Cygwin: mmap: allow remapping part of an existing anonymous mapping

[newlib-cygwin.git] / newlib / libc / posix / regcomp.c

/*-
 * Copyright (c) 1992, 1993, 1994 Henry Spencer.
 * Copyright (c) 1992, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Henry Spencer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)regcomp.c   8.5 (Berkeley) 3/20/94
 */

#ifndef _NO_REGEX

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)regcomp.c   8.5 (Berkeley) 3/20/94";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>

#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <stdlib.h>
#include <regex.h>

#include "collate.h"

#include "utils.h"
#include "regex2.h"

#include "cclass.h"
#include "cname.h"

/*
 * parse structure, passed up and down to avoid global variables and
 * other clumsinesses
 */
struct parse {
        char *next;             /* next character in RE */
        char *end;              /* end of string (-> NUL normally) */
        int error;              /* has an error been seen? */
        sop *strip;             /* malloced strip */
        sopno ssize;            /* malloced strip size (allocated) */
        sopno slen;             /* malloced strip length (used) */
        int ncsalloc;           /* number of csets allocated */
        struct re_guts *g;
#       define  NPAREN  10      /* we need to remember () 1-9 for back refs */
        sopno pbegin[NPAREN];   /* -> ( ([0] unused) */
        sopno pend[NPAREN];     /* -> ) ([0] unused) */
};

/* ========= begin header generated by ./mkh ========= */
#ifdef __cplusplus
extern "C" {
#endif

/* === regcomp.c === */
static void p_ere(struct parse *p, int stop);
static void p_ere_exp(struct parse *p);
static void p_str(struct parse *p);
static void p_bre(struct parse *p, int end1, int end2);
static int p_simp_re(struct parse *p, int starordinary);
static int p_count(struct parse *p);
static void p_bracket(struct parse *p);
static void p_b_term(struct parse *p, cset *cs);
static void p_b_cclass(struct parse *p, cset *cs);
static void p_b_eclass(struct parse *p, cset *cs);
static char p_b_symbol(struct parse *p);
static char p_b_coll_elem(struct parse *p, int endc);
static char othercase(int ch);
static void bothcases(struct parse *p, int ch);
static void ordinary(struct parse *p, int ch);
static void nonnewline(struct parse *p);
static void repeat(struct parse *p, sopno start, int from, int to);
static int seterr(struct parse *p, int e);
static cset *allocset(struct parse *p);
static void freeset(struct parse *p, cset *cs);
static int freezeset(struct parse *p, cset *cs);
static int firstch(struct parse *p, cset *cs);
static int nch(struct parse *p, cset *cs);
#if used
static void mcadd(struct parse *p, cset *cs, char *cp);
static void mcsub(cset *cs, char *cp);
static int mcin(cset *cs, char *cp);
static char *mcfind(cset *cs, char *cp);
#endif
static void mcinvert(struct parse *p, cset *cs);
static void mccase(struct parse *p, cset *cs);
static int isinsets(struct re_guts *g, int c);
static int samesets(struct re_guts *g, int c1, int c2);
static void categorize(struct parse *p, struct re_guts *g);
static sopno dupl(struct parse *p, sopno start, sopno finish);
static void doemit(struct parse *p, sop op, size_t opnd);
static void doinsert(struct parse *p, sop op, size_t opnd, sopno pos);
static void dofwd(struct parse *p, sopno pos, sop value);
static void enlarge(struct parse *p, sopno size);
static void stripsnug(struct parse *p, struct re_guts *g);
static void findmust(struct parse *p, struct re_guts *g);
static int altoffset(sop *scan, int offset, int mccs);
static void computejumps(struct parse *p, struct re_guts *g);
static void computematchjumps(struct parse *p, struct re_guts *g);
static sopno pluscount(struct parse *p, struct re_guts *g);

#ifdef __cplusplus
}
#endif
/* ========= end header generated by ./mkh ========= */

static char nuls[10];           /* place to point scanner in event of error */

/*
 * macros for use with parse structure
 * BEWARE:  these know that the parse structure is named `p' !!!
 */
#define PEEK()  (*p->next)
#define PEEK2() (*(p->next+1))
#define MORE()  (p->next < p->end)
#define MORE2() (p->next+1 < p->end)
#define SEE(c)  (MORE() && PEEK() == (c))
#define SEETWO(a, b)    (MORE() && MORE2() && PEEK() == (a) && PEEK2() == (b))
#define EAT(c)  ((SEE(c)) ? (NEXT(), 1) : 0)
#define EATTWO(a, b)    ((SEETWO(a, b)) ? (NEXT2(), 1) : 0)
#define NEXT()  (p->next++)
#define NEXT2() (p->next += 2)
#define NEXTn(n)        (p->next += (n))
#define GETNEXT()       (*p->next++)
#define SETERROR(e)     seterr(p, (e))
#define REQUIRE(co, e)  ((co) || SETERROR(e))
#define MUSTSEE(c, e)   (REQUIRE(MORE() && PEEK() == (c), e))
#define MUSTEAT(c, e)   (REQUIRE(MORE() && GETNEXT() == (c), e))
#define MUSTNOTSEE(c, e)        (REQUIRE(!MORE() || PEEK() != (c), e))
#define EMIT(op, sopnd) doemit(p, (sop)(op), (size_t)(sopnd))
#define INSERT(op, pos) doinsert(p, (sop)(op), HERE()-(pos)+1, pos)
#define AHEAD(pos)              dofwd(p, pos, HERE()-(pos))
#define ASTERN(sop, pos)        EMIT(sop, HERE()-pos)
#define HERE()          (p->slen)
#define THERE()         (p->slen - 1)
#define THERETHERE()    (p->slen - 2)
#define DROP(n) (p->slen -= (n))

#ifndef NDEBUG
static int never = 0;           /* for use in asserts; shuts lint up */
#else
#define never   0               /* some <assert.h>s have bugs too */
#endif

/* Macro used by computejump()/computematchjump() */
#define MIN(a,b)        ((a)<(b)?(a):(b))

/*
 - regcomp - interface for parser and compilation
 = extern int regcomp(regex_t *__restrict, const char *__restrict, int);
 = #define      REG_BASIC       0000
 = #define      REG_EXTENDED    0001
 = #define      REG_ICASE       0002
 = #define      REG_NOSUB       0004
 = #define      REG_NEWLINE     0010
 = #define      REG_NOSPEC      0020
 = #define      REG_PEND        0040
 = #define      REG_DUMP        0200
 */
int                             /* 0 success, otherwise REG_something */
regcomp(preg, pattern, cflags)
regex_t *__restrict preg;
const char *__restrict pattern;
int cflags;
{
        struct parse pa;
        struct re_guts *g;
        struct parse *p = &pa;
        int i;
        size_t len;
#ifdef REDEBUG
#       define  GOODFLAGS(f)    (f)
#else
#       define  GOODFLAGS(f)    ((f)&~REG_DUMP)
#endif

        cflags = GOODFLAGS(cflags);
        if ((cflags&REG_EXTENDED) && (cflags&REG_NOSPEC))
                return(REG_INVARG);

        if (cflags&REG_PEND) {
                if (preg->re_endp < pattern)
                        return(REG_INVARG);
                len = preg->re_endp - pattern;
        } else
                len = strlen((char *)pattern);

