1 /* Searching in a string. 2 Copyright (C) 2005 Free Software Foundation, Inc. 3 Written by Bruno Haible <bruno@clisp.org>, 2005. 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 2, 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 16 along with this program; if not, write to the Free Software Foundation, 17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 18 19 #ifdef HAVE_CONFIG_H 20 # include <config.h> 21 #endif 22 23 /* Specification. */ 24 #include "strstr.h" 25 26 #include <stddef.h> /* for NULL */ 27 28 #if HAVE_MBRTOWC 29 # include "mbuiter.h" 30 #endif 31 32 /* Find the first occurrence of NEEDLE in HAYSTACK. */ 33 char * 34 strstr (const char *haystack, const char *needle) 35 { 36 /* Be careful not to look at the entire extent of haystack or needle 37 until needed. This is useful because of these two cases: 38 - haystack may be very long, and a match of needle found early, 39 - needle may be very long, and not even a short initial segment of 40 needle may be found in haystack. */ 41 #if HAVE_MBRTOWC 42 if (MB_CUR_MAX > 1) 43 { 44 mbui_iterator_t iter_needle; 45 46 mbui_init (iter_needle, needle); 47 if (mbui_avail (iter_needle)) 48 { 49 mbui_iterator_t iter_haystack; 50 51 mbui_init (iter_haystack, haystack); 52 for (;; mbui_advance (iter_haystack)) 53 { 54 if (!mbui_avail (iter_haystack)) 55 /* No match. */ 56 return NULL; 57 58 if (mb_equal (mbui_cur (iter_haystack), mbui_cur (iter_needle))) 59 /* The first character matches. */ 60 { 61 mbui_iterator_t rhaystack; 62 mbui_iterator_t rneedle; 63 64 memcpy (&rhaystack, &iter_haystack, sizeof (mbui_iterator_t)); 65 mbui_advance (rhaystack); 66 67 mbui_init (rneedle, needle); 68 if (!mbui_avail (rneedle)) 69 abort (); 70 mbui_advance (rneedle); 71 72 for (;; mbui_advance (rhaystack), mbui_advance (rneedle)) 73 { 74 if (!mbui_avail (rneedle)) 75 /* Found a match. */ 76 return (char *) mbui_cur_ptr (iter_haystack); 77 if (!mbui_avail (rhaystack)) 78 /* No match. */ 79 return NULL; 80 if (!mb_equal (mbui_cur (rhaystack), mbui_cur (rneedle))) 81 /* Nothing in this round. */ 82 break; 83 } 84 } 85 } 86 } 87 else 88 return (char *) haystack; 89 } 90 else 91 #endif 92 { 93 if (*needle != '\0') 94 { 95 /* Speed up the following searches of needle by caching its first 96 character. */ 97 char b = *needle++; 98 99 for (;; haystack++) 100 { 101 if (*haystack == '\0') 102 /* No match. */ 103 return NULL; 104 if (*haystack == b) 105 /* The first character matches. */ 106 { 107 const char *rhaystack = haystack + 1; 108 const char *rneedle = needle; 109 110 for (;; rhaystack++, rneedle++) 111 { 112 if (*rneedle == '\0') 113 /* Found a match. */ 114 return (char *) haystack; 115 if (*rhaystack == '\0') 116 /* No match. */ 117 return NULL; 118 if (*rhaystack != *rneedle) 119 /* Nothing in this round. */ 120 break; 121 } 122 } 123 } 124 } 125 else 126 return (char *) haystack; 127 } 128 } 129