mf_soundex.c

/* Copyright (C) 2000 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */

/****************************************************************
*       SOUNDEX ALGORITHM in C                                  *
*                                                               *
*       The basic Algorithm source is taken from EDN Nov.       *
*       14, 1985 pg. 36.                                        *
*                                                               *
*       As a test Those in Illinois will find that the          *
*       first group of numbers in their drivers license         *
*       number is the soundex number for their last name.       *
*                                                               *
*       RHW  PC-IBBS ID. #1230                                  *
*                                                               *
*       As an extension if remove_garbage is set then all non-  *
*       alpha characters are skipped                            *
*                                                               *
*       Note, that this implementation corresponds to the       *
*       original version of the algorithm, not to the more      *
*       popular "enhanced" version, described by Knuth.         *
****************************************************************/

#include "mysys_priv.h"
#include <m_ctype.h>
#include "my_static.h"

static char get_scode(CHARSET_INFO * cs, char **ptr,pbool remove_garbage);

                /* outputed string is 4 byte long */
                /* out_pntr can be == in_pntr */

void soundex(CHARSET_INFO * cs,register char * out_pntr, char * in_pntr,
             pbool remove_garbage)
{
  char ch,last_ch;
  reg3 char * end;
  register uchar *map=cs->to_upper;

  if (remove_garbage)
  {
    while (*in_pntr && !my_isalpha(cs,*in_pntr)) /* Skip pre-space */
      in_pntr++;
  }
  *out_pntr++ = map[(uchar)*in_pntr];   /* Copy first letter             */
  last_ch = get_scode(cs,&in_pntr,0);   /* code of the first letter      */
                                        /* for the first 'double-letter  */
                                        /* check.                        */
  end=out_pntr+3;                       /* Loop on input letters until   */
                                        /* end of input (null) or output */
                                        /* letter code count = 3         */

  in_pntr++;
  while (out_pntr < end && (ch = get_scode(cs,&in_pntr,remove_garbage)) != 0)
  {
    in_pntr++;
    if ((ch != '0') && (ch != last_ch)) /* if not skipped or double */
    {
      *out_pntr++ = ch;                 /* letter, copy to output */
    }                                   /* for next double-letter check */
    last_ch = ch;                       /* save code of last input letter */
  }
  while (out_pntr < end)
    *out_pntr++ = '0';
  *out_pntr=0;                          /* end string */
  return;
} /* soundex */


  /*
    If alpha, map input letter to soundex code.
    If not alpha and remove_garbage is set then skip to next char
    else return 0
    */

static char get_scode(CHARSET_INFO * cs,char **ptr, pbool remove_garbage)
{
  uchar ch;

  if (remove_garbage)
  {
    while (**ptr && !my_isalpha(cs,**ptr))
      (*ptr)++;
  }
  ch=my_toupper(cs,**ptr);
  if (ch < 'A' || ch > 'Z')
  {
    if (my_isalpha(cs,ch))              /* If extended alfa (country spec) */
      return '0';                       /* threat as vokal */
    return 0;                           /* Can't map */
  }
  return(soundex_map[ch-'A']);
} /* get_scode */