text: /* gutf8.c - Operations on UTF-8 strings.
   *
   * Copyright (C) 1999 Tom Tromey
   * Copyright (C) 2000 Red Hat, Inc.
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library 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
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, see <http://www.gnu.org/licenses/>.
   */
  
  #include "config.h"
  
  #include <stdlib.h>
  #ifdef HAVE_CODESET
  #include <langinfo.h>
  #endif
  #include <string.h>
  
  #ifdef G_PLATFORM_WIN32
  #include <stdio.h>
  #define STRICT
  #include <windows.h>
  #undef STRICT
  #endif
  
  #include "gconvert.h"
  #include "ghash.h"
  #include "gstrfuncs.h"
  #include "gtestutils.h"
  #include "gtypes.h"
  #include "gthread.h"
  #include "glibintl.h"
  
  #define UTF8_COMPUTE(Char, Mask, Len)					      \
    if (Char < 128)							      \
      {									      \
        Len = 1;								      \
        Mask = 0x7f;							      \
      }									      \
    else if ((Char & 0xe0) == 0xc0)					      \
      {									      \
        Len = 2;								      \
        Mask = 0x1f;							      \
      }									      \
    else if ((Char & 0xf0) == 0xe0)					      \
      {									      \
        Len = 3;								      \
        Mask = 0x0f;							      \
      }									      \
    else if ((Char & 0xf8) == 0xf0)					      \
      {									      \
        Len = 4;								      \
        Mask = 0x07;							      \
      }									      \
    else if ((Char & 0xfc) == 0xf8)					      \
      {									      \
        Len = 5;								      \
        Mask = 0x03;							      \
      }									      \
    else if ((Char & 0xfe) == 0xfc)					      \
      {									      \
        Len = 6;								      \
        Mask = 0x01;							      \
      }									      \
    else									      \
      Len = -1;
  
  #define UTF8_LENGTH(Char)              \
    ((Char) < 0x80 ? 1 :                 \
     ((Char) < 0x800 ? 2 :               \
      ((Char) < 0x10000 ? 3 :            \
       ((Char) < 0x200000 ? 4 :          \
        ((Char) < 0x4000000 ? 5 : 6)))))
     
  
  #define UTF8_GET(Result, Chars, Count, Mask, Len)			      \
    (Result) = (Chars)[0] & (Mask);					      \
    for ((Count) = 1; (Count) < (Len); ++(Count))				      \
      {									      \
        if (((Chars)[(Count)] & 0xc0) != 0x80)				      \
  	{								      \
  	  (Result) = -1;						      \
  	  break;							      \
  	}								      \
        (Result) <<= 6;							      \
        (Result) |= ((Chars)[(Count)] & 0x3f);				      \
      }
      
  /*
   * Check whether a Unicode (5.2) char is in a valid range.
   *
   * The first check comes from the Unicode guarantee to never encode
   * a point above 0x0010ffff, since UTF-16 couldn't represent it.
   * 
   * The second check covers surrogate pairs (category Cs).
   *
   * @param Char the character
   */
  #define UNICODE_VALID(Char)                   \
      ((Char) < 0x110000 &&                     \
       (((Char) & 0xFFFFF800) != 0xD800))
  
      
  static const gchar utf8_skip_data[256] = {
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
    3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,6,6,1,1
  };
  
  const gchar * const g_utf8_skip = utf8_skip_data;
  
  /**
   * g_utf8_find_prev_char:
   * @str: pointer to the beginning of a UTF-8 encoded string
   * @p: pointer to some position within @str
   * 
   * Given a position @p with a UTF-8 encoded string @str, find the start
   * of the previous UTF-8 character starting before @p. Returns %NULL if no
   * UTF-8 characters are present in @str before @p.
   *
   * @p does not have to be at the beginning of a UTF-8 character. No check
   * is made to see if the character found is actually valid other than
   * it starts with an appropriate byte.
   *
   * Returns: (transfer none) (nullable): a pointer to the found character or %NULL.
   */
  gchar *
  g_utf8_find_prev_char (const gchar *str,
  		       const gchar *p)
  {
    while (p > str)
      {
        --p;
        if ((*p & 0xc0) != 0x80)
  	return (gchar *)p;
      }
    return NULL;
  }
  
  /**
   * g_utf8_find_next_char:
   * @p: a pointer to a position within a UTF-8 encoded string
   * @end: (nullable): a pointer to the byte following the end of the string,
   *     or %NULL to indicate that the string is nul-terminated
   *
   * Finds the start of the next UTF-8 character in the string after @p.
   *
   * @p does not have to be at the beginning of a UTF-8 character. No check
   * is made to see if the character found is actually valid other than
   * it starts with an appropriate byte.
   * 
   * If @end is %NULL, the return value will never be %NULL: if the end of the
   * string is reached, a pointer to the terminating nul byte is returned. If
   * @end is non-%NULL, the return value will be %NULL if the end of the string
   * is reached.
   *
   * Returns: (transfer none) (nullable): a pointer to the found character or %NULL if @end is
   *    set and is reached
   */
  gchar *
  g_utf8_find_next_char (const gchar *p,
  		       const gchar *end)
  {
    if (end)
      {
        for (++p; p < end && (*p & 0xc0) == 0x80; ++p)
          ;
        return (p >= end) ? NULL : (gchar *)p;
      }
    else
      {
        for (++p; (*p & 0xc0) == 0x80; ++p)
          ;
        return (gchar *)p;
      }
  }
  
  /**
   * g_utf8_prev_char:
   * @p: a pointer to a position within a UTF-8 encoded string
   *
   * Finds the previous UTF-8 character in the string before @p.
   *
   * @p does not have to be at the beginning of a UTF-8 character. No check
   * is made to see if the character found is actually valid other than
   * it starts with an appropriate byte. If @p might be the first
   * character of the string, you must use g_utf8_find_prev_char() instead.
   * 
   * Returns: (transfer none) (not nullable): a pointer to the found character
   */
  gchar *
  g_utf8_prev_char (const gchar *p)
  {
    while (TRUE)
      {
        p--;
        if ((*p & 0xc0) != 0x80)
  	return (gchar *)p;
      }
  }
   
