Fix: Data races on cursor state in OpenGL backends

[openttd-github.git] / src / string.cpp

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file string.cpp Handling of C-type strings (char*). */

#include "stdafx.h"
#include "debug.h"
#include "core/alloc_func.hpp"
#include "core/math_func.hpp"
#include "string_func.h"
#include "string_base.h"

#include "table/control_codes.h"

#include <stdarg.h>
#include <ctype.h> /* required for tolower() */
#include <sstream>

#ifdef _MSC_VER
#include <errno.h> // required by vsnprintf implementation for MSVC
#endif

#ifdef _WIN32
#include "os/windows/win32.h"
#endif

#ifdef WITH_UNISCRIBE
#include "os/windows/string_uniscribe.h"
#endif

#ifdef WITH_ICU_I18N
/* Required by strnatcmp. */
#include <unicode/ustring.h>
#include "language.h"
#include "gfx_func.h"
#endif /* WITH_ICU_I18N */

#if defined(WITH_COCOA)
#include "os/macosx/string_osx.h"
#endif

/* The function vsnprintf is used internally to perform the required formatting
 * tasks. As such this one must be allowed, and makes sure it's terminated. */
#include "safeguards.h"
#undef vsnprintf

/**
 * Safer implementation of vsnprintf; same as vsnprintf except:
 * - last instead of size, i.e. replace sizeof with lastof.
 * - return gives the amount of characters added, not what it would add.
 * @param str    buffer to write to up to last
 * @param last   last character we may write to
 * @param format the formatting (see snprintf)
 * @param ap     the list of arguments for the format
 * @return the number of added characters
 */
int CDECL vseprintf(char *str, const char *last, const char *format, va_list ap)
{
        ptrdiff_t diff = last - str;
        if (diff < 0) return 0;
        return std::min(static_cast<int>(diff), vsnprintf(str, diff + 1, format, ap));
}

/**
 * Appends characters from one string to another.
 *
 * Appends the source string to the destination string with respect of the
 * terminating null-character and and the last pointer to the last element
 * in the destination buffer. If the last pointer is set to nullptr no
 * boundary check is performed.
 *
 * @note usage: strecat(dst, src, lastof(dst));
 * @note lastof() applies only to fixed size arrays
 *
 * @param dst The buffer containing the target string
 * @param src The buffer containing the string to append
 * @param last The pointer to the last element of the destination buffer
 * @return The pointer to the terminating null-character in the destination buffer
 */
char *strecat(char *dst, const char *src, const char *last)
{
        assert(dst <= last);
        while (*dst != '\0') {
                if (dst == last) return dst;
                dst++;
        }

        return strecpy(dst, src, last);
}


/**
 * Copies characters from one buffer to another.
 *
 * Copies the source string to the destination buffer with respect of the
 * terminating null-character and the last pointer to the last element in
 * the destination buffer. If the last pointer is set to nullptr no boundary
 * check is performed.
 *
 * @note usage: strecpy(dst, src, lastof(dst));
 * @note lastof() applies only to fixed size arrays
 *
 * @param dst The destination buffer
 * @param src The buffer containing the string to copy
 * @param last The pointer to the last element of the destination buffer
 * @return The pointer to the terminating null-character in the destination buffer
 */
char *strecpy(char *dst, const char *src, const char *last)
{
        assert(dst <= last);
        while (dst != last && *src != '\0') {
                *dst++ = *src++;
        }
        *dst = '\0';

        if (dst == last && *src != '\0') {
#if defined(STRGEN) || defined(SETTINGSGEN)
                error("String too long for destination buffer");
#else /* STRGEN || SETTINGSGEN */
                DEBUG(misc, 0, "String too long for destination buffer");
#endif /* STRGEN || SETTINGSGEN */
        }
        return dst;
}

/**
 * Create a duplicate of the given string.
 * @param s    The string to duplicate.
 * @param last The last character that is safe to duplicate. If nullptr, the whole string is duplicated.
 * @note The maximum length of the resulting string might therefore be last - s + 1.
 * @return The duplicate of the string.
 */
char *stredup(const char *s, const char *last)
{
        size_t len = last == nullptr ? strlen(s) : ttd_strnlen(s, last - s + 1);
        char *tmp = CallocT<char>(len + 1);
        memcpy(tmp, s, len);
        return tmp;
}

