1 /*
2 Copyright (c) 1994 Cygnus Support.
3 All rights reserved.
4
5 Redistribution and use in source and binary forms are permitted
6 provided that the above copyright notice and this paragraph are
7 duplicated in all such forms and that any documentation,
8 and/or other materials related to such
9 distribution and use acknowledge that the software was developed
10 at Cygnus Support, Inc. Cygnus Support, Inc. may not be used to
11 endorse or promote products derived from this software without
12 specific prior written permission.
13 THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
14 IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
15 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
16 */
17 /*
18 FUNCTION
19 <<strcmp>>---character string compare
20
21 INDEX
22 strcmp
23
24 SYNOPSIS
25 #include <string.h>
26 int strcmp(const char *<[a]>, const char *<[b]>);
27
28 DESCRIPTION
29 <<strcmp>> compares the string at <[a]> to
30 the string at <[b]>.
31
32 RETURNS
33 If <<*<[a]>>> sorts lexicographically after <<*<[b]>>>,
34 <<strcmp>> returns a number greater than zero. If the two
35 strings match, <<strcmp>> returns zero. If <<*<[a]>>>
36 sorts lexicographically before <<*<[b]>>>, <<strcmp>> returns a
37 number less than zero.
38
39 PORTABILITY
40 <<strcmp>> is ANSI C.
41
42 <<strcmp>> requires no supporting OS subroutines.
43
44 QUICKREF
45 strcmp ansi pure
46 */
47
48 #include <string.h>
49 #include <limits.h>
50 #include <stdint.h>
51
52 /* Nonzero if either X or Y is not aligned on a "long" boundary. */
53 #define UNALIGNED(X, Y) \
54 (((uintptr_t)X & (sizeof (long) - 1)) | ((uintptr_t)Y & (sizeof (long) - 1)))
55
56 /* DETECTNULL returns nonzero if (long)X contains a NULL byte. */
57 #if LONG_MAX == 2147483647L
58 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
59 #else
60 #if LONG_MAX == 9223372036854775807L
61 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
62 #else
63 #error long int is not a 32bit or 64bit type.
64 #endif
65 #endif
66
67 #ifndef DETECTNULL
68 #error long int is not a 32bit or 64bit byte
69 #endif
70
71 int
strcmp(const char * s1,const char * s2)72 strcmp (const char *s1,
73 const char *s2)
74 {
75 #if (defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)) && !defined(FAST_STRCMP)
76 while (*s1 != '\0' && *s1 == *s2)
77 {
78 s1++;
79 s2++;
80 }
81
82 return (*(unsigned char *) s1) - (*(unsigned char *) s2);
83 #else
84 unsigned long *a1;
85 unsigned long *a2;
86
87 /* If s1 or s2 are unaligned, then compare bytes. */
88 if (!UNALIGNED (s1, s2))
89 {
90 /* If s1 and s2 are word-aligned, compare them a word at a time. */
91 a1 = (unsigned long*)s1;
92 a2 = (unsigned long*)s2;
93 while (*a1 == *a2)
94 {
95 /* To get here, *a1 == *a2, thus if we find a null in *a1,
96 then the strings must be equal, so return zero. */
97 if (DETECTNULL (*a1))
98 return 0;
99
100 a1++;
101 a2++;
102 }
103
104 /* A difference was detected in last few bytes of s1, so search bytewise */
105 s1 = (char*)a1;
106 s2 = (char*)a2;
107 }
108
109 while (*s1 != '\0' && *s1 == *s2)
110 {
111 s1++;
112 s2++;
113 }
114 return (*(unsigned char *) s1) - (*(unsigned char *) s2);
115 #endif /* not PREFER_SIZE_OVER_SPEED */
116 }
117