        /* do the mallocs early so failure handling is easy */
        g = (struct re_guts *)malloc(sizeof(struct re_guts) +
                                                        (NC-1)*sizeof(cat_t));
        if (g == NULL)
                return(REG_ESPACE);
        p->ssize = len/(size_t)2*(size_t)3 + (size_t)1; /* ugh */
        p->strip = (sop *)malloc(p->ssize * sizeof(sop));
        p->slen = 0;
        if (p->strip == NULL) {
                free((char *)g);
                return(REG_ESPACE);
        }

        /* set things up */
        p->g = g;
        p->next = (char *)pattern;      /* convenience; we do not modify it */
        p->end = p->next + len;
        p->error = 0;
        p->ncsalloc = 0;
        for (i = 0; i < NPAREN; i++) {
                p->pbegin[i] = 0;
                p->pend[i] = 0;
        }
        g->csetsize = NC;
        g->sets = NULL;
        g->setbits = NULL;
        g->ncsets = 0;
        g->cflags = cflags;
        g->iflags = 0;
        g->nbol = 0;
        g->neol = 0;
        g->must = NULL;
        g->moffset = -1;
        g->charjump = NULL;
        g->matchjump = NULL;
        g->mlen = 0;
        g->nsub = 0;
        g->ncategories = 1;     /* category 0 is "everything else" */
        g->categories = &g->catspace[-(CHAR_MIN)];
        (void) memset((char *)g->catspace, 0, NC*sizeof(cat_t));
        g->backrefs = 0;

        /* do it */
        EMIT(OEND, 0);
        g->firststate = THERE();
        if (cflags&REG_EXTENDED)
                p_ere(p, OUT);
        else if (cflags&REG_NOSPEC)
                p_str(p);
        else
                p_bre(p, OUT, OUT);
        EMIT(OEND, 0);
        g->laststate = THERE();

        /* tidy up loose ends and fill things in */
        categorize(p, g);
        stripsnug(p, g);
        findmust(p, g);
        /* only use Boyer-Moore algorithm if the pattern is bigger
         * than three characters
         */
        if(g->mlen > 3) {
                computejumps(p, g);
                computematchjumps(p, g);
                if(g->matchjump == NULL && g->charjump != NULL) {
                        free(g->charjump);
                        g->charjump = NULL;
                }
        }
        g->nplus = pluscount(p, g);
        g->magic = MAGIC2;
        preg->re_nsub = g->nsub;
        preg->re_g = g;
        preg->re_magic = MAGIC1;
#ifndef REDEBUG
        /* not debugging, so can't rely on the assert() in regexec() */
        if (g->iflags&BAD)
                SETERROR(REG_ASSERT);
#endif

        /* win or lose, we're done */
        if (p->error != 0)      /* lose */
                regfree(preg);
        return(p->error);
}

/*
 - p_ere - ERE parser top level, concatenation and alternation
 == static void p_ere(struct parse *p, int stop);
 */
static void
p_ere(
        struct parse *p,
        int stop                        /* character this ERE should end at */
)
{
        char c;
        sopno prevback = 0;
        sopno prevfwd = 0;
        sopno conc;
        int first = 1;          /* is this the first alternative? */

        for (;;) {
                /* do a bunch of concatenated expressions */
                conc = HERE();
                while (MORE() && (c = PEEK()) != '|' && c != stop)
                        p_ere_exp(p);
                (void)REQUIRE(HERE() != conc, REG_EMPTY);       /* require nonempty */

                if (!EAT('|'))
                        break;          /* NOTE BREAK OUT */

                if (first) {
                        INSERT(OCH_, conc);     /* offset is wrong */
                        prevfwd = conc;
                        prevback = conc;
                        first = 0;
                }
                ASTERN(OOR1, prevback);
                prevback = THERE();
                AHEAD(prevfwd);                 /* fix previous offset */
                prevfwd = HERE();
                EMIT(OOR2, 0);                  /* offset is very wrong */
        }

        if (!first) {           /* tail-end fixups */
                AHEAD(prevfwd);
                ASTERN(O_CH, prevback);
        }

        assert(!MORE() || SEE(stop));
}

/*
 - p_ere_exp - parse one subERE, an atom possibly followed by a repetition op
 == static void p_ere_exp(struct parse *p);
 */
static void
p_ere_exp(struct parse *p)
{
        char c;
        sopno pos;
        int count;
        int count2;
        sopno subno;
        int wascaret = 0;

        assert(MORE());         /* caller should have ensured this */
        c = GETNEXT();

        pos = HERE();
        switch (c) {
        case '(':
                (void)REQUIRE(MORE(), REG_EPAREN);
                p->g->nsub++;
                subno = p->g->nsub;
                if (subno < NPAREN)
                        p->pbegin[subno] = HERE();
                EMIT(OLPAREN, subno);
                if (!SEE(')'))
                        p_ere(p, ')');
                if (subno < NPAREN) {
                        p->pend[subno] = HERE();
                        assert(p->pend[subno] != 0);
                }
                EMIT(ORPAREN, subno);
                (void)MUSTEAT(')', REG_EPAREN);
                break;
#ifndef POSIX_MISTAKE
        case ')':               /* happens only if no current unmatched ( */
                /*
                 * You may ask, why the ifndef?  Because I didn't notice
                 * this until slightly too late for 1003.2, and none of the
                 * other 1003.2 regular-expression reviewers noticed it at
                 * all.  So an unmatched ) is legal POSIX, at least until
                 * we can get it fixed.
                 */
                SETERROR(REG_EPAREN);
                break;
#endif
        case '^':
                EMIT(OBOL, 0);
                p->g->iflags |= USEBOL;
                p->g->nbol++;
                wascaret = 1;
                break;
        case '$':
                EMIT(OEOL, 0);
                p->g->iflags |= USEEOL;
                p->g->neol++;
                break;
        case '|':
                SETERROR(REG_EMPTY);
                break;
        case '*':
        case '+':
        case '?':
                SETERROR(REG_BADRPT);
                break;
        case '.':
                if (p->g->cflags&REG_NEWLINE)
                        nonnewline(p);
                else
                        EMIT(OANY, 0);
                break;
        case '[':
                p_bracket(p);
                break;
        case '\\':
                (void)REQUIRE(MORE(), REG_EESCAPE);
                c = GETNEXT();
                ordinary(p, c);
                break;
        case '{':               /* okay as ordinary except if digit follows */
                (void)REQUIRE(!MORE() || !isdigit((uch)PEEK()), REG_BADRPT);
                /* FALLTHROUGH */
        default:
                ordinary(p, c);
                break;
        }

        if (!MORE())
                return;
        c = PEEK();
        /* we call { a repetition if followed by a digit */
        if (!( c == '*' || c == '+' || c == '?' ||
                                (c == '{' && MORE2() && isdigit((uch)PEEK2())) ))
                return;         /* no repetition, we're done */
        NEXT();