/**
 * Format, "printf", into a newly allocated string.
 * @param str The formatting string.
 * @return The formatted string. You must free this!
 */
char *CDECL str_fmt(const char *str, ...)
{
        char buf[4096];
        va_list va;

        va_start(va, str);
        int len = vseprintf(buf, lastof(buf), str, va);
        va_end(va);
        char *p = MallocT<char>(len + 1);
        memcpy(p, buf, len + 1);
        return p;
}

/**
 * Scan the string for old values of SCC_ENCODED and fix it to
 * it's new, static value.
 * @param str the string to scan
 * @param last the last valid character of str
 */
void str_fix_scc_encoded(char *str, const char *last)
{
        while (str <= last && *str != '\0') {
                size_t len = Utf8EncodedCharLen(*str);
                if ((len == 0 && str + 4 > last) || str + len > last) break;

                WChar c;
                Utf8Decode(&c, str);
                if (c == '\0') break;

                if (c == 0xE028 || c == 0xE02A) {
                        c = SCC_ENCODED;
                }
                str += Utf8Encode(str, c);
        }
        *str = '\0';
}


template <class T>
static void str_validate(T &dst, const char *str, const char *last, StringValidationSettings settings)
{
        /* Assume the ABSOLUTE WORST to be in str as it comes from the outside. */

        while (str <= last && *str != '\0') {
                size_t len = Utf8EncodedCharLen(*str);
                /* If the character is unknown, i.e. encoded length is 0
                 * we assume worst case for the length check.
                 * The length check is needed to prevent Utf8Decode to read
                 * over the terminating '\0' if that happens to be placed
                 * within the encoding of an UTF8 character. */
                if ((len == 0 && str + 4 > last) || str + len > last) break;

                WChar c;
                len = Utf8Decode(&c, str);
                /* It's possible to encode the string termination character
                 * into a multiple bytes. This prevents those termination
                 * characters to be skipped */
                if (c == '\0') break;

                if ((IsPrintable(c) && (c < SCC_SPRITE_START || c > SCC_SPRITE_END)) || ((settings & SVS_ALLOW_CONTROL_CODE) != 0 && c == SCC_ENCODED)) {
                        /* Copy the character back. Even if dst is current the same as str
                         * (i.e. no characters have been changed) this is quicker than
                         * moving the pointers ahead by len */
                        do {
                                *dst++ = *str++;
                        } while (--len != 0);
                } else if ((settings & SVS_ALLOW_NEWLINE) != 0 && c == '\n') {
                        *dst++ = *str++;
                } else {
                        if ((settings & SVS_ALLOW_NEWLINE) != 0 && c == '\r' && str[1] == '\n') {
                                str += len;
                                continue;
                        }
                        /* Replace the undesirable character with a question mark */
                        str += len;
                        if ((settings & SVS_REPLACE_WITH_QUESTION_MARK) != 0) *dst++ = '?';
                }
        }
}

/**
 * Scans the string for valid characters and if it finds invalid ones,
 * replaces them with a question mark '?' (if not ignored)
 * @param str the string to validate
 * @param last the last valid character of str
 * @param settings the settings for the string validation.
 */
void str_validate(char *str, const char *last, StringValidationSettings settings)
{
        char *dst = str;
        str_validate(dst, str, last, settings);
        *dst = '\0';
}

/**
 * Scans the string for valid characters and if it finds invalid ones,
 * replaces them with a question mark '?' (if not ignored)
 * @param str the string to validate
 * @param settings the settings for the string validation.
 */
std::string str_validate(const std::string &str, StringValidationSettings settings)
{
        auto buf = str.data();
        auto last = buf + str.size();

        std::ostringstream dst;
        std::ostreambuf_iterator<char> dst_iter(dst);
        str_validate(dst_iter, buf, last, settings);

        return dst.str();
}

/**
 * Scans the string for valid characters and if it finds invalid ones,
 * replaces them with a question mark '?'.
 * @param str the string to validate
 */
void ValidateString(const char *str)
{
        /* We know it is '\0' terminated. */
        str_validate(const_cast<char *>(str), str + strlen(str) + 1);
}


