path: root/src/plugins/custom/regmark/metaphone.c

/*
 * Copyright (c) 2009, Rambler media
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *       * Redistributions of source code must retain the above copyright
 *         notice, this list of conditions and the following disclaimer.
 *       * Redistributions in binary form must reproduce the above copyright
 *         notice, this list of conditions and the following disclaimer in the
 *         documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY Rambler media ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL Rambler BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This is implementation of metaphone algorithm that was originally written by
 * Michael G Schwern <schwern@pobox.com> as perl XS module
 */

/*
 * I suppose I could have been using a character pointer instead of
 * accesssing the array directly... 
 */

#include "../../../config.h"
#include "metaphone.h"

/*
 * Look at the next letter in the word 
 */
#define Next_Letter (g_ascii_toupper (word[w_idx+1]))
/*
 * Look at the current letter in the word 
 */
#define Curr_Letter (g_ascii_toupper(word[w_idx]))
/*
 * Go N letters back. 
 */
#define Look_Back_Letter(n) (w_idx >= n ? g_ascii_toupper(word[w_idx-n]) : '\0')
/*
 * Previous letter.  I dunno, should this return null on failure? 
 */
#define Prev_Letter (Look_Back_Letter(1))
/*
 * Look two letters down.  It makes sure you don't walk off the string. 
 */
#define After_Next_Letter   (Next_Letter != '\0' ? g_ascii_toupper(word[w_idx+2]) \
                                                 : '\0')
#define Look_Ahead_Letter(n) (g_ascii_toupper(Lookahead(word+w_idx, n)))

#define  SH 	'X'
#define  TH		'0'

/*-- Character encoding array & accessing macros --*/
/* Stolen directly out of the book... */
char _codes[26] = {
	1,16,4,16,9,2,4,16,9,2,0,2,2,2,1,4,0,2,4,4,1,0,0,0,8,0
/*  a  b c  d e f g  h i j k l m n o p q r s t u v w x y z */
};


/*
 * Allows us to safely look ahead an arbitrary # of letters 
 */
/*
 * I probably could have just used strlen... 
 */
static char
Lookahead (char *word, int how_far)
{
    char            letter_ahead = '\0';	/* null by default */
    int             idx;
    for (idx = 0; word[idx] != '\0' && idx < how_far; idx++);
    /*
     * Edge forward in the string... 
     */

    letter_ahead = word[idx];	/* idx will be either == to how_far or at
				 * the end of the string */
    return letter_ahead;
}


/*
 * phonize one letter 
 */
#define Phonize(c)  {(*phoned_word)[p_idx++] = c;}
/*
 * Slap a null character on the end of the phoned word 
 */
#define End_Phoned_Word {(*phoned_word)[p_idx] = '\0';}
/*
 * How long is the phoned word? 
 */
#define Phone_Len   (p_idx)

/*
 * Note is a letter is a 'break' in the word 
 */
#define Isbreak(c)  (!g_ascii_isalpha(c))


gboolean
metaphone (char *word, int max_phonemes, char **phoned_word)
{
    int             w_idx = 0;	/* point in the phonization we're at. */
    int             p_idx = 0;	/* end of the phoned phrase */

    /*-- Parameter checks --*/
    /*
     * Assume largest possible if we're given no limit 
     */
    if (max_phonemes == 0) {
		max_phonemes = strlen (word);
	}

    /*-- Allocate memory for our phoned_phrase --*/
	*phoned_word = g_malloc (max_phonemes * sizeof (char));

