diff options
Diffstat (limited to 'ext/standard/levenshtein.c')
| -rw-r--r-- | ext/standard/levenshtein.c | 198 |
1 files changed, 43 insertions, 155 deletions
diff --git a/ext/standard/levenshtein.c b/ext/standard/levenshtein.c index d157cf7fab..080c86a327 100644 --- a/ext/standard/levenshtein.c +++ b/ext/standard/levenshtein.c @@ -23,162 +23,47 @@ #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"); @@ -202,8 +87,11 @@ PHP_FUNCTION(levenshtein) } 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 */ @@ -216,11 +104,11 @@ PHP_FUNCTION(levenshtein) 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; |