        (void)REQUIRE(!wascaret, REG_BADRPT);
        switch (c) {
        case '*':       /* implemented as +? */
                /* this case does not require the (y|) trick, noKLUDGE */
                INSERT(OPLUS_, pos);
                ASTERN(O_PLUS, pos);
                INSERT(OQUEST_, pos);
                ASTERN(O_QUEST, pos);
                break;
        case '+':
                INSERT(OPLUS_, pos);
                ASTERN(O_PLUS, pos);
                break;
        case '?':
                /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
                INSERT(OCH_, pos);              /* offset slightly wrong */
                ASTERN(OOR1, pos);              /* this one's right */
                AHEAD(pos);                     /* fix the OCH_ */
                EMIT(OOR2, 0);                  /* offset very wrong... */
                AHEAD(THERE());                 /* ...so fix it */
                ASTERN(O_CH, THERETHERE());
                break;
        case '{':
                count = p_count(p);
                if (EAT(',')) {
                        if (isdigit((uch)PEEK())) {
                                count2 = p_count(p);
                                (void)REQUIRE(count <= count2, REG_BADBR);
                        } else          /* single number with comma */
                                count2 = INFINITY;
                } else          /* just a single number */
                        count2 = count;
                repeat(p, pos, count, count2);
                if (!EAT('}')) {        /* error heuristics */
                        while (MORE() && PEEK() != '}')
                                NEXT();
                        (void)REQUIRE(MORE(), REG_EBRACE);
                        SETERROR(REG_BADBR);
                }
                break;
        }

        if (!MORE())
                return;
        c = PEEK();
        if (!( c == '*' || c == '+' || c == '?' ||
                                (c == '{' && MORE2() && isdigit((uch)PEEK2())) ) )
                return;
        SETERROR(REG_BADRPT);
}

/*
 - p_str - string (no metacharacters) "parser"
 == static void p_str(struct parse *p);
 */
static void
p_str(struct parse *p)
{
        (void)REQUIRE(MORE(), REG_EMPTY);
        while (MORE())
                ordinary(p, GETNEXT());
}

/*
 - p_bre - BRE parser top level, anchoring and concatenation
 == static void p_bre(struct parse *p, int end1, \
 ==     int end2);
 * Giving end1 as OUT essentially eliminates the end1/end2 check.
 *
 * This implementation is a bit of a kludge, in that a trailing $ is first
 * taken as an ordinary character and then revised to be an anchor.  The
 * only undesirable side effect is that '$' gets included as a character
 * category in such cases.  This is fairly harmless; not worth fixing.
 * The amount of lookahead needed to avoid this kludge is excessive.
 */
static void
p_bre(
        struct parse *p,
        int end1,                       /* first terminating character */
        int end2                        /* second terminating character */
)
{
        sopno start = HERE();
        int first = 1;                  /* first subexpression? */
        int wasdollar = 0;

        if (EAT('^')) {
                EMIT(OBOL, 0);
                p->g->iflags |= USEBOL;
                p->g->nbol++;
        }
        while (MORE() && !SEETWO(end1, end2)) {
                wasdollar = p_simp_re(p, first);
                first = 0;
        }
        if (wasdollar) {        /* oops, that was a trailing anchor */
                DROP(1);
                EMIT(OEOL, 0);
                p->g->iflags |= USEEOL;
                p->g->neol++;
        }

        (void)REQUIRE(HERE() != start, REG_EMPTY);      /* require nonempty */
}

/*
 - p_simp_re - parse a simple RE, an atom possibly followed by a repetition
 == static int p_simp_re(struct parse *p, int starordinary);
 */
static int                      /* was the simple RE an unbackslashed $? */
p_simp_re(
        struct parse *p,
        int starordinary                /* is a leading * an ordinary character? */
)
{
        int c;
        int count;
        int count2;
        sopno pos;
        int i;
        sopno subno;
#       define  BACKSL  (1<<CHAR_BIT)

        pos = HERE();           /* repetion op, if any, covers from here */

        assert(MORE());         /* caller should have ensured this */
        c = GETNEXT();
        if (c == '\\') {
                (void)REQUIRE(MORE(), REG_EESCAPE);
                c = BACKSL | GETNEXT();
        }
        switch (c) {
        case '.':
                if (p->g->cflags&REG_NEWLINE)
                        nonnewline(p);
                else
                        EMIT(OANY, 0);
                break;
        case '[':
                p_bracket(p);
                break;
        case BACKSL|'{':
                SETERROR(REG_BADRPT);
                break;
        case BACKSL|'(':
                p->g->nsub++;
                subno = p->g->nsub;
                if (subno < NPAREN)
                        p->pbegin[subno] = HERE();
                EMIT(OLPAREN, subno);
                /* the MORE here is an error heuristic */
                if (MORE() && !SEETWO('\\', ')'))
                        p_bre(p, '\\', ')');
                if (subno < NPAREN) {
                        p->pend[subno] = HERE();
                        assert(p->pend[subno] != 0);
                }
                EMIT(ORPAREN, subno);
                (void)REQUIRE(EATTWO('\\', ')'), REG_EPAREN);
                break;
        case BACKSL|')':        /* should not get here -- must be user */
        case BACKSL|'}':
                SETERROR(REG_EPAREN);
                break;
        case BACKSL|'1':
        case BACKSL|'2':
        case BACKSL|'3':
        case BACKSL|'4':
        case BACKSL|'5':
        case BACKSL|'6':
        case BACKSL|'7':
        case BACKSL|'8':
        case BACKSL|'9':
                i = (c&~BACKSL) - '0';
                assert(i < NPAREN);
                if (p->pend[i] != 0) {
                        assert(i <= p->g->nsub);
                        EMIT(OBACK_, i);
                        assert(p->pbegin[i] != 0);
                        assert(OP(p->strip[p->pbegin[i]]) == OLPAREN);
                        assert(OP(p->strip[p->pend[i]]) == ORPAREN);
                        (void) dupl(p, p->pbegin[i]+1, p->pend[i]);
                        EMIT(O_BACK, i);
                } else
                        SETERROR(REG_ESUBREG);
                p->g->backrefs = 1;
                break;
        case '*':
                (void)REQUIRE(starordinary, REG_BADRPT);
                /* FALLTHROUGH */
        default:
                ordinary(p, (char)c);
                break;
        }

        if (EAT('*')) {         /* implemented as +? */
                /* this case does not require the (y|) trick, noKLUDGE */
                INSERT(OPLUS_, pos);
                ASTERN(O_PLUS, pos);
                INSERT(OQUEST_, pos);
                ASTERN(O_QUEST, pos);
        } else if (EATTWO('\\', '{')) {
                count = p_count(p);
                if (EAT(',')) {
                        if (MORE() && isdigit((uch)PEEK())) {
                                count2 = p_count(p);
                                (void)REQUIRE(count <= count2, REG_BADBR);
                        } else          /* single number with comma */
                                count2 = INFINITY;
                } else          /* just a single number */
                        count2 = count;
                repeat(p, pos, count, count2);
                if (!EATTWO('\\', '}')) {       /* error heuristics */
                        while (MORE() && !SEETWO('\\', '}'))
                                NEXT();
                        (void)REQUIRE(MORE(), REG_EBRACE);
                        SETERROR(REG_BADBR);
                }
        } else if (c == '$')     /* $ (but not \$) ends it */
                return(1);

        return(0);
}

/*
 - p_count - parse a repetition count
 == static int p_count(struct parse *p);
 */
static int                      /* the value */
p_count(struct parse *p)
{
        int count = 0;
        int ndigits = 0;

        while (MORE() && isdigit((uch)PEEK()) && count <= DUPMAX) {
                count = count*10 + (GETNEXT() - '0');
                ndigits++;
        }

        (void)REQUIRE(ndigits > 0 && count <= DUPMAX, REG_BADBR);
        return(count);
}

/*
 - p_bracket - parse a bracketed character list
 == static void p_bracket(struct parse *p);
 *
 * Note a significant property of this code:  if the allocset() did SETERROR,
 * no set operations are done.
 */
static void
p_bracket(struct parse *p)
{
        cset *cs = allocset(p);
        int invert = 0;

