1 /*
2 FUNCTION
3 <<memcmp>>---compare two memory areas
4
5 INDEX
6 memcmp
7
8 ANSI_SYNOPSIS
9 #include <string.h>
10 int memcmp(const void *<[s1]>, const void *<[s2]>, size_t <[n]>);
11
12 TRAD_SYNOPSIS
13 #include <string.h>
14 int memcmp(<[s1]>, <[s2]>, <[n]>)
15 void *<[s1]>;
16 void *<[s2]>;
17 size_t <[n]>;
18
19 DESCRIPTION
20 This function compares not more than <[n]> characters of the
21 object pointed to by <[s1]> with the object pointed to by <[s2]>.
22
23
24 RETURNS
25 The function returns an integer greater than, equal to or
26 less than zero according to whether the object pointed to by
27 <[s1]> is greater than, equal to or less than the object
28 pointed to by <[s2]>.
29
30 PORTABILITY
31 <<memcmp>> is ANSI C.
32
33 <<memcmp>> requires no supporting OS subroutines.
34
35 QUICKREF
36 memcmp ansi pure
37 */
38
39 #include <section_config.h>
40 #include <basic_types.h>
41
42 #include <string.h>
43
44 /* Nonzero if either X or Y is not aligned on a "long" boundary. */
45 #define UNALIGNED(X, Y) \
46 (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
47
48 /* How many bytes are copied each iteration of the word copy loop. */
49 #define LBLOCKSIZE (sizeof (long))
50
51 /* Threshhold for punting to the byte copier. */
52 #define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE)
53
54 LIBC_ROM_TEXT_SECTION
55 _LONG_CALL_
_memcmp(const void * m1,const void * m2,size_t n)56 int _memcmp(const void * m1 , const void * m2 , size_t n)
57 {
58 #if defined(PREFER_SIZE_OVER_SPEED)
59 unsigned char *s1 = (unsigned char *) m1;
60 unsigned char *s2 = (unsigned char *) m2;
61
62 while (n--)
63 {
64 if (*s1 != *s2)
65 {
66 return *s1 - *s2;
67 }
68 s1++;
69 s2++;
70 }
71 return 0;
72 #else
73 unsigned char *s1 = (unsigned char *) m1;
74 unsigned char *s2 = (unsigned char *) m2;
75 unsigned long *a1;
76 unsigned long *a2;
77
78 /* If the size is too small, or either pointer is unaligned,
79 then we punt to the byte compare loop. Hopefully this will
80 not turn up in inner loops. */
81 if (!TOO_SMALL(n) && !UNALIGNED(s1,s2))
82 {
83 /* Otherwise, load and compare the blocks of memory one
84 word at a time. */
85 a1 = (unsigned long*) s1;
86 a2 = (unsigned long*) s2;
87 while (n >= LBLOCKSIZE)
88 {
89 if (*a1 != *a2)
90 break;
91 a1++;
92 a2++;
93 n -= LBLOCKSIZE;
94 }
95
96 /* check m mod LBLOCKSIZE remaining characters */
97
98 s1 = (unsigned char*)a1;
99 s2 = (unsigned char*)a2;
100 }
101
102 while (n--)
103 {
104 if (*s1 != *s2)
105 return *s1 - *s2;
106 s1++;
107 s2++;
108 }
109
110 return 0;
111 #endif /* not PREFER_SIZE_OVER_SPEED */
112 }
113
114