1 files changed, 56 insertions, 0 deletions
diff --git a/lib/wcsstr-impl.h b/lib/wcsstr-impl.h
new file mode 100644
index 00000000..b5f094e8
--- /dev/null
+++ b/lib/wcsstr-impl.h
@@ -0,0 +1,56 @@
+/* Locate a substring in a wide string.
+   Copyright (C) 1999, 2011-2024 Free Software Foundation, Inc.
+
+   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/>.  */
+
+/* Written by Eric Blake, 2008.  */
+
+#define AVAILABLE(h, h_l, j, n_l)                       \
+  (!MEMCHR0 ((h) + (h_l), (j) + (n_l) - (h_l))          \
+   && ((h_l) = (j) + (n_l)))
+#include "wcs-two-way.h"
+
+RETURN_TYPE
+FUNC (const UNIT *haystack_start, const UNIT *needle_start)
+{
+  const UNIT *haystack = haystack_start;
+  const UNIT *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 &= *haystack++ == *needle++;
+  if (*needle)
+    return NULL;
+  if (ok)
+    return (RETURN_TYPE) haystack_start;
+
+  /* Reduce the size of haystack using STRCHR, since it has a smaller
+     linear coefficient than the Two-Way algorithm.  */
+  needle_len = needle - needle_start;
+  haystack = STRCHR (haystack_start + 1, *needle_start);
+  if (!haystack || __builtin_expect (needle_len == 1, 0))
+    return (RETURN_TYPE) haystack;
+  needle -= needle_len;
+  haystack_len = (haystack > haystack_start + needle_len ? 1
+                  : needle_len + haystack_start - haystack);
+
+  /* Perform the search.  */
+  return two_way_short_needle (haystack, haystack_len,
+                               needle, needle_len);
+}