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92 lines
2.9 KiB
C
92 lines
2.9 KiB
C
/*
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+----------------------------------------------------------------------+
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| Copyright (c) The PHP Group |
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+----------------------------------------------------------------------+
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| This source file is subject to version 3.01 of the PHP license, |
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| that is bundled with this package in the file LICENSE, and is |
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| available through the world-wide-web at the following url: |
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| https://www.php.net/license/3_01.txt |
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| If you did not receive a copy of the PHP license and are unable to |
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| obtain it through the world-wide-web, please send a note to |
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| license@php.net so we can mail you a copy immediately. |
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+----------------------------------------------------------------------+
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| Author: Hartmut Holzgraefe <hholzgra@php.net> |
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+----------------------------------------------------------------------+
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*/
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#include "php.h"
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/* {{{ reference_levdist
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* reference implementation, only optimized for memory usage, not speed */
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static zend_long reference_levdist(const zend_string *string1, const zend_string *string2, zend_long cost_ins, zend_long cost_rep, zend_long cost_del )
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{
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zend_long *p1, *p2, *tmp;
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zend_long c0, c1, c2;
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size_t i1, i2;
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if (ZSTR_LEN(string1) == 0) {
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return ZSTR_LEN(string2) * cost_ins;
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}
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if (ZSTR_LEN(string2) == 0) {
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return ZSTR_LEN(string1) * cost_del;
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}
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/* When all costs are equal, levenshtein fulfills the requirements of a metric, which means
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* that the distance is symmetric. If string1 is shorter than string 2 we can save memory (and CPU time)
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* by having shorter rows (p1 & p2). */
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if (ZSTR_LEN(string1) < ZSTR_LEN(string2) && cost_ins == cost_rep && cost_rep == cost_del) {
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const zend_string *tmp = string1;
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string1 = string2;
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string2 = tmp;
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}
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p1 = safe_emalloc((ZSTR_LEN(string2) + 1), sizeof(zend_long), 0);
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p2 = safe_emalloc((ZSTR_LEN(string2) + 1), sizeof(zend_long), 0);
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for (i2 = 0; i2 <= ZSTR_LEN(string2); i2++) {
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p1[i2] = i2 * cost_ins;
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}
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for (i1 = 0; i1 < ZSTR_LEN(string1) ; i1++) {
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p2[0] = p1[0] + cost_del;
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for (i2 = 0; i2 < ZSTR_LEN(string2); i2++) {
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c0 = p1[i2] + ((ZSTR_VAL(string1)[i1] == ZSTR_VAL(string2)[i2]) ? 0 : cost_rep);
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c1 = p1[i2 + 1] + cost_del;
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if (c1 < c0) {
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c0 = c1;
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}
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c2 = p2[i2] + cost_ins;
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if (c2 < c0) {
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c0 = c2;
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}
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p2[i2 + 1] = c0;
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}
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tmp = p1;
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p1 = p2;
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p2 = tmp;
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}
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c0 = p1[ZSTR_LEN(string2)];
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efree(p1);
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efree(p2);
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return c0;
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}
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/* }}} */
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/* {{{ Calculate Levenshtein distance between two strings */
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PHP_FUNCTION(levenshtein)
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{
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zend_string *string1, *string2;
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zend_long cost_ins = 1;
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zend_long cost_rep = 1;
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zend_long cost_del = 1;
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if (zend_parse_parameters(ZEND_NUM_ARGS(), "SS|lll", &string1, &string2, &cost_ins, &cost_rep, &cost_del) == FAILURE) {
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RETURN_THROWS();
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}
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RETURN_LONG(reference_levdist(string1, string2, cost_ins, cost_rep, cost_del));
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}
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/* }}} */
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