        /* Dept of Truly Sickening Special-Case Kludges */
        if (p->next + 5 < p->end && strncmp(p->next, "[:<:]]", 6) == 0) {
                EMIT(OBOW, 0);
                NEXTn(6);
                return;
        }
        if (p->next + 5 < p->end && strncmp(p->next, "[:>:]]", 6) == 0) {
                EMIT(OEOW, 0);
                NEXTn(6);
                return;
        }

        if (EAT('^'))
                invert++;       /* make note to invert set at end */
        if (EAT(']'))
                CHadd(cs, ']');
        else if (EAT('-'))
                CHadd(cs, '-');
        while (MORE() && PEEK() != ']' && !SEETWO('-', ']'))
                p_b_term(p, cs);
        if (EAT('-'))
                CHadd(cs, '-');
        (void)MUSTEAT(']', REG_EBRACK);

        if (p->error != 0)      /* don't mess things up further */
                return;

        if (p->g->cflags&REG_ICASE) {
                int i;
                int ci;

                for (i = p->g->csetsize - 1; i >= 0; i--)
                        if (CHIN(cs, i) && isalpha(i)) {
                                ci = othercase(i);
                                if (ci != i)
                                        CHadd(cs, ci);
                        }
                if (cs->multis != NULL)
                        mccase(p, cs);
        }
        if (invert) {
                int i;

                for (i = p->g->csetsize - 1; i >= 0; i--)
                        if (CHIN(cs, i))
                                CHsub(cs, i);
                        else
                                CHadd(cs, i);
                if (p->g->cflags&REG_NEWLINE)
                        CHsub(cs, '\n');
                if (cs->multis != NULL)
                        mcinvert(p, cs);
        }

        assert(cs->multis == NULL);             /* xxx */

        if (nch(p, cs) == 1) {          /* optimize singleton sets */
                ordinary(p, firstch(p, cs));
                freeset(p, cs);
        } else
                EMIT(OANYOF, freezeset(p, cs));
}

/*
 - p_b_term - parse one term of a bracketed character list
 == static void p_b_term(struct parse *p, cset *cs);
 */
static void
p_b_term(
        struct parse *p,
        cset *cs
)
{
        char c;
        char start, finish;
        int i;

        /* classify what we've got */
        switch ((MORE()) ? PEEK() : '\0') {
        case '[':
                c = (MORE2()) ? PEEK2() : '\0';
                break;
        case '-':
                SETERROR(REG_ERANGE);
                return;                 /* NOTE RETURN */
                break;
        default:
                c = '\0';
                break;
        }

        switch (c) {
        case ':':               /* character class */
                NEXT2();
                (void)REQUIRE(MORE(), REG_EBRACK);
                c = PEEK();
                (void)REQUIRE(c != '-' && c != ']', REG_ECTYPE);
                p_b_cclass(p, cs);
                (void)REQUIRE(MORE(), REG_EBRACK);
                (void)REQUIRE(EATTWO(':', ']'), REG_ECTYPE);
                break;
        case '=':               /* equivalence class */
                NEXT2();
                (void)REQUIRE(MORE(), REG_EBRACK);
                c = PEEK();
                (void)REQUIRE(c != '-' && c != ']', REG_ECOLLATE);
                p_b_eclass(p, cs);
                (void)REQUIRE(MORE(), REG_EBRACK);
                (void)REQUIRE(EATTWO('=', ']'), REG_ECOLLATE);
                break;
        default:                /* symbol, ordinary character, or range */
/* xxx revision needed for multichar stuff */
                start = p_b_symbol(p);
                if (SEE('-') && MORE2() && PEEK2() != ']') {
                        /* range */
                        NEXT();
                        if (EAT('-'))
                                finish = '-';
                        else
                                finish = p_b_symbol(p);
                } else
                        finish = start;
                if (start == finish)
                        CHadd(cs, start);
                else {
                        if (__collate_load_error) {
                                (void)REQUIRE((uch)start <= (uch)finish, REG_ERANGE);
                                for (i = (uch)start; i <= (uch)finish; i++)
                                        CHadd(cs, i);
                        } else {
                                (void)REQUIRE(__collate_range_cmp(start, finish) <= 0, REG_ERANGE);
                                for (i = CHAR_MIN; i <= CHAR_MAX; i++) {
                                        if (   __collate_range_cmp(start, i) <= 0
                                            && __collate_range_cmp(i, finish) <= 0
                                           )
                                                CHadd(cs, i);
                                }
                        }
                }
                break;
        }
}

/*
 - p_b_cclass - parse a character-class name and deal with it
 == static void p_b_cclass(struct parse *p, cset *cs);
 */
static void
p_b_cclass(
        struct parse *p,
        cset *cs
)
{
        int c;
        char *sp = p->next;
        struct cclass *cp;
        size_t len;

        while (MORE() && isalpha((uch)PEEK()))
                NEXT();
        len = p->next - sp;
        for (cp = cclasses; cp->name != NULL; cp++)
                if (strncmp(cp->name, sp, len) == 0 && cp->name[len] == '\0')
                        break;
        if (cp->name == NULL) {
                /* oops, didn't find it */
                SETERROR(REG_ECTYPE);
                return;
        }

        switch (cp->fidx) {
        case CALNUM:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isalnum((uch)c))
                                CHadd(cs, c);
                break;
        case CALPHA:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isalpha((uch)c))
                                CHadd(cs, c);
                break;
        case CBLANK:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isblank((uch)c))
                                CHadd(cs, c);
                break;
        case CCNTRL:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (iscntrl((uch)c))
                                CHadd(cs, c);
                break;
        case CDIGIT:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isdigit((uch)c))
                                CHadd(cs, c);
                break;
        case CGRAPH:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isgraph((uch)c))
                                CHadd(cs, c);
                break;
        case CLOWER:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (islower((uch)c))
                                CHadd(cs, c);
                break;
        case CPRINT:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isprint((uch)c))
                                CHadd(cs, c);
                break;
        case CPUNCT:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (ispunct((uch)c))
                                CHadd(cs, c);
                break;
        case CSPACE:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isspace((uch)c))
                                CHadd(cs, c);
                break;
        case CUPPER:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isupper((uch)c))
                                CHadd(cs, c);
                break;
        case CXDIGIT:
                for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                        if (isxdigit((uch)c))
                                CHadd(cs, c);
                break;
        }
#if 0
        for (u = cp->multis; *u != '\0'; u += strlen(u) + 1)
                MCadd(p, cs, u);
#endif
}

/*
 - p_b_eclass - parse an equivalence-class name and deal with it
 == static void p_b_eclass(struct parse *p, cset *cs);
 *
 * This implementation is incomplete. xxx
 */
static void
p_b_eclass(
        struct parse *p,
        cset *cs
)
{
        char c;

        c = p_b_coll_elem(p, '=');
        CHadd(cs, c);
}

/*
 - p_b_symbol - parse a character or [..]ed multicharacter collating symbol
 == static char p_b_symbol(struct parse *p);
 */
static char                     /* value of symbol */
p_b_symbol(struct parse *p)
{
        char value;

        (void)REQUIRE(MORE(), REG_EBRACK);
        if (!EATTWO('[', '.'))
                return(GETNEXT());

        /* collating symbol */
        value = p_b_coll_elem(p, '.');
        (void)REQUIRE(EATTWO('.', ']'), REG_ECOLLATE);
        return(value);
}

