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authorAndreas Rottmann <a.rottmann@gmx.at>2009-09-14 12:32:44 +0200
committerAndreas Rottmann <a.rottmann@gmx.at>2009-09-14 12:32:44 +0200
commitfa095a4504cbe668e4244547e2c141597bea4ecf (patch)
tree06135820a286ffec47804e75fbf8a147e92acd2e /lib/unistr/u8-prev.c
Imported Upstream version 0.9.1upstream/0.9.1
Diffstat (limited to 'lib/unistr/u8-prev.c')
-rw-r--r--lib/unistr/u8-prev.c93
1 files changed, 93 insertions, 0 deletions
diff --git a/lib/unistr/u8-prev.c b/lib/unistr/u8-prev.c
new file mode 100644
index 00000000..245d22ff
--- /dev/null
+++ b/lib/unistr/u8-prev.c
@@ -0,0 +1,93 @@
+/* Iterate over previous character in UTF-8 string.
+ Copyright (C) 2002, 2006-2007 Free Software Foundation, Inc.
+ Written by Bruno Haible <bruno@clisp.org>, 2002.
+
+ 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 "unistr.h"
+
+const uint8_t *
+u8_prev (ucs4_t *puc, const uint8_t *s, const uint8_t *start)
+{
+ /* Keep in sync with unistr.h and utf8-ucs4.c. */
+ if (s != start)
+ {
+ uint8_t c_1 = s[-1];
+
+ if (c_1 < 0x80)
+ {
+ *puc = c_1;
+ return s - 1;
+ }
+#if CONFIG_UNICODE_SAFETY
+ if ((c_1 ^ 0x80) < 0x40)
+#endif
+ if (s - 1 != start)
+ {
+ uint8_t c_2 = s[-2];
+
+ if (c_2 >= 0xc2 && c_2 < 0xe0)
+ {
+ *puc = ((unsigned int) (c_2 & 0x1f) << 6)
+ | (unsigned int) (c_1 ^ 0x80);
+ return s - 2;
+ }
+#if CONFIG_UNICODE_SAFETY
+ if ((c_2 ^ 0x80) < 0x40)
+#endif
+ if (s - 2 != start)
+ {
+ uint8_t c_3 = s[-3];
+
+ if (c_3 >= 0xe0 && c_3 < 0xf0
+#if CONFIG_UNICODE_SAFETY
+ && (c_3 >= 0xe1 || c_2 >= 0xa0)
+ && (c_3 != 0xed || c_2 < 0xa0)
+#endif
+ )
+ {
+ *puc = ((unsigned int) (c_3 & 0x0f) << 12)
+ | ((unsigned int) (c_2 ^ 0x80) << 6)
+ | (unsigned int) (c_1 ^ 0x80);
+ return s - 3;
+ }
+#if CONFIG_UNICODE_SAFETY
+ if ((c_3 ^ 0x80) < 0x40)
+#endif
+ if (s - 3 != start)
+ {
+ uint8_t c_4 = s[-4];
+
+ if (c_4 >= 0xf0 && c_4 < 0xf8
+#if CONFIG_UNICODE_SAFETY
+ && (c_4 >= 0xf1 || c_3 >= 0x90)
+ && (c_4 < 0xf4 || (c_4 == 0xf4 && c_3 < 0x90))
+#endif
+ )
+ {
+ *puc = ((unsigned int) (c_4 & 0x07) << 18)
+ | ((unsigned int) (c_3 ^ 0x80) << 12)
+ | ((unsigned int) (c_2 ^ 0x80) << 6)
+ | (unsigned int) (c_1 ^ 0x80);
+ return s - 4;
+ }
+ }
+ }
+ }
+ }
+ return NULL;
+}