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-rw-r--r--lib/unigbrk/u8-grapheme-prev.c54
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diff --git a/lib/unigbrk/u8-grapheme-prev.c b/lib/unigbrk/u8-grapheme-prev.c
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+/* Previous grapheme cluster function.
+ Copyright (C) 2010-2015 Free Software Foundation, Inc.
+ Written by Ben Pfaff <blp@cs.stanford.edu>, 2010.
+
+ This program is free software: you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published
+ by the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+/* Specification. */
+#include "unigbrk.h"
+
+#include "unistr.h"
+
+const uint8_t *
+u8_grapheme_prev (const uint8_t *s, const uint8_t *start)
+{
+ ucs4_t next;
+
+ if (s == start)
+ return NULL;
+
+ s = u8_prev (&next, s, start);
+ while (s != start)
+ {
+ const uint8_t *prev_s;
+ ucs4_t prev;
+
+ prev_s = u8_prev (&prev, s, start);
+ if (prev_s == NULL)
+ {
+ /* Ill-formed UTF-8 encoding. */
+ return start;
+ }
+
+ if (uc_is_grapheme_break (prev, next))
+ break;
+
+ s = prev_s;
+ next = prev;
+ }
+
+ return s;
+}