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-rw-r--r--lib/unistr/u16-cmp.c54
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diff --git a/lib/unistr/u16-cmp.c b/lib/unistr/u16-cmp.c
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+/* 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;
+}