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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 | */ | ||