Imported Upstream version 0.9.1upstream/0.9.1

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;
+}