  /**
   * g_utf8_strlen:
   * @p: pointer to the start of a UTF-8 encoded string
   * @max: the maximum number of bytes to examine. If @max
   *       is less than 0, then the string is assumed to be
   *       nul-terminated. If @max is 0, @p will not be examined and
   *       may be %NULL. If @max is greater than 0, up to @max
   *       bytes are examined
   *
   * Computes the length of the string in characters, not including
   * the terminating nul character. If the @max'th byte falls in the
   * middle of a character, the last (partial) character is not counted.
   *
   * Returns: the length of the string in characters
   */
  glong
  g_utf8_strlen (const gchar *p,
                 gssize       max)
  {
    glong len = 0;
    const gchar *start = p;
    g_return_val_if_fail (p != NULL || max == 0, 0);
  
    if (max < 0)
      {
        while (*p)
          {
            p = g_utf8_next_char (p);
            ++len;
          }
      }
    else
      {
        if (max == 0 || !*p)
          return 0;
  
        p = g_utf8_next_char (p);
  
        while (p - start < max && *p)
          {
            ++len;
            p = g_utf8_next_char (p);
          }
  
        /* only do the last len increment if we got a complete
         * char (don't count partial chars)
         */
        if (p - start <= max)
          ++len;
      }
  
    return len;
  }
  
  /**
   * g_utf8_substring:
   * @str: a UTF-8 encoded string
   * @start_pos: a character offset within @str
   * @end_pos: another character offset within @str
   *
   * Copies a substring out of a UTF-8 encoded string.
   * The substring will contain @end_pos - @start_pos characters.
   *
   * Returns: (transfer full): a newly allocated copy of the requested
   *     substring. Free with g_free() when no longer needed.
   *
   * Since: 2.30
   */
  gchar *
  g_utf8_substring (const gchar *str,
                    glong        start_pos,
                    glong        end_pos)
  {
    gchar *start, *end, *out;
  
    start = g_utf8_offset_to_pointer (str, start_pos);
    end = g_utf8_offset_to_pointer (start, end_pos - start_pos);
  
    out = g_malloc (end - start + 1);
    memcpy (out, start, end - start);
    out[end - start] = 0;
  
    return out;
  }
  
  /**
   * g_utf8_get_char:
   * @p: a pointer to Unicode character encoded as UTF-8
   * 
   * Converts a sequence of bytes encoded as UTF-8 to a Unicode character.
   *
   * If @p does not point to a valid UTF-8 encoded character, results
   * are undefined. If you are not sure that the bytes are complete
   * valid Unicode characters, you should use g_utf8_get_char_validated()
   * instead.
   * 
   * Returns: the resulting character
   */
  gunichar
  g_utf8_get_char (const gchar *p)
  {
    int i, mask = 0, len;
    gunichar result;
    unsigned char c = (unsigned char) *p;
  
    UTF8_COMPUTE (c, mask, len);
    if (len == -1)
      return (gunichar)-1;
    UTF8_GET (result, p, i, mask, len);
  
    return result;
  }
  
  /**
   * g_utf8_offset_to_pointer:
   * @str: a UTF-8 encoded string
   * @offset: a character offset within @str
   *
   * Converts from an integer character offset to a pointer to a position
   * within the string.
   *
   * Since 2.10, this function allows to pass a negative @offset to
   * step backwards. It is usually worth stepping backwards from the end
   * instead of forwards if @offset is in the last fourth of the string,
   * since moving forward is about 3 times faster than moving backward.
   *
   * Note that this function doesn't abort when reaching the end of @str.
   * Therefore you should be sure that @offset is within string boundaries
   * before calling that function. Call g_utf8_strlen() when unsure.
   * This limitation exists as this function is called frequently during
   * text rendering and therefore has to be as fast as possible.
   *
   * Returns: (transfer none): the resulting pointer
   */
  gchar *
  g_utf8_offset_to_pointer  (const gchar *str,
  			   glong        offset)
  {
    const gchar *s = str;
  
    if (offset > 0) 
      while (offset--)
        s = g_utf8_next_char (s);
    else
      {
        const char *s1;
  
        /* This nice technique for fast backwards stepping 
         * through a UTF-8 string was dubbed "stutter stepping" 
         * by its inventor, Larry Ewing.
         */
        while (offset)
  	{
  	  s1 = s;
  	  s += offset;
  	  while ((*s & 0xc0) == 0x80)
  	    s--;
  
  	  offset += g_utf8_pointer_to_offset (s, s1);
  	}
      }
  
    return (gchar *)s;
  }
  
  /**
   * g_utf8_pointer_to_offset:
   * @str: a UTF-8 encoded string
   * @pos: a pointer to a position within @str
   * 
   * Converts from a pointer to position within a string to an integer
   * character offset.
   *
   * Since 2.10, this function allows @pos to be before @str, and returns
   * a negative offset in this case.
   * 
   * Returns: the resulting character offset
   */
  glong    
  g_utf8_pointer_to_offset (const gchar *str,
  			  const gchar *pos)
  {
    const gchar *s = str;
    glong offset = 0;    
  
    if (pos < str) 
      offset = - g_utf8_pointer_to_offset (pos, str);
    else
      while (s < pos)
        {
  	s = g_utf8_next_char (s);
  	offset++;
        }
    
    return offset;
  }
  
  
  /**
   * g_utf8_strncpy:
   * @dest: (transfer none): buffer to fill with characters from @src
   * @src: UTF-8 encoded string
   * @n: character count
   * 
   * Like the standard C strncpy() function, but copies a given number
   * of characters instead of a given number of bytes. The @src string
   * must be valid UTF-8 encoded text. (Use g_utf8_validate() on all
   * text before trying to use UTF-8 utility functions with it.)
   * 
   * Note you must ensure @dest is at least 4 * @n to fit the
   * largest possible UTF-8 characters
   *
   * Returns: (transfer none): @dest
   */
  gchar *
  g_utf8_strncpy (gchar       *dest,
  		const gchar *src,
  		gsize        n)
  {
    const gchar *s = src;
    while (n && *s)
      {
        s = g_utf8_next_char(s);
        n--;
      }
    strncpy(dest, src, s - src);
    dest[s - src] = 0;
    return dest;
  }
  
