1 /*
2 Copyright (c) 2002 Jeff Johnston <jjohnstn@redhat.com>
3 */
4 /*
5 FUNCTION
6 <<mempcpy>>---copy memory regions and return end pointer
7
8 SYNOPSIS
9 #include <string.h>
10 void* mempcpy(void *<[out]>, const void *<[in]>, size_t <[n]>);
11
12 DESCRIPTION
13 This function copies <[n]> bytes from the memory region
14 pointed to by <[in]> to the memory region pointed to by
15 <[out]>.
16
17 If the regions overlap, the behavior is undefined.
18
19 RETURNS
20 <<mempcpy>> returns a pointer to the byte following the
21 last byte copied to the <[out]> region.
22
23 PORTABILITY
24 <<mempcpy>> is a GNU extension.
25
26 <<mempcpy>> requires no supporting OS subroutines.
27
28 */
29
30 #include <_ansi.h>
31 #include <stddef.h>
32 #include <limits.h>
33 #include <string.h>
34 #include <stdint.h>
35
36 /* Nonzero if either X or Y is not aligned on a "long" boundary. */
37 #define UNALIGNED(X, Y) \
38 (((uintptr_t)X & (sizeof (long) - 1)) | ((uintptr_t)Y & (sizeof (long) - 1)))
39
40 /* How many bytes are copied each iteration of the 4X unrolled loop. */
41 #define BIGBLOCKSIZE (sizeof (long) << 2)
42
43 /* How many bytes are copied each iteration of the word copy loop. */
44 #define LITTLEBLOCKSIZE (sizeof (long))
45
46 /* Threshhold for punting to the byte copier. */
47 #define TOO_SMALL(LEN) ((LEN) < BIGBLOCKSIZE)
48
49 void *
mempcpy(void * dst0,const void * src0,size_t len0)50 mempcpy (void *dst0,
51 const void *src0,
52 size_t len0)
53 {
54 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
55 char *dst = (char *) dst0;
56 char *src = (char *) src0;
57
58 while (len0--)
59 {
60 *dst++ = *src++;
61 }
62
63 return dst;
64 #else
65 char *dst = dst0;
66 const char *src = src0;
67 long *aligned_dst;
68 const long *aligned_src;
69
70 /* If the size is small, or either SRC or DST is unaligned,
71 then punt into the byte copy loop. This should be rare. */
72 if (!TOO_SMALL(len0) && !UNALIGNED (src, dst))
73 {
74 aligned_dst = (long*)dst;
75 aligned_src = (long*)src;
76
77 /* Copy 4X long words at a time if possible. */
78 while (len0 >= BIGBLOCKSIZE)
79 {
80 *aligned_dst++ = *aligned_src++;
81 *aligned_dst++ = *aligned_src++;
82 *aligned_dst++ = *aligned_src++;
83 *aligned_dst++ = *aligned_src++;
84 len0 -= BIGBLOCKSIZE;
85 }
86
87 /* Copy one long word at a time if possible. */
88 while (len0 >= LITTLEBLOCKSIZE)
89 {
90 *aligned_dst++ = *aligned_src++;
91 len0 -= LITTLEBLOCKSIZE;
92 }
93
94 /* Pick up any residual with a byte copier. */
95 dst = (char*)aligned_dst;
96 src = (char*)aligned_src;
97 }
98
99 while (len0--)
100 *dst++ = *src++;
101
102 return dst;
103 #endif /* not PREFER_SIZE_OVER_SPEED */
104 }
105
