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