb_cSymbol, "succ", sym_succ, 0);
    rb_define_method(rb_cSymbol, "next", sym_succ, 0);

    rb_define_method(rb_cSymbol, "<=>", sym_cmp, 1);
    rb_define_method(rb_cSymbol, "casecmp", sym_casecmp, 1);
    rb_define_method(rb_cSymbol, "=~", sym_match, 1);
    rb_define_method(rb_cSymbol, "===", sym_eqq, 1);

    rb_define_method(rb_cSymbol, "[]", sym_aref, -1);
    rb_define_method(rb_cSymbol, "slice", sym_aref, -1);
    rb_define_method(rb_cSymbol, "length", sym_length, 0);
    rb_define_method(rb_cSymbol, "size", sym_length, 0);
    rb_define_method(rb_cSymbol, "empty?", sym_empty, 0);
    rb_define_method(rb_cSymbol, "match", sym_match, 1);

    rb_define_method(rb_cSymbol, "upcase", sym_upcase, 0);
    rb_define_method(rb_cSymbol, "downcase", sym_downcase, 0);
    rb_define_method(rb_cSymbol, "capitalize", sym_capitalize, 0);
    rb_define_method(rb_cSymbol, "swapcase", sym_swapcase, 0);

    rb_define_method(rb_cSymbol, "encoding", sym_encoding, 0);
}