/**
 * Checks whether the given string is valid, i.e. contains only
 * valid (printable) characters and is properly terminated.
 * @param str  The string to validate.
 * @param last The last character of the string, i.e. the string
 *             must be terminated here or earlier.
 */
bool StrValid(const char *str, const char *last)
{
        /* Assume the ABSOLUTE WORST to be in str as it comes from the outside. */

        while (str <= last && *str != '\0') {
                size_t len = Utf8EncodedCharLen(*str);
                /* Encoded length is 0 if the character isn't known.
                 * The length check is needed to prevent Utf8Decode to read
                 * over the terminating '\0' if that happens to be placed
                 * within the encoding of an UTF8 character. */
                if (len == 0 || str + len > last) return false;

                WChar c;
                len = Utf8Decode(&c, str);
                if (!IsPrintable(c) || (c >= SCC_SPRITE_START && c <= SCC_SPRITE_END)) {
                        return false;
                }

                str += len;
        }

        return *str == '\0';
}

/** Scans the string for colour codes and strips them */
void str_strip_colours(char *str)
{
        char *dst = str;
        WChar c;
        size_t len;

        for (len = Utf8Decode(&c, str); c != '\0'; len = Utf8Decode(&c, str)) {
                if (c < SCC_BLUE || c > SCC_BLACK) {
                        /* Copy the character back. Even if dst is current the same as str
                         * (i.e. no characters have been changed) this is quicker than
                         * moving the pointers ahead by len */
                        do {
                                *dst++ = *str++;
                        } while (--len != 0);
                } else {
                        /* Just skip (strip) the colour codes */
                        str += len;
                }
        }
        *dst = '\0';
}

/**
 * Get the length of an UTF-8 encoded string in number of characters
 * and thus not the number of bytes that the encoded string contains.
 * @param s The string to get the length for.
 * @return The length of the string in characters.
 */
size_t Utf8StringLength(const char *s)
{
        size_t len = 0;
        const char *t = s;
        while (Utf8Consume(&t) != 0) len++;
        return len;
}


/**
 * Convert a given ASCII string to lowercase.
 * NOTE: only support ASCII characters, no UTF8 fancy. As currently
 * the function is only used to lowercase data-filenames if they are
 * not found, this is sufficient. If more, or general functionality is
 * needed, look to r7271 where it was removed because it was broken when
 * using certain locales: eg in Turkish the uppercase 'I' was converted to
 * '?', so just revert to the old functionality
 * @param str string to convert
 * @return String has changed.
 */
bool strtolower(char *str)
{
        bool changed = false;
        for (; *str != '\0'; str++) {
                char new_str = tolower(*str);
                changed |= new_str != *str;
                *str = new_str;
        }
        return changed;
}

bool strtolower(std::string &str, std::string::size_type offs)
{
        bool changed = false;
        for (auto ch = str.begin() + offs; ch != str.end(); ++ch) {
                auto new_ch = static_cast<char>(tolower(static_cast<unsigned char>(*ch)));
                changed |= new_ch != *ch;
                *ch = new_ch;
        }
        return changed;
}

/**
 * Only allow certain keys. You can define the filter to be used. This makes
 *  sure no invalid keys can get into an editbox, like BELL.
 * @param key character to be checked
 * @param afilter the filter to use
 * @return true or false depending if the character is printable/valid or not
 */
bool IsValidChar(WChar key, CharSetFilter afilter)
{
        switch (afilter) {
                case CS_ALPHANUMERAL:  return IsPrintable(key);
                case CS_NUMERAL:       return (key >= '0' && key <= '9');
                case CS_NUMERAL_SPACE: return (key >= '0' && key <= '9') || key == ' ';
                case CS_ALPHA:         return IsPrintable(key) && !(key >= '0' && key <= '9');
                case CS_HEXADECIMAL:   return (key >= '0' && key <= '9') || (key >= 'a' && key <= 'f') || (key >= 'A' && key <= 'F');
                default: NOT_REACHED();
        }
}

#ifdef _WIN32
#if defined(_MSC_VER) && _MSC_VER < 1900
/**
 * Almost POSIX compliant implementation of \c vsnprintf for VC compiler.
 * The difference is in the value returned on output truncation. This
 * implementation returns size whereas a POSIX implementation returns
 * size or more (the number of bytes that would be written to str
 * had size been sufficiently large excluding the terminating null byte).
 */
int CDECL vsnprintf(char *str, size_t size, const char *format, va_list ap)
{
        if (size == 0) return 0;

        errno = 0;
        int ret = _vsnprintf(str, size, format, ap);

        if (ret < 0) {
                if (errno != ERANGE) {
                        /* There's a formatting error, better get that looked
                         * at properly instead of ignoring it. */
                        NOT_REACHED();
                }
        } else if ((size_t)ret < size) {
                /* The buffer is big enough for the number of
                 * characters stored (excluding null), i.e.
                 * the string has been null-terminated. */
                return ret;
        }

