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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4349 | Serge | 1 | /* |
| 2 | FUNCTION |
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| 3 | < |
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| 4 | |||
| 5 | INDEX |
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| 6 | strncmp |
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| 7 | |||
| 8 | ANSI_SYNOPSIS |
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| 9 | #include |
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| 10 | int strncmp(const char *<[a]>, const char * <[b]>, size_t <[length]>); |
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| 11 | |||
| 12 | TRAD_SYNOPSIS |
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| 13 | #include |
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| 14 | int strncmp(<[a]>, <[b]>, <[length]>) |
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| 15 | char *<[a]>; |
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| 16 | char *<[b]>; |
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| 17 | size_t <[length]> |
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| 18 | |||
| 19 | DESCRIPTION |
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| 20 | < |
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| 21 | from the string at <[a]> to the string at <[b]>. |
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| 22 | |||
| 23 | RETURNS |
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| 24 | If <<*<[a]>>> sorts lexicographically after <<*<[b]>>>, |
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| 25 | < |
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| 26 | strings are equivalent, < |
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| 27 | sorts lexicographically before <<*<[b]>>>, < |
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| 28 | number less than zero. |
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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 | strncmp ansi pure |
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| 37 | */ |
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| 38 | |||
| 39 | #include |
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| 40 | #include |
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| 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 | /* DETECTNULL returns nonzero if (long)X contains a NULL byte. */ |
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| 47 | #if LONG_MAX == 2147483647L |
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| 48 | #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) |
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| 49 | #else |
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| 50 | #if LONG_MAX == 9223372036854775807L |
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| 51 | #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) |
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| 52 | #else |
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| 53 | #error long int is not a 32bit or 64bit type. |
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| 54 | #endif |
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| 55 | #endif |
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| 56 | |||
| 57 | #ifndef DETECTNULL |
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| 58 | #error long int is not a 32bit or 64bit byte |
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| 59 | #endif |
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| 60 | |||
| 61 | int |
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| 62 | _DEFUN (strncmp, (s1, s2, n), |
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| 63 | _CONST char *s1 _AND |
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| 64 | _CONST char *s2 _AND |
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| 65 | size_t n) |
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| 66 | { |
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| 67 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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| 68 | if (n == 0) |
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| 69 | return 0; |
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| 70 | |||
| 71 | while (n-- != 0 && *s1 == *s2) |
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| 72 | { |
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| 73 | if (n == 0 || *s1 == '\0') |
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| 74 | break; |
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| 75 | s1++; |
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| 76 | s2++; |
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| 77 | } |
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| 78 | |||
| 79 | return (*(unsigned char *) s1) - (*(unsigned char *) s2); |
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| 80 | #else |
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| 81 | unsigned long *a1; |
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| 82 | unsigned long *a2; |
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| 83 | |||
| 84 | if (n == 0) |
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| 85 | return 0; |
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| 86 | |||
| 87 | /* If s1 or s2 are unaligned, then compare bytes. */ |
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| 88 | if (!UNALIGNED (s1, s2)) |
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| 89 | { |
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| 90 | /* If s1 and s2 are word-aligned, compare them a word at a time. */ |
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| 91 | a1 = (unsigned long*)s1; |
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| 92 | a2 = (unsigned long*)s2; |
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| 93 | while (n >= sizeof (long) && *a1 == *a2) |
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| 94 | { |
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| 95 | n -= sizeof (long); |
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| 96 | |||
| 97 | /* If we've run out of bytes or hit a null, return zero |
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| 98 | since we already know *a1 == *a2. */ |
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| 99 | if (n == 0 || DETECTNULL (*a1)) |
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| 100 | return 0; |
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| 101 | |||
| 102 | a1++; |
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| 103 | a2++; |
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| 104 | } |
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| 105 | |||
| 106 | /* A difference was detected in last few bytes of s1, so search bytewise */ |
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| 107 | s1 = (char*)a1; |
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| 108 | s2 = (char*)a2; |
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| 109 | } |
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| 110 | |||
| 111 | while (n-- > 0 && *s1 == *s2) |
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| 112 | { |
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| 113 | /* If we've run out of bytes or hit a null, return zero |
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| 114 | since we already know *s1 == *s2. */ |
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| 115 | if (n == 0 || *s1 == '\0') |
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| 116 | return 0; |
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| 117 | s1++; |
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| 118 | s2++; |
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| 119 | } |
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| 120 | return (*(unsigned char *) s1) - (*(unsigned char *) s2); |
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| 121 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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| 122 | } |