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+/* c-strcasestr.c -- case insensitive substring search in C locale
+ Copyright (C) 2005-2022 Free Software Foundation, Inc.
+ Written by Bruno Haible <bruno@clisp.org>, 2005.
+
+ This file 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 2.1 of the
+ License, or (at your option) any later version.
+
+ This file 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 <https://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+/* Specification. */
+#include "c-strcasestr.h"
+
+#include <stdbool.h>
+#include <string.h>
+
+#include "c-ctype.h"
+#include "c-strcase.h"
+
+/* Two-Way algorithm. */
+#define RETURN_TYPE char *
+#define AVAILABLE(h, h_l, j, n_l) \
+ (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
+ && ((h_l) = (j) + (n_l)))
+#define CANON_ELEMENT c_tolower
+#define CMP_FUNC(p1, p2, l) \
+ c_strncasecmp ((const char *) (p1), (const char *) (p2), l)
+#include "str-two-way.h"
+
+/* Find the first occurrence of NEEDLE in HAYSTACK, using case-insensitive
+ comparison from the C locale, regardless of the current locale. */
+char *
+c_strcasestr (const char *haystack_start, const char *needle_start)
+{
+ const char *haystack = haystack_start;
+ const char *needle = needle_start;
+ size_t needle_len; /* Length of NEEDLE. */
+ size_t haystack_len; /* Known minimum length of HAYSTACK. */
+ bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
+
+ /* Determine length of NEEDLE, and in the process, make sure
+ HAYSTACK is at least as long (no point processing all of a long
+ NEEDLE if HAYSTACK is too short). */
+ while (*haystack && *needle)
+ ok &= (c_tolower ((unsigned char) *haystack++)
+ == c_tolower ((unsigned char) *needle++));
+ if (*needle)
+ return NULL;
+ if (ok)
+ return (char *) haystack_start;
+ needle_len = needle - needle_start;
+ haystack = haystack_start + 1;
+ haystack_len = needle_len - 1;
+
+ /* Perform the search. Abstract memory is considered to be an array
+ of 'unsigned char' values, not an array of 'char' values. See
+ ISO C 99 section 6.2.6.1. */
+ if (needle_len < LONG_NEEDLE_THRESHOLD)
+ return two_way_short_needle ((const unsigned char *) haystack,
+ haystack_len,
+ (const unsigned char *) needle_start,
+ needle_len);
+ return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
+ (const unsigned char *) needle_start,
+ needle_len);
+}
+
+#undef LONG_NEEDLE_THRESHOLD