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/* Previous grapheme cluster function.
Copyright (C) 2010-2022 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 uint16_t *
u16_grapheme_prev (const uint16_t *s, const uint16_t *start)
{
ucs4_t next;
if (s == start)
return NULL;
s = u16_prev (&next, s, start);
while (s != start)
{
const uint16_t *prev_s;
ucs4_t prev;
prev_s = u16_prev (&prev, s, start);
if (prev_s == NULL)
{
/* Ill-formed UTF-16 encoding. */
return start;
}
if (uc_is_grapheme_break (prev, next))
break;
s = prev_s;
next = prev;
}
return s;
}
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