  /* unicode_strchr */
  
  /**
   * g_unichar_to_utf8:
   * @c: a Unicode character code
   * @outbuf: (out caller-allocates) (optional): output buffer, must have at
   *       least 6 bytes of space. If %NULL, the length will be computed and
   *       returned and nothing will be written to @outbuf.
   * 
   * Converts a single character to UTF-8.
   * 
   * Returns: number of bytes written
   */
  int
  g_unichar_to_utf8 (gunichar c,
  		   gchar   *outbuf)
  {
    /* If this gets modified, also update the copy in g_string_insert_unichar() */
    guint len = 0;    
    int first;
    int i;
  
    if (c < 0x80)
      {
        first = 0;
        len = 1;
      }
    else if (c < 0x800)
      {
        first = 0xc0;
        len = 2;
      }
    else if (c < 0x10000)
      {
        first = 0xe0;
        len = 3;
      }
     else if (c < 0x200000)
      {
        first = 0xf0;
        len = 4;
      }
    else if (c < 0x4000000)
      {
        first = 0xf8;
        len = 5;
      }
    else
      {
        first = 0xfc;
        len = 6;
      }
  
    if (outbuf)
      {
        for (i = len - 1; i > 0; --i)
  	{
  	  outbuf[i] = (c & 0x3f) | 0x80;
  	  c >>= 6;
  	}
        outbuf[0] = c | first;
      }
  
    return len;
  }
  
  /**
   * g_utf8_strchr:
   * @p: a nul-terminated UTF-8 encoded string
   * @len: the maximum length of @p
   * @c: a Unicode character
   * 
   * Finds the leftmost occurrence of the given Unicode character
   * in a UTF-8 encoded string, while limiting the search to @len bytes.
   * If @len is -1, allow unbounded search.
   * 
   * Returns: (transfer none) (nullable): %NULL if the string does not contain the character,
   *     otherwise, a pointer to the start of the leftmost occurrence
   *     of the character in the string.
   */
  gchar *
  g_utf8_strchr (const char *p,
  	       gssize      len,
  	       gunichar    c)
  {
    gchar ch[10];
  
    gint charlen = g_unichar_to_utf8 (c, ch);
    ch[charlen] = '\0';
    
    return g_strstr_len (p, len, ch);
  }
  
  
  /**
   * g_utf8_strrchr:
   * @p: a nul-terminated UTF-8 encoded string
   * @len: the maximum length of @p
   * @c: a Unicode character
   * 
   * Find the rightmost occurrence of the given Unicode character
   * in a UTF-8 encoded string, while limiting the search to @len bytes.
   * If @len is -1, allow unbounded search.
   * 
   * Returns: (transfer none) (nullable): %NULL if the string does not contain the character,
   *     otherwise, a pointer to the start of the rightmost occurrence
   *     of the character in the string.
   */
  gchar *
  g_utf8_strrchr (const char *p,
  		gssize      len,
  		gunichar    c)
  {
    gchar ch[10];
  
    gint charlen = g_unichar_to_utf8 (c, ch);
    ch[charlen] = '\0';
    
    return g_strrstr_len (p, len, ch);
  }
  
  
  /* Like g_utf8_get_char, but take a maximum length
   * and return (gunichar)-2 on incomplete trailing character;
   * also check for malformed or overlong sequences
   * and return (gunichar)-1 in this case.
   */
  static inline gunichar
  g_utf8_get_char_extended (const  gchar *p,
  			  gssize max_len)
  {
    guint i, len;
    gunichar min_code;
    gunichar wc = (guchar) *p;
    const gunichar partial_sequence = (gunichar) -2;
    const gunichar malformed_sequence = (gunichar) -1;
  
    if (wc < 0x80)
      {
        return wc;
      }
    else if (G_UNLIKELY (wc < 0xc0))
      {
        return malformed_sequence;
      }
    else if (wc < 0xe0)
      {
        len = 2;
        wc &= 0x1f;
        min_code = 1 << 7;
      }
    else if (wc < 0xf0)
      {
        len = 3;
        wc &= 0x0f;
        min_code = 1 << 11;
      }
    else if (wc < 0xf8)
      {
        len = 4;
        wc &= 0x07;
        min_code = 1 << 16;
      }
    else if (wc < 0xfc)
      {
        len = 5;
        wc &= 0x03;
        min_code = 1 << 21;
      }
    else if (wc < 0xfe)
      {
        len = 6;
        wc &= 0x01;
        min_code = 1 << 26;
      }
    else
      {
        return malformed_sequence;
      }
  
    if (G_UNLIKELY (max_len >= 0 && len > max_len))
      {
        for (i = 1; i < max_len; i++)
  	{
  	  if ((((guchar *)p)[i] & 0xc0) != 0x80)
  	    return malformed_sequence;
  	}
        return partial_sequence;
      }
  
    for (i = 1; i < len; ++i)
      {
        gunichar ch = ((guchar *)p)[i];
  
        if (G_UNLIKELY ((ch & 0xc0) != 0x80))
  	{
  	  if (ch)
  	    return malformed_sequence;
  	  else
  	    return partial_sequence;
  	}
  
        wc <<= 6;
        wc |= (ch & 0x3f);
      }
  
    if (G_UNLIKELY (wc < min_code))
      return malformed_sequence;
  
    return wc;
  }
  
  /**
   * g_utf8_get_char_validated:
   * @p: a pointer to Unicode character encoded as UTF-8
   * @max_len: the maximum number of bytes to read, or -1 if @p is nul-terminated
   *
   * Convert a sequence of bytes encoded as UTF-8 to a Unicode character.
   * This function checks for incomplete characters, for invalid characters
   * such as characters that are out of the range of Unicode, and for
   * overlong encodings of valid characters.
   *
   * Note that g_utf8_get_char_validated() returns (gunichar)-2 if
   * @max_len is positive and any of the bytes in the first UTF-8 character
   * sequence are nul.
   * 
   * Returns: the resulting character. If @p points to a partial
   *     sequence at the end of a string that could begin a valid 
   *     character (or if @max_len is zero), returns (gunichar)-2; 
   *     otherwise, if @p does not point to a valid UTF-8 encoded 
   *     Unicode character, returns (gunichar)-1.
   */
  gunichar
  g_utf8_get_char_validated (const gchar *p,
  			   gssize       max_len)
  {
    gunichar result;
  
    if (max_len == 0)
      return (gunichar)-2;
  
    result = g_utf8_get_char_extended (p, max_len);
  
    /* Disallow codepoint U+0000 as it’s a nul byte,
     * and all string handling in GLib is nul-terminated */
    if (result == 0 && max_len > 0)
      return (gunichar) -2;
  
    if (result & 0x80000000)
      return result;
    else if (!UNICODE_VALID (result))
      return (gunichar)-1;
    else
      return result;
  }
  
  #define CONT_BYTE_FAST(p) ((guchar)*p++ & 0x3f)
  