    /*-- The first phoneme has to be processed specially. --*/
    /*
     * Find our first letter 
     */
    for (; ! g_ascii_isalpha (Curr_Letter); w_idx++) {
		/*
		* On the off chance we were given nothing but crap... 
		*/
		if (Curr_Letter == '\0') {
			End_Phoned_Word 
			return TRUE;	/* For testing */
		}
    }

    switch (Curr_Letter) {
	/*
	 * AE becomes E 
	 */
    case 'A':
	if (Next_Letter == 'E') {
	    Phonize ('E');
	    w_idx += 2;
	}
	/*
	 * Remember, preserve vowels at the beginning 
	 */
	else {
	    Phonize ('A');
	    w_idx++;
	}
	break;
	/*
	 * [GKP]N becomes N 
	 */
    case 'G':
    case 'K':
    case 'P':
	if (Next_Letter == 'N') {
	    Phonize ('N');
	    w_idx += 2;
	}
	break;
	/*
	 * WH becomes H, WR becomes R W if followed by a vowel 
	 */
    case 'W':
	if (Next_Letter == 'H' || Next_Letter == 'R') {
	    Phonize (Next_Letter);
	    w_idx += 2;
	} else if (isvowel (Next_Letter)) {
	    Phonize ('W');
	    w_idx += 2;
	}
	/*
	 * else ignore 
	 */
	break;
	/*
	 * X becomes S 
	 */
    case 'X':
	Phonize ('S');
	w_idx++;
	break;
	/*
	 * Vowels are kept 
	 */
	/*
	 * We did A already case 'A': case 'a': 
	 */
    case 'E':
    case 'I':
    case 'O':
    case 'U':
	Phonize (Curr_Letter);
	w_idx++;
	break;
    default:
	/*
	 * do nothing 
	 */
	break;
    }



    /*
     * On to the metaphoning 
     */
    for (; Curr_Letter != '\0' &&
	 (max_phonemes == 0 || Phone_Len < max_phonemes); w_idx++) {
	/*
	 * How many letters to skip because an eariler encoding handled
	 * multiple letters 
	 */
	unsigned short int skip_letter = 0;


	/*
	 * THOUGHT: It would be nice if, rather than having things like...
	 * well, SCI.  For SCI you encode the S, then have to remember to
	 * skip the C.  So the phonome SCI invades both S and C.  It would
	 * be better, IMHO, to skip the C from the S part of the encoding.
	 * Hell, I'm trying it. 
	 */

	/*
	 * Ignore non-alphas 
	 */
	if (! g_ascii_isalpha (Curr_Letter))
	    continue;

	/*
	 * Drop duplicates, except CC 
	 */
	if (Curr_Letter == Prev_Letter && Curr_Letter != 'C')
	    continue;

