wcsmbs/wcsstr.c

   1 /* Locate a substring in a wide-character string.
   2    Copyright (C) 1995-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <wchar.h>
  20 #include <string.h>
  21
  22 #define AVAILABLE(h, h_l, j, n_l)                                       \
  23   (((j) + (n_l) <= (h_l))                                               \
  24    || ((h_l) += __wcsnlen ((void*)((h) + (h_l)), (n_l) + 128),          \
  25        (j) + (n_l) <= (h_l)))
  26 #include "wcs-two-way.h"
  27
  28 #ifndef WCSSTR
  29 # define WCSSTR wcsstr
  30 #endif
  31
  32 wchar_t *
  33 WCSSTR (const wchar_t *haystack, const wchar_t *needle)
  34 {
  35   /* Ensure haystack length is at least as long as needle length.
  36      Since a match may occur early on in a huge haystack, use strnlen
  37      and read ahead a few cachelines for improved performance.  */
  38   size_t ne_len = __wcslen (needle);
  39   size_t hs_len = __wcsnlen (haystack, ne_len | 128);
  40   if (hs_len < ne_len)
  41     return NULL;
  42
  43   /* Check whether we have a match.  This improves performance since we
  44      avoid initialization overheads.  */
  45   if (__wmemcmp (haystack, needle, ne_len) == 0)
  46     return (wchar_t *) haystack;
  47
  48   return two_way_short_needle (haystack, hs_len, needle, ne_len);
  49 }
  50 /* This alias is for backward compatibility with drafts of the ISO C
  51    standard.  Unfortunately the Unix(TM) standard requires this name.  */
  52 weak_alias (wcsstr, wcswcs)