  /**
   * g_utf8_to_ucs4_fast:
   * @str: a UTF-8 encoded string
   * @len: the maximum length of @str to use, in bytes. If @len < 0,
   *     then the string is nul-terminated.
   * @items_written: (out caller-allocates) (optional): location to store the
   *     number of characters in the result, or %NULL.
   *
   * Convert a string from UTF-8 to a 32-bit fixed width
   * representation as UCS-4, assuming valid UTF-8 input.
   * This function is roughly twice as fast as g_utf8_to_ucs4()
   * but does no error checking on the input. A trailing 0 character
   * will be added to the string after the converted text.
   * 
   * Returns: (transfer full): a pointer to a newly allocated UCS-4 string.
   *     This value must be freed with g_free().
   */
  gunichar *
  g_utf8_to_ucs4_fast (const gchar *str,
  		     glong        len,              
  		     glong       *items_written)    
  {
    gunichar *result;
    gint n_chars, i;
    const gchar *p;
  
    g_return_val_if_fail (str != NULL, NULL);
  
    p = str;
    n_chars = 0;
    if (len < 0)
      {
        while (*p)
  	{
  	  p = g_utf8_next_char (p);
  	  ++n_chars;
  	}
      }
    else
      {
        while (p < str + len && *p)
  	{
  	  p = g_utf8_next_char (p);
  	  ++n_chars;
  	}
      }
    
    result = g_new (gunichar, n_chars + 1);
    
    p = str;
    for (i=0; i < n_chars; i++)
      {
        guchar first = (guchar)*p++;
        gunichar wc;
  
        if (first < 0xc0)
  	{
            /* We really hope first < 0x80, but we don't want to test an
             * extra branch for invalid input, which this function
             * does not care about. Handling unexpected continuation bytes
             * here will do the least damage. */
  	  wc = first;
  	}
        else
  	{
            gunichar c1 = CONT_BYTE_FAST(p);
            if (first < 0xe0)
              {
                wc = ((first & 0x1f) << 6) | c1;
              }
            else
              {
                gunichar c2 = CONT_BYTE_FAST(p);
                if (first < 0xf0)
                  {
                    wc = ((first & 0x0f) << 12) | (c1 << 6) | c2;
                  }
                else
                  {
                    gunichar c3 = CONT_BYTE_FAST(p);
                    wc = ((first & 0x07) << 18) | (c1 << 12) | (c2 << 6) | c3;
                    if (G_UNLIKELY (first >= 0xf8))
                      {
                        /* This can't be valid UTF-8, but g_utf8_next_char()
                         * and company allow out-of-range sequences */
                        gunichar mask = 1 << 20;
                        while ((wc & mask) != 0)
                          {
                            wc <<= 6;
                            wc |= CONT_BYTE_FAST(p);
                            mask <<= 5;
                          }
                        wc &= mask - 1;
                      }
                  }
              }
  	}
        result[i] = wc;
      }
    result[i] = 0;
  
    if (items_written)
      *items_written = i;
  
    return result;
  }
  
  static gpointer
  try_malloc_n (gsize n_blocks, gsize n_block_bytes, GError **error)
  {
      gpointer ptr = g_try_malloc_n (n_blocks, n_block_bytes);
      if (ptr == NULL)
        g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_NO_MEMORY,
                             _("Failed to allocate memory"));
      return ptr;
  }
  
  /**
   * g_utf8_to_ucs4:
   * @str: a UTF-8 encoded string
   * @len: the maximum length of @str to use, in bytes. If @len < 0,
   *     then the string is nul-terminated.
   * @items_read: (out caller-allocates) (optional): location to store number of
    *    bytes read, or %NULL.
   *     If %NULL, then %G_CONVERT_ERROR_PARTIAL_INPUT will be
   *     returned in case @str contains a trailing partial
   *     character. If an error occurs then the index of the
   *     invalid input is stored here.
   * @items_written: (out caller-allocates) (optional): location to store number
   *     of characters written or %NULL. The value here stored does not include
   *     the trailing 0 character.
   * @error: location to store the error occurring, or %NULL to ignore
   *     errors. Any of the errors in #GConvertError other than
   *     %G_CONVERT_ERROR_NO_CONVERSION may occur.
   *
   * Convert a string from UTF-8 to a 32-bit fixed width
   * representation as UCS-4. A trailing 0 character will be added to the
   * string after the converted text.
   * 
   * Returns: (transfer full): a pointer to a newly allocated UCS-4 string.
   *     This value must be freed with g_free(). If an error occurs,
   *     %NULL will be returned and @error set.
   */
  gunichar *
  g_utf8_to_ucs4 (const gchar *str,
  		glong        len,             
  		glong       *items_read,      
  		glong       *items_written,   
  		GError     **error)
  {
    gunichar *result = NULL;
    gint n_chars, i;
    const gchar *in;
    
    in = str;
    n_chars = 0;
    while ((len < 0 || str + len - in > 0) && *in)
      {
        gunichar wc = g_utf8_get_char_extended (in, len < 0 ? 6 : str + len - in);
        if (wc & 0x80000000)
  	{
  	  if (wc == (gunichar)-2)
  	    {
  	      if (items_read)
  		break;
  	      else
  		g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_PARTIAL_INPUT,
                                       _("Partial character sequence at end of input"));
  	    }
  	  else
  	    g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                   _("Invalid byte sequence in conversion input"));
  
  	  goto err_out;
  	}
  
        n_chars++;
  
        in = g_utf8_next_char (in);
      }
  
    result = try_malloc_n (n_chars + 1, sizeof (gunichar), error);
    if (result == NULL)
        goto err_out;
  
    in = str;
    for (i=0; i < n_chars; i++)
      {
        result[i] = g_utf8_get_char (in);
        in = g_utf8_next_char (in);
      }
    result[i] = 0;
  
    if (items_written)
      *items_written = n_chars;
  
   err_out:
    if (items_read)
      *items_read = in - str;
  
    return result;
  }
  
  /**
   * g_ucs4_to_utf8:
   * @str: a UCS-4 encoded string
   * @len: the maximum length (number of characters) of @str to use. 
   *     If @len < 0, then the string is nul-terminated.
   * @items_read: (out caller-allocates) (optional): location to store number of
   *     characters read, or %NULL.
   * @items_written: (out caller-allocates) (optional): location to store number
   *     of bytes written or %NULL. The value here stored does not include the
   *     trailing 0 byte.
   * @error: location to store the error occurring, or %NULL to ignore
   *         errors. Any of the errors in #GConvertError other than
   *         %G_CONVERT_ERROR_NO_CONVERSION may occur.
   *
   * Convert a string from a 32-bit fixed width representation as UCS-4.
   * to UTF-8. The result will be terminated with a 0 byte.
   * 
   * Returns: (transfer full): a pointer to a newly allocated UTF-8 string.
   *     This value must be freed with g_free(). If an error occurs,
   *     %NULL will be returned and @error set. In that case, @items_read
   *     will be set to the position of the first invalid input character.
   */
  gchar *
  g_ucs4_to_utf8 (const gunichar *str,
  		glong           len,              
  		glong          *items_read,       
  		glong          *items_written,    
  		GError        **error)
  {
    gint result_length;
    gchar *result = NULL;
    gchar *p;
    gint i;
  
    result_length = 0;
    for (i = 0; len < 0 || i < len ; i++)
      {
        if (!str[i])
  	break;
  
        if (str[i] >= 0x80000000)
  	{
  	  g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                 _("Character out of range for UTF-8"));
  	  goto err_out;
  	}
        
        result_length += UTF8_LENGTH (str[i]);
      }
  
    result = try_malloc_n (result_length + 1, 1, error);
    if (result == NULL)
        goto err_out;
  
    p = result;
  
    i = 0;
    while (p < result + result_length)
      p += g_unichar_to_utf8 (str[i++], p);
    
