Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 1 | /* stringlib: fastsearch implementation */ |
| 2 | |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 3 | #define STRINGLIB_FASTSEARCH_H |
| 4 | |
| 5 | /* fast search/count implementation, based on a mix between boyer- |
| 6 | moore and horspool, with a few more bells and whistles on the top. |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 7 | for some more background, see: http://effbot.org/zone/stringlib.htm */ |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 8 | |
| 9 | /* note: fastsearch may access s[n], which isn't a problem when using |
| 10 | Python's ordinary string types, but may cause problems if you're |
| 11 | using this code in other contexts. also, the count mode returns -1 |
| 12 | if there cannot possible be a match in the target string, and 0 if |
| 13 | it has actually checked for matches, but didn't find any. callers |
| 14 | beware! */ |
| 15 | |
| 16 | #define FAST_COUNT 0 |
| 17 | #define FAST_SEARCH 1 |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 18 | #define FAST_RSEARCH 2 |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 19 | |
Antoine Pitrou | f068f94 | 2010-01-13 14:19:12 +0000 | [diff] [blame] | 20 | #if LONG_BIT >= 128 |
| 21 | #define STRINGLIB_BLOOM_WIDTH 128 |
| 22 | #elif LONG_BIT >= 64 |
| 23 | #define STRINGLIB_BLOOM_WIDTH 64 |
| 24 | #elif LONG_BIT >= 32 |
| 25 | #define STRINGLIB_BLOOM_WIDTH 32 |
| 26 | #else |
| 27 | #error "LONG_BIT is smaller than 32" |
| 28 | #endif |
| 29 | |
| 30 | #define STRINGLIB_BLOOM_ADD(mask, ch) \ |
| 31 | ((mask |= (1UL << ((ch) & (STRINGLIB_BLOOM_WIDTH -1))))) |
| 32 | #define STRINGLIB_BLOOM(mask, ch) \ |
| 33 | ((mask & (1UL << ((ch) & (STRINGLIB_BLOOM_WIDTH -1))))) |
Antoine Pitrou | f2c5484 | 2010-01-13 08:07:53 +0000 | [diff] [blame] | 34 | |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 35 | |
| 36 | Py_LOCAL_INLINE(Py_ssize_t) |
| 37 | STRINGLIB(fastsearch_memchr_1char)(const STRINGLIB_CHAR* s, Py_ssize_t n, |
| 38 | STRINGLIB_CHAR ch, unsigned char needle, |
| 39 | Py_ssize_t maxcount, int mode) |
| 40 | { |
| 41 | void *candidate; |
| 42 | const STRINGLIB_CHAR *found; |
| 43 | |
| 44 | #define DO_MEMCHR(memchr, s, needle, nchars) do { \ |
| 45 | candidate = memchr((const void *) (s), (needle), (nchars) * sizeof(STRINGLIB_CHAR)); \ |
Antoine Pitrou | ca8aa4a | 2012-09-20 20:56:47 +0200 | [diff] [blame] | 46 | found = (const STRINGLIB_CHAR *) _Py_ALIGN_DOWN(candidate, sizeof(STRINGLIB_CHAR)); \ |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 47 | } while (0) |
| 48 | |
| 49 | if (mode == FAST_SEARCH) { |
Victor Stinner | b3f5501 | 2012-08-02 23:05:01 +0200 | [diff] [blame] | 50 | const STRINGLIB_CHAR *ptr = s; |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 51 | const STRINGLIB_CHAR *e = s + n; |
Victor Stinner | b3f5501 | 2012-08-02 23:05:01 +0200 | [diff] [blame] | 52 | while (ptr < e) { |
| 53 | DO_MEMCHR(memchr, ptr, needle, e - ptr); |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 54 | if (found == NULL) |
| 55 | return -1; |
| 56 | if (sizeof(STRINGLIB_CHAR) == 1 || *found == ch) |
Victor Stinner | b3f5501 | 2012-08-02 23:05:01 +0200 | [diff] [blame] | 57 | return (found - s); |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 58 | /* False positive */ |
Victor Stinner | b3f5501 | 2012-08-02 23:05:01 +0200 | [diff] [blame] | 59 | ptr = found + 1; |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 60 | } |
| 61 | return -1; |
| 62 | } |
| 63 | #ifdef HAVE_MEMRCHR |
| 64 | /* memrchr() is a GNU extension, available since glibc 2.1.91. |
| 65 | it doesn't seem as optimized as memchr(), but is still quite |
| 66 | faster than our hand-written loop in FASTSEARCH below */ |
| 67 | else if (mode == FAST_RSEARCH) { |
| 68 | while (n > 0) { |
| 69 | DO_MEMCHR(memrchr, s, needle, n); |
| 70 | if (found == NULL) |
| 71 | return -1; |
