[444] | 1 | /* |
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| 2 | FUNCTION |
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| 3 | <<strncpy>>---counted copy string |
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| 4 | |
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| 5 | INDEX |
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| 6 | strncpy |
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| 7 | |
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| 8 | SYNOPSIS |
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| 9 | #include <string.h> |
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| 10 | char *strncpy(char *restrict <[dst]>, const char *restrict <[src]>, |
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| 11 | size_t <[length]>); |
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| 12 | |
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| 13 | DESCRIPTION |
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| 14 | <<strncpy>> copies not more than <[length]> characters from the |
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| 15 | the string pointed to by <[src]> (including the terminating |
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| 16 | null character) to the array pointed to by <[dst]>. If the |
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| 17 | string pointed to by <[src]> is shorter than <[length]> |
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| 18 | characters, null characters are appended to the destination |
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| 19 | array until a total of <[length]> characters have been |
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| 20 | written. |
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| 21 | |
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| 22 | RETURNS |
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| 23 | This function returns the initial value of <[dst]>. |
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| 24 | |
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| 25 | PORTABILITY |
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| 26 | <<strncpy>> is ANSI C. |
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| 27 | |
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| 28 | <<strncpy>> requires no supporting OS subroutines. |
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| 29 | |
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| 30 | QUICKREF |
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| 31 | strncpy ansi pure |
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| 32 | */ |
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| 33 | |
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| 34 | #include <string.h> |
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| 35 | #include <limits.h> |
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| 36 | |
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| 37 | /*SUPPRESS 560*/ |
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| 38 | /*SUPPRESS 530*/ |
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| 39 | |
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| 40 | /* Nonzero if either X or Y is not aligned on a "long" boundary. */ |
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| 41 | #define UNALIGNED(X, Y) \ |
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| 42 | (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1))) |
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| 43 | |
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| 44 | #if LONG_MAX == 2147483647L |
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| 45 | #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) |
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| 46 | #else |
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| 47 | #if LONG_MAX == 9223372036854775807L |
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| 48 | /* Nonzero if X (a long int) contains a NULL byte. */ |
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| 49 | #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) |
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| 50 | #else |
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| 51 | #error long int is not a 32bit or 64bit type. |
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| 52 | #endif |
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| 53 | #endif |
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| 54 | |
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| 55 | #ifndef DETECTNULL |
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| 56 | #error long int is not a 32bit or 64bit byte |
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| 57 | #endif |
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| 58 | |
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| 59 | #define TOO_SMALL(LEN) ((LEN) < sizeof (long)) |
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| 60 | |
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| 61 | char * |
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| 62 | strncpy (char *__restrict dst0, |
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| 63 | const char *__restrict src0, |
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| 64 | size_t count) |
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| 65 | { |
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| 66 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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| 67 | char *dscan; |
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| 68 | const char *sscan; |
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| 69 | |
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| 70 | dscan = dst0; |
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| 71 | sscan = src0; |
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| 72 | while (count > 0) |
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| 73 | { |
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| 74 | --count; |
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| 75 | if ((*dscan++ = *sscan++) == '\0') |
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| 76 | break; |
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| 77 | } |
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| 78 | while (count-- > 0) |
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| 79 | *dscan++ = '\0'; |
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| 80 | |
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| 81 | return dst0; |
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| 82 | #else |
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| 83 | char *dst = dst0; |
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| 84 | const char *src = src0; |
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| 85 | long *aligned_dst; |
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| 86 | const long *aligned_src; |
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| 87 | |
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| 88 | /* If SRC and DEST is aligned and count large enough, then copy words. */ |
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| 89 | if (!UNALIGNED (src, dst) && !TOO_SMALL (count)) |
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| 90 | { |
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| 91 | aligned_dst = (long*)dst; |
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| 92 | aligned_src = (long*)src; |
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| 93 | |
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| 94 | /* SRC and DEST are both "long int" aligned, try to do "long int" |
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| 95 | sized copies. */ |
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| 96 | while (count >= sizeof (long int) && !DETECTNULL(*aligned_src)) |
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| 97 | { |
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| 98 | count -= sizeof (long int); |
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| 99 | *aligned_dst++ = *aligned_src++; |
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| 100 | } |
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| 101 | |
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| 102 | dst = (char*)aligned_dst; |
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| 103 | src = (char*)aligned_src; |
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| 104 | } |
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| 105 | |
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| 106 | while (count > 0) |
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| 107 | { |
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| 108 | --count; |
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| 109 | if ((*dst++ = *src++) == '\0') |
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| 110 | break; |
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| 111 | } |
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| 112 | |
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| 113 | while (count-- > 0) |
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| 114 | *dst++ = '\0'; |
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| 115 | |
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| 116 | return dst0; |
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| 117 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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| 118 | } |
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