root/standard/levenshtein.c

DEFINITIONS

1. reference_levdist
2. custom_levdist
3. PHP_FUNCTION

/*
   +----------------------------------------------------------------------+
   | PHP Version 5                                                        |
   +----------------------------------------------------------------------+
   | Copyright (c) 1997-2013 The PHP Group                                |
   +----------------------------------------------------------------------+
   | This source file is subject to version 3.01 of the PHP license,      |
   | that is bundled with this package in the file LICENSE, and is        |
   | available through the world-wide-web at the following url:           |
   | http://www.php.net/license/3_01.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 <hholzgra@php.net>                        |
   +----------------------------------------------------------------------+
 */
/* $Id$ */

#include "php.h"
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include "php_string.h"

#define LEVENSHTEIN_MAX_LENGTH 255

/* {{{ reference_levdist
 * 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 )
{
        int *p1, *p2, *tmp;
        int i1, i2, c0, c1, c2;

        if (l1 == 0) {
                return l2 * cost_ins;
        }
        if (l2 == 0) {
                return l1 * cost_del;
        }

        if ((l1 > LEVENSHTEIN_MAX_LENGTH) || (l2 > LEVENSHTEIN_MAX_LENGTH)) {
                return -1;
        }
        p1 = safe_emalloc((l2 + 1), sizeof(int), 0);
        p2 = safe_emalloc((l2 + 1), sizeof(int), 0);

        for (i2 = 0; i2 <= l2; i2++) {
                p1[i2] = i2 * cost_ins;
        }
        for (i1 = 0; i1 < l1 ; i1++) {
                p2[0] = p1[0] + cost_del;

                for (i2 = 0; i2 < l2; i2++) {
                        c0 = p1[i2] + ((s1[i1] == s2[i2]) ? 0 : cost_rep);
                        c1 = p1[i2 + 1] + cost_del;
                        if (c1 < c0) {
                                c0 = c1;
                        }
                        c2 = p2[i2] + cost_ins;
                        if (c2 < c0) {
                                c0 = c2;
                        }
                        p2[i2 + 1] = c0;
                }
                tmp = p1;
                p1 = p2;
                p2 = tmp;
        }
        c0 = p1[l2];

        efree(p1);
        efree(p2);

        return c0;
}
/* }}} */

/* {{{ custom_levdist
 */
static int custom_levdist(char *str1, char *str2, char *callback_name TSRMLS_DC)
{
        php_error_docref(NULL TSRMLS_CC, E_WARNING, "The general Levenshtein support is not there yet");
        /* not there yet */

        return -1;
}
/* }}} */

/* {{{ proto int levenshtein(string str1, string str2[, int cost_ins, int cost_rep, int cost_del])
   Calculate Levenshtein distance between two strings */
PHP_FUNCTION(levenshtein)
{
        int argc = ZEND_NUM_ARGS();
        char *str1, *str2;
        char *callback_name;
        int str1_len, str2_len, callback_len;
        long cost_ins, cost_rep, cost_del;
        int distance = -1;

        switch (argc) {
                case 2: /* just two strings: use maximum performance version */
                        if (zend_parse_parameters(2 TSRMLS_CC, "ss", &str1, &str1_len, &str2, &str2_len) == FAILURE) {
                                return;
                        }
                        distance = reference_levdist(str1, str1_len, str2, str2_len, 1, 1, 1);
                        break;

                case 5: /* more general version: calc cost by ins/rep/del weights */
                        if (zend_parse_parameters(5 TSRMLS_CC, "sslll", &str1, &str1_len, &str2, &str2_len, &cost_ins, &cost_rep, &cost_del) == FAILURE) {
                                return;
                        }
                        distance = reference_levdist(str1, str1_len, str2, str2_len, cost_ins, cost_rep, cost_del);
                        break;

                case 3: /* most general version: calc cost by user-supplied function */
                        if (zend_parse_parameters(3 TSRMLS_CC, "sss", &str1, &str1_len, &str2, &str2_len, &callback_name, &callback_len) == FAILURE) {
                                return;
                        }
                        distance = custom_levdist(str1, str2, callback_name TSRMLS_CC);
                        break;

                default:
                        WRONG_PARAM_COUNT;
        }

        if (distance < 0 && /* TODO */ ZEND_NUM_ARGS() != 3) {
                php_error_docref(NULL TSRMLS_CC, E_WARNING, "Argument string(s) too long");
        }

        RETURN_LONG(distance);
}
/* }}} */

/*
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 * End:
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 */