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1693 | serge | 1 | /* |
2 | FUNCTION |
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3 | < |
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4 | |||
5 | INDEX |
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6 | memmove |
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7 | |||
8 | ANSI_SYNOPSIS |
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9 | #include |
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10 | void *memmove(void *<[dst]>, const void *<[src]>, size_t <[length]>); |
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11 | |||
12 | TRAD_SYNOPSIS |
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13 | #include |
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14 | void *memmove(<[dst]>, <[src]>, <[length]>) |
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15 | void *<[dst]>; |
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16 | void *<[src]>; |
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17 | size_t <[length]>; |
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18 | |||
19 | DESCRIPTION |
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20 | This function moves <[length]> characters from the block of |
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21 | memory starting at <<*<[src]>>> to the memory starting at |
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22 | <<*<[dst]>>>. < |
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23 | at <<*<[dst]>>> even if the two areas overlap. |
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24 | |||
25 | |||
26 | RETURNS |
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27 | The function returns <[dst]> as passed. |
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28 | |||
29 | PORTABILITY |
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30 | < |
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31 | |||
32 | < |
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33 | |||
34 | QUICKREF |
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35 | memmove ansi pure |
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36 | */ |
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37 | |||
38 | #include |
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39 | #include <_ansi.h> |
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40 | #include |
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41 | #include |
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42 | |||
43 | /* Nonzero if either X or Y is not aligned on a "long" boundary. */ |
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44 | #define UNALIGNED(X, Y) \ |
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45 | (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1))) |
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46 | |||
47 | /* How many bytes are copied each iteration of the 4X unrolled loop. */ |
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48 | #define BIGBLOCKSIZE (sizeof (long) << 2) |
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49 | |||
50 | /* How many bytes are copied each iteration of the word copy loop. */ |
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51 | #define LITTLEBLOCKSIZE (sizeof (long)) |
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52 | |||
53 | /* Threshhold for punting to the byte copier. */ |
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54 | #define TOO_SMALL(LEN) ((LEN) < BIGBLOCKSIZE) |
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55 | |||
56 | /*SUPPRESS 20*/ |
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57 | _PTR |
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58 | _DEFUN (memmove, (dst_void, src_void, length), |
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59 | _PTR dst_void _AND |
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60 | _CONST _PTR src_void _AND |
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61 | size_t length) |
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62 | { |
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63 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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64 | char *dst = dst_void; |
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65 | _CONST char *src = src_void; |
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66 | |||
67 | if (src < dst && dst < src + length) |
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68 | { |
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69 | /* Have to copy backwards */ |
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70 | src += length; |
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71 | dst += length; |
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72 | while (length--) |
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73 | { |
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74 | *--dst = *--src; |
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75 | } |
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76 | } |
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77 | else |
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78 | { |
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79 | while (length--) |
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80 | { |
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81 | *dst++ = *src++; |
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82 | } |
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83 | } |
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84 | |||
85 | return dst_void; |
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86 | #else |
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87 | char *dst = dst_void; |
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88 | _CONST char *src = src_void; |
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89 | long *aligned_dst; |
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90 | _CONST long *aligned_src; |
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91 | |||
92 | if (src < dst && dst < src + length) |
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93 | { |
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94 | /* Destructive overlap...have to copy backwards */ |
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95 | src += length; |
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96 | dst += length; |
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97 | while (length--) |
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98 | { |
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99 | *--dst = *--src; |
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100 | } |
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101 | } |
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102 | else |
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103 | { |
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104 | /* Use optimizing algorithm for a non-destructive copy to closely |
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105 | match memcpy. If the size is small or either SRC or DST is unaligned, |
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106 | then punt into the byte copy loop. This should be rare. */ |
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107 | if (!TOO_SMALL(length) && !UNALIGNED (src, dst)) |
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108 | { |
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109 | aligned_dst = (long*)dst; |
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110 | aligned_src = (long*)src; |
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111 | |||
112 | /* Copy 4X long words at a time if possible. */ |
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113 | while (length >= BIGBLOCKSIZE) |
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114 | { |
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115 | *aligned_dst++ = *aligned_src++; |
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116 | *aligned_dst++ = *aligned_src++; |
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117 | *aligned_dst++ = *aligned_src++; |
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118 | *aligned_dst++ = *aligned_src++; |
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119 | length -= BIGBLOCKSIZE; |
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120 | } |
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121 | |||
122 | /* Copy one long word at a time if possible. */ |
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123 | while (length >= LITTLEBLOCKSIZE) |
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124 | { |
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125 | *aligned_dst++ = *aligned_src++; |
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126 | length -= LITTLEBLOCKSIZE; |
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127 | } |
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128 | |||
129 | /* Pick up any residual with a byte copier. */ |
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130 | dst = (char*)aligned_dst; |
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131 | src = (char*)aligned_src; |
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132 | } |
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133 | |||
134 | while (length--) |
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135 | { |
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136 | *dst++ = *src++; |
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137 | } |
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138 | } |
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139 | |||
140 | return dst_void; |
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141 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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142 | }>>>>>><> |