/*
 - p_b_coll_elem - parse a collating-element name and look it up
 == static char p_b_coll_elem(struct parse *p, int endc);
 */
static char                     /* value of collating element */
p_b_coll_elem(
        struct parse *p,
        int endc                        /* name ended by endc,']' */
)
{
        char *sp = p->next;
        struct cname *cp;
        int len;

        while (MORE() && !SEETWO(endc, ']'))
                NEXT();
        if (!MORE()) {
                SETERROR(REG_EBRACK);
                return(0);
        }
        len = p->next - sp;
        for (cp = cnames; cp->name != NULL; cp++)
                if (strncmp(cp->name, sp, len) == 0 && cp->name[len] == '\0')
                        return(cp->code);       /* known name */
        if (len == 1)
                return(*sp);    /* single character */
        SETERROR(REG_ECOLLATE);                 /* neither */
        return(0);
}

/*
 - othercase - return the case counterpart of an alphabetic
 == static char othercase(int ch);
 */
static char                     /* if no counterpart, return ch */
othercase(
        int ch
)
{
        ch = (uch)ch;
        assert(isalpha(ch));
        if (isupper(ch))
                return(tolower(ch));
        else if (islower(ch))
                return(toupper(ch));
        else                    /* peculiar, but could happen */
                return(ch);
}

/*
 - bothcases - emit a dualcase version of a two-case character
 == static void bothcases(struct parse *p, int ch);
 *
 * Boy, is this implementation ever a kludge...
 */
static void
bothcases(
        struct parse *p,
        int ch
)
{
        char *oldnext = p->next;
        char *oldend = p->end;
        char bracket[3];

        ch = (uch)ch;
        assert(othercase(ch) != ch);    /* p_bracket() would recurse */
        p->next = bracket;
        p->end = bracket+2;
        bracket[0] = ch;
        bracket[1] = ']';
        bracket[2] = '\0';
        p_bracket(p);
        assert(p->next == bracket+2);
        p->next = oldnext;
        p->end = oldend;
}

/*
 - ordinary - emit an ordinary character
 == static void ordinary(struct parse *p, int ch);
 */
static void
ordinary(
        struct parse *p,
        int ch
)
{
        cat_t *cap = p->g->categories;

        if ((p->g->cflags&REG_ICASE) && isalpha((uch)ch) && othercase(ch) != ch)
                bothcases(p, ch);
        else {
                EMIT(OCHAR, (uch)ch);
                if (cap[ch] == 0)
                        cap[ch] = p->g->ncategories++;
        }
}

/*
 - nonnewline - emit REG_NEWLINE version of OANY
 == static void nonnewline(struct parse *p);
 *
 * Boy, is this implementation ever a kludge...
 */
static void
nonnewline(
        struct parse *p
)
{
        char *oldnext = p->next;
        char *oldend = p->end;
        char bracket[4];

        p->next = bracket;
        p->end = bracket+3;
        bracket[0] = '^';
        bracket[1] = '\n';
        bracket[2] = ']';
        bracket[3] = '\0';
        p_bracket(p);
        assert(p->next == bracket+3);
        p->next = oldnext;
        p->end = oldend;
}

/*
 - repeat - generate code for a bounded repetition, recursively if needed
 == static void repeat(struct parse *p, sopno start, int from, int to);
 */
static void
repeat(
        struct parse *p,
        sopno start,                    /* operand from here to end of strip */
        int from,                       /* repeated from this number */
        int to                          /* to this number of times (maybe INFINITY) */
)
{
        sopno finish = HERE();
#       define  N       2
#       define  INF     3
#       define  REP(f, t)       ((f)*8 + (t))
#       define  MAP(n)  (((n) <= 1) ? (n) : ((n) == INFINITY) ? INF : N)
        sopno copy;

        if (p->error != 0)      /* head off possible runaway recursion */
                return;

        assert(from <= to);

        switch (REP(MAP(from), MAP(to))) {
        case REP(0, 0):                 /* must be user doing this */
                DROP(finish-start);     /* drop the operand */
                break;
        case REP(0, 1):                 /* as x{1,1}? */
        case REP(0, N):                 /* as x{1,n}? */
        case REP(0, INF):               /* as x{1,}? */
                /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
                INSERT(OCH_, start);            /* offset is wrong... */
                repeat(p, start+1, 1, to);
                ASTERN(OOR1, start);
                AHEAD(start);                   /* ... fix it */
                EMIT(OOR2, 0);
                AHEAD(THERE());
                ASTERN(O_CH, THERETHERE());
                break;
        case REP(1, 1):                 /* trivial case */
                /* done */
                break;
        case REP(1, N):                 /* as x?x{1,n-1} */
                /* KLUDGE: emit y? as (y|) until subtle bug gets fixed */
                INSERT(OCH_, start);
                ASTERN(OOR1, start);
                AHEAD(start);
                EMIT(OOR2, 0);                  /* offset very wrong... */
                AHEAD(THERE());                 /* ...so fix it */
                ASTERN(O_CH, THERETHERE());
                copy = dupl(p, start+1, finish+1);
                assert(copy == finish+4);
                repeat(p, copy, 1, to-1);
                break;
        case REP(1, INF):               /* as x+ */
                INSERT(OPLUS_, start);
                ASTERN(O_PLUS, start);
                break;
        case REP(N, N):                 /* as xx{m-1,n-1} */
                copy = dupl(p, start, finish);
                repeat(p, copy, from-1, to-1);
                break;
        case REP(N, INF):               /* as xx{n-1,INF} */
                copy = dupl(p, start, finish);
                repeat(p, copy, from-1, to);
                break;
        default:                        /* "can't happen" */
                SETERROR(REG_ASSERT);   /* just in case */
                break;
        }
}

/*
 - seterr - set an error condition
 == static int seterr(struct parse *p, int e);
 */
static int                      /* useless but makes type checking happy */
seterr(
        struct parse *p,
        int e
)
{
        if (p->error == 0)      /* keep earliest error condition */
                p->error = e;
        p->next = nuls;         /* try to bring things to a halt */
        p->end = nuls;
        return(0);              /* make the return value well-defined */
}

/*
 - allocset - allocate a set of characters for []
 == static cset *allocset(struct parse *p);
 */
static cset *
allocset(struct parse *p)
{
        int no = p->g->ncsets++;
        size_t nc;
        size_t nbytes;
        cset *cs;
        size_t css = (size_t)p->g->csetsize;
        int i;

        if (no >= p->ncsalloc) {        /* need another column of space */
                p->ncsalloc += CHAR_BIT;
                nc = p->ncsalloc;
                assert(nc % CHAR_BIT == 0);
                nbytes = nc / CHAR_BIT * css;
                if (p->g->sets == NULL)
                        p->g->sets = (cset *)malloc(nc * sizeof(cset));
                else
                        p->g->sets = (cset *)reallocf((char *)p->g->sets,
                                                        nc * sizeof(cset));
                if (p->g->setbits == NULL)
                        p->g->setbits = (uch *)malloc(nbytes);
                else {
                        p->g->setbits = (uch *)reallocf((char *)p->g->setbits,
                                                                nbytes);
                        /* xxx this isn't right if setbits is now NULL */
                        for (i = 0; i < no; i++)
                                p->g->sets[i].ptr = p->g->setbits + css*(i/CHAR_BIT);
                }
                if (p->g->sets != NULL && p->g->setbits != NULL)
                        (void) memset((char *)p->g->setbits + (nbytes - css),
                                                                0, css);
                else {
                        no = 0;
                        SETERROR(REG_ESPACE);
                        /* caller's responsibility not to do set ops */
                }
        }

        assert(p->g->sets != NULL);     /* xxx */
        cs = &p->g->sets[no];
        cs->ptr = p->g->setbits + css*((no)/CHAR_BIT);
        cs->mask = 1 << ((no) % CHAR_BIT);
        cs->hash = 0;
        cs->smultis = 0;
        cs->multis = NULL;

        return(cs);
}

/*
 - freeset - free a now-unused set
 == static void freeset(struct parse *p, cset *cs);
 */
static void
freeset(
        struct parse *p,
        cset *cs
)
{
        int i;
        cset *top = &p->g->sets[p->g->ncsets];
        size_t css = (size_t)p->g->csetsize;

        for (i = 0; i < css; i++)
                CHsub(cs, i);
        if (cs == top-1)        /* recover only the easy case */
                p->g->ncsets--;
}

