symbian-qemu-0.9.1-12/python-2.6.1/Objects/stringlib/fastsearch.h
author martin.trojer@nokia.com
Fri, 31 Jul 2009 15:01:17 +0100
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permissions -rw-r--r--
Initial QEMU (symbian-qemu-0.9.1-12) import
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/* 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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*/