| 1 | /* stringlib: fastsearch implementation */
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| 2 |
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| 3 | #ifndef STRINGLIB_FASTSEARCH_H
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| 4 | #define STRINGLIB_FASTSEARCH_H
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| 5 |
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| 6 | /* fast search/count implementation, based on a mix between boyer-
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| 7 | moore and horspool, with a few more bells and whistles on the top.
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| 8 | for some more background, see: http://effbot.org/zone/stringlib.htm */
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| 9 |
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| 10 | /* note: fastsearch may access s[n], which isn't a problem when using
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| 11 | Python's ordinary string types, but may cause problems if you're
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| 12 | using this code in other contexts. also, the count mode returns -1
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| 13 | if there cannot possible be a match in the target string, and 0 if
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| 14 | it has actually checked for matches, but didn't find any. callers
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| 15 | beware! */
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| 16 |
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| 17 | #define FAST_COUNT 0
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| 18 | #define FAST_SEARCH 1
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| 19 | #define FAST_RSEARCH 2
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| 20 |
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| 21 | #if LONG_BIT >= 128
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| 22 | #define STRINGLIB_BLOOM_WIDTH 128
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| 23 | #elif LONG_BIT >= 64
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| 24 | #define STRINGLIB_BLOOM_WIDTH 64
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| 25 | #elif LONG_BIT >= 32
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| 26 | #define STRINGLIB_BLOOM_WIDTH 32
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| 27 | #else
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| 28 | #error "LONG_BIT is smaller than 32"
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| 29 | #endif
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| 30 |
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| 31 | #define STRINGLIB_BLOOM_ADD(mask, ch) \
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| 32 | ((mask |= (1UL << ((ch) & (STRINGLIB_BLOOM_WIDTH -1)))))
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| 33 | #define STRINGLIB_BLOOM(mask, ch) \
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| 34 | ((mask & (1UL << ((ch) & (STRINGLIB_BLOOM_WIDTH -1)))))
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| 35 |
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| 36 | Py_LOCAL_INLINE(Py_ssize_t)
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| 37 | fastsearch(const STRINGLIB_CHAR* s, Py_ssize_t n,
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| 38 | const STRINGLIB_CHAR* p, Py_ssize_t m,
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| 39 | Py_ssize_t maxcount, int mode)
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| 40 | {
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| 41 | unsigned long mask;
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| 42 | Py_ssize_t skip, count = 0;
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| 43 | Py_ssize_t i, j, mlast, w;
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| 44 |
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| 45 | w = n - m;
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| 46 |
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| 47 | if (w < 0 || (mode == FAST_COUNT && maxcount == 0))
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| 48 | return -1;
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| 49 |
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| 50 | /* look for special cases */
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| 51 | if (m <= 1) {
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| 52 | if (m <= 0)
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| 53 | return -1;
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| 54 | /* use special case for 1-character strings */
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| 55 | if (mode == FAST_COUNT) {
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| 56 | for (i = 0; i < n; i++)
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| 57 | if (s[i] == p[0]) {
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| 58 | count++;
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| 59 | if (count == maxcount)
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| 60 | return maxcount;
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| 61 | }
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| 62 | return count;
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| 63 | } else if (mode == FAST_SEARCH) {
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| 64 | for (i = 0; i < n; i++)
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| 65 | if (s[i] == p[0])
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| 66 | return i;
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| 67 | } else { /* FAST_RSEARCH */
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| 68 | for (i = n - 1; i > -1; i--)
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| 69 | if (s[i] == p[0])
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| 70 | return i;
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| 71 | }
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| 72 | return -1;
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| 73 | }
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| 74 |
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| 75 | mlast = m - 1;
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| 76 | skip = mlast - 1;
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| 77 | mask = 0;
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| 78 |
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| 79 | if (mode != FAST_RSEARCH) {
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| 80 |
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| 81 | /* create compressed boyer-moore delta 1 table */
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| 82 |
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| 83 | /* process pattern[:-1] */
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| 84 | for (i = 0; i < mlast; i++) {
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| 85 | STRINGLIB_BLOOM_ADD(mask, p[i]);
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| 86 | if (p[i] == p[mlast])
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| 87 | skip = mlast - i - 1;
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| 88 | }
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| 89 | /* process pattern[-1] outside the loop */
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| 90 | STRINGLIB_BLOOM_ADD(mask, p[mlast]);
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| 91 |
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| 92 | for (i = 0; i <= w; i++) {
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| 93 | /* note: using mlast in the skip path slows things down on x86 */
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| 94 | if (s[i+m-1] == p[m-1]) {
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| 95 | /* candidate match */
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| 96 | for (j = 0; j < mlast; j++)
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| 97 | if (s[i+j] != p[j])
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| 98 | break;
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| 99 | if (j == mlast) {
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| 100 | /* got a match! */
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| 101 | if (mode != FAST_COUNT)
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| 102 | return i;
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| 103 | count++;
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| 104 | if (count == maxcount)
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| 105 | return maxcount;
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| 106 | i = i + mlast;
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| 107 | continue;
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| 108 | }
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| 109 | /* miss: check if next character is part of pattern */
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| 110 | if (!STRINGLIB_BLOOM(mask, s[i+m]))
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| 111 | i = i + m;
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| 112 | else
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| 113 | i = i + skip;
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| 114 | } else {
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| 115 | /* skip: check if next character is part of pattern */
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| 116 | if (!STRINGLIB_BLOOM(mask, s[i+m]))
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| 117 | i = i + m;
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| 118 | }
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| 119 | }
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| 120 | } else { /* FAST_RSEARCH */
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| 121 |
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| 122 | /* create compressed boyer-moore delta 1 table */
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| 123 |
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| 124 | /* process pattern[0] outside the loop */
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| 125 | STRINGLIB_BLOOM_ADD(mask, p[0]);
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| 126 | /* process pattern[:0:-1] */
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| 127 | for (i = mlast; i > 0; i--) {
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| 128 | STRINGLIB_BLOOM_ADD(mask, p[i]);
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| 129 | if (p[i] == p[0])
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| 130 | skip = i - 1;
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| 131 | }
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| 132 |
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| 133 | for (i = w; i >= 0; i--) {
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| 134 | if (s[i] == p[0]) {
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| 135 | /* candidate match */
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| 136 | for (j = mlast; j > 0; j--)
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| 137 | if (s[i+j] != p[j])
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| 138 | break;
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| 139 | if (j == 0)
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| 140 | /* got a match! */
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| 141 | return i;
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| 142 | /* miss: check if previous character is part of pattern */
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| 143 | if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1]))
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| 144 | i = i - m;
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| 145 | else
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| 146 | i = i - skip;
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| 147 | } else {
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| 148 | /* skip: check if previous character is part of pattern */
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| 149 | if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1]))
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| 150 | i = i - m;
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| 151 | }
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| 152 | }
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| 153 | }
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| 154 |
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| 155 | if (mode != FAST_COUNT)
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| 156 | return -1;
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| 157 | return count;
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| 158 | }
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| 159 |
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| 160 | #endif
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