    *p = '\0';
  
    if (items_written)
      *items_written = p - result;
  
   err_out:
    if (items_read)
      *items_read = i;
  
    return result;
  }
  
  #define SURROGATE_VALUE(h,l) (((h) - 0xd800) * 0x400 + (l) - 0xdc00 + 0x10000)
  
  /**
   * g_utf16_to_utf8:
   * @str: a UTF-16 encoded string
   * @len: the maximum length (number of #gunichar2) of @str to use. 
   *     If @len < 0, then the string is nul-terminated.
   * @items_read: (out caller-allocates) (optional): location to store number of
   *     words read, or %NULL. If %NULL, then %G_CONVERT_ERROR_PARTIAL_INPUT will
   *     be returned in case @str contains a trailing partial character. If
   *     an error occurs then the index of the invalid input is stored here.
   * @items_written: (out caller-allocates) (optional): location to store number
   *     of bytes written, or %NULL. The value stored here does not include the
   *     trailing 0 byte.
   * @error: location to store the error occurring, or %NULL to ignore
   *     errors. Any of the errors in #GConvertError other than
   *     %G_CONVERT_ERROR_NO_CONVERSION may occur.
   *
   * Convert a string from UTF-16 to UTF-8. The result will be
   * terminated with a 0 byte.
   *
   * Note that the input is expected to be already in native endianness,
   * an initial byte-order-mark character is not handled specially.
   * g_convert() can be used to convert a byte buffer of UTF-16 data of
   * ambiguous endianess.
   *
   * Further note that this function does not validate the result
   * string; it may e.g. include embedded NUL characters. The only
   * validation done by this function is to ensure that the input can
   * be correctly interpreted as UTF-16, i.e. it doesn't contain
   * things unpaired surrogates.
   *
   * Returns: (transfer full): a pointer to a newly allocated UTF-8 string.
   *     This value must be freed with g_free(). If an error occurs,
   *     %NULL will be returned and @error set.
   **/
  gchar *
  g_utf16_to_utf8 (const gunichar2  *str,
  		 glong             len,
  		 glong            *items_read,
  		 glong            *items_written,
  		 GError          **error)
  {
    /* This function and g_utf16_to_ucs4 are almost exactly identical -
     * The lines that differ are marked.
     */
    const gunichar2 *in;
    gchar *out;
    gchar *result = NULL;
    gint n_bytes;
    gunichar high_surrogate;
  
    g_return_val_if_fail (str != NULL, NULL);
  
    n_bytes = 0;
    in = str;
    high_surrogate = 0;
    while ((len < 0 || in - str < len) && *in)
      {
        gunichar2 c = *in;
        gunichar wc;
  
        if (c >= 0xdc00 && c < 0xe000) /* low surrogate */
  	{
  	  if (high_surrogate)
  	    {
  	      wc = SURROGATE_VALUE (high_surrogate, c);
  	      high_surrogate = 0;
  	    }
  	  else
  	    {
  	      g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                     _("Invalid sequence in conversion input"));
  	      goto err_out;
  	    }
  	}
        else
  	{
  	  if (high_surrogate)
  	    {
  	      g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                     _("Invalid sequence in conversion input"));
  	      goto err_out;
  	    }
  
  	  if (c >= 0xd800 && c < 0xdc00) /* high surrogate */
  	    {
  	      high_surrogate = c;
  	      goto next1;
  	    }
  	  else
  	    wc = c;
  	}
  
        /********** DIFFERENT for UTF8/UCS4 **********/
        n_bytes += UTF8_LENGTH (wc);
  
      next1:
        in++;
      }
  
    if (high_surrogate && !items_read)
      {
        g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_PARTIAL_INPUT,
                             _("Partial character sequence at end of input"));
        goto err_out;
      }
    
    /* At this point, everything is valid, and we just need to convert
     */
    /********** DIFFERENT for UTF8/UCS4 **********/
    result = try_malloc_n (n_bytes + 1, 1, error);
    if (result == NULL)
        goto err_out;
  
    high_surrogate = 0;
    out = result;
    in = str;
    while (out < result + n_bytes)
      {
        gunichar2 c = *in;
        gunichar wc;
  
        if (c >= 0xdc00 && c < 0xe000) /* low surrogate */
  	{
  	  wc = SURROGATE_VALUE (high_surrogate, c);
  	  high_surrogate = 0;
  	}
        else if (c >= 0xd800 && c < 0xdc00) /* high surrogate */
  	{
  	  high_surrogate = c;
  	  goto next2;
  	}
        else
  	wc = c;
  
        /********** DIFFERENT for UTF8/UCS4 **********/
        out += g_unichar_to_utf8 (wc, out);
  
      next2:
        in++;
      }
    
    /********** DIFFERENT for UTF8/UCS4 **********/
    *out = '\0';
  
    if (items_written)
      /********** DIFFERENT for UTF8/UCS4 **********/
      *items_written = out - result;
  
   err_out:
    if (items_read)
      *items_read = in - str;
  
    return result;
  }
  
  /**
   * g_utf16_to_ucs4:
   * @str: a UTF-16 encoded string
   * @len: the maximum length (number of #gunichar2) of @str to use. 
   *     If @len < 0, then the string is nul-terminated.
   * @items_read: (out caller-allocates) (optional): location to store number of
   *     words read, or %NULL. If %NULL, then %G_CONVERT_ERROR_PARTIAL_INPUT will
   *     be returned in case @str contains a trailing partial character. If
   *     an error occurs then the index of the invalid input is stored here.
   * @items_written: (out caller-allocates) (optional): location to store number
   *     of characters written, or %NULL. The value stored here does not include
   *     the trailing 0 character.
   * @error: location to store the error occurring, or %NULL to ignore
   *     errors. Any of the errors in #GConvertError other than
   *     %G_CONVERT_ERROR_NO_CONVERSION may occur.
   *
   * Convert a string from UTF-16 to UCS-4. The result will be
   * nul-terminated.
   * 
   * Returns: (transfer full): a pointer to a newly allocated UCS-4 string.
   *     This value must be freed with g_free(). If an error occurs,
   *     %NULL will be returned and @error set.
   */
  gunichar *
  g_utf16_to_ucs4 (const gunichar2  *str,
  		 glong             len,              
  		 glong            *items_read,       
  		 glong            *items_written,    
  		 GError          **error)
  {
    const gunichar2 *in;
    gchar *out;
    gchar *result = NULL;
    gint n_bytes;
    gunichar high_surrogate;
  
