lib/unistr/u8-uctomb-aux.c

   1 /* Conversion UCS-4 to UTF-8.
   2    Copyright (C) 2002, 2006-2007, 2009-2021 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2002.
   4
   5    This program is free software: you can redistribute it and/or modify it
   6    under the terms of the GNU Lesser General Public License as published
   7    by the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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 License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include "unistr.h"
  22
  23 #include "attribute.h"
  24
  25 int
  26 u8_uctomb_aux (uint8_t *s, ucs4_t uc, ptrdiff_t n)
  27 {
  28   int count;
  29
  30   if (uc < 0x80)
  31     /* The case n >= 1 is already handled by the caller.  */
  32     return -2;
  33   else if (uc < 0x800)
  34     count = 2;
  35   else if (uc < 0x10000)
  36     {
  37       if (uc < 0xd800 || uc >= 0xe000)
  38         count = 3;
  39       else
  40         return -1;
  41     }
  42   else if (uc < 0x110000)
  43     count = 4;
  44   else
  45     return -1;
  46
  47   if (n < count)
  48     return -2;
  49
  50   switch (count) /* note: code falls through cases! */
  51     {
  52     case 4: s[3] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x10000;
  53       FALLTHROUGH;
  54     case 3: s[2] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x800;
  55       FALLTHROUGH;
  56     case 2: s[1] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0xc0;
  57   /*case 1:*/ s[0] = uc;
  58     }
  59   return count;
  60 }