summaryrefslogtreecommitdiff
path: root/lib/unigbrk/u32-grapheme-prev.c
blob: a6b6983aa25a35ae058425b492f1999801236633 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
/* Previous grapheme cluster function.
   Copyright (C) 2010-2024 Free Software Foundation, Inc.
   Written by Ben Pfaff <blp@cs.stanford.edu>, 2010.

   This file is free software.
   It is dual-licensed under "the GNU LGPLv3+ or the GNU GPLv2+".
   You can redistribute it and/or modify it under either
     - the terms of the GNU Lesser General Public License as published
       by the Free Software Foundation, either version 3, or (at your
       option) any later version, or
     - the terms of the GNU General Public License as published by the
       Free Software Foundation; either version 2, or (at your option)
       any later version, or
     - the same dual license "the GNU LGPLv3+ or the GNU GPLv2+".

   This file 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
   Lesser General Public License and the GNU General Public License
   for more details.

   You should have received a copy of the GNU Lesser General Public
   License and of the GNU General Public License along with this
   program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include "unigbrk.h"

#include "unistr.h"

const uint32_t *
u32_grapheme_prev (const uint32_t *s, const uint32_t *start)
{
  ucs4_t next;

  if (s == start)
    return NULL;

  u32_prev (&next, s, start);
  for (s--; s != start; s--)
    {
      ucs4_t prev;

      if (u32_prev (&prev, s, start) == NULL)
        {
          /* Ill-formed UTF-32 encoding. */
          return start;
        }

      if (uc_is_grapheme_break (prev, next))
        break;

      next = prev;
    }

  return s;
}