c99.h

libiconv是一个很不错的字符集转换库。程序接口也很简单

/*
 * Copyright (C) 1999-2002 Free Software Foundation, Inc.
 * This file is part of the GNU LIBICONV Library.
 *
 * The GNU LIBICONV Library is free software; you can redistribute it
 * and/or modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * The GNU LIBICONV 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with the GNU LIBICONV Library; see the file COPYING.LIB.
 * If not, write to the Free Software Foundation, Inc., 59 Temple Place -
 * Suite 330, Boston, MA 02111-1307, USA.
 */

/*
 * C99
 * This is ASCII with \uXXXX and \UXXXXXXXX escape sequences, denoting Unicode
 * characters. See ISO/IEC 9899:1999, section 6.4.3.
 * The treatment of control characters in the range U+0080..U+009F is not
 * specified; we pass them through unmodified.
 */

static int
c99_mbtowc (conv_t conv, ucs4_t *pwc, const unsigned char *s, int n)
{
  unsigned char c;
  ucs4_t wc;
  int i;

  c = s[0];
  if (c < 0xa0) {
    if (c != '\\') {
      *pwc = c;
      return 1;
    }
    if (n < 2)
      return RET_TOOFEW(0);
    c = s[1];
    if (c == 'u') {
      wc = 0;
      for (i = 2; i < 6; i++) {
        if (n <= i)
          return RET_TOOFEW(0);
        c = s[i];
        if (c >= '0' && c <= '9')
          c -= '0';
        else if (c >= 'A' && c <= 'Z')
          c -= 'A'-10;
        else if (c >= 'a' && c <= 'z')
          c -= 'a'-10;
        else
          goto simply_backslash;
        wc |= (ucs4_t) c << (4 * (5-i));
      }
      if ((wc >= 0x00a0 && !(wc >= 0xd800 && wc < 0xe000))
          || wc == 0x0024 || wc == 0x0040 || wc == 0x0060) {
        *pwc = wc;
        return 6;
      }
    } else if (c == 'U') {
      wc = 0;
      for (i = 2; i < 10; i++) {
        if (n <= i)
          return RET_TOOFEW(0);
        c = s[i];
        if (c >= '0' && c <= '9')
          c -= '0';
        else if (c >= 'A' && c <= 'Z')
          c -= 'A'-10;
        else if (c >= 'a' && c <= 'z')
          c -= 'a'-10;
        else
          goto simply_backslash;
        wc |= (ucs4_t) c << (4 * (9-i));
      }
      if ((wc >= 0x00a0 && !(wc >= 0xd800 && wc < 0xe000))
          || wc == 0x0024 || wc == 0x0040 || wc == 0x0060) {
        *pwc = wc;
        return 10;
      }
    } else
      goto simply_backslash;
  }
  return RET_ILSEQ;
simply_backslash:
  *pwc = '\\';
  return 1;
}

static int
c99_wctomb (conv_t conv, unsigned char *r, ucs4_t wc, int n)
{
  if (wc < 0xa0) {
    *r = wc;
    return 1;
  } else {
    int result;
    unsigned char u;
    if (wc < 0x10000) {
      result = 6;
      u = 'u';
    } else {
      result = 10;
      u = 'U';
    }
    if (n >= result) {
      int count;
      r[0] = '\\';
      r[1] = u;
      r += 2;
      for (count = result-3; count >= 0; count--) {
        unsigned int i = (wc >> (4*count)) & 0x0f;
        *r++ = (i < 10 ? '0'+i : 'a'-10+i);
      }
      return result;
    } else
      return RET_TOOSMALL;
  }
}