        /* The buffer is too small for _vsnprintf to write the
         * null-terminator at its end and return size. */
        str[size - 1] = '\0';
        return (int)size;
}
#endif /* _MSC_VER */

#endif /* _WIN32 */

/**
 * Safer implementation of snprintf; same as snprintf except:
 * - last instead of size, i.e. replace sizeof with lastof.
 * - return gives the amount of characters added, not what it would add.
 * @param str    buffer to write to up to last
 * @param last   last character we may write to
 * @param format the formatting (see snprintf)
 * @return the number of added characters
 */
int CDECL seprintf(char *str, const char *last, const char *format, ...)
{
        va_list ap;

        va_start(ap, format);
        int ret = vseprintf(str, last, format, ap);
        va_end(ap);
        return ret;
}


/**
 * Convert the md5sum to a hexadecimal string representation
 * @param buf buffer to put the md5sum into
 * @param last last character of buffer (usually lastof(buf))
 * @param md5sum the md5sum itself
 * @return a pointer to the next character after the md5sum
 */
char *md5sumToString(char *buf, const char *last, const uint8 md5sum[16])
{
        char *p = buf;

        for (uint i = 0; i < 16; i++) {
                p += seprintf(p, last, "%02X", md5sum[i]);
        }

        return p;
}


/* UTF-8 handling routines */


/**
 * Decode and consume the next UTF-8 encoded character.
 * @param c Buffer to place decoded character.
 * @param s Character stream to retrieve character from.
 * @return Number of characters in the sequence.
 */
size_t Utf8Decode(WChar *c, const char *s)
{
        assert(c != nullptr);

        if (!HasBit(s[0], 7)) {
                /* Single byte character: 0xxxxxxx */
                *c = s[0];
                return 1;
        } else if (GB(s[0], 5, 3) == 6) {
                if (IsUtf8Part(s[1])) {
                        /* Double byte character: 110xxxxx 10xxxxxx */
                        *c = GB(s[0], 0, 5) << 6 | GB(s[1], 0, 6);
                        if (*c >= 0x80) return 2;
                }
        } else if (GB(s[0], 4, 4) == 14) {
                if (IsUtf8Part(s[1]) && IsUtf8Part(s[2])) {
                        /* Triple byte character: 1110xxxx 10xxxxxx 10xxxxxx */
                        *c = GB(s[0], 0, 4) << 12 | GB(s[1], 0, 6) << 6 | GB(s[2], 0, 6);
                        if (*c >= 0x800) return 3;
                }
        } else if (GB(s[0], 3, 5) == 30) {
                if (IsUtf8Part(s[1]) && IsUtf8Part(s[2]) && IsUtf8Part(s[3])) {
                        /* 4 byte character: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
                        *c = GB(s[0], 0, 3) << 18 | GB(s[1], 0, 6) << 12 | GB(s[2], 0, 6) << 6 | GB(s[3], 0, 6);
                        if (*c >= 0x10000 && *c <= 0x10FFFF) return 4;
                }
        }

        /* DEBUG(misc, 1, "[utf8] invalid UTF-8 sequence"); */
        *c = '?';
        return 1;
}


/**
 * Encode a unicode character and place it in the buffer.
 * @tparam T Type of the buffer.
 * @param buf Buffer to place character.
 * @param c   Unicode character to encode.
 * @return Number of characters in the encoded sequence.
 */
template <class T>
inline size_t Utf8Encode(T buf, WChar c)
{
        if (c < 0x80) {
                *buf = c;
                return 1;
        } else if (c < 0x800) {
                *buf++ = 0xC0 + GB(c,  6, 5);
                *buf   = 0x80 + GB(c,  0, 6);
                return 2;
        } else if (c < 0x10000) {
                *buf++ = 0xE0 + GB(c, 12, 4);
                *buf++ = 0x80 + GB(c,  6, 6);
                *buf   = 0x80 + GB(c,  0, 6);
                return 3;
        } else if (c < 0x110000) {
                *buf++ = 0xF0 + GB(c, 18, 3);
                *buf++ = 0x80 + GB(c, 12, 6);
                *buf++ = 0x80 + GB(c,  6, 6);
                *buf   = 0x80 + GB(c,  0, 6);
                return 4;
        }

