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Rev | Author | Line No. | Line |
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4349 | Serge | 1 | /* |
2 | FUNCTION |
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3 | < |
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4 | |||
5 | INDEX |
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6 | memcmp |
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7 | |||
8 | ANSI_SYNOPSIS |
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9 | #include |
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10 | int memcmp(const void *<[s1]>, const void *<[s2]>, size_t <[n]>); |
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11 | |||
12 | TRAD_SYNOPSIS |
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13 | #include |
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14 | int memcmp(<[s1]>, <[s2]>, <[n]>) |
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15 | void *<[s1]>; |
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16 | void *<[s2]>; |
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17 | size_t <[n]>; |
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18 | |||
19 | DESCRIPTION |
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20 | This function compares not more than <[n]> characters of the |
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21 | object pointed to by <[s1]> with the object pointed to by <[s2]>. |
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22 | |||
23 | |||
24 | RETURNS |
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25 | The function returns an integer greater than, equal to or |
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26 | less than zero according to whether the object pointed to by |
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27 | <[s1]> is greater than, equal to or less than the object |
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28 | pointed to by <[s2]>. |
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29 | |||
30 | PORTABILITY |
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31 | < |
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32 | |||
33 | < |
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34 | |||
35 | QUICKREF |
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36 | memcmp ansi pure |
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37 | */ |
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38 | |||
39 | #include |
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40 | |||
41 | |||
42 | /* Nonzero if either X or Y is not aligned on a "long" boundary. */ |
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43 | #define UNALIGNED(X, Y) \ |
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44 | (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1))) |
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45 | |||
46 | /* How many bytes are copied each iteration of the word copy loop. */ |
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47 | #define LBLOCKSIZE (sizeof (long)) |
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48 | |||
49 | /* Threshhold for punting to the byte copier. */ |
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50 | #define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE) |
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51 | |||
52 | int |
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53 | _DEFUN (memcmp, (m1, m2, n), |
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54 | _CONST _PTR m1 _AND |
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55 | _CONST _PTR m2 _AND |
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56 | size_t n) |
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57 | { |
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58 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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59 | unsigned char *s1 = (unsigned char *) m1; |
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60 | unsigned char *s2 = (unsigned char *) m2; |
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61 | |||
62 | while (n--) |
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63 | { |
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64 | if (*s1 != *s2) |
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65 | { |
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66 | return *s1 - *s2; |
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67 | } |
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68 | s1++; |
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69 | s2++; |
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70 | } |
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71 | return 0; |
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72 | #else |
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73 | unsigned char *s1 = (unsigned char *) m1; |
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74 | unsigned char *s2 = (unsigned char *) m2; |
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75 | unsigned long *a1; |
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76 | unsigned long *a2; |
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77 | |||
78 | /* If the size is too small, or either pointer is unaligned, |
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79 | then we punt to the byte compare loop. Hopefully this will |
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80 | not turn up in inner loops. */ |
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81 | if (!TOO_SMALL(n) && !UNALIGNED(s1,s2)) |
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82 | { |
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83 | /* Otherwise, load and compare the blocks of memory one |
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84 | word at a time. */ |
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85 | a1 = (unsigned long*) s1; |
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86 | a2 = (unsigned long*) s2; |
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87 | while (n >= LBLOCKSIZE) |
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88 | { |
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89 | if (*a1 != *a2) |
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90 | break; |
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91 | a1++; |
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92 | a2++; |
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93 | n -= LBLOCKSIZE; |
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94 | } |
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95 | |||
96 | /* check m mod LBLOCKSIZE remaining characters */ |
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97 | |||
98 | s1 = (unsigned char*)a1; |
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99 | s2 = (unsigned char*)a2; |
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100 | } |
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101 | |||
102 | while (n--) |
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103 | { |
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104 | if (*s1 != *s2) |
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105 | return *s1 - *s2; |
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106 | s1++; |
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107 | s2++; |
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108 | } |
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109 | |||
110 | return 0; |
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111 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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112 | }> |
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113 |