    g_return_val_if_fail (str != NULL, NULL);
  
    n_bytes = 0;
    in = str;
    high_surrogate = 0;
    while ((len < 0 || in - str < len) && *in)
      {
        gunichar2 c = *in;
  
        if (c >= 0xdc00 && c < 0xe000) /* low surrogate */
  	{
  	  if (high_surrogate)
  	    {
  	      high_surrogate = 0;
  	    }
  	  else
  	    {
  	      g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                     _("Invalid sequence in conversion input"));
  	      goto err_out;
  	    }
  	}
        else
  	{
  	  if (high_surrogate)
  	    {
  	      g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                     _("Invalid sequence in conversion input"));
  	      goto err_out;
  	    }
  
  	  if (c >= 0xd800 && c < 0xdc00) /* high surrogate */
  	    {
  	      high_surrogate = c;
  	      goto next1;
  	    }
  	}
  
        /********** DIFFERENT for UTF8/UCS4 **********/
        n_bytes += sizeof (gunichar);
  
      next1:
        in++;
      }
  
    if (high_surrogate && !items_read)
      {
        g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_PARTIAL_INPUT,
                             _("Partial character sequence at end of input"));
        goto err_out;
      }
    
    /* At this point, everything is valid, and we just need to convert
     */
    /********** DIFFERENT for UTF8/UCS4 **********/
    result = try_malloc_n (n_bytes + 4, 1, error);
    if (result == NULL)
        goto err_out;
  
    high_surrogate = 0;
    out = result;
    in = str;
    while (out < result + n_bytes)
      {
        gunichar2 c = *in;
        gunichar wc;
  
        if (c >= 0xdc00 && c < 0xe000) /* low surrogate */
  	{
  	  wc = SURROGATE_VALUE (high_surrogate, c);
  	  high_surrogate = 0;
  	}
        else if (c >= 0xd800 && c < 0xdc00) /* high surrogate */
  	{
  	  high_surrogate = c;
  	  goto next2;
  	}
        else
  	wc = c;
  
        /********** DIFFERENT for UTF8/UCS4 **********/
        *(gunichar *)out = wc;
        out += sizeof (gunichar);
  
      next2:
        in++;
      }
  
    /********** DIFFERENT for UTF8/UCS4 **********/
    *(gunichar *)out = 0;
  
    if (items_written)
      /********** DIFFERENT for UTF8/UCS4 **********/
      *items_written = (out - result) / sizeof (gunichar);
  
   err_out:
    if (items_read)
      *items_read = in - str;
  
    return (gunichar *)result;
  }
  
  /**
   * g_utf8_to_utf16:
   * @str: a UTF-8 encoded string
   * @len: the maximum length (number of bytes) of @str to use.
   *     If @len < 0, then the string is nul-terminated.
   * @items_read: (out caller-allocates) (optional): location to store number of
   *     bytes read, or %NULL. If %NULL, then %G_CONVERT_ERROR_PARTIAL_INPUT will
   *     be returned in case @str contains a trailing partial character. If
   *     an error occurs then the index of the invalid input is stored here.
   * @items_written: (out caller-allocates) (optional): location to store number
   *     of #gunichar2 written, or %NULL. The value stored here does not include
   *     the trailing 0.
   * @error: location to store the error occurring, or %NULL to ignore
   *     errors. Any of the errors in #GConvertError other than
   *     %G_CONVERT_ERROR_NO_CONVERSION may occur.
   *
   * Convert a string from UTF-8 to UTF-16. A 0 character will be
   * added to the result after the converted text.
   *
   * Returns: (transfer full): a pointer to a newly allocated UTF-16 string.
   *     This value must be freed with g_free(). If an error occurs,
   *     %NULL will be returned and @error set.
   */
  gunichar2 *
  g_utf8_to_utf16 (const gchar *str,
  		 glong        len,
  		 glong       *items_read,
  		 glong       *items_written,
  		 GError     **error)
  {
    gunichar2 *result = NULL;
    gint n16;
    const gchar *in;
    gint i;
  
    g_return_val_if_fail (str != NULL, NULL);
  
    in = str;
    n16 = 0;
    while ((len < 0 || str + len - in > 0) && *in)
      {
        gunichar wc = g_utf8_get_char_extended (in, len < 0 ? 6 : str + len - in);
        if (wc & 0x80000000)
  	{
  	  if (wc == (gunichar)-2)
  	    {
  	      if (items_read)
  		break;
  	      else
  		g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_PARTIAL_INPUT,
                                       _("Partial character sequence at end of input"));
  	    }
  	  else
  	    g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                   _("Invalid byte sequence in conversion input"));
  
  	  goto err_out;
  	}
  
        if (wc < 0xd800)
  	n16 += 1;
        else if (wc < 0xe000)
  	{
  	  g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                 _("Invalid sequence in conversion input"));
  
  	  goto err_out;
  	}
        else if (wc < 0x10000)
  	n16 += 1;
        else if (wc < 0x110000)
  	n16 += 2;
        else
  	{
  	  g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                 _("Character out of range for UTF-16"));
  
  	  goto err_out;
  	}
        
        in = g_utf8_next_char (in);
      }
  
    result = try_malloc_n (n16 + 1, sizeof (gunichar2), error);
    if (result == NULL)
        goto err_out;
  
    in = str;
    for (i = 0; i < n16;)
      {
        gunichar wc = g_utf8_get_char (in);
  
        if (wc < 0x10000)
  	{
  	  result[i++] = wc;
  	}
        else
  	{
  	  result[i++] = (wc - 0x10000) / 0x400 + 0xd800;
  	  result[i++] = (wc - 0x10000) % 0x400 + 0xdc00;
  	}
        
        in = g_utf8_next_char (in);
      }
  
    result[i] = 0;
  
    if (items_written)
      *items_written = n16;
  