        /* DEBUG(misc, 1, "[utf8] can't UTF-8 encode value 0x%X", c); */
        *buf = '?';
        return 1;
}

size_t Utf8Encode(char *buf, WChar c)
{
        return Utf8Encode<char *>(buf, c);
}

size_t Utf8Encode(std::ostreambuf_iterator<char> &buf, WChar c)
{
        return Utf8Encode<std::ostreambuf_iterator<char> &>(buf, c);
}

/**
 * Properly terminate an UTF8 string to some maximum length
 * @param s string to check if it needs additional trimming
 * @param maxlen the maximum length the buffer can have.
 * @return the new length in bytes of the string (eg. strlen(new_string))
 * @note maxlen is the string length _INCLUDING_ the terminating '\0'
 */
size_t Utf8TrimString(char *s, size_t maxlen)
{
        size_t length = 0;

        for (const char *ptr = strchr(s, '\0'); *s != '\0';) {
                size_t len = Utf8EncodedCharLen(*s);
                /* Silently ignore invalid UTF8 sequences, our only concern trimming */
                if (len == 0) len = 1;

                /* Take care when a hard cutoff was made for the string and
                 * the last UTF8 sequence is invalid */
                if (length + len >= maxlen || (s + len > ptr)) break;
                s += len;
                length += len;
        }

        *s = '\0';
        return length;
}

#ifdef DEFINE_STRCASESTR
char *strcasestr(const char *haystack, const char *needle)
{
        size_t hay_len = strlen(haystack);
        size_t needle_len = strlen(needle);
        while (hay_len >= needle_len) {
                if (strncasecmp(haystack, needle, needle_len) == 0) return const_cast<char *>(haystack);

                haystack++;
                hay_len--;
        }

        return nullptr;
}
#endif /* DEFINE_STRCASESTR */

/**
 * Skip some of the 'garbage' in the string that we don't want to use
 * to sort on. This way the alphabetical sorting will work better as
 * we would be actually using those characters instead of some other
 * characters such as spaces and tildes at the begin of the name.
 * @param str The string to skip the initial garbage of.
 * @return The string with the garbage skipped.
 */
static const char *SkipGarbage(const char *str)
{
        while (*str != '\0' && (*str < '0' || IsInsideMM(*str, ';', '@' + 1) || IsInsideMM(*str, '[', '`' + 1) || IsInsideMM(*str, '{', '~' + 1))) str++;
        return str;
}

/**
 * Compares two strings using case insensitive natural sort.
 *
 * @param s1 First string to compare.
 * @param s2 Second string to compare.
 * @param ignore_garbage_at_front Skip punctuation characters in the front
 * @return Less than zero if s1 < s2, zero if s1 == s2, greater than zero if s1 > s2.
 */
int strnatcmp(const char *s1, const char *s2, bool ignore_garbage_at_front)
{
        if (ignore_garbage_at_front) {
                s1 = SkipGarbage(s1);
                s2 = SkipGarbage(s2);
        }

#ifdef WITH_ICU_I18N
        if (_current_collator) {
                UErrorCode status = U_ZERO_ERROR;
                int result = _current_collator->compareUTF8(s1, s2, status);
                if (U_SUCCESS(status)) return result;
        }
#endif /* WITH_ICU_I18N */

#if defined(_WIN32) && !defined(STRGEN) && !defined(SETTINGSGEN)
        int res = OTTDStringCompare(s1, s2);
        if (res != 0) return res - 2; // Convert to normal C return values.
#endif

#if defined(WITH_COCOA) && !defined(STRGEN) && !defined(SETTINGSGEN)
        int res = MacOSStringCompare(s1, s2);
        if (res != 0) return res - 2; // Convert to normal C return values.
#endif

        /* Do a normal comparison if ICU is missing or if we cannot create a collator. */
        return strcasecmp(s1, s2);
}

#ifdef WITH_UNISCRIBE

/* static */ StringIterator *StringIterator::Create()
{
        return new UniscribeStringIterator();
}

#elif defined(WITH_ICU_I18N)

#include <unicode/utext.h>
#include <unicode/brkiter.h>

/** String iterator using ICU as a backend. */
class IcuStringIterator : public StringIterator
{
        icu::BreakIterator *char_itr; ///< ICU iterator for characters.
        icu::BreakIterator *word_itr; ///< ICU iterator for words.

