1 /* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2015 Free Software 2 Foundation, Inc. 3 This file is part of the GNU C Library. 4 5 This program is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 3, or (at your option) 8 any later version. 9 10 This program 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 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License along 16 with this program; if not, see <http://www.gnu.org/licenses/>. */ 17 18 /* This particular implementation was written by Eric Blake, 2008. */ 19 20 #ifndef _LIBC 21 # include <config.h> 22 #endif 23 24 /* Specification of strstr. */ 25 #include <string.h> 26 27 #include <stdbool.h> 28 29 #ifndef _LIBC 30 # define __builtin_expect(expr, val) (expr) 31 #endif 32 33 #define RETURN_TYPE char * 34 #define AVAILABLE(h, h_l, j, n_l) \ 35 (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \ 36 && ((h_l) = (j) + (n_l))) 37 #include "str-two-way.h" 38 39 /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK 40 if NEEDLE is empty, otherwise NULL if NEEDLE is not found in 41 HAYSTACK. */ 42 char * 43 strstr (const char *haystack_start, const char *needle_start) 44 { 45 const char *haystack = haystack_start; 46 const char *needle = needle_start; 47 size_t needle_len; /* Length of NEEDLE. */ 48 size_t haystack_len; /* Known minimum length of HAYSTACK. */ 49 bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */ 50 51 /* Determine length of NEEDLE, and in the process, make sure 52 HAYSTACK is at least as long (no point processing all of a long 53 NEEDLE if HAYSTACK is too short). */ 54 while (*haystack && *needle) 55 ok &= *haystack++ == *needle++; 56 if (*needle) 57 return NULL; 58 if (ok) 59 return (char *) haystack_start; 60 61 /* Reduce the size of haystack using strchr, since it has a smaller 62 linear coefficient than the Two-Way algorithm. */ 63 needle_len = needle - needle_start; 64 haystack = strchr (haystack_start + 1, *needle_start); 65 if (!haystack || __builtin_expect (needle_len == 1, 0)) 66 return (char *) haystack; 67 needle -= needle_len; 68 haystack_len = (haystack > haystack_start + needle_len ? 1 69 : needle_len + haystack_start - haystack); 70 71 /* Perform the search. Abstract memory is considered to be an array 72 of 'unsigned char' values, not an array of 'char' values. See 73 ISO C 99 section 6.2.6.1. */ 74 if (needle_len < LONG_NEEDLE_THRESHOLD) 75 return two_way_short_needle ((const unsigned char *) haystack, 76 haystack_len, 77 (const unsigned char *) needle, needle_len); 78 return two_way_long_needle ((const unsigned char *) haystack, haystack_len, 79 (const unsigned char *) needle, needle_len); 80 } 81 82 #undef LONG_NEEDLE_THRESHOLD 83