	switch (Curr_Letter) {
	    /*
	     * B -> B unless in MB 
	     */
	case 'B':
	    if (Prev_Letter != 'M')
		Phonize ('B');
	    break;
	    /*
	     * 'sh' if -CIA- or -CH, but not SCH, except SCHW. (SCHW is
	     * handled in S) S if -CI-, -CE- or -CY- dropped if -SCI-,
	     * SCE-, -SCY- (handed in S) else K 
	     */
	case 'C':
	    if (MAKESOFT (Next_Letter)) {	/* C[IEY] */
			if (After_Next_Letter == 'A' && Next_Letter == 'I') {	/* CIA 
										*/
				Phonize (SH);
			}
			/*
			* SC[IEY] 
			*/
			else if (Prev_Letter == 'S') {
				/*
				* Dropped 
				*/
			} else {
				Phonize ('S');
			}
	    } else if (Next_Letter == 'H') {
#ifndef USE_TRADITIONAL_METAPHONE
			if (After_Next_Letter == 'R' || Prev_Letter == 'S') {	/* Christ, 
										* School 
										*/
				Phonize ('K');
			} else {
				Phonize (SH);
			}
#else
			Phonize (SH);
#endif
			skip_letter++;
	    } else {
			Phonize ('K');
	    }
	    break;
	    /*
	     * J if in -DGE-, -DGI- or -DGY- else T 
	     */
	case 'D':
	    if (Next_Letter == 'G' && MAKESOFT (After_Next_Letter)) {
			Phonize ('J');
			skip_letter++;
	    } else {
			Phonize ('T');
		}
	    break;
	    /*
	     * F if in -GH and not B--GH, D--GH, -H--GH, -H---GH else
	     * dropped if -GNED, -GN, else dropped if -DGE-, -DGI- or
	     * -DGY- (handled in D) else J if in -GE-, -GI, -GY and not GG
	     * else K 
	     */
	case 'G':
	    if (Next_Letter == 'H') {
			if (!(NOGHTOF (Look_Back_Letter (3)) ||
				Look_Back_Letter (4) == 'H')) {
				Phonize ('F');
				skip_letter++;
			} else {
				/*
				* silent 
				*/
			}
	    } else if (Next_Letter == 'N') {
			if (Isbreak (After_Next_Letter) ||
				(After_Next_Letter == 'E' &&
				Look_Ahead_Letter (3) == 'D')) {
				/*
				* dropped 
				*/
			} else {
				Phonize ('K');
			}
	    } else if (MAKESOFT (Next_Letter) && Prev_Letter != 'G') {
			Phonize ('J');
	    } else {
			Phonize ('K');
	    }
	    break;
	    /*
	     * H if before a vowel and not after C,G,P,S,T 
	     */
	case 'H':
	    if (isvowel (Next_Letter) && !AFFECTH (Prev_Letter)) {
			Phonize ('H');
		}
	    break;
	    /*
	     * dropped if after C else K 
	     */
	case 'K':
	    if (Prev_Letter != 'C') {
			Phonize ('K');
		}
	    break;
	    /*
	     * F if before H else P 
	     */
	case 'P':
	    if (Next_Letter == 'H') {
			Phonize ('F');
	    } else {
			Phonize ('P');
	    }
	    break;
	    /*
	     * K 
	     */
	case 'Q':
	    Phonize ('K');
	    break;
	    /*
	     * 'sh' in -SH-, -SIO- or -SIA- or -SCHW- else S 
	     */
	case 'S':
	    if (Next_Letter == 'I' &&
		     (After_Next_Letter == 'O' || After_Next_Letter == 'A')) {
			Phonize (SH);
	    } else if (Next_Letter == 'H') {
			Phonize (SH);
			skip_letter++;
	    }
#ifndef USE_TRADITIONAL_METAPHONE
	    else if (Next_Letter == 'C' &&
		     Look_Ahead_Letter (2) == 'H' &&
		     Look_Ahead_Letter (3) == 'W') {
			Phonize (SH);
			skip_letter += 2;
	    }
#endif
	    else {
			Phonize ('S');
	    }
	    break;
	    /*
	     * 'sh' in -TIA- or -TIO- else 'th' before H else T 
	     */
	case 'T':
	    if (Next_Letter == 'I' &&
		(After_Next_Letter == 'O' || After_Next_Letter == 'A')) {
			Phonize (SH);
	    } else if (Next_Letter == 'H') {
			Phonize (TH);
			skip_letter++;
	    } else {
			Phonize ('T');
	    }
	    break;
	    /*
	     * F 
	     */
	case 'V':
	    Phonize ('F');
	    break;
	    /*
	     * W before a vowel, else dropped 
	     */
	case 'W':
	    if (isvowel (Next_Letter)) {
			Phonize ('W');
		}
	    break;
	    /*
	     * KS 
	     */
	case 'X':
	    Phonize ('K');
	    Phonize ('S');
	    break;
	    /*
	     * Y if followed by a vowel 
	     */
	case 'Y':
	    if (isvowel (Next_Letter)) {
			Phonize ('Y');
		}
	    break;
	    /*
	     * S 
	     */
	case 'Z':
	    Phonize ('S');
	    break;
	    /*
	     * No transformation 
	     */
	case 'F':
	case 'J':
	case 'L':
	case 'M':
	case 'N':
	case 'R':
	    Phonize (Curr_Letter);
	    break;
	default:
	    /*
	     * nothing 
	     */
	    break;
	}			/* END SWITCH */

	w_idx += skip_letter;
    }				/* END FOR */

    End_Phoned_Word;

    return TRUE;
}