/*

 * utf8.c       -- UTF-8 routines

 *

 * Copyright (C) 2006 Reimar Döffinger <Reimar.Doeffinger@stud.uni-karlsruhe.de>

 *

 * This program 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; either version 2 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

 * General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307

 * USA

 */

#include "utf8.h"

char *prev_char(char *str, const char *limit)

{

  if (str <= limit)

    return str;

  str--;

  if (utf8_mode)

    while ((str > limit) && ((*str & 0xc0) == 0x80))

      str--;

  return str;

}

char *next_char(char *str)

{

  if (!*str)

    return str;

  str++;

  if (utf8_mode)

    while ((*str & 0xc0) == 0x80)

      str++;

  return str;

}

unsigned get_char(const char *str)

{

  unsigned char *strp = (unsigned char *)str;

  unsigned c = *strp++;

  unsigned mask = 0x80;

  int len = -1;

  if (!utf8_mode)

    return c;

  while (c & mask) {

    mask >>= 1;

    len++;

  }

  if (len <= 0 || len > 4)

    goto no_utf8;

  c &= mask - 1;

  while ((*strp & 0xc0) == 0x80) {

    if (len-- <= 0)

      goto no_utf8;

    c = (c << 6) | (*strp++ & 0x3f);

  }

  if (len)

    goto no_utf8;

  return c;

no_utf8:

  return *str;

}

char *put_char(char *str, unsigned c)

{

  int mask = 0xffffffc0;

  int i = 4;

  char code[5];

  if (!utf8_mode || c < 128) {

    *str++ = c;

    return str;

  }

  while (c & mask) {

    code[i--] = 0x80 | (c & 0x3f);

    c >>= 6;

    mask >>= 1;

    if (i < 0) {

      *str++ = '?';

      return str;

    }

  }

  code[i] = (mask << 1) | c;

  for (; i < 5; i++)

    *str++ = code[i];

  return str;

}