1 /*
2 FUNCTION
3 <<strncmp>>---character string compare
4
5 INDEX
6 strncmp
7
8 ANSI_SYNOPSIS
9 #include <string.h>
10 int strncmp(const char *<[a]>, const char * <[b]>, size_t <[length]>);
11
12 TRAD_SYNOPSIS
13 #include <string.h>
14 int strncmp(<[a]>, <[b]>, <[length]>)
15 char *<[a]>;
16 char *<[b]>;
17 size_t <[length]>
18
19 DESCRIPTION
20 <<strncmp>> compares up to <[length]> characters
21 from the string at <[a]> to the string at <[b]>.
22
23 RETURNS
24 If <<*<[a]>>> sorts lexicographically after <<*<[b]>>>,
25 <<strncmp>> returns a number greater than zero. If the two
26 strings are equivalent, <<strncmp>> returns zero. If <<*<[a]>>>
27 sorts lexicographically before <<*<[b]>>>, <<strncmp>> returns a
28 number less than zero.
29
30 PORTABILITY
31 <<strncmp>> is ANSI C.
32
33 <<strncmp>> requires no supporting OS subroutines.
34
35 QUICKREF
36 strncmp ansi pure
37 */
38
39 #include <section_config.h>
40 #include <basic_types.h>
41
42 #include <string.h>
43 #include <limits.h>
44
45 /* Nonzero if either X or Y is not aligned on a "long" boundary. */
46 #define UNALIGNED(X, Y) \
47 (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
48
49 /* DETECTNULL returns nonzero if (long)X contains a NULL byte. */
50 #if LONG_MAX == 2147483647L
51 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
52 #else
53 #if LONG_MAX == 9223372036854775807L
54 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
55 #else
56 #error long int is not a 32bit or 64bit type.
57 #endif
58 #endif
59
60 #ifndef DETECTNULL
61 #error long int is not a 32bit or 64bit byte
62 #endif
63
64 LIBC_ROM_TEXT_SECTION
65 _LONG_CALL_
_strncmp(const char * s1,const char * s2,size_t n)66 int _strncmp(const char *s1 , const char *s2 , size_t n)
67 {
68 #if defined(PREFER_SIZE_OVER_SPEED)
69 if (n == 0)
70 return 0;
71
72 while (n-- != 0 && *s1 == *s2)
73 {
74 if (n == 0 || *s1 == '\0')
75 break;
76 s1++;
77 s2++;
78 }
79
80 return (*(unsigned char *) s1) - (*(unsigned char *) s2);
81 #else
82 unsigned long *a1;
83 unsigned long *a2;
84
85 if (n == 0)
86 return 0;
87
88 /* If s1 or s2 are unaligned, then compare bytes. */
89 if (!UNALIGNED (s1, s2))
90 {
91 /* If s1 and s2 are word-aligned, compare them a word at a time. */
92 a1 = (unsigned long*)s1;
93 a2 = (unsigned long*)s2;
94 while (n >= sizeof (long) && *a1 == *a2)
95 {
96 n -= sizeof (long);
97
98 /* If we've run out of bytes or hit a null, return zero
99 since we already know *a1 == *a2. */
100 if (n == 0 || DETECTNULL (*a1))
101 return 0;
102
103 a1++;
104 a2++;
105 }
106
107 /* A difference was detected in last few bytes of s1, so search bytewise */
108 s1 = (char*)a1;
109 s2 = (char*)a2;
110 }
111
112 while (n-- > 0 && *s1 == *s2)
113 {
114 /* If we've run out of bytes or hit a null, return zero
115 since we already know *s1 == *s2. */
116 if (n == 0 || *s1 == '\0')
117 return 0;
118 s1++;
119 s2++;
120 }
121 return (*(unsigned char *) s1) - (*(unsigned char *) s2);
122 #endif /* not PREFER_SIZE_OVER_SPEED */
123 }
124