New modules 'unistr/u8-cmp', 'unistr/u16-cmp', 'unistr/u32-cmp'.

[gnulib.git] / lib / unistr / u16-cmp.c

diff --git a/lib/unistr/u16-cmp.c b/lib/unistr/u16-cmp.c
new file mode 100644 (file)
index 0000000..3b2b4c8
--- /dev/null
+++ b/lib/unistr/u16-cmp.c
@@ -0,0 +1,56 @@
+/* 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 Library General Public License as published
+   by the Free Software Foundation; either version 2, 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+   USA.  */
+
+#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;
+}