| 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/stringlib */
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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 |
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| 20 | Py_LOCAL_INLINE(Py_ssize_t)
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| 21 | fastsearch(const STRINGLIB_CHAR* s, Py_ssize_t n,
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| 22 | const STRINGLIB_CHAR* p, Py_ssize_t m,
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| 23 | int mode)
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| 24 | {
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| 25 | long mask;
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| 26 | Py_ssize_t skip, count = 0;
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| 27 | Py_ssize_t i, j, mlast, w;
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| 28 |
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| 29 | w = n - m;
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| 30 |
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| 31 | if (w < 0)
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| 32 | return -1;
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| 33 |
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| 34 | /* look for special cases */
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| 35 | if (m <= 1) {
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| 36 | if (m <= 0)
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| 37 | return -1;
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| 38 | /* use special case for 1-character strings */
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| 39 | if (mode == FAST_COUNT) {
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| 40 | for (i = 0; i < n; i++)
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| 41 | if (s[i] == p[0])
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| 42 | count++;
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| 43 | return count;
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| 44 | } else {
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| 45 | for (i = 0; i < n; i++)
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| 46 | if (s[i] == p[0])
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| 47 | return i;
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| 48 | }
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| 49 | return -1;
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| 50 | }
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| 51 |
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| 52 | mlast = m - 1;
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| 53 |
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| 54 | /* create compressed boyer-moore delta 1 table */
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| 55 | skip = mlast - 1;
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| 56 | /* process pattern[:-1] */
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| 57 | for (mask = i = 0; i < mlast; i++) {
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| 58 | mask |= (1 << (p[i] & 0x1F));
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| 59 | if (p[i] == p[mlast])
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| 60 | skip = mlast - i - 1;
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| 61 | }
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| 62 | /* process pattern[-1] outside the loop */
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| 63 | mask |= (1 << (p[mlast] & 0x1F));
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| 64 |
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| 65 | for (i = 0; i <= w; i++) {
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| 66 | /* note: using mlast in the skip path slows things down on x86 */
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| 67 | if (s[i+m-1] == p[m-1]) {
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| 68 | /* candidate match */
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| 69 | for (j = 0; j < mlast; j++)
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| 70 | if (s[i+j] != p[j])
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| 71 | break;
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| 72 | if (j == mlast) {
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| 73 | /* got a match! */
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| 74 | if (mode != FAST_COUNT)
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| 75 | return i;
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| 76 | count++;
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| 77 | i = i + mlast;
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| 78 | continue;
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| 79 | }
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| 80 | /* miss: check if next character is part of pattern */
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| 81 | if (!(mask & (1 << (s[i+m] & 0x1F))))
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| 82 | i = i + m;
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| 83 | else
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| 84 | i = i + skip;
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| 85 | } else {
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| 86 | /* skip: check if next character is part of pattern */
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| 87 | if (!(mask & (1 << (s[i+m] & 0x1F))))
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| 88 | i = i + m;
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| 89 | }
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| 90 | }
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| 91 |
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| 92 | if (mode != FAST_COUNT)
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| 93 | return -1;
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| 94 | return count;
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| 95 | }
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| 96 |
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| 97 | #endif
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| 98 |
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| 99 | /*
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| 100 | Local variables:
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| 101 | c-basic-offset: 4
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| 102 | indent-tabs-mode: nil
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| 103 | End:
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| 104 | */
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