/*
 - freezeset - final processing on a set of characters
 == static int freezeset(struct parse *p, cset *cs);
 *
 * The main task here is merging identical sets.  This is usually a waste
 * of time (although the hash code minimizes the overhead), but can win
 * big if REG_ICASE is being used.  REG_ICASE, by the way, is why the hash
 * is done using addition rather than xor -- all ASCII [aA] sets xor to
 * the same value!
 */
static int                      /* set number */
freezeset(
        struct parse *p,
        cset *cs
)
{
        short h = cs->hash;
        int i;
        cset *top = &p->g->sets[p->g->ncsets];
        cset *cs2;
        size_t css = (size_t)p->g->csetsize;

        /* look for an earlier one which is the same */
        for (cs2 = &p->g->sets[0]; cs2 < top; cs2++)
                if (cs2->hash == h && cs2 != cs) {
                        /* maybe */
                        for (i = 0; i < css; i++)
                                if (!!CHIN(cs2, i) != !!CHIN(cs, i))
                                        break;          /* no */
                        if (i == css)
                                break;                  /* yes */
                }

        if (cs2 < top) {        /* found one */
                freeset(p, cs);
                cs = cs2;
        }

        return((int)(cs - p->g->sets));
}

/*
 - firstch - return first character in a set (which must have at least one)
 == static int firstch(struct parse *p, cset *cs);
 */
static int                      /* character; there is no "none" value */
firstch(
        struct parse *p,
        cset *cs
)
{
        int i;
        size_t css = (size_t)p->g->csetsize;

        for (i = 0; i < css; i++)
                if (CHIN(cs, i))
                        return((char)i);
        assert(never);
        return(0);              /* arbitrary */
}

/*
 - nch - number of characters in a set
 == static int nch(struct parse *p, cset *cs);
 */
static int
nch(
        struct parse *p,
        cset *cs
)
{
        int i;
        size_t css = (size_t)p->g->csetsize;
        int n = 0;

        for (i = 0; i < css; i++)
                if (CHIN(cs, i))
                        n++;
        return(n);
}

#if used
/*
 - mcadd - add a collating element to a cset
 == static void mcadd(struct parse *p, cset *cs, \
 ==     char *cp);
 */
static void
mcadd(p, cs, cp)
struct parse *p;
cset *cs;
char *cp;
{
        size_t oldend = cs->smultis;

        cs->smultis += strlen(cp) + 1;
        if (cs->multis == NULL)
                cs->multis = malloc(cs->smultis);
        else
                cs->multis = reallocf(cs->multis, cs->smultis);
        if (cs->multis == NULL) {
                SETERROR(REG_ESPACE);
                return;
        }

        (void) strcpy(cs->multis + oldend - 1, cp);
        cs->multis[cs->smultis - 1] = '\0';
}

/*
 - mcsub - subtract a collating element from a cset
 == static void mcsub(cset *cs, char *cp);
 */
static void
mcsub(cs, cp)
cset *cs;
char *cp;
{
        char *fp = mcfind(cs, cp);
        size_t len = strlen(fp);

        assert(fp != NULL);
        (void) memmove(fp, fp + len + 1,
                                cs->smultis - (fp + len + 1 - cs->multis));
        cs->smultis -= len;

        if (cs->smultis == 0) {
                free(cs->multis);
                cs->multis = NULL;
                return;
        }

        cs->multis = reallocf(cs->multis, cs->smultis);
        assert(cs->multis != NULL);
}

/*
 - mcin - is a collating element in a cset?
 == static int mcin(cset *cs, char *cp);
 */
static int
mcin(cs, cp)
cset *cs;
char *cp;
{
        return(mcfind(cs, cp) != NULL);
}

/*
 - mcfind - find a collating element in a cset
 == static char *mcfind(cset *cs, char *cp);
 */
static char *
mcfind(cs, cp)
cset *cs;
char *cp;
{
        char *p;

        if (cs->multis == NULL)
                return(NULL);
        for (p = cs->multis; *p != '\0'; p += strlen(p) + 1)
                if (strcmp(cp, p) == 0)
                        return(p);
        return(NULL);
}
#endif

/*
 - mcinvert - invert the list of collating elements in a cset
 == static void mcinvert(struct parse *p, cset *cs);
 *
 * This would have to know the set of possibilities.  Implementation
 * is deferred.
 */
static void
mcinvert(
        struct parse *p,
        cset *cs
)
{
        assert(cs->multis == NULL);     /* xxx */
}

/*
 - mccase - add case counterparts of the list of collating elements in a cset
 == static void mccase(struct parse *p, cset *cs);
 *
 * This would have to know the set of possibilities.  Implementation
 * is deferred.
 */
static void
mccase(
        struct parse *p,
        cset *cs
)
{
        assert(cs->multis == NULL);     /* xxx */
}

/*
 - isinsets - is this character in any sets?
 == static int isinsets(struct re_guts *g, int c);
 */
static int                      /* predicate */
isinsets(
        struct re_guts *g,
        int c
)
{
        uch *col;
        int i;
        int ncols = (g->ncsets+(CHAR_BIT-1)) / CHAR_BIT;
        unsigned uc = (uch)c;

        for (i = 0, col = g->setbits; i < ncols; i++, col += g->csetsize)
                if (col[uc] != 0)
                        return(1);
        return(0);
}

/*
 - samesets - are these two characters in exactly the same sets?
 == static int samesets(struct re_guts *g, int c1, int c2);
 */
static int                      /* predicate */
samesets(
        struct re_guts *g,
        int c1,
        int c2
)
{
        uch *col;
        int i;
        int ncols = (g->ncsets+(CHAR_BIT-1)) / CHAR_BIT;
        unsigned uc1 = (uch)c1;
        unsigned uc2 = (uch)c2;

        for (i = 0, col = g->setbits; i < ncols; i++, col += g->csetsize)
                if (col[uc1] != col[uc2])
                        return(0);
        return(1);
}

/*
 - categorize - sort out character categories
 == static void categorize(struct parse *p, struct re_guts *g);
 */
static void
categorize(
        struct parse *p,
        struct re_guts *g
)
{
        cat_t *cats = g->categories;
        int c;
        int c2;
        cat_t cat;

        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        for (c = CHAR_MIN; c <= CHAR_MAX; c++)
                if (cats[c] == 0 && isinsets(g, c)) {
                        cat = g->ncategories++;
                        cats[c] = cat;
                        for (c2 = c+1; c2 <= CHAR_MAX; c2++)
                                if (cats[c2] == 0 && samesets(g, c, c2))
                                        cats[c2] = cat;
                }
}

