| 1 | /* |
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| 2 | FUNCTION |
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| 3 | <<strcat>>---concatenate strings |
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| 4 | |
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| 5 | INDEX |
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| 6 | strcat |
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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 *strcat(char *restrict <[dst]>, const char *restrict <[src]>); |
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| 11 | |
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| 12 | DESCRIPTION |
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| 13 | <<strcat>> appends a copy of the string pointed to by <[src]> |
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| 14 | (including the terminating null character) to the end of the |
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| 15 | string pointed to by <[dst]>. The initial character of |
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| 16 | <[src]> overwrites the null character at the end of <[dst]>. |
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| 17 | |
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| 18 | RETURNS |
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| 19 | This function returns the initial value of <[dst]> |
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| 20 | |
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| 21 | PORTABILITY |
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| 22 | <<strcat>> is ANSI C. |
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| 23 | |
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| 24 | <<strcat>> requires no supporting OS subroutines. |
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| 25 | |
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| 26 | QUICKREF |
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| 27 | strcat ansi pure |
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| 28 | */ |
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| 29 | |
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| 30 | #include <string.h> |
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| 31 | #include <limits.h> |
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| 32 | |
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| 33 | /* Nonzero if X is aligned on a "long" boundary. */ |
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| 34 | #define ALIGNED(X) \ |
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| 35 | (((long)X & (sizeof (long) - 1)) == 0) |
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| 36 | |
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| 37 | #if LONG_MAX == 2147483647L |
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| 38 | #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) |
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| 39 | #else |
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| 40 | #if LONG_MAX == 9223372036854775807L |
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| 41 | /* Nonzero if X (a long int) contains a NULL byte. */ |
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| 42 | #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) |
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| 43 | #else |
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| 44 | #error long int is not a 32bit or 64bit type. |
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| 45 | #endif |
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| 46 | #endif |
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| 47 | |
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| 48 | #ifndef DETECTNULL |
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| 49 | #error long int is not a 32bit or 64bit byte |
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| 50 | #endif |
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| 51 | |
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| 52 | |
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| 53 | /*SUPPRESS 560*/ |
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| 54 | /*SUPPRESS 530*/ |
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| 55 | |
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| 56 | char * |
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| 57 | strcat (char *__restrict s1, |
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| 58 | const char *__restrict s2) |
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| 59 | { |
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| 60 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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| 61 | char *s = s1; |
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| 62 | |
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| 63 | while (*s1) |
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| 64 | s1++; |
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| 65 | |
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| 66 | while (*s1++ = *s2++) |
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| 67 | ; |
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| 68 | return s; |
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| 69 | #else |
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| 70 | char *s = s1; |
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| 71 | |
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| 72 | |
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| 73 | /* Skip over the data in s1 as quickly as possible. */ |
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| 74 | if (ALIGNED (s1)) |
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| 75 | { |
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| 76 | unsigned long *aligned_s1 = (unsigned long *)s1; |
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| 77 | while (!DETECTNULL (*aligned_s1)) |
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| 78 | aligned_s1++; |
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| 79 | |
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| 80 | s1 = (char *)aligned_s1; |
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| 81 | } |
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| 82 | |
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| 83 | while (*s1) |
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| 84 | s1++; |
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| 85 | |
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| 86 | /* s1 now points to the its trailing null character, we can |
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| 87 | just use strcpy to do the work for us now. |
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| 88 | |
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| 89 | ?!? We might want to just include strcpy here. |
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| 90 | Also, this will cause many more unaligned string copies because |
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| 91 | s1 is much less likely to be aligned. I don't know if its worth |
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| 92 | tweaking strcpy to handle this better. */ |
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| 93 | strcpy (s1, s2); |
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| 94 | |
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| 95 | return s; |
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| 96 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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| 97 | } |
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