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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