| 72 | n = found - s; |
| 73 | if (sizeof(STRINGLIB_CHAR) == 1 || *found == ch) |
| 74 | return n; |
| 75 | /* False positive */ |
| 76 | } |
| 77 | return -1; |
| 78 | } |
| 79 | #endif |
| 80 | else { |
| 81 | assert(0); /* Should never get here */ |
| 82 | return 0; |
| 83 | } |
| 84 | |
| 85 | #undef DO_MEMCHR |
| 86 | } |
| 87 | |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 88 | Py_LOCAL_INLINE(Py_ssize_t) |
Martin v. Löwis | d63a3b8 | 2011-09-28 07:41:54 +0200 | [diff] [blame] | 89 | FASTSEARCH(const STRINGLIB_CHAR* s, Py_ssize_t n, |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 90 | const STRINGLIB_CHAR* p, Py_ssize_t m, |
Antoine Pitrou | f2c5484 | 2010-01-13 08:07:53 +0000 | [diff] [blame] | 91 | Py_ssize_t maxcount, int mode) |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 92 | { |
Antoine Pitrou | f068f94 | 2010-01-13 14:19:12 +0000 | [diff] [blame] | 93 | unsigned long mask; |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 94 | Py_ssize_t skip, count = 0; |
| 95 | Py_ssize_t i, j, mlast, w; |
| 96 | |
| 97 | w = n - m; |
| 98 | |
Antoine Pitrou | f2c5484 | 2010-01-13 08:07:53 +0000 | [diff] [blame] | 99 | if (w < 0 || (mode == FAST_COUNT && maxcount == 0)) |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 100 | return -1; |
| 101 | |
| 102 | /* look for special cases */ |
| 103 | if (m <= 1) { |
| 104 | if (m <= 0) |
| 105 | return -1; |
| 106 | /* use special case for 1-character strings */ |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 107 | if (n > 10 && (mode == FAST_SEARCH |
| 108 | #ifdef HAVE_MEMRCHR |
| 109 | || mode == FAST_RSEARCH |
| 110 | #endif |
| 111 | )) { |
| 112 | /* use memchr if we can choose a needle without two many likely |
| 113 | false positives */ |
| 114 | unsigned char needle; |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 115 | needle = p[0] & 0xff; |
Victor Stinner | 8cc70dc | 2011-10-11 23:22:22 +0200 | [diff] [blame] | 116 | #if STRINGLIB_SIZEOF_CHAR > 1 |
Antoine Pitrou | 5b9f4c1 | 2011-10-17 19:21:04 +0200 | [diff] [blame] | 117 | /* If looking for a multiple of 256, we'd have too |
Antoine Pitrou | c198d05 | 2011-10-13 18:07:37 +0200 | [diff] [blame] | 118 | many false positives looking for the '\0' byte in UCS2 |
| 119 | and UCS4 representations. */ |
Antoine Pitrou | dda339e | 2011-10-13 17:58:11 +0200 | [diff] [blame] | 120 | if (needle != 0) |
Victor Stinner | 8cc70dc | 2011-10-11 23:22:22 +0200 | [diff] [blame] | 121 | #endif |
Antoine Pitrou | 2c3b230 | 2011-10-11 20:29:21 +0200 | [diff] [blame] | 122 | return STRINGLIB(fastsearch_memchr_1char) |
| 123 | (s, n, p[0], needle, maxcount, mode); |
| 124 | } |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 125 | if (mode == FAST_COUNT) { |
| 126 | for (i = 0; i < n; i++) |
Antoine Pitrou | f2c5484 | 2010-01-13 08:07:53 +0000 | [diff] [blame] | 127 | if (s[i] == p[0]) { |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 128 | count++; |
Antoine Pitrou | f2c5484 | 2010-01-13 08:07:53 +0000 | [diff] [blame] | 129 | if (count == maxcount) |
| 130 | return maxcount; |
| 131 | } |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 132 | return count; |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 133 | } else if (mode == FAST_SEARCH) { |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 134 | for (i = 0; i < n; i++) |
| 135 | if (s[i] == p[0]) |
| 136 | return i; |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 137 | } else { /* FAST_RSEARCH */ |
| 138 | for (i = n - 1; i > -1; i--) |
| 139 | if (s[i] == p[0]) |
| 140 | return i; |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 141 | } |
| 142 | return -1; |
| 143 | } |
| 144 | |
| 145 | mlast = m - 1; |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 146 | skip = mlast - 1; |
Antoine Pitrou | f2c5484 | 2010-01-13 08:07:53 +0000 | [diff] [blame] | 147 | mask = 0; |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 148 | |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 149 | if (mode != FAST_RSEARCH) { |
