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