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|
/*
+----------------------------------------------------------------------+
| Php HTML Embedded Scripting Language Version 3.0 |
+----------------------------------------------------------------------+
| Copyright (c) 1997-2000 PHP Development Team (See Credits file) |
+----------------------------------------------------------------------+
| This program is free software; you can redistribute it and/or modify |
| it under the terms of one of the following licenses: |
| |
| A) the GNU General Public License as published by the Free Software |
| Foundation; either version 2 of the License, or (at your option) |
| any later version. |
| |
| B) the PHP License as published by the PHP Development Team and |
| included in the distribution in the file: LICENSE |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of both licenses referred to here. |
| If you did not, or have any questions about PHP licensing, please |
| contact core@php.net. |
+----------------------------------------------------------------------+
| Authors: Hartmut Holzgraefe <hartmut@six.de> |
+----------------------------------------------------------------------+
*/
/* $Id: levenshtein.c,v 1.3 2000/05/23 20:13:41 hholzgra Exp $ */
#include <stdio.h>
#include "php.h"
#include "internal_functions.h"
#include "reg.h"
#include "post.h"
#include "php3_string.h"
static int calc_levdist(const char *s1, const char *s2) /* faster, but obfuscated */
{
register char *p1,*p2;
register int i,j,n;
int l1=0,l2=0;
char r[512];
const char *tmp;
/* skip equal start sequence, if any */
while(*s1==*s2) {
if(!*s1) break;
s1++; s2++;
}
/* if we already used up one string, then
the result is the length of the other */
if(*s1=='\0') return strlen(s2);
if(*s2=='\0') return strlen(s1);
/* length count */
while(*s1++) l1++;
while(*s2++) l2++;
/* cut of equal tail sequence, if any */
while(*--s1 == *--s2) {
l1--; l2--;
}
/* reset pointers, adjust length */
s1-=l1++;
s2-=l2++;
/* possible dist to great? */
if(abs(l1-l2)>=255) return -1;
/* swap if l2 longer than l1 */
if(l1<l2) {
tmp=s1; s1=s2; s2=tmp;
l1 ^= l2; l2 ^= l1; l1 ^= l2;
}
/* fill initial row */
n=(*s1!=*s2);
for(i=0,p1=r;i<l1;i++,*p1++=n++,p1++) {/*empty*/}
/* calc. rowwise */
for(j=1;j<l2;j++) {
/* init pointers and col#0 */
p1 = r + !(j&1);
p2 = r + (j&1);
n=*p1+1;
*p2++=n;p2++;
s2++;
/* foreach column */
for(i=1;i<l1;i++) {
if(*p1<n) n=*p1+(*(s1+i)!=*(s2)); /* replace cheaper than delete? */
p1++;
if(*++p1<n) n=*p1+1; /* insert cheaper then insert ? */
*p2++=n++; /* update field and cost for next col's delete */
p2++;
}
}
/* return result */
return n-1;
}
/* {{{ proto int levenshtein(string str1, string str2)
Calculate Levenshtein distance between two strings */
void php3_levenshtein(INTERNAL_FUNCTION_PARAMETERS)
{
pval *str1, *str2;
int l;
if (ARG_COUNT(ht) != 2 || getParameters(ht, 2, &str1, &str2) == FAILURE) {
WRONG_PARAM_COUNT;
}
convert_to_string(str1);
convert_to_string(str2);
l = calc_levdist(str1->value.str.val, str2->value.str.val);
if(l<0) {
php3_error(E_WARNING,"levenshtein(): argument string(s) too long");
}
RETURN_LONG(l);
}
/* }}} */
|
