diff options
Diffstat (limited to 'wcsmbs/wcsstr.c')
| -rw-r--r-- | wcsmbs/wcsstr.c | 95 |
1 files changed, 23 insertions, 72 deletions
diff --git a/wcsmbs/wcsstr.c b/wcsmbs/wcsstr.c index b49630c1cf..b8485725c4 100644 --- a/wcsmbs/wcsstr.c +++ b/wcsmbs/wcsstr.c @@ -1,4 +1,5 @@ -/* Copyright (C) 1995-2024 Free Software Foundation, Inc. +/* Locate a substring in a wide-character string. + Copyright (C) 1995-2024 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -15,18 +16,14 @@ License along with the GNU C Library; if not, see <https://www.gnu.org/licenses/>. */ -/* - * The original strstr() file contains the following comment: - * - * My personal strstr() implementation that beats most other algorithms. - * Until someone tells me otherwise, I assume that this is the - * fastest implementation of strstr() in C. - * I deliberately chose not to comment it. You should have at least - * as much fun trying to understand it, as I had to write it :-). - * - * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */ - #include <wchar.h> +#include <string.h> + +#define AVAILABLE(h, h_l, j, n_l) \ + (((j) + (n_l) <= (h_l)) \ + || ((h_l) += __wcsnlen ((void*)((h) + (h_l)), (n_l) + 128), \ + (j) + (n_l) <= (h_l))) +#include "wcs-two-way.h" #ifndef WCSSTR # define WCSSTR wcsstr @@ -35,66 +32,20 @@ wchar_t * WCSSTR (const wchar_t *haystack, const wchar_t *needle) { - wchar_t b, c; - - if ((b = *needle) != L'\0') - { - haystack--; /* possible ANSI violation */ - do - if ((c = *++haystack) == L'\0') - goto ret0; - while (c != b); - - if (!(c = *++needle)) - goto foundneedle; - ++needle; - goto jin; - - for (;;) - { - wchar_t a; - const wchar_t *rhaystack, *rneedle; - - do - { - if (!(a = *++haystack)) - goto ret0; - if (a == b) - break; - if ((a = *++haystack) == L'\0') - goto ret0; -shloop: ; - } - while (a != b); - -jin: if (!(a = *++haystack)) - goto ret0; - - if (a != c) - goto shloop; - - if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle))) - do - { - if (a == L'\0') - goto foundneedle; - if (*++rhaystack != (a = *++needle)) - break; - if (a == L'\0') - goto foundneedle; - } - while (*++rhaystack == (a = *++needle)); - - needle = rneedle; /* took the register-poor approach */ - - if (a == L'\0') - break; - } - } -foundneedle: - return (wchar_t*) haystack; -ret0: - return NULL; + /* Ensure haystack length is at least as long as needle length. + Since a match may occur early on in a huge haystack, use strnlen + and read ahead a few cachelines for improved performance. */ + size_t ne_len = __wcslen (needle); + size_t hs_len = __wcsnlen (haystack, ne_len | 128); + if (hs_len < ne_len) + return NULL; + + /* Check whether we have a match. This improves performance since we + avoid initialization overheads. */ + if (__wmemcmp (haystack, needle, ne_len) == 0) + return (wchar_t *) haystack; + + return two_way_short_needle (haystack, hs_len, needle, ne_len); } /* This alias is for backward compatibility with drafts of the ISO C standard. Unfortunately the Unix(TM) standard requires this name. */ |