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| 1 | +/* stringlib: fastsearch implementation */ | |
| 2 | + | |
| 3 | +#ifndef STRINGLIB_FASTSEARCH_H | |
| 4 | +#define STRINGLIB_FASTSEARCH_H | |
| 5 | + | |
| 6 | +/* fast search/count implementation, based on a mix between boyer- | |
| 7 | + moore and horspool, with a few more bells and whistles on the top. | |
| 8 | + for some more background, see: http://effbot.org/stringlib */ | |
| 9 | + | |
| 10 | +/* note: fastsearch may access s[n], which isn't a problem when using | |
| 11 | + Python's ordinary string types, but may cause problems if you're | |
| 12 | + using this code in other contexts. also, the count mode returns -1 | |
| 13 | + if there cannot possible be a match in the target string, and 0 if | |
| 14 | + it has actually checked for matches, but didn't find any. callers | |
| 15 | + beware! */ | |
| 16 | + | |
| 17 | +#define FAST_COUNT 0 | |
| 18 | +#define FAST_SEARCH 1 | |
| 19 | + | |
| 20 | +Py_LOCAL_INLINE(Py_ssize_t) | |
| 21 | +fastsearch(const STRINGLIB_CHAR* s, Py_ssize_t n, | |
| 22 | + const STRINGLIB_CHAR* p, Py_ssize_t m, | |
| 23 | + int mode) | |
| 24 | +{ | |
| 25 | + long mask; | |
| 26 | + Py_ssize_t skip, count = 0; | |
| 27 | + Py_ssize_t i, j, mlast, w; | |
| 28 | + | |
| 29 | + w = n - m; | |
| 30 | + | |
| 31 | + if (w < 0) | |
| 32 | + return -1; | |
| 33 | + | |
| 34 | + /* look for special cases */ | |
| 35 | + if (m <= 1) { | |
| 36 | + if (m <= 0) | |
| 37 | + return -1; | |
| 38 | + /* use special case for 1-character strings */ | |
| 39 | + if (mode == FAST_COUNT) { | |
| 40 | + for (i = 0; i < n; i++) | |
| 41 | + if (s[i] == p[0]) | |
| 42 | + count++; | |
| 43 | + return count; | |
| 44 | + } else { | |
| 45 | + for (i = 0; i < n; i++) | |
| 46 | + if (s[i] == p[0]) | |
| 47 | + return i; | |
| 48 | + } | |
| 49 | + return -1; | |
| 50 | + } | |
| 51 | + | |
| 52 | + mlast = m - 1; | |
| 53 | + | |
| 54 | + /* create compressed boyer-moore delta 1 table */ | |
| 55 | + skip = mlast - 1; | |
| 56 | + /* process pattern[:-1] */ | |
| 57 | + for (mask = i = 0; i < mlast; i++) { | |
| 58 | + mask |= (1 << (p[i] & 0x1F)); | |
| 59 | + if (p[i] == p[mlast]) | |
| 60 | + skip = mlast - i - 1; | |
| 61 | + } | |
| 62 | + /* process pattern[-1] outside the loop */ | |
| 63 | + mask |= (1 << (p[mlast] & 0x1F)); | |
| 64 | + | |
| 65 | + for (i = 0; i <= w; i++) { | |
| 66 | + /* note: using mlast in the skip path slows things down on x86 */ | |
| 67 | + if (s[i+m-1] == p[m-1]) { | |
| 68 | + /* candidate match */ | |
| 69 | + for (j = 0; j < mlast; j++) | |
| 70 | + if (s[i+j] != p[j]) | |
| 71 | + break; | |
| 72 | + if (j == mlast) { | |
| 73 | + /* got a match! */ | |
| 74 | + if (mode != FAST_COUNT) | |
| 75 | + return i; | |
| 76 | + count++; | |
| 77 | + i = i + mlast; | |
| 78 | + continue; | |
| 79 | + } | |
| 80 | + /* miss: check if next character is part of pattern */ | |
| 81 | + if (!(mask & (1 << (s[i+m] & 0x1F)))) | |
| 82 | + i = i + m; | |
| 83 | + else | |
| 84 | + i = i + skip; | |
| 85 | + } else { | |
| 86 | + /* skip: check if next character is part of pattern */ | |
| 87 | + if (!(mask & (1 << (s[i+m] & 0x1F)))) | |
| 88 | + i = i + m; | |
| 89 | + } | |
| 90 | + } | |
| 91 | + | |
| 92 | + if (mode != FAST_COUNT) | |
| 93 | + return -1; | |
| 94 | + return count; | |
| 95 | +} | |
| 96 | + | |
| 97 | +#endif | |
| 98 | + | |
| 99 | +/* | |
| 100 | +Local variables: | |
| 101 | +c-basic-offset: 4 | |
| 102 | +indent-tabs-mode: nil | |
| 103 | +End: | |
| 104 | +*/ | |