lib/utf16.h

   1 /*
   2  * Copyright (C) 1999-2001 Free Software Foundation, Inc.
   3  * This file is part of the GNU LIBICONV Library.
   4  *
   5  * The GNU LIBICONV Library is free software; you can redistribute it
   6  * and/or modify it under the terms of the GNU Library General Public
   7  * License as published by the Free Software Foundation; either version 2
   8  * of the License, or (at your option) any later version.
   9  *
  10  * The GNU LIBICONV Library is distributed in the hope that it will be
  11  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Library General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Library General Public
  16  * License along with the GNU LIBICONV Library; see the file COPYING.LIB.
  17  * If not, write to the Free Software Foundation, Inc., 59 Temple Place -
  18  * Suite 330, Boston, MA 02111-1307, USA.
  19  */
  20
  21 /*
  22  * UTF-16
  23  */
  24
  25 /* Specification: RFC 2781 */
  26
  27 /* Here we accept FFFE/FEFF marks as endianness indicators everywhere
  28    in the stream, not just at the beginning. (This is contrary to what
  29    RFC 2781 section 3.2 specifies, but it allows concatenation of byte
  30    sequences to work flawlessly, while disagreeing with the RFC behaviour
  31    only for strings containing U+FEFF characters, which is quite rare.)
  32    The default is big-endian. */
  33 /* The state is 0 if big-endian, 1 if little-endian. */
  34 static int
  35 utf16_mbtowc (conv_t conv, ucs4_t *pwc, const unsigned char *s, int n)
  36 {
  37   state_t state = conv->istate;
  38   int count = 0;
  39   for (; n >= 2;) {
  40     ucs4_t wc = (state ? s[0] + (s[1] << 8) : (s[0] << 8) + s[1]);
  41     if (wc == 0xfeff) {
  42     } else if (wc == 0xfffe) {
  43       state ^= 1;
  44     } else if (wc >= 0xd800 && wc < 0xdc00) {
  45       if (n >= 4) {
  46         ucs4_t wc2 = (state ? s[2] + (s[3] << 8) : (s[2] << 8) + s[3]);
  47         if (!(wc2 >= 0xdc00 && wc2 < 0xe000))
  48           return RET_ILSEQ;
  49         *pwc = 0x10000 + ((wc - 0xd800) << 10) + (wc2 - 0xdc00);
  50         conv->istate = state;
  51         return count+4;
  52       } else
  53         break;
  54     } else if (wc >= 0xdc00 && wc < 0xe000) {
  55       return RET_ILSEQ;
  56     } else {
  57       *pwc = wc;
  58       conv->istate = state;
  59       return count+2;
  60     }
  61     s += 2; n -= 2; count += 2;
  62   }
  63   conv->istate = state;
  64   return RET_TOOFEW(count);
  65 }
  66
  67 /* We output UTF-16 in big-endian order, with byte-order mark.
  68    See RFC 2781 section 3.3 for a rationale: Some document formats
  69    mandate a BOM; the file concatenation issue is not so severe as
  70    long as the above utf16_mbtowc function is used. */
  71 /* The state is 0 at the beginning, 1 after the BOM has been written. */
  72 static int
  73 utf16_wctomb (conv_t conv, unsigned char *r, ucs4_t wc, int n)
  74 {
  75   if (wc != 0xfffe && !(wc >= 0xd800 && wc < 0xe000)) {
  76     int count = 0;
  77     if (!conv->ostate) {
  78       if (n >= 2) {
  79         r[0] = 0xFE;
  80         r[1] = 0xFF;
  81         r += 2; n -= 2; count += 2;
  82       } else
  83         return RET_TOOSMALL;
  84     }
  85     if (wc < 0x10000) {
  86       if (n >= 2) {
  87         r[0] = (unsigned char) (wc >> 8);
  88         r[1] = (unsigned char) wc;
  89         conv->ostate = 1;
  90         return count+2;
  91       } else
  92         return RET_TOOSMALL;
  93     }
  94     else if (wc < 0x110000) {
  95       if (n >= 4) {
  96         ucs4_t wc1 = 0xd800 + ((wc - 0x10000) >> 10);
  97         ucs4_t wc2 = 0xdc00 + ((wc - 0x10000) & 0x3ff);
  98         r[0] = (unsigned char) (wc1 >> 8);
  99         r[1] = (unsigned char) wc1;
 100         r[2] = (unsigned char) (wc2 >> 8);
 101         r[3] = (unsigned char) wc2;
 102         conv->ostate = 1;
 103         return count+4;
 104       } else
 105         return RET_TOOSMALL;
 106     }
 107   }
 108   return RET_ILUNI;
 109 }