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|
/*
+----------------------------------------------------------------------+
| PHP version 4.0 |
+----------------------------------------------------------------------+
| Copyright (c) 1997, 1998, 1999, 2000 The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 2.02 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available at through the world-wide-web at |
| http://www.php.net/license/2_02.txt. |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Author: Hartmut Holzgraefe <hartmut@six.de> |
+----------------------------------------------------------------------+
*/
/* $Id$ */
#include "php.h"
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include "php_string.h"
/* faster, but obfuscated, all operations have a cost of 1 */
static int fastest_levdist(const char *s1, const char *s2)
{
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=1;
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 replace ? */
*p2++=n++; /* update field and cost for next col's delete */
p2++;
}
}
/* return result */
return n-1;
}
static int weighted_levdist( const char *s1
, const char *s2
, const int cost_ins
, const int cost_rep
, const int cost_del
)
{
register int *p1,*p2;
register int i,j,n,c;
int l1=0,l2=0;
int 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;
}
if((l1==1)&&(l2==1)) {
n= cost_del+cost_ins;
return n<cost_rep?n:cost_rep;
}
/* fill initial row */
n=cost_ins;
for(i=0,p1=r;i<l1;i++,*p1++=n,p1++) {n+=cost_ins;}
/* calc. rowwise */
for(j=1;j<l2;j++) {
/* init pointers and col#0 */
p1 = r + !(j&1);
p2 = r + (j&1);
n=*p1+cost_del;
*p2++=n;p2++;
s2++;
/* foreach column */
for(i=1;i<l1;i++) {
c = *p1; if(*(s1+i)!=*(s2)) c+=cost_rep;
if(c<n) n=c; /* replace cheaper than delete? */
p1++;
c= *++p1+cost_ins;
if(c<n) n=c; /* insert cheaper then replace ? */
*p2++=n; /* update field and cost for next col's delete */
n+=cost_del; /* update field and cost for next col's delete */
p2++;
}
}
/* return result */
return n-=cost_del;
}
static int custom_levdist(char *str1,char *str2,char *callback_name)
{
php_error(E_WARNING,"the general Levenshtein support is not there yet");
/* not there yet */
return -1;
}
/* {{{ proto int levenshtein(string str1, string str2)
Calculate Levenshtein distance between two strings */
PHP_FUNCTION(levenshtein)
{
zval **str1, **str2, **cost_ins, **cost_rep, **cost_del,**callback_name;
int distance=-1;
switch(ZEND_NUM_ARGS()) {
case 2: /* just two string: use maximum performance version */
if (zend_get_parameters_ex(2, &str1, &str2) == FAILURE) {
WRONG_PARAM_COUNT;
}
convert_to_string_ex(str1);
convert_to_string_ex(str2);
distance = fastest_levdist((*str1)->value.str.val, (*str2)->value.str.val);
break;
case 5: /* more general version: calc cost by ins/rep/del weights */
if (zend_get_parameters_ex(5, &str1, &str2, &cost_ins, &cost_rep, &cost_del) == FAILURE) {
WRONG_PARAM_COUNT;
}
convert_to_string_ex(str1);
convert_to_string_ex(str2);
convert_to_long_ex(cost_ins);
convert_to_long_ex(cost_rep);
convert_to_long_ex(cost_del);
distance = weighted_levdist((*str1)->value.str.val
, (*str2)->value.str.val
, (*cost_ins)->value.lval
, (*cost_rep)->value.lval
, (*cost_del)->value.lval
);
break;
case 3: /* most general version: calc cost by user-supplied function */
if (zend_get_parameters_ex(3, &str1, &str2, &callback_name) == FAILURE) {
WRONG_PARAM_COUNT;
}
convert_to_string_ex(str1);
convert_to_string_ex(str2);
convert_to_string_ex(callback_name);
distance = custom_levdist((*str1)->value.str.val
, (*str2)->value.str.val
, (*callback_name)->value.str.val
);
break;
default:
WRONG_PARAM_COUNT;
}
if(distance<0) {
php_error(E_WARNING,"levenshtein(): argument string(s) too long");
}
RETURN_LONG(distance);
}
/* }}} */
|