/*
 - dupl - emit a duplicate of a bunch of sops
 == static sopno dupl(struct parse *p, sopno start, sopno finish);
 */
static sopno                    /* start of duplicate */
dupl(
        struct parse *p,
        sopno start,                    /* from here */
        sopno finish                    /* to this less one */
)
{
        sopno ret = HERE();
        sopno len = finish - start;

        assert(finish >= start);
        if (len == 0)
                return(ret);
        enlarge(p, p->ssize + len);     /* this many unexpected additions */
        assert(p->ssize >= p->slen + len);
        (void) memcpy((char *)(p->strip + p->slen),
                (char *)(p->strip + start), (size_t)len*sizeof(sop));
        p->slen += len;
        return(ret);
}

/*
 - doemit - emit a strip operator
 == static void doemit(struct parse *p, sop op, size_t opnd);
 *
 * It might seem better to implement this as a macro with a function as
 * hard-case backup, but it's just too big and messy unless there are
 * some changes to the data structures.  Maybe later.
 */
static void
doemit(
        struct parse *p,
        sop op,
        size_t opnd
)
{
        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        /* deal with oversize operands ("can't happen", more or less) */
        assert(opnd < 1<<OPSHIFT);

        /* deal with undersized strip */
        if (p->slen >= p->ssize)
                enlarge(p, (p->ssize+1) / 2 * 3);       /* +50% */
        assert(p->slen < p->ssize);

        /* finally, it's all reduced to the easy case */
        p->strip[p->slen++] = SOP(op, opnd);
}

/*
 - doinsert - insert a sop into the strip
 == static void doinsert(struct parse *p, sop op, size_t opnd, sopno pos);
 */
static void
doinsert(
        struct parse *p,
        sop op,
        size_t opnd,
        sopno pos
)
{
        sopno sn;
        sop s;
        int i;

        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        sn = HERE();
        EMIT(op, opnd);         /* do checks, ensure space */
        assert(HERE() == sn+1);
        s = p->strip[sn];

        /* adjust paren pointers */
        assert(pos > 0);
        for (i = 1; i < NPAREN; i++) {
                if (p->pbegin[i] >= pos) {
                        p->pbegin[i]++;
                }
                if (p->pend[i] >= pos) {
                        p->pend[i]++;
                }
        }

        memmove((char *)&p->strip[pos+1], (char *)&p->strip[pos],
                                                (HERE()-pos-1)*sizeof(sop));
        p->strip[pos] = s;
}

/*
 - dofwd - complete a forward reference
 == static void dofwd(struct parse *p, sopno pos, sop value);
 */
static void
dofwd(
        struct parse *p,
        sopno pos,
        sop value
)
{
        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        assert(value < 1<<OPSHIFT);
        p->strip[pos] = OP(p->strip[pos]) | value;
}

/*
 - enlarge - enlarge the strip
 == static void enlarge(struct parse *p, sopno size);
 */
static void
enlarge(
        struct parse *p,
        sopno size
)
{
        sop *sp;

        if (p->ssize >= size)
                return;

        sp = (sop *)realloc(p->strip, size*sizeof(sop));
        if (sp == NULL) {
                SETERROR(REG_ESPACE);
                return;
        }
        p->strip = sp;
        p->ssize = size;
}

/*
 - stripsnug - compact the strip
 == static void stripsnug(struct parse *p, struct re_guts *g);
 */
static void
stripsnug(
        struct parse *p,
        struct re_guts *g
)
{
        g->nstates = p->slen;
        g->strip = (sop *)realloc((char *)p->strip, p->slen * sizeof(sop));
        if (g->strip == NULL) {
                SETERROR(REG_ESPACE);
                g->strip = p->strip;
        }
}

/*
 - findmust - fill in must and mlen with longest mandatory literal string
 == static void findmust(struct parse *p, struct re_guts *g);
 *
 * This algorithm could do fancy things like analyzing the operands of |
 * for common subsequences.  Someday.  This code is simple and finds most
 * of the interesting cases.
 *
 * Note that must and mlen got initialized during setup.
 */
static void
findmust(
        struct parse *p,
        struct re_guts *g
)
{
        sop *scan;
        sop *start = NULL;
        sop *newstart = NULL;
        sopno newlen;
        sop s;
        char *cp;
        sopno i;
        int offset;
        int cs, mccs;

        /* avoid making error situations worse */
        if (p->error != 0)
                return;

        /* Find out if we can handle OANYOF or not */
        mccs = 0;
        for (cs = 0; cs < g->ncsets; cs++)
                if (g->sets[cs].multis != NULL)
                        mccs = 1;

        /* find the longest OCHAR sequence in strip */
        newlen = 0;
        offset = 0;
        g->moffset = 0;
        scan = g->strip + 1;
        do {
                s = *scan++;
                switch (OP(s)) {
                case OCHAR:             /* sequence member */
                        if (newlen == 0)                /* new sequence */
                                newstart = scan - 1;
                        newlen++;
                        break;
                case OPLUS_:            /* things that don't break one */
                case OLPAREN:
                case ORPAREN:
                        break;
                case OQUEST_:           /* things that must be skipped */
                case OCH_:
                        offset = altoffset(scan, offset, mccs);
                        scan--;
                        do {
                                scan += OPND(s);
                                s = *scan;
                                /* assert() interferes w debug printouts */
                                if (OP(s) != O_QUEST && OP(s) != O_CH &&
                                                        OP(s) != OOR2) {
                                        g->iflags |= BAD;
                                        return;
                                }
                        } while (OP(s) != O_QUEST && OP(s) != O_CH);
                        /* fallthrough */
                case OBOW:              /* things that break a sequence */
                case OEOW:
                case OBOL:
                case OEOL:
                case O_QUEST:
                case O_CH:
                case OEND:
                        if (newlen > g->mlen) {         /* ends one */
                                start = newstart;
                                g->mlen = newlen;
                                if (offset > -1) {
                                        g->moffset += offset;
                                        offset = newlen;
                                } else
                                        g->moffset = offset;
                        } else {
                                if (offset > -1)
                                        offset += newlen;
                        }
                        newlen = 0;
                        break;
                case OANY:
                        if (newlen > g->mlen) {         /* ends one */
                                start = newstart;
                                g->mlen = newlen;
                                if (offset > -1) {
                                        g->moffset += offset;
                                        offset = newlen;
                                } else
                                        g->moffset = offset;
                        } else {
                                if (offset > -1)
                                        offset += newlen;
                        }
                        if (offset > -1)
                                offset++;
                        newlen = 0;
                        break;
                case OANYOF:            /* may or may not invalidate offset */
                        /* First, everything as OANY */
                        if (newlen > g->mlen) {         /* ends one */
                                start = newstart;
                                g->mlen = newlen;
                                if (offset > -1) {
                                        g->moffset += offset;
                                        offset = newlen;
                                } else
                                        g->moffset = offset;
                        } else {
                                if (offset > -1)
                                        offset += newlen;
                        }
                        if (offset > -1)
                                offset++;
                        newlen = 0;
                        /* And, now, if we found out we can't deal with
                         * it, make offset = -1.
                         */
                        if (mccs)
                                offset = -1;
                        break;
                default:
                        /* Anything here makes it impossible or too hard
                         * to calculate the offset -- so we give up;
                         * save the last known good offset, in case the
                         * must sequence doesn't occur later.
                         */
                        if (newlen > g->mlen) {         /* ends one */
                                start = newstart;
                                g->mlen = newlen;
                                if (offset > -1)
                                        g->moffset += offset;
                                else
                                        g->moffset = offset;
                        }
                        offset = -1;
                        newlen = 0;
                        break;
                }
        } while (OP(s) != OEND);

        if (g->mlen == 0) {             /* there isn't one */
                g->moffset = -1;
                return;
        }