| 150 | |
| 151 | /* create compressed boyer-moore delta 1 table */ |
| 152 | |
| 153 | /* process pattern[:-1] */ |
Antoine Pitrou | f2c5484 | 2010-01-13 08:07:53 +0000 | [diff] [blame] | 154 | for (i = 0; i < mlast; i++) { |
Antoine Pitrou | f068f94 | 2010-01-13 14:19:12 +0000 | [diff] [blame] | 155 | STRINGLIB_BLOOM_ADD(mask, p[i]); |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 156 | if (p[i] == p[mlast]) |
| 157 | skip = mlast - i - 1; |
| 158 | } |
| 159 | /* process pattern[-1] outside the loop */ |
Antoine Pitrou | f068f94 | 2010-01-13 14:19:12 +0000 | [diff] [blame] | 160 | STRINGLIB_BLOOM_ADD(mask, p[mlast]); |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 161 | |
| 162 | for (i = 0; i <= w; i++) { |
| 163 | /* note: using mlast in the skip path slows things down on x86 */ |
| 164 | if (s[i+m-1] == p[m-1]) { |
| 165 | /* candidate match */ |
| 166 | for (j = 0; j < mlast; j++) |
| 167 | if (s[i+j] != p[j]) |
| 168 | break; |
| 169 | if (j == mlast) { |
| 170 | /* got a match! */ |
| 171 | if (mode != FAST_COUNT) |
| 172 | return i; |
| 173 | count++; |
Antoine Pitrou | f2c5484 | 2010-01-13 08:07:53 +0000 | [diff] [blame] | 174 | if (count == maxcount) |
| 175 | return maxcount; |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 176 | i = i + mlast; |
| 177 | continue; |
| 178 | } |
| 179 | /* miss: check if next character is part of pattern */ |
Antoine Pitrou | f068f94 | 2010-01-13 14:19:12 +0000 | [diff] [blame] | 180 | if (!STRINGLIB_BLOOM(mask, s[i+m])) |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 181 | i = i + m; |
| 182 | else |
| 183 | i = i + skip; |
| 184 | } else { |
| 185 | /* skip: check if next character is part of pattern */ |
Antoine Pitrou | f068f94 | 2010-01-13 14:19:12 +0000 | [diff] [blame] | 186 | if (!STRINGLIB_BLOOM(mask, s[i+m])) |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 187 | i = i + m; |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 188 | } |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 189 | } |
| 190 | } else { /* FAST_RSEARCH */ |
| 191 | |
| 192 | /* create compressed boyer-moore delta 1 table */ |
| 193 | |
| 194 | /* process pattern[0] outside the loop */ |
Antoine Pitrou | f068f94 | 2010-01-13 14:19:12 +0000 | [diff] [blame] | 195 | STRINGLIB_BLOOM_ADD(mask, p[0]); |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 196 | /* process pattern[:0:-1] */ |
| 197 | for (i = mlast; i > 0; i--) { |
Antoine Pitrou | f068f94 | 2010-01-13 14:19:12 +0000 | [diff] [blame] | 198 | STRINGLIB_BLOOM_ADD(mask, p[i]); |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 199 | if (p[i] == p[0]) |
| 200 | skip = i - 1; |
| 201 | } |
| 202 | |
| 203 | for (i = w; i >= 0; i--) { |
| 204 | if (s[i] == p[0]) { |
| 205 | /* candidate match */ |
| 206 | for (j = mlast; j > 0; j--) |
| 207 | if (s[i+j] != p[j]) |
| 208 | break; |
| 209 | if (j == 0) |
| 210 | /* got a match! */ |
| 211 | return i; |
| 212 | /* miss: check if previous character is part of pattern */ |
Florent Xicluna | eb6f3ea | 2010-08-08 22:07:16 +0000 | [diff] [blame] | 213 | if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1])) |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 214 | i = i - m; |
| 215 | else |
| 216 | i = i - skip; |
| 217 | } else { |
| 218 | /* skip: check if previous character is part of pattern */ |
Florent Xicluna | eb6f3ea | 2010-08-08 22:07:16 +0000 | [diff] [blame] | 219 | if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1])) |
Antoine Pitrou | da2ecaf | 2010-01-02 21:40:36 +0000 | [diff] [blame] | 220 | i = i - m; |
| 221 | } |
Thomas Wouters | 477c8d5 | 2006-05-27 19:21:47 +0000 | [diff] [blame] | 222 | } |
| 223 | } |
| 224 | |
| 225 | if (mode != FAST_COUNT) |
| 226 | return -1; |
| 227 | return count; |
| 228 | } |
| 229 | |