code:
/* Iterate over previous character in UTF-8 string.
   Copyright (C) 2002, 2006-2007, 2009-2010 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2002.

   This program 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 3 of the License, or
   (at your option) any later version.

   This program 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 program.  If not, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include "unistr.h"

const uint8_t *
u8_prev (ucs4_t *puc, const uint8_t *s, const uint8_t *start)
{
  /* Keep in sync with unistr.h and utf8-ucs4.c.  */
  if (s != start)
    {
      uint8_t c_1 = s[-1];

      if (c_1 < 0x80)
        {
          *puc = c_1;
          return s - 1;
        }
#if CONFIG_UNICODE_SAFETY
      if ((c_1 ^ 0x80) < 0x40)
#endif
        if (s - 1 != start)
          {
            uint8_t c_2 = s[-2];

            if (c_2 >= 0xc2 && c_2 < 0xe0)
              {
                *puc = ((unsigned int) (c_2 & 0x1f) << 6)
                       | (unsigned int) (c_1 ^ 0x80);
                return s - 2;
              }
#if CONFIG_UNICODE_SAFETY
            if ((c_2 ^ 0x80) < 0x40)
#endif
              if (s - 2 != start)
                {
                  uint8_t c_3 = s[-3];

                  if (c_3 >= 0xe0 && c_3 < 0xf0
#if CONFIG_UNICODE_SAFETY
                      && (c_3 >= 0xe1 || c_2 >= 0xa0)
                      && (c_3 != 0xed || c_2 < 0xa0)
#endif
                     )
                    {
                      *puc = ((unsigned int) (c_3 & 0x0f) << 12)
                             | ((unsigned int) (c_2 ^ 0x80) << 6)
                             | (unsigned int) (c_1 ^ 0x80);
                      return s - 3;
                    }
#if CONFIG_UNICODE_SAFETY
                  if ((c_3 ^ 0x80) < 0x40)
#endif
                    if (s - 3 != start)
                      {
                        uint8_t c_4 = s[-4];

                        if (c_4 >= 0xf0 && c_4 < 0xf8
#if CONFIG_UNICODE_SAFETY
                            && (c_4 >= 0xf1 || c_3 >= 0x90)
                            && (c_4 < 0xf4 || (c_4 == 0xf4 && c_3 < 0x90))
#endif
                           )
                          {
                            *puc = ((unsigned int) (c_4 & 0x07) << 18)
                                   | ((unsigned int) (c_3 ^ 0x80) << 12)
                                   | ((unsigned int) (c_2 ^ 0x80) << 6)
                                   | (unsigned int) (c_1 ^ 0x80);
                            return s - 4;
                          }
                      }
                }
          }
    }
  return NULL;
}


code:
/* Conversion UCS-4 to UTF-8.
   Copyright (C) 2002, 2006-2007, 2009-2010 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2002.

   This program 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 3 of the License, or
   (at your option) any later version.

   This program 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 program.  If not, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include "unistr.h"

int
u8_uctomb_aux (uint8_t *s, ucs4_t uc, int n)
{
  int count;

  if (uc < 0x80)
    /* The case n >= 1 is already handled by the caller.  */
    return -2;
  else if (uc < 0x800)
    count = 2;
  else if (uc < 0x10000)
    {
      if (uc < 0xd800 || uc >= 0xe000)
        count = 3;
      else
        return -1;
    }
#if 0
  else if (uc < 0x200000)
    count = 4;
  else if (uc < 0x4000000)
    count = 5;
  else if (uc <= 0x7fffffff)
    count = 6;
#else
  else if (uc < 0x110000)
    count = 4;
#endif
  else
    return -1;

  if (n < count)
    return -2;

  switch (count) /* note: code falls through cases! */
    {
#if 0
    case 6: s[5] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x4000000;
    case 5: s[4] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x200000;
#endif
    case 4: s[3] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x10000;
    case 3: s[2] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x800;
    case 2: s[1] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0xc0;
  /*case 1:*/ s[0] = uc;
    }
  return count;
}

license: mit


code:
/* Store a character in UTF-8 string.
   Copyright (C) 2002, 2005-2006, 2009-2010 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2002.

   This program 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 3 of the License, or
   (at your option) any later version.

   This program 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 program.  If not, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

#if defined IN_LIBUNISTRING
/* Tell unistr.h to declare u8_uctomb as 'extern', not 'static inline'.  */
# include "unistring-notinline.h"
#endif

/* Specification.  */
#include "unistr.h"

#if !HAVE_INLINE

int
u8_uctomb (uint8_t *s, ucs4_t uc, int n)
{
  if (uc < 0x80)
    {
      if (n > 0)
        {
          s[0] = uc;
          return 1;
        }
      /* else return -2, below.  */
    }
  else
    {
      int count;

      if (uc < 0x800)
        count = 2;
      else if (uc < 0x10000)
        {
          if (uc < 0xd800 || uc >= 0xe000)
            count = 3;
          else
            return -1;
        }
#if 0
      else if (uc < 0x200000)
        count = 4;
      else if (uc < 0x4000000)
        count = 5;
      else if (uc <= 0x7fffffff)
        count = 6;
#else
      else if (uc < 0x110000)
        count = 4;
#endif
      else
        return -1;

      if (n >= count)
        {
          switch (count) /* note: code falls through cases! */
            {
#if 0
            case 6: s[5] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x4000000;
            case 5: s[4] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x200000;
#endif
            case 4: s[3] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x10000;
            case 3: s[2] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x800;
            case 2: s[1] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0xc0;
          /*case 1:*/ s[0] = uc;
            }
          return count;
        }
    }
  return -2;
}

#endif


code:
/* Elementary types for the GNU UniString library.
   Copyright (C) 2002, 2005-2006, 2009-2010 Free Software Foundation, Inc.

   This program 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 3 of the License, or
   (at your option) any later version.

   This program 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 program.  If not, see <http://www.gnu.org/licenses/>.  */

#ifndef _UNITYPES_H
#define _UNITYPES_H

/* Get uint8_t, uint16_t, uint32_t.  */
#include <stdint.h>

/* Type representing a Unicode character.  */
typedef uint32_t ucs4_t;

#endif /* _UNITYPES_H */