lib/c32rtomb.c

   1 /* Convert 32-bit wide character to multibyte character.
   2    Copyright (C) 2020-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>, 2020.  */
  18
  19 #include <config.h>
  20
  21 /* Specification.  */
  22 #include <uchar.h>
  23
  24 #include <errno.h>
  25 #include <wchar.h>
  26
  27 #include "attribute.h" /* FALLTHROUGH */
  28 #include "localcharset.h"
  29 #include "streq.h"
  30
  31 #if GL_CHAR32_T_IS_UNICODE
  32 # include "lc-charset-unicode.h"
  33 #endif
  34
  35 size_t
  36 c32rtomb (char *s, char32_t wc, mbstate_t *ps)
  37 #undef c32rtomb
  38 {
  39 #if HAVE_WORKING_MBRTOC32
  40
  41 # if C32RTOMB_RETVAL_BUG
  42   if (s == NULL)
  43     /* We know the NUL wide character corresponds to the NUL character.  */
  44     return 1;
  45 # endif
  46
  47   return c32rtomb (s, wc, ps);
  48
  49 #elif _GL_SMALL_WCHAR_T
  50
  51   if (s == NULL)
  52     return wcrtomb (NULL, 0, ps);
  53   else
  54     {
  55       /* Special-case all encodings that may produce wide character values
  56          > WCHAR_MAX.  */
  57       const char *encoding = locale_charset ();
  58       if (STREQ_OPT (encoding, "UTF-8", 'U', 'T', 'F', '-', '8', 0, 0, 0, 0))
  59         {
  60           /* Special-case the UTF-8 encoding.  Assume that the wide-character
  61              encoding in a UTF-8 locale is UCS-2 or, equivalently, UTF-16.  */
  62           if (wc < 0x80)
  63             {
  64               s[0] = (unsigned char) wc;
  65               return 1;
  66             }
  67           else
  68             {
  69               int count;
  70
  71               if (wc < 0x800)
  72                 count = 2;
  73               else if (wc < 0x10000)
  74                 {
  75                   if (wc < 0xd800 || wc >= 0xe000)
  76                     count = 3;
  77                   else
  78                     {
  79                       errno = EILSEQ;
  80                       return (size_t)(-1);
  81                     }
  82                 }
  83               else if (wc < 0x110000)
  84                 count = 4;
  85               else
  86                 {
  87                   errno = EILSEQ;
  88                   return (size_t)(-1);
  89                 }
  90
  91               switch (count) /* note: code falls through cases! */
  92                 {
  93                 case 4: s[3] = 0x80 | (wc & 0x3f); wc = wc >> 6; wc |= 0x10000;
  94                   FALLTHROUGH;
  95                 case 3: s[2] = 0x80 | (wc & 0x3f); wc = wc >> 6; wc |= 0x800;
  96                   FALLTHROUGH;
  97                 case 2: s[1] = 0x80 | (wc & 0x3f); wc = wc >> 6; wc |= 0xc0;
  98               /*case 1:*/ s[0] = wc;
  99                 }
 100               return count;
 101             }
 102         }
 103       else
 104         {
 105           if ((wchar_t) wc == wc)
 106             return wcrtomb (s, (wchar_t) wc, ps);
 107           else
 108             {
 109               errno = EILSEQ;
 110               return (size_t)(-1);
 111             }
 112         }
 113     }
 114
 115 #else
 116
 117   /* char32_t and wchar_t are equivalent.  */
 118 # if GL_CHAR32_T_IS_UNICODE && GL_CHAR32_T_VS_WCHAR_T_NEEDS_CONVERSION
 119   if (wc != 0)
 120     {
 121       wc = unicode_to_locale_encoding (wc);
 122       if (wc == 0)
 123         {
 124           errno = EILSEQ;
 125           return (size_t)(-1);
 126         }
 127     }
 128 # endif
 129   return wcrtomb (s, (wchar_t) wc, ps);
 130
 131 #endif
 132 }