#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)
+/* reference implementation, only optimized for memory usage, not speed */
+static int reference_levdist(const char *s1, int l1,
+ const char *s2, int l2,
+ int cost_ins, int cost_rep, int cost_del )
{
- 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++;
+ int *p1,*p2,*tmp;
+ int i1,i2,c0,c1,c2;
+ if(l1==0) return l2*cost_ins;
+ if(l2==0) return l1*cost_del;
+
+ p1=malloc(l2*sizeof(int));
+ p2=malloc(l2*sizeof(int));
+
+ p1[0]=(s1[0]==s2[0])?0:cost_rep;
+
+ for(i2=1;i2<l2;i2++)
+ p1[i2]=i2*cost_ins;
+
+ for(i1=1;i1<l1;i1++)
+ {
+ p2[0]=i1*cost_del;
+ for(i2=1;i2<l2;i2++)
+ {
+ c0=p1[i2-1]+((s1[i1]==s2[i2])?0:cost_rep);
+ c1=p1[i2]+cost_del; if(c1<c0) c0=c1;
+ c2=p2[i2-1]+cost_ins; if(c2<c0) c0=c2;
+ p2[i2]=c0;
+ }
+ tmp=p1; p1=p2; p2=tmp;
+ }
- /* possible dist to great? */
- if(abs(l1-l2)>=255) return -1;
+ c0=p1[l2-1];
- /* swap if l2 longer than l1 */
- if(l1<l2) {
- tmp=s1; s1=s2; s2=tmp;
- l1 ^= l2; l2 ^= l1; l1 ^= l2;
- }
+ free(p1);
+ free(p2);
-
- /* 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;
+ return c0;
}
-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");
}
convert_to_string_ex(str1);
convert_to_string_ex(str2);
-
- distance = fastest_levdist((*str1)->value.str.val, (*str2)->value.str.val);
+
+ distance = reference_levdist((*str1)->value.str.val,(*str1)->value.str.len,
+ (*str2)->value.str.val,(*str2)->value.str.len,
+ 1,1,1);
+
break;
case 5: /* more general version: calc cost by ins/rep/del weights */
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
+ distance = reference_levdist((*str1)->value.str.val,(*str1)->value.str.len,
+ (*str2)->value.str.val,(*str2)->value.str.len,
+ (*cost_ins)->value.lval,
+ (*cost_rep)->value.lval,
+ (*cost_del)->value.lval
);
break;
--- /dev/null
+--TEST--
+levenshtein() function test
+--POST--
+--GET--
+--FILE--
+<?php
+
+function test_me($title,$expect,$text1,$text2,$cost1=0,$cost2=0,$cost3=0) {
+
+ if($cost1==0)
+ $result=levenshtein($text1,$text2);
+ else
+ $result=levenshtein($text1,$text2,$cost1,$cost2,$cost3);
+
+ if($result==$expect) return 0;
+
+ echo "$title: result is $result instead of $expect ";
+ echo "for '$text1'/'$text2' ";
+ if($cost1) echo "($cost1:$cost2:$cost3)";
+ echo "\n";
+
+ return 1;
+}
+
+$n=0;
+
+$n += test_me("equal" , 0, "12345", "12345");
+$n += test_me("1st empty" , 3, "", "xzy");
+$n += test_me("2nd empty" , 3, "xzy", "");
+$n += test_me("both empty" , 0, "", "");
+$n += test_me("1 char" , 1, "1", "2");
+$n += test_me("2 char swap", 2, "12", "21");
+
+$n += test_me("inexpensive delete", 2, "2121", "11", 2, 1, 1);
+$n += test_me("expensive delete" , 10, "2121", "11", 2, 1, 5);
+$n += test_me("inexpensive insert", 2, "11", "2121", 1, 1, 1);
+$n += test_me("expensive insert" , 10, "11", "2121", 5, 1, 1);
+
+$n += test_me("expensive replace" , 3, "111", "121", 2, 3, 2);
+$n += test_me("very expensive replace", 4, "111", "121", 2, 9, 2);
+
+$n += test_me("bug #7368", 2, "13458", "12345");
+$n += test_me("bug #7368", 2, "1345", "1234");
+
+$n += test_me("bug #6562", 1, "debugg", "debug");
+$n += test_me("bug #6562", 1, "ddebug", "debug");
+$n += test_me("bug #6562", 2, "debbbug", "debug");
+$n += test_me("bug #6562", 1, "debugging", "debuging");
+
+echo ($n==0)?"all passed\n":"$n failed\n";
+
+?>
+--EXPECT--
+all passed
projects / php / commitdiff