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