usr/src/lib/libc/port/gen/strstr.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
  24  */
  25
  26 /*      Copyright (c) 1988 AT&T */
  27 /*        All Rights Reserved   */
  28
  29 #include "lint.h"
  30 #include <string.h>
  31 #include <stddef.h>
  32 #include <sys/types.h>
  33
  34 /*
  35  * strstr() locates the first occurrence in the string as1 of
  36  * the sequence of characters (excluding the terminating null
  37  * character) in the string as2.  strstr() returns a pointer
  38  * to the located string, or a null pointer if the string is
  39  * not found.  If as2 is empty, the function returns as1.
  40  */
  41
  42 char *
  43 strstr(const char *as1, const char *as2)
  44 {
  45         const char *s1, *s2;
  46         const char *tptr;
  47         char c;
  48
  49         s1 = as1;
  50         s2 = as2;
  51
  52         if (s2 == NULL || *s2 == '\0')
  53                 return ((char *)s1);
  54
  55         c = *s2;
  56         while (*s1 != '\0') {
  57                 if (c == *s1++) {
  58                         tptr = s1;
  59                         while ((c = *++s2) == *s1++ && c != '\0')
  60                                 continue;
  61                         if (c == '\0')
  62                                 return ((char *)tptr - 1);
  63                         s1 = tptr;
  64                         s2 = as2;
  65                         c = *s2;
  66                 }
  67         }
  68
  69         return (NULL);
  70 }
  71
  72 /*
  73  * strnstr() locates the first occurrence in the string as1 of
  74  * the sequence of characters (excluding the terminating null
  75  * character) in the string as2, where not more than n characters
  76  * from the string as1 are searched.  strnstr() returns a pointer
  77  * to the located string, or a null pointer if the string is
  78  * not found.  If as2 is empty, the function returns as1.
  79  */
  80
  81 char *
  82 strnstr(const char *as1, const char *as2, size_t n)
  83 {
  84         const char *s1, *s2;
  85         const char *tptr;
  86         size_t k;
  87         char c;
  88
  89         s1 = as1;
  90         s2 = as2;
  91
  92         if (s2 == NULL || *s2 == '\0')
  93                 return ((char *)s1);
  94
  95         c = *s2;
  96         while (*s1 != '\0' && n--) {
  97                 if (c == *s1++) {
  98                         k = n;
  99                         tptr = s1;
 100                         while ((c = *++s2) == *s1++ && c != '\0' && k--)
 101                                 continue;
 102                         if (c == '\0')
 103                                 return ((char *)tptr - 1);
 104                         s1 = tptr;
 105                         s2 = as2;
 106                         c = *s2;
 107                 }
 108         }
 109
 110         return (NULL);
 111 }