Rev 4872 | Details | Compare with Previous | Last modification | View Log | RSS feed
| 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 | strlen |
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| 7 | |||
| 8 | ANSI_SYNOPSIS |
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| 9 | #include |
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| 10 | size_t strlen(const char *<[str]>); |
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| 11 | |||
| 12 | TRAD_SYNOPSIS |
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| 13 | #include |
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| 14 | size_t strlen(<[str]>) |
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| 15 | char *<[src]>; |
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| 16 | |||
| 17 | DESCRIPTION |
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| 18 | The < |
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| 19 | starting at <<*<[str]>>> by counting chararacters until it |
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| 20 | reaches a < |
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| 21 | |||
| 22 | RETURNS |
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| 23 | < |
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| 24 | |||
| 25 | PORTABILITY |
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| 26 | < |
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| 27 | |||
| 28 | < |
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| 29 | |||
| 30 | QUICKREF |
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| 31 | strlen ansi pure |
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| 32 | */ |
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| 33 | |||
| 34 | #include <_ansi.h> |
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| 35 | #include |
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| 36 | #include |
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| 37 | |||
| 38 | #define LBLOCKSIZE (sizeof (long)) |
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| 39 | #define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1)) |
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| 40 | |||
| 41 | #if LONG_MAX == 2147483647L |
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| 42 | #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) |
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| 43 | #else |
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| 44 | #if LONG_MAX == 9223372036854775807L |
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| 45 | /* Nonzero if X (a long int) contains a NULL byte. */ |
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| 46 | #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) |
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| 47 | #else |
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| 48 | #error long int is not a 32bit or 64bit type. |
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| 49 | #endif |
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| 50 | #endif |
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| 51 | |||
| 52 | #ifndef DETECTNULL |
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| 53 | #error long int is not a 32bit or 64bit byte |
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| 54 | #endif |
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| 55 | |||
| 56 | size_t |
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| 57 | _DEFUN (strlen, (str), |
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| 58 | _CONST char *str) |
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| 59 | { |
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| 60 | _CONST char *start = str; |
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| 61 | |||
| 62 | #if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__) |
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| 63 | unsigned long *aligned_addr; |
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| 64 | |||
| 65 | /* Align the pointer, so we can search a word at a time. */ |
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| 66 | while (UNALIGNED (str)) |
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| 67 | { |
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| 68 | if (!*str) |
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| 69 | return str - start; |
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| 70 | str++; |
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| 71 | } |
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| 72 | |||
| 73 | /* If the string is word-aligned, we can check for the presence of |
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| 74 | a null in each word-sized block. */ |
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| 75 | aligned_addr = (unsigned long *)str; |
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| 76 | while (!DETECTNULL (*aligned_addr)) |
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| 77 | aligned_addr++; |
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| 78 | |||
| 79 | /* Once a null is detected, we check each byte in that block for a |
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| 80 | precise position of the null. */ |
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| 81 | str = (char *) aligned_addr; |
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| 82 | |||
| 83 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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| 84 | |||
| 85 | while (*str) |
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| 86 | str++; |
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| 87 | return str - start; |
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| 88 | } |