   err_out:
    if (items_read)
      *items_read = in - str;
    
    return result;
  }
  
  /**
   * g_ucs4_to_utf16:
   * @str: a UCS-4 encoded string
   * @len: the maximum length (number of characters) of @str to use. 
   *     If @len < 0, then the string is nul-terminated.
   * @items_read: (out caller-allocates) (optional): location to store number of
   *     bytes read, or %NULL. If an error occurs then the index of the invalid
   *     input is stored here.
   * @items_written: (out caller-allocates) (optional): location to store number
   *     of #gunichar2  written, or %NULL. The value stored here does not include
   *     the trailing 0.
   * @error: location to store the error occurring, or %NULL to ignore
   *     errors. Any of the errors in #GConvertError other than
   *     %G_CONVERT_ERROR_NO_CONVERSION may occur.
   *
   * Convert a string from UCS-4 to UTF-16. A 0 character will be
   * added to the result after the converted text.
   * 
   * Returns: (transfer full): a pointer to a newly allocated UTF-16 string.
   *     This value must be freed with g_free(). If an error occurs,
   *     %NULL will be returned and @error set.
   */
  gunichar2 *
  g_ucs4_to_utf16 (const gunichar  *str,
  		 glong            len,              
  		 glong           *items_read,       
  		 glong           *items_written,    
  		 GError         **error)
  {
    gunichar2 *result = NULL;
    gint n16;
    gint i, j;
  
    n16 = 0;
    i = 0;
    while ((len < 0 || i < len) && str[i])
      {
        gunichar wc = str[i];
  
        if (wc < 0xd800)
  	n16 += 1;
        else if (wc < 0xe000)
  	{
  	  g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                 _("Invalid sequence in conversion input"));
  
  	  goto err_out;
  	}
        else if (wc < 0x10000)
  	n16 += 1;
        else if (wc < 0x110000)
  	n16 += 2;
        else
  	{
  	  g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                 _("Character out of range for UTF-16"));
  
  	  goto err_out;
  	}
  
        i++;
      }
  
    result = try_malloc_n (n16 + 1, sizeof (gunichar2), error);
    if (result == NULL)
        goto err_out;
  
    for (i = 0, j = 0; j < n16; i++)
      {
        gunichar wc = str[i];
  
        if (wc < 0x10000)
  	{
  	  result[j++] = wc;
  	}
        else
  	{
  	  result[j++] = (wc - 0x10000) / 0x400 + 0xd800;
  	  result[j++] = (wc - 0x10000) % 0x400 + 0xdc00;
  	}
      }
    result[j] = 0;
  
    if (items_written)
      *items_written = n16;
    
   err_out:
    if (items_read)
      *items_read = i;
    
    return result;
  }
  
  #define VALIDATE_BYTE(mask, expect)                      \
    G_STMT_START {                                         \
      if (G_UNLIKELY((*(guchar *)p & (mask)) != (expect))) \
        goto error;                                        \
    } G_STMT_END
  
  /* see IETF RFC 3629 Section 4 */
  
  static const gchar *
  fast_validate (const char *str)
  
  {
    const gchar *p;
  
    for (p = str; *p; p++)
      {
        if (*(guchar *)p < 128)
  	/* done */;
        else 
  	{
  	  const gchar *last;
  
  	  last = p;
  	  if (*(guchar *)p < 0xe0) /* 110xxxxx */
  	    {
  	      if (G_UNLIKELY (*(guchar *)p < 0xc2))
  		goto error;
  	    }
  	  else
  	    {
  	      if (*(guchar *)p < 0xf0) /* 1110xxxx */
  		{
  		  switch (*(guchar *)p++ & 0x0f)
  		    {
  		    case 0:
  		      VALIDATE_BYTE(0xe0, 0xa0); /* 0xa0 ... 0xbf */
  		      break;
  		    case 0x0d:
  		      VALIDATE_BYTE(0xe0, 0x80); /* 0x80 ... 0x9f */
  		      break;
  		    default:
  		      VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  		    }
  		}
  	      else if (*(guchar *)p < 0xf5) /* 11110xxx excluding out-of-range */
  		{
  		  switch (*(guchar *)p++ & 0x07)
  		    {
  		    case 0:
  		      VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  		      if (G_UNLIKELY((*(guchar *)p & 0x30) == 0))
  			goto error;
  		      break;
  		    case 4:
  		      VALIDATE_BYTE(0xf0, 0x80); /* 0x80 ... 0x8f */
  		      break;
  		    default:
  		      VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  		    }
  		  p++;
  		  VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  		}
  	      else
  		goto error;
  	    }
  
  	  p++;
  	  VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  
  	  continue;
  
  	error:
  	  return last;
  	}
      }
  
    return p;
  }
  
  static const gchar *
  fast_validate_len (const char *str,
  		   gssize      max_len)
  
  {
    const gchar *p;
  
    g_assert (max_len >= 0);
  
    for (p = str; ((p - str) < max_len) && *p; p++)
      {
        if (*(guchar *)p < 128)
  	/* done */;
        else 
  	{
  	  const gchar *last;
  
  	  last = p;
  	  if (*(guchar *)p < 0xe0) /* 110xxxxx */
  	    {
  	      if (G_UNLIKELY (max_len - (p - str) < 2))
  		goto error;
  	      
  	      if (G_UNLIKELY (*(guchar *)p < 0xc2))
  		goto error;
  	    }
  	  else
  	    {
  	      if (*(guchar *)p < 0xf0) /* 1110xxxx */
  		{
  		  if (G_UNLIKELY (max_len - (p - str) < 3))
  		    goto error;
  
  		  switch (*(guchar *)p++ & 0x0f)
  		    {
  		    case 0:
  		      VALIDATE_BYTE(0xe0, 0xa0); /* 0xa0 ... 0xbf */
  		      break;
  		    case 0x0d:
  		      VALIDATE_BYTE(0xe0, 0x80); /* 0x80 ... 0x9f */
  		      break;
  		    default:
  		      VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  		    }
  		}
  	      else if (*(guchar *)p < 0xf5) /* 11110xxx excluding out-of-range */
  		{
  		  if (G_UNLIKELY (max_len - (p - str) < 4))
  		    goto error;
  
  		  switch (*(guchar *)p++ & 0x07)
  		    {
  		    case 0:
  		      VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  		      if (G_UNLIKELY((*(guchar *)p & 0x30) == 0))
  			goto error;
  		      break;
  		    case 4:
  		      VALIDATE_BYTE(0xf0, 0x80); /* 0x80 ... 0x8f */
  		      break;
  		    default:
  		      VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  		    }
  		  p++;
  		  VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  		}
  	      else
  		goto error;
  	    }
  