        /* turn it into a character string */
        g->must = malloc((size_t)g->mlen + 1);
        if (g->must == NULL) {          /* argh; just forget it */
                g->mlen = 0;
                g->moffset = -1;
                return;
        }
        cp = g->must;
        scan = start;
        for (i = g->mlen; i > 0; i--) {
                while (OP(s = *scan++) != OCHAR)
                        continue;
                assert(cp < g->must + g->mlen);
                *cp++ = (char)OPND(s);
        }
        assert(cp == g->must + g->mlen);
        *cp++ = '\0';           /* just on general principles */
}

/*
 - altoffset - choose biggest offset among multiple choices
 == static int altoffset(sop *scan, int offset, int mccs);
 *
 * Compute, recursively if necessary, the largest offset among multiple
 * re paths.
 */
static int
altoffset(
        sop *scan,
        int offset,
        int mccs
)
{
        int largest;
        int try;
        sop s;

        /* If we gave up already on offsets, return */
        if (offset == -1)
                return -1;

        largest = 0;
        try = 0;
        s = *scan++;
        while (OP(s) != O_QUEST && OP(s) != O_CH) {
                switch (OP(s)) {
                case OOR1:
                        if (try > largest)
                                largest = try;
                        try = 0;
                        break;
                case OQUEST_:
                case OCH_:
                        try = altoffset(scan, try, mccs);
                        if (try == -1)
                                return -1;
                        scan--;
                        do {
                                scan += OPND(s);
                                s = *scan;
                                if (OP(s) != O_QUEST && OP(s) != O_CH &&
                                                        OP(s) != OOR2)
                                        return -1;
                        } while (OP(s) != O_QUEST && OP(s) != O_CH);
                        /* We must skip to the next position, or we'll
                         * leave altoffset() too early.
                         */
                        scan++;
                        break;
                case OANYOF:
                        if (mccs)
                                return -1;
                case OCHAR:
                case OANY:
                        try++;
                case OBOW:
                case OEOW:
                case OLPAREN:
                case ORPAREN:
                case OOR2:
                        break;
                default:
                        try = -1;
                        break;
                }
                if (try == -1)
                        return -1;
                s = *scan++;
        }

        if (try > largest)
                largest = try;

        return largest+offset;
}

/*
 - computejumps - compute char jumps for BM scan
 == static void computejumps(struct parse *p, struct re_guts *g);
 *
 * This algorithm assumes g->must exists and is has size greater than
 * zero. It's based on the algorithm found on Computer Algorithms by
 * Sara Baase.
 *
 * A char jump is the number of characters one needs to jump based on
 * the value of the character from the text that was mismatched.
 */
static void
computejumps(
        struct parse *p,
        struct re_guts *g
)
{
        int ch;
        int mindex;

        /* Avoid making errors worse */
        if (p->error != 0)
                return;

        g->charjump = (int*) malloc((NC + 1) * sizeof(int));
        if (g->charjump == NULL)        /* Not a fatal error */
                return;
        /* Adjust for signed chars, if necessary */
        g->charjump = &g->charjump[-(CHAR_MIN)];

        /* If the character does not exist in the pattern, the jump
         * is equal to the number of characters in the pattern.
         */
        for (ch = CHAR_MIN; ch < (CHAR_MAX + 1); ch++)
                g->charjump[ch] = g->mlen;

        /* If the character does exist, compute the jump that would
         * take us to the last character in the pattern equal to it
         * (notice that we match right to left, so that last character
         * is the first one that would be matched).
         */
        for (mindex = 0; mindex < g->mlen; mindex++)
                g->charjump[(unsigned char) g->must[mindex]] = g->mlen - mindex - 1;
}

/*
 - computematchjumps - compute match jumps for BM scan
 == static void computematchjumps(struct parse *p, struct re_guts *g);
 *
 * This algorithm assumes g->must exists and is has size greater than
 * zero. It's based on the algorithm found on Computer Algorithms by
 * Sara Baase.
 *
 * A match jump is the number of characters one needs to advance based
 * on the already-matched suffix.
 * Notice that all values here are minus (g->mlen-1), because of the way
 * the search algorithm works.
 */
static void
computematchjumps(
        struct parse *p,
        struct re_guts *g
)
{
        int mindex;             /* General "must" iterator */
        int suffix;             /* Keeps track of matching suffix */
        int ssuffix;            /* Keeps track of suffixes' suffix */
        int* pmatches;          /* pmatches[k] points to the next i
                                 * such that i+1...mlen is a substring
                                 * of k+1...k+mlen-i-1
                                 */

        /* Avoid making errors worse */
        if (p->error != 0)
                return;

        pmatches = (int*) malloc(g->mlen * sizeof(unsigned int));
        if (pmatches == NULL) {
                g->matchjump = NULL;
                return;
        }

        g->matchjump = (int*) malloc(g->mlen * sizeof(unsigned int));
        if (g->matchjump == NULL) {     /* Not a fatal error */
                free(pmatches);
                return;
        }

        /* Set maximum possible jump for each character in the pattern */
        for (mindex = 0; mindex < g->mlen; mindex++)
                g->matchjump[mindex] = 2*g->mlen - mindex - 1;

        /* Compute pmatches[] */
        for (mindex = g->mlen - 1, suffix = g->mlen; mindex >= 0;
            mindex--, suffix--) {
                pmatches[mindex] = suffix;

                /* If a mismatch is found, interrupting the substring,
                 * compute the matchjump for that position. If no
                 * mismatch is found, then a text substring mismatched
                 * against the suffix will also mismatch against the
                 * substring.
                 */
                while (suffix < g->mlen
                    && g->must[mindex] != g->must[suffix]) {
                        g->matchjump[suffix] = MIN(g->matchjump[suffix],
                            g->mlen - mindex - 1);
                        suffix = pmatches[suffix];
                }
        }

        /* Compute the matchjump up to the last substring found to jump
         * to the beginning of the largest must pattern prefix matching
         * it's own suffix.
         */
        for (mindex = 0; mindex <= suffix; mindex++)
                g->matchjump[mindex] = MIN(g->matchjump[mindex],
                    g->mlen + suffix - mindex);

        ssuffix = pmatches[suffix];
        while (suffix < g->mlen) {
                while (suffix <= ssuffix && suffix < g->mlen) {
                        g->matchjump[suffix] = MIN(g->matchjump[suffix],
                            g->mlen + ssuffix - suffix);
                        suffix++;
                }
                if (suffix < g->mlen)
                        ssuffix = pmatches[ssuffix];
        }

        free(pmatches);
}

/*
 - pluscount - count + nesting
 == static sopno pluscount(struct parse *p, struct re_guts *g);
 */
static sopno                    /* nesting depth */
pluscount(
        struct parse *p,
        struct re_guts *g
)
{
        sop *scan;
        sop s;
        sopno plusnest = 0;
        sopno maxnest = 0;

        if (p->error != 0)
                return(0);      /* there may not be an OEND */

        scan = g->strip + 1;
        do {
                s = *scan++;
                switch (OP(s)) {
                case OPLUS_:
                        plusnest++;
                        break;
                case O_PLUS:
                        if (plusnest > maxnest)
                                maxnest = plusnest;
                        plusnest--;
                        break;
                }
        } while (OP(s) != OEND);
        if (plusnest != 0)
                g->iflags |= BAD;
        return(maxnest);
}

#endif /* !_NO_REGEX  */