deb-goldedplus/goldlib/gall/gfuzzy.cpp

//  This may look like C code, but it is really -*- C++ -*-

//  ------------------------------------------------------------------
//  The Goldware Library
//  Copyright (C) 1990-1999 Odinn Sorensen
//  ------------------------------------------------------------------
//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Library General Public
//  License as published by the Free Software Foundation; either
//  version 2 of the License, or (at your option) any later version.
//
//  This library 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
//  Library General Public License for more details.
//
//  You should have received a copy of the GNU Library General Public
//  License along with this program; if not, write to the Free
//  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
//  MA 02111-1307, USA
//  ------------------------------------------------------------------
//  $Id$
//  ------------------------------------------------------------------
//  Fuzzy string search.
//  ------------------------------------------------------------------
//
//  C++ port and cleanup by Odinn Sorensen, August 1992.
//  Dusted off and re-used, March 1994.
//  Converted to C++ class, December 1997.
//
//  Original source: APPROX.C (found in SNIP1091).
//  Original author: John Rex, August 1988.
//
//  References: (1) Computer Algorithms, by Sara Baase Addison-Wesley,
//                  1988, pp 242-4.
//              (2) Hall PAV, Dowling GR: "Approximate string match-
//                  ing", ACM Computing Surveys, 12:381-402, 1980.
//
//  Usage:
//
//    pattern, string - Search for pattern in text
//    degree          - Degree of allowed mismatch (no of chars)
//
//    init(pattern, degree, casing) - Setup routine
//    findfirst(string)             - Find first match
//    findnext()                    - Find next match
//
//  Searching is finished when findfirst/next() returns false
//
//  ------------------------------------------------------------------

#include <gctype.h>
#include <gstrall.h>
#include <gmemdbg.h>
#include <gfuzzy.h>


//  ------------------------------------------------------------------

gfuzzy::gfuzzy() {

  ldiffs = NULL;
}


//  ------------------------------------------------------------------

gfuzzy::~gfuzzy() {

  throw_deletearray(ldiffs);
}


//  ------------------------------------------------------------------
//  Fuzzy search init

void gfuzzy::init(const char* pat, int fuzzydegree, bool case_sensitive) {

  casing = case_sensitive;
  degree = fuzzydegree;
  pattern = pat;
  plen = strlen(pattern);

  ldiffs = new int [(plen+1)*4];
  throw_new(ldiffs);
}


//  ------------------------------------------------------------------

bool gfuzzy::findfirst(const char* string) {

  textloc = -1;
  text  = string;
  start = text;

  ldiff = ldiffs;
  rdiff = ldiff + plen + 1;
  loffs = rdiff + plen + 1;
  roffs = loffs + plen + 1;

  for(int i=0; i<=plen; i++) {
    rdiff[i] = i;   // Initial values for right-hand column
    roffs[i] = 1;
  }

  return findnext();
}


//  ------------------------------------------------------------------
//  Fuzzy search next

bool gfuzzy::findnext() {

  if(start) {

    start = NULL;
    howclose = -1;

    while(start == NULL) {       // Start computing columns

      if(text[++textloc] == NUL)  // Out of text to search!
        break;

      int* temp = rdiff;  // Move right-hand column to left ...
      rdiff = ldiff;      // ... so that we can compute new ...
      ldiff = temp;       // ... right-hand column
      rdiff[0] = 0;       // Top (boundary) row

      temp = roffs;       // And swap offset arrays, too
      roffs = loffs;
      loffs = temp;
      roffs[1] = 0;

      for(int i=0; i<plen; i++) {   // Run through pattern

        // Compute a, b, & c as the three adjacent cells ...
        bool charmatch;
        if(casing)
          charmatch = pattern[i] == text[textloc];
        else
          charmatch = toupper(pattern[i]) == toupper(text[textloc]);
        int a = ldiff[i] + (charmatch ? 0 : 1);
        int b = ldiff[i+1] + 1;
        int c = rdiff[i] + 1;

        // ... now pick minimum ...
        if(b < a)
          a = b;
        if(c < a)
          a = c;

        // ... and store
        rdiff[i+1] = a;
      }

      // Now update offset array
      // The values in the offset arrays are added to the
      // current location to determine the beginning of the
      // mismatched substring. (See refs for details)

      if(plen > 1) {
        for(int i=2; i<=plen; i++) {
          if(ldiff[i-1] < rdiff[i])
            roffs[i] = loffs[i-1] - 1;
          else if(rdiff[i-1] < rdiff[i])
            roffs[i] = roffs[i-1];
          else if(ldiff[i] < rdiff[i])
            roffs[i] = loffs[i] - 1;
          else  // Then we have ldiff[i-1] == rdiff[i]
            roffs[i] = loffs[i-1] - 1;
        }
      }

      // Now, do we have an approximate match?
      if(rdiff[plen] <= degree) {  // indeed so!
        end = text + textloc;
        start = end + roffs[plen];
        howclose = rdiff[plen];
      }
    }
  }

  return make_bool(start);
}


//  ------------------------------------------------------------------