soundex.c

Go to the documentation of this file.

/*
   +----------------------------------------------------------------------+
   | Copyright (c) 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:           |
   | https://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: Bjørn Borud - Guardian Networks AS <borud@guardian.no>       |
   +----------------------------------------------------------------------+
 */
 
#include "php.h"
#include <stdlib.h>
#include <ctype.h>
 
/* Simple soundex algorithm as described by Knuth in TAOCP, vol 3 */
/* {{{ Calculate the soundex key of a string */
PHP_FUNCTION(soundex)
{
    char    *str;
    size_t  i, _small, str_len, code, last;
    char    soundex[4 + 1];
 
    static const char soundex_table[26] =
    {0,                         /* A */
     '1',                       /* B */
     '2',                       /* C */
     '3',                       /* D */
     0,                         /* E */
     '1',                       /* F */
     '2',                       /* G */
     0,                         /* H */
     0,                         /* I */
     '2',                       /* J */
     '2',                       /* K */
     '4',                       /* L */
     '5',                       /* M */
     '5',                       /* N */
     0,                         /* O */
     '1',                       /* P */
     '2',                       /* Q */
     '6',                       /* R */
     '2',                       /* S */
     '3',                       /* T */
     0,                         /* U */
     '1',                       /* V */
     0,                         /* W */
     '2',                       /* X */
     0,                         /* Y */
     '2'};                      /* Z */
 
    ZEND_PARSE_PARAMETERS_START(1, 1)
        Z_PARAM_STRING(str, str_len)
    ZEND_PARSE_PARAMETERS_END();
 
    /* build soundex string */
    last = -1;
    for (i = 0, _small = 0; i < str_len && _small < 4; i++) {
        /* convert chars to upper case and strip non-letter chars */
        /* BUG: should also map here accented letters used in non */
        /* English words or names (also found in English text!): */
        /* esstsett, thorn, n-tilde, c-cedilla, s-caron, ... */
        code = toupper((int)(unsigned char)str[i]);
        if (code >= 'A' && code <= 'Z') {
            if (_small == 0) {
                /* remember first valid char */
                soundex[_small++] = (char)code;
                last = soundex_table[code - 'A'];
            }
            else {
                /* ignore sequences of consonants with same soundex */
                /* code in trail, and vowels unless they separate */
                /* consonant letters */
                code = soundex_table[code - 'A'];
                if (code != last) {
                    if (code != 0) {
                        soundex[_small++] = (char)code;
                    }
                    last = code;
                }
            }
        }
    }
    /* pad with '0' and terminate with 0 ;-) */
    while (_small < 4) {
        soundex[_small++] = '0';
    }
    soundex[_small] = '\0';
 
    RETURN_STRINGL(soundex, _small);
}
/* }}} */