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104 lines
2.8 KiB
C
104 lines
2.8 KiB
C
/* stringlib: fastsearch implementation */
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#ifndef STRINGLIB_FASTSEARCH_H
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#define STRINGLIB_FASTSEARCH_H
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/* fast search/count implementation, based on a mix between boyer-
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moore and horspool, with a few more bells and whistles on the top.
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for some more background, see: http://effbot.org/stringlib */
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/* note: fastsearch may access s[n], which isn't a problem when using
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Python's ordinary string types, but may cause problems if you're
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using this code in other contexts. also, the count mode returns -1
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if there cannot possible be a match in the target string, and 0 if
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it has actually checked for matches, but didn't find any. callers
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beware! */
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#define FAST_COUNT 0
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#define FAST_SEARCH 1
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Py_LOCAL_INLINE(Py_ssize_t)
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fastsearch(const STRINGLIB_CHAR* s, Py_ssize_t n,
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const STRINGLIB_CHAR* p, Py_ssize_t m,
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int mode)
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{
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long mask;
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Py_ssize_t skip, count = 0;
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Py_ssize_t i, j, mlast, w;
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w = n - m;
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if (w < 0)
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return -1;
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/* look for special cases */
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if (m <= 1) {
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if (m <= 0)
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return -1;
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/* use special case for 1-character strings */
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if (mode == FAST_COUNT) {
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for (i = 0; i < n; i++)
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if (s[i] == p[0])
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count++;
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return count;
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} else {
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for (i = 0; i < n; i++)
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if (s[i] == p[0])
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return i;
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}
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return -1;
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}
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mlast = m - 1;
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/* create compressed boyer-moore delta 1 table */
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skip = mlast - 1;
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/* process pattern[:-1] */
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for (mask = i = 0; i < mlast; i++) {
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mask |= (1 << (p[i] & 0x1F));
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if (p[i] == p[mlast])
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skip = mlast - i - 1;
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}
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/* process pattern[-1] outside the loop */
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mask |= (1 << (p[mlast] & 0x1F));
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for (i = 0; i <= w; i++) {
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/* note: using mlast in the skip path slows things down on x86 */
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if (s[i+m-1] == p[m-1]) {
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/* candidate match */
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for (j = 0; j < mlast; j++)
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if (s[i+j] != p[j])
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break;
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if (j == mlast) {
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/* got a match! */
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if (mode != FAST_COUNT)
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return i;
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count++;
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i = i + mlast;
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continue;
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}
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/* miss: check if next character is part of pattern */
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if (!(mask & (1 << (s[i+m] & 0x1F))))
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i = i + m;
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else
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i = i + skip;
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} else {
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/* skip: check if next character is part of pattern */
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if (!(mask & (1 << (s[i+m] & 0x1F))))
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i = i + m;
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}
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}
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if (mode != FAST_COUNT)
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return -1;
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return count;
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}
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#endif
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/*
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Local variables:
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c-basic-offset: 4
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indent-tabs-mode: nil
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End:
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*/
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