1 // SPDX-License-Identifier: BSD-3-Clause 2 /* 3 * Copyright (c) 1994-2009 Red Hat, Inc. 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions are met: 8 * 9 * 1. Redistributions of source code must retain the above copyright notice, 10 * this list of conditions and the following disclaimer. 11 * 12 * 2. Redistributions in binary form must reproduce the above copyright notice, 13 * this list of conditions and the following disclaimer in the documentation 14 * and/or other materials provided with the distribution. 15 * 16 * 3. Neither the name of the copyright holder nor the names of its 17 * contributors may be used to endorse or promote products derived from this 18 * software without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 21 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 24 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 30 * POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 /* 34 FUNCTION 35 <<strncmp>>---character string compare 36 37 INDEX 38 strncmp 39 40 ANSI_SYNOPSIS 41 #include <string.h> 42 int strncmp(const char *<[a]>, const char * <[b]>, size_t <[length]>); 43 44 TRAD_SYNOPSIS 45 #include <string.h> 46 int strncmp(<[a]>, <[b]>, <[length]>) 47 char *<[a]>; 48 char *<[b]>; 49 size_t <[length]> 50 51 DESCRIPTION 52 <<strncmp>> compares up to <[length]> characters 53 from the string at <[a]> to the string at <[b]>. 54 55 RETURNS 56 If <<*<[a]>>> sorts lexicographically after <<*<[b]>>>, 57 <<strncmp>> returns a number greater than zero. If the two 58 strings are equivalent, <<strncmp>> returns zero. If <<*<[a]>>> 59 sorts lexicographically before <<*<[b]>>>, <<strncmp>> returns a 60 number less than zero. 61 62 PORTABILITY 63 <<strncmp>> is ANSI C. 64 65 <<strncmp>> requires no supporting OS subroutines. 66 67 QUICKREF 68 strncmp ansi pure 69 */ 70 71 #include "_ansi.h" 72 #include <string.h> 73 #include <limits.h> 74 75 /* Nonzero if either X or Y is not aligned on a "long" boundary. */ 76 #define UNALIGNED(X, Y) \ 77 (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1))) 78 79 /* DETECTNULL returns nonzero if (long)X contains a NULL byte. */ 80 #if LONG_MAX == 2147483647L 81 #define DETECTNULL(X) (((X) - 0x01010101L) & ~(X) & 0x80808080UL) 82 #else 83 #if LONG_MAX == 9223372036854775807L 84 #define DETECTNULL(X) (((X) - 0x0101010101010101L) & ~(X) & \ 85 0x8080808080808080UL) 86 #else 87 #error long int is not a 32bit or 64bit type. 88 #endif 89 #endif 90 91 #ifndef DETECTNULL 92 #error long int is not a 32bit or 64bit byte 93 #endif 94 95 int 96 _DEFUN (strncmp, (s1, s2, n), 97 _CONST char *s1 _AND 98 _CONST char *s2 _AND 99 size_t n) 100 { 101 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) 102 if (n == 0) 103 return 0; 104 105 while (n-- != 0 && *s1 == *s2) 106 { 107 if (n == 0 || *s1 == '\0') 108 break; 109 s1++; 110 s2++; 111 } 112 113 return (*(unsigned char *) s1) - (*(unsigned char *) s2); 114 #else 115 unsigned long *a1; 116 unsigned long *a2; 117 118 if (n == 0) 119 return 0; 120 121 /* If s1 or s2 are unaligned, then compare bytes. */ 122 if (!UNALIGNED (s1, s2)) 123 { 124 /* If s1 and s2 are word-aligned, compare them a word at a time. */ 125 a1 = (unsigned long*)s1; 126 a2 = (unsigned long*)s2; 127 while (n >= sizeof (long) && *a1 == *a2) 128 { 129 n -= sizeof (long); 130 131 /* If we've run out of bytes or hit a null, return zero 132 since we already know *a1 == *a2. */ 133 if (n == 0 || DETECTNULL (*a1)) 134 return 0; 135 136 a1++; 137 a2++; 138 } 139 140 /* A difference was detected in last few bytes of s1, so search bytewise */ 141 s1 = (char*)a1; 142 s2 = (char*)a2; 143 } 144 145 while (n-- > 0 && *s1 == *s2) 146 { 147 /* If we've run out of bytes or hit a null, return zero 148 since we already know *s1 == *s2. */ 149 if (n == 0 || *s1 == '\0') 150 return 0; 151 s1++; 152 s2++; 153 } 154 return (*(unsigned char *) s1) - (*(unsigned char *) s2); 155 #endif /* not PREFER_SIZE_OVER_SPEED */ 156 } 157