        std::vector<UChar> utf16_str;      ///< UTF-16 copy of the string.
        std::vector<size_t> utf16_to_utf8; ///< Mapping from UTF-16 code point position to index in the UTF-8 source string.

public:
        IcuStringIterator() : char_itr(nullptr), word_itr(nullptr)
        {
                UErrorCode status = U_ZERO_ERROR;
                this->char_itr = icu::BreakIterator::createCharacterInstance(icu::Locale(_current_language != nullptr ? _current_language->isocode : "en"), status);
                this->word_itr = icu::BreakIterator::createWordInstance(icu::Locale(_current_language != nullptr ? _current_language->isocode : "en"), status);

                this->utf16_str.push_back('\0');
                this->utf16_to_utf8.push_back(0);
        }

        ~IcuStringIterator() override
        {
                delete this->char_itr;
                delete this->word_itr;
        }

        void SetString(const char *s) override
        {
                const char *string_base = s;

                /* Unfortunately current ICU versions only provide rudimentary support
                 * for word break iterators (especially for CJK languages) in combination
                 * with UTF-8 input. As a work around we have to convert the input to
                 * UTF-16 and create a mapping back to UTF-8 character indices. */
                this->utf16_str.clear();
                this->utf16_to_utf8.clear();

                while (*s != '\0') {
                        size_t idx = s - string_base;

                        WChar c = Utf8Consume(&s);
                        if (c < 0x10000) {
                                this->utf16_str.push_back((UChar)c);
                        } else {
                                /* Make a surrogate pair. */
                                this->utf16_str.push_back((UChar)(0xD800 + ((c - 0x10000) >> 10)));
                                this->utf16_str.push_back((UChar)(0xDC00 + ((c - 0x10000) & 0x3FF)));
                                this->utf16_to_utf8.push_back(idx);
                        }
                        this->utf16_to_utf8.push_back(idx);
                }
                this->utf16_str.push_back('\0');
                this->utf16_to_utf8.push_back(s - string_base);

                UText text = UTEXT_INITIALIZER;
                UErrorCode status = U_ZERO_ERROR;
                utext_openUChars(&text, this->utf16_str.data(), this->utf16_str.size() - 1, &status);
                this->char_itr->setText(&text, status);
                this->word_itr->setText(&text, status);
                this->char_itr->first();
                this->word_itr->first();
        }

        size_t SetCurPosition(size_t pos) override
        {
                /* Convert incoming position to an UTF-16 string index. */
                uint utf16_pos = 0;
                for (uint i = 0; i < this->utf16_to_utf8.size(); i++) {
                        if (this->utf16_to_utf8[i] == pos) {
                                utf16_pos = i;
                                break;
                        }
                }

                /* isBoundary has the documented side-effect of setting the current
                 * position to the first valid boundary equal to or greater than
                 * the passed value. */
                this->char_itr->isBoundary(utf16_pos);
                return this->utf16_to_utf8[this->char_itr->current()];
        }

        size_t Next(IterType what) override
        {
                int32_t pos;
                switch (what) {
                        case ITER_CHARACTER:
                                pos = this->char_itr->next();
                                break;

                        case ITER_WORD:
                                pos = this->word_itr->following(this->char_itr->current());
                                /* The ICU word iterator considers both the start and the end of a word a valid
                                 * break point, but we only want word starts. Move to the next location in
                                 * case the new position points to whitespace. */
                                while (pos != icu::BreakIterator::DONE &&
                                                IsWhitespace(Utf16DecodeChar((const uint16 *)&this->utf16_str[pos]))) {
                                        int32_t new_pos = this->word_itr->next();
                                        /* Don't set it to DONE if it was valid before. Otherwise we'll return END
                                         * even though the iterator wasn't at the end of the string before. */
                                        if (new_pos == icu::BreakIterator::DONE) break;
                                        pos = new_pos;
                                }

                                this->char_itr->isBoundary(pos);
                                break;

                        default:
                                NOT_REACHED();
                }

                return pos == icu::BreakIterator::DONE ? END : this->utf16_to_utf8[pos];
        }

        size_t Prev(IterType what) override
        {
                int32_t pos;
                switch (what) {
                        case ITER_CHARACTER:
                                pos = this->char_itr->previous();
                                break;

