1 files changed, 54 insertions, 0 deletions
diff --git a/lib/unistr/u16-cmp.c b/lib/unistr/u16-cmp.c
new file mode 100644
index 00000000..0130d271
--- /dev/null
+++ b/lib/unistr/u16-cmp.c
@@ -0,0 +1,54 @@
+/* Compare pieces of UTF-16 strings.
+   Copyright (C) 1999, 2002, 2006 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"
+
+int
+u16_cmp (const uint16_t *s1, const uint16_t *s2, size_t n)
+{
+  /* Note that the UTF-16 encoding does NOT preserve lexicographic order.
+     Namely, if uc1 is a 16-bit character and [uc2a,uc2b] is a surrogate pair,
+     we must enforce uc1 < [uc2a,uc2b], even if uc1 > uc2a.  */
+  for (; n > 0;)
+    {
+      uint16_t c1 = *s1++;
+      uint16_t c2 = *s2++;
+      if (c1 == c2)
+	{
+	  n--;
+	  continue;
+	}
+      if (c1 < 0xd800 || c1 >= 0xe000)
+	{
+	  if (!(c2 < 0xd800 || c2 >= 0xe000))
+	    /* c2 is a surrogate, but c1 is not.  */
+	    return -1;
+	}
+      else
+	{
+	  if (c2 < 0xd800 || c2 >= 0xe000)
+	    /* c1 is a surrogate, but c2 is not.  */
+	    return 1;
+	}
+      return (int)c1 - (int)c2;
+      /* > 0 if c1 > c2, < 0 if c1 < c2. */
+    }
+  return 0;
+}