wcsmbs/c8rtomb.c

   1 /* UTF-8 to multibyte conversion.
   2    Copyright (C) 2022-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <uchar.h>
  21 #include <wchar.h>
  22
  23
  24 /* This is the private state used if PS is NULL.  */
  25 static mbstate_t state;
  26
  27 size_t
  28 c8rtomb (char *s, char8_t c8, mbstate_t *ps)
  29 {
  30   /* This implementation depends on the converter invoked by wcrtomb not
  31      needing to retain state in either the top most bit of ps->__count or
  32      in ps->__value between invocations.  This implementation uses the
  33      top most bit of ps->__count to indicate that trailing code units are
  34      expected and uses ps->__value to store previously seen code units.  */
  35
  36   wchar_t wc;
  37
  38   if (ps == NULL)
  39     ps = &state;
  40
  41   if (s == NULL)
  42     {
  43       /* if 's' is a null pointer, behave as if u8'\0' was passed as 'c8'.  If
  44          this occurs for an incomplete code unit sequence, then an error will
  45          be reported below.  */
  46       c8 = u8""[0];
  47     }
  48
  49   if (! (ps->__count & 0x80000000))
  50     {
  51       /* Initial state.  */
  52       if ((c8 >= 0x80 && c8 <= 0xC1) || c8 >= 0xF5)
  53         {
  54           /* An invalid lead code unit.  */
  55           __set_errno (EILSEQ);
  56           return -1;
  57         }
  58       if (c8 >= 0xC2)
  59         {
  60           /* A valid lead code unit.  */
  61           ps->__count |= 0x80000000;
  62           ps->__value.__wchb[0] = c8;
  63           ps->__value.__wchb[3] = 1;
  64           return 0;
  65         }
  66       /* A single byte (ASCII) code unit.  */
  67       wc = c8;
  68     }
  69   else
  70     {
  71       char8_t cu1 = ps->__value.__wchb[0];
  72       if (ps->__value.__wchb[3] == 1)
  73         {
  74           /* A single lead code unit was previously seen.  */
  75           if ((c8 < 0x80 || c8 > 0xBF)
  76               || (cu1 == 0xE0 && c8 < 0xA0)
  77               || (cu1 == 0xED && c8 > 0x9F)
  78               || (cu1 == 0xF0 && c8 < 0x90)
  79               || (cu1 == 0xF4 && c8 > 0x8F))
  80             {
  81               /* An invalid second code unit.  */
  82               __set_errno (EILSEQ);
  83               return -1;
  84             }
  85           if (cu1 >= 0xE0)
  86             {
  87               /* A three or four code unit sequence.  */
  88               ps->__value.__wchb[1] = c8;
  89               ++ps->__value.__wchb[3];
  90               return 0;
  91             }
  92           wc = ((cu1 & 0x1F) << 6)
  93                + (c8 & 0x3F);
  94         }
  95       else
  96         {
  97           char8_t cu2 = ps->__value.__wchb[1];
  98           /* A three or four byte code unit sequence.  */
  99           if (c8 < 0x80 || c8 > 0xBF)
 100             {
 101               /* An invalid third or fourth code unit.  */
 102               __set_errno (EILSEQ);
 103               return -1;
 104             }
 105           if (ps->__value.__wchb[3] == 2 && cu1 >= 0xF0)
 106             {
 107               /* A four code unit sequence.  */
 108               ps->__value.__wchb[2] = c8;
 109               ++ps->__value.__wchb[3];
 110               return 0;
 111             }
 112           if (cu1 < 0xF0)
 113             {
 114               wc = ((cu1 & 0x0F) << 12)
 115                    + ((cu2 & 0x3F) << 6)
 116                    + (c8 & 0x3F);
 117             }
 118           else
 119             {
 120               char8_t cu3 = ps->__value.__wchb[2];
 121               wc = ((cu1 & 0x07) << 18)
 122                    + ((cu2 & 0x3F) << 12)
 123                    + ((cu3 & 0x3F) << 6)
 124                    + (c8 & 0x3F);
 125             }
 126         }
 127       ps->__count &= 0x7fffffff;
 128       ps->__value.__wch = 0;
 129     }
 130
 131   return wcrtomb (s, wc, ps);
 132 }