                        case ITER_WORD:
                                pos = this->word_itr->preceding(this->char_itr->current());
                                /* The ICU word iterator considers both the start and the end of a word a valid
                                 * break point, but we only want word starts. Move to the previous location in
                                 * case the new position points to whitespace. */
                                while (pos != icu::BreakIterator::DONE &&
                                                IsWhitespace(Utf16DecodeChar((const uint16 *)&this->utf16_str[pos]))) {
                                        int32_t new_pos = this->word_itr->previous();
                                        /* Don't set it to DONE if it was valid before. Otherwise we'll return END
                                         * even though the iterator wasn't at the start of the string before. */
                                        if (new_pos == icu::BreakIterator::DONE) break;
                                        pos = new_pos;
                                }

                                this->char_itr->isBoundary(pos);
                                break;

                        default:
                                NOT_REACHED();
                }

                return pos == icu::BreakIterator::DONE ? END : this->utf16_to_utf8[pos];
        }
};

/* static */ StringIterator *StringIterator::Create()
{
        return new IcuStringIterator();
}

#else

/** Fallback simple string iterator. */
class DefaultStringIterator : public StringIterator
{
        const char *string; ///< Current string.
        size_t len;         ///< String length.
        size_t cur_pos;     ///< Current iteration position.

public:
        DefaultStringIterator() : string(nullptr), len(0), cur_pos(0)
        {
        }

        virtual void SetString(const char *s)
        {
                this->string = s;
                this->len = strlen(s);
                this->cur_pos = 0;
        }

        virtual size_t SetCurPosition(size_t pos)
        {
                assert(this->string != nullptr && pos <= this->len);
                /* Sanitize in case we get a position inside an UTF-8 sequence. */
                while (pos > 0 && IsUtf8Part(this->string[pos])) pos--;
                return this->cur_pos = pos;
        }

        virtual size_t Next(IterType what)
        {
                assert(this->string != nullptr);

                /* Already at the end? */
                if (this->cur_pos >= this->len) return END;

                switch (what) {
                        case ITER_CHARACTER: {
                                WChar c;
                                this->cur_pos += Utf8Decode(&c, this->string + this->cur_pos);
                                return this->cur_pos;
                        }

                        case ITER_WORD: {
                                WChar c;
                                /* Consume current word. */
                                size_t offs = Utf8Decode(&c, this->string + this->cur_pos);
                                while (this->cur_pos < this->len && !IsWhitespace(c)) {
                                        this->cur_pos += offs;
                                        offs = Utf8Decode(&c, this->string + this->cur_pos);
                                }
                                /* Consume whitespace to the next word. */
                                while (this->cur_pos < this->len && IsWhitespace(c)) {
                                        this->cur_pos += offs;
                                        offs = Utf8Decode(&c, this->string + this->cur_pos);
                                }

                                return this->cur_pos;
                        }

                        default:
                                NOT_REACHED();
                }

                return END;
        }

        virtual size_t Prev(IterType what)
        {
                assert(this->string != nullptr);

                /* Already at the beginning? */
                if (this->cur_pos == 0) return END;

                switch (what) {
                        case ITER_CHARACTER:
                                return this->cur_pos = Utf8PrevChar(this->string + this->cur_pos) - this->string;

                        case ITER_WORD: {
                                const char *s = this->string + this->cur_pos;
                                WChar c;
                                /* Consume preceding whitespace. */
                                do {
                                        s = Utf8PrevChar(s);
                                        Utf8Decode(&c, s);
                                } while (s > this->string && IsWhitespace(c));
                                /* Consume preceding word. */
                                while (s > this->string && !IsWhitespace(c)) {
                                        s = Utf8PrevChar(s);
                                        Utf8Decode(&c, s);
                                }
                                /* Move caret back to the beginning of the word. */
                                if (IsWhitespace(c)) Utf8Consume(&s);

                                return this->cur_pos = s - this->string;
                        }

                        default:
                                NOT_REACHED();
                }

                return END;
        }
};

#if defined(WITH_COCOA) && !defined(STRGEN) && !defined(SETTINGSGEN)
/* static */ StringIterator *StringIterator::Create()
{
        StringIterator *i = OSXStringIterator::Create();
        if (i != nullptr) return i;

        return new DefaultStringIterator();
}
#else
/* static */ StringIterator *StringIterator::Create()
{
        return new DefaultStringIterator();
}
#endif /* defined(WITH_COCOA) && !defined(STRGEN) && !defined(SETTINGSGEN) */

#endif