  	  p++;
  	  VALIDATE_BYTE(0xc0, 0x80); /* 10xxxxxx */
  
  	  continue;
  
  	error:
  	  return last;
  	}
      }
  
    return p;
  }
  
  /**
   * g_utf8_validate:
   * @str: (array length=max_len) (element-type guint8): a pointer to character data
   * @max_len: max bytes to validate, or -1 to go until NUL
   * @end: (out) (optional) (transfer none): return location for end of valid data
   * 
   * Validates UTF-8 encoded text. @str is the text to validate;
   * if @str is nul-terminated, then @max_len can be -1, otherwise
   * @max_len should be the number of bytes to validate.
   * If @end is non-%NULL, then the end of the valid range
   * will be stored there (i.e. the start of the first invalid 
   * character if some bytes were invalid, or the end of the text 
   * being validated otherwise).
   *
   * Note that g_utf8_validate() returns %FALSE if @max_len is 
   * positive and any of the @max_len bytes are nul.
   *
   * Returns %TRUE if all of @str was valid. Many GLib and GTK+
   * routines require valid UTF-8 as input; so data read from a file
   * or the network should be checked with g_utf8_validate() before
   * doing anything else with it.
   * 
   * Returns: %TRUE if the text was valid UTF-8
   */
  gboolean
  g_utf8_validate (const char   *str,
  		 gssize        max_len,    
  		 const gchar **end)
  
  {
    const gchar *p;
  
    if (max_len >= 0)
      return g_utf8_validate_len (str, max_len, end);
  
    p = fast_validate (str);
  
    if (end)
      *end = p;
  
    if (*p != '\0')
      return FALSE;
    else
      return TRUE;
  }
  
  /**
   * g_utf8_validate_len:
   * @str: (array length=max_len) (element-type guint8): a pointer to character data
   * @max_len: max bytes to validate
   * @end: (out) (optional) (transfer none): return location for end of valid data
   *
   * Validates UTF-8 encoded text.
   *
   * As with g_utf8_validate(), but @max_len must be set, and hence this function
   * will always return %FALSE if any of the bytes of @str are nul.
   *
   * Returns: %TRUE if the text was valid UTF-8
   * Since: 2.60
   */
  gboolean
  g_utf8_validate_len (const char   *str,
                       gsize         max_len,
                       const gchar **end)
  
  {
    const gchar *p;
  
    p = fast_validate_len (str, max_len);
  
    if (end)
      *end = p;
  
    if (p != str + max_len)
      return FALSE;
    else
      return TRUE;
  }
  
  /**
   * g_unichar_validate:
   * @ch: a Unicode character
   * 
   * Checks whether @ch is a valid Unicode character. Some possible
   * integer values of @ch will not be valid. 0 is considered a valid
   * character, though it's normally a string terminator.
   * 
   * Returns: %TRUE if @ch is a valid Unicode character
   **/
  gboolean
  g_unichar_validate (gunichar ch)
  {
    return UNICODE_VALID (ch);
  }
  
  /**
   * g_utf8_strreverse:
   * @str: a UTF-8 encoded string
   * @len: the maximum length of @str to use, in bytes. If @len < 0,
   *     then the string is nul-terminated.
   *
   * Reverses a UTF-8 string. @str must be valid UTF-8 encoded text. 
   * (Use g_utf8_validate() on all text before trying to use UTF-8 
   * utility functions with it.)
   *
   * This function is intended for programmatic uses of reversed strings.
   * It pays no attention to decomposed characters, combining marks, byte 
   * order marks, directional indicators (LRM, LRO, etc) and similar 
   * characters which might need special handling when reversing a string 
   * for display purposes.
   *
   * Note that unlike g_strreverse(), this function returns
   * newly-allocated memory, which should be freed with g_free() when
   * no longer needed. 
   *
   * Returns: (transfer full): a newly-allocated string which is the reverse of @str
   *
   * Since: 2.2
   */
  gchar *
  g_utf8_strreverse (const gchar *str,
  		   gssize       len)
  {
    gchar *r, *result;
    const gchar *p;
  
    if (len < 0)
      len = strlen (str);
  
    result = g_new (gchar, len + 1);
    r = result + len;
    p = str;
    while (r > result)
      {
        gchar *m, skip = g_utf8_skip[*(guchar*) p];
        r -= skip;
        g_assert (r >= result);
        for (m = r; skip; skip--)
          *m++ = *p++;
      }
    result[len] = 0;
  
    return result;
  }
  
  /**
   * g_utf8_make_valid:
   * @str: string to coerce into UTF-8
   * @len: the maximum length of @str to use, in bytes. If @len < 0,
   *     then the string is nul-terminated.
   *
   * If the provided string is valid UTF-8, return a copy of it. If not,
   * return a copy in which bytes that could not be interpreted as valid Unicode
   * are replaced with the Unicode replacement character (U+FFFD).
   *
   * For example, this is an appropriate function to use if you have received
   * a string that was incorrectly declared to be UTF-8, and you need a valid
   * UTF-8 version of it that can be logged or displayed to the user, with the
   * assumption that it is close enough to ASCII or UTF-8 to be mostly
   * readable as-is.
   *
   * Returns: (transfer full): a valid UTF-8 string whose content resembles @str
   *
   * Since: 2.52
   */
  gchar *
  g_utf8_make_valid (const gchar *str,
                     gssize       len)
  {
    GString *string;
    const gchar *remainder, *invalid;
    gsize remaining_bytes, valid_bytes;
  
    g_return_val_if_fail (str != NULL, NULL);
  
    if (len < 0)
      len = strlen (str);
  
    string = NULL;
    remainder = str;
    remaining_bytes = len;
  
    while (remaining_bytes != 0) 
      {
        if (g_utf8_validate (remainder, remaining_bytes, &invalid)) 
  	break;
        valid_bytes = invalid - remainder;
      
        if (string == NULL) 
  	string = g_string_sized_new (remaining_bytes);
  
        g_string_append_len (string, remainder, valid_bytes);
        /* append U+FFFD REPLACEMENT CHARACTER */
        g_string_append (string, "\357\277\275");
        
        remaining_bytes -= valid_bytes + 1;
        remainder = invalid + 1;
      }
    
    if (string == NULL)
      return g_strndup (str, len);
    
    g_string_append_len (string, remainder, remaining_bytes);
    g_string_append_c (string, '\0');
  
    g_assert (g_utf8_validate (string->str, -1, NULL));
  
    return g_string_free (string, FALSE);
  }
  