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118 lines
3.1 KiB
C
118 lines
3.1 KiB
C
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/*
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+----------------------------------------------------------------------+
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| PHP version 4.0 |
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+----------------------------------------------------------------------+
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| Copyright (c) 1997, 1998, 1999, 2000 The PHP Group |
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+----------------------------------------------------------------------+
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| This source file is subject to version 2.02 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 at through the world-wide-web at |
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| http://www.php.net/license/2_02.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: Bj<EFBFBD>rn Borud - Guardian Networks AS <borud@guardian.no> |
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+----------------------------------------------------------------------+
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*/
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/* $Id$ */
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#include "php.h"
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#include <stdlib.h>
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#include <errno.h>
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#include <ctype.h>
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#include "php_string.h"
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int calc_levdist(const char *s1, const char *s2) /* faster, but obfuscated */
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{
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register char *p1,*p2;
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register int i,j,n;
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int l1=0,l2=0;
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char r[512];
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/* skip equal start sequence, if any */
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while(*s1==*s2) {
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if(!*s1) break;
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s1++; s2++;
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}
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/* if we already used up one string, then
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the result is the length of the other */
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if(*s1=='\0') return strlen(s2);
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if(*s2=='\0') return strlen(s1);
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/* length count */
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while(*s1++) l1++;
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while(*s2++) l2++;
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/* cut of equal tail sequence, if any */
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while(*--s1 == *--s2) {
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l1--; l2--;
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}
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/* reset pointers, adjust length */
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s1-=l1++;
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s2-=l2++;
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/* possible dist to great? */
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if(abs(l1-l2)>=255) return -1;
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/* swap if l2 longer than l1 */
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if(l1<l2) {
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(long)s1 ^= (long)s2; (long)s2 ^= (long)s1; (long)s1 ^= (long)s2;
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l1 ^= l2; l2 ^= l1; l1 ^= l2;
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}
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/* fill initial row */
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n=(*s1!=*s2);
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for(i=0,p1=r;i<l1;i++,*p1++=n++,p1++) {/*empty*/}
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/* calc. rowwise */
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for(j=1;j<l2;j++) {
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/* init pointers and col#0 */
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p1 = r + !(j&1);
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p2 = r + (j&1);
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n=*p1+1;
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*p2++=n;p2++;
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s2++;
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/* foreach column */
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for(i=1;i<l1;i++) {
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if(*p1<n) n=*p1+(*(s1+i)!=*(s2)); /* replace cheaper than delete? */
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p1++;
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if(*++p1<n) n=*p1+1; /* insert cheaper then insert ? */
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*p2++=n++; /* update field and cost for next col's delete */
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p2++;
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}
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}
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/* return result */
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return n-1;
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}
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/* {{{ proto int levdist(string str1, string str2)
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Calculate Levenshtein distance between two strings */
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PHP_FUNCTION(levdist){
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zval **str1, **str2;
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int l;
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if (ARG_COUNT(ht) != 2 || zend_get_parameters_ex(2, &str1, &str2) == FAILURE) {
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WRONG_PARAM_COUNT;
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}
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convert_to_string_ex(str1);
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convert_to_string_ex(str2);
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l = calc_levdist((*str1)->value.str.val, (*str2)->value.str.val);
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if(l<0) {
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php_error(E_WARNING,"levdist(): argument string(s) to long");
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}
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RETURN_LONG(l);
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}
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/* }}} */
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