| 1 | /* |
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| 2 | FUNCTION |
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| 3 | <<strstr>>---find string segment |
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| 4 | |
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| 5 | INDEX |
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| 6 | strstr |
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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 *strstr(const char *<[s1]>, const char *<[s2]>); |
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| 11 | |
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| 12 | DESCRIPTION |
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| 13 | Locates the first occurrence in the string pointed to by <[s1]> of |
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| 14 | the sequence of characters in the string pointed to by <[s2]> |
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| 15 | (excluding the terminating null character). |
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| 16 | |
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| 17 | RETURNS |
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| 18 | Returns a pointer to the located string segment, or a null |
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| 19 | pointer if the string <[s2]> is not found. If <[s2]> points to |
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| 20 | a string with zero length, <[s1]> is returned. |
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| 21 | |
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| 22 | PORTABILITY |
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| 23 | <<strstr>> is ANSI C. |
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| 24 | |
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| 25 | <<strstr>> requires no supporting OS subroutines. |
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| 26 | |
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| 27 | QUICKREF |
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| 28 | strstr ansi pure |
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| 29 | */ |
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| 30 | |
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| 31 | #include <string.h> |
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| 32 | |
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| 33 | #if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__) |
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| 34 | # define RETURN_TYPE char * |
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| 35 | # define AVAILABLE(h, h_l, j, n_l) \ |
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| 36 | (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \ |
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| 37 | && ((h_l) = (j) + (n_l))) |
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| 38 | # include "str-two-way.h" |
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| 39 | #endif |
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| 40 | |
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| 41 | char * |
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| 42 | strstr (const char *searchee, |
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| 43 | const char *lookfor) |
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| 44 | { |
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| 45 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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| 46 | |
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| 47 | /* Less code size, but quadratic performance in the worst case. */ |
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| 48 | if (*searchee == 0) |
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| 49 | { |
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| 50 | if (*lookfor) |
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| 51 | return (char *) NULL; |
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| 52 | return (char *) searchee; |
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| 53 | } |
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| 54 | |
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| 55 | while (*searchee) |
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| 56 | { |
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| 57 | size_t i; |
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| 58 | i = 0; |
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| 59 | |
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| 60 | while (1) |
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| 61 | { |
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| 62 | if (lookfor[i] == 0) |
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| 63 | { |
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| 64 | return (char *) searchee; |
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| 65 | } |
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| 66 | |
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| 67 | if (lookfor[i] != searchee[i]) |
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| 68 | { |
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| 69 | break; |
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| 70 | } |
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| 71 | i++; |
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| 72 | } |
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| 73 | searchee++; |
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| 74 | } |
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| 75 | |
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| 76 | return (char *) NULL; |
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| 77 | |
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| 78 | #else /* compilation for speed */ |
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| 79 | |
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| 80 | /* Larger code size, but guaranteed linear performance. */ |
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| 81 | const char *haystack = searchee; |
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| 82 | const char *needle = lookfor; |
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| 83 | size_t needle_len; /* Length of NEEDLE. */ |
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| 84 | size_t haystack_len; /* Known minimum length of HAYSTACK. */ |
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| 85 | int ok = 1; /* True if NEEDLE is prefix of HAYSTACK. */ |
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| 86 | |
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| 87 | /* Determine length of NEEDLE, and in the process, make sure |
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| 88 | HAYSTACK is at least as long (no point processing all of a long |
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| 89 | NEEDLE if HAYSTACK is too short). */ |
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| 90 | while (*haystack && *needle) |
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| 91 | ok &= *haystack++ == *needle++; |
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| 92 | if (*needle) |
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| 93 | return NULL; |
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| 94 | if (ok) |
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| 95 | return (char *) searchee; |
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| 96 | |
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| 97 | /* Reduce the size of haystack using strchr, since it has a smaller |
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| 98 | linear coefficient than the Two-Way algorithm. */ |
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| 99 | needle_len = needle - lookfor; |
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| 100 | haystack = strchr (searchee + 1, *lookfor); |
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| 101 | if (!haystack || needle_len == 1) |
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| 102 | return (char *) haystack; |
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| 103 | haystack_len = (haystack > searchee + needle_len ? 1 |
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| 104 | : needle_len + searchee - haystack); |
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| 105 | |
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| 106 | /* Perform the search. */ |
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| 107 | if (needle_len < LONG_NEEDLE_THRESHOLD) |
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| 108 | return two_way_short_needle ((const unsigned char *) haystack, |
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| 109 | haystack_len, |
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| 110 | (const unsigned char *) lookfor, needle_len); |
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| 111 | return two_way_long_needle ((const unsigned char *) haystack, haystack_len, |
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| 112 | (const unsigned char *) lookfor, needle_len); |
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| 113 | #endif /* compilation for speed */ |
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| 114 | } |
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