org.egothor.stemmer.Diff Maven / Gradle / Ivy
/*
Egothor Software License version 1.00
Copyright (C) 1997-2004 Leo Galambos.
Copyright (C) 2002-2004 "Egothor developers"
on behalf of the Egothor Project.
All rights reserved.
This software is copyrighted by the "Egothor developers". If this
license applies to a single file or document, the "Egothor developers"
are the people or entities mentioned as copyright holders in that file
or document. If this license applies to the Egothor project as a
whole, the copyright holders are the people or entities mentioned in
the file CREDITS. This file can be found in the same location as this
license in the distribution.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
1. Redistributions of source code must retain the above copyright
notice, the list of contributors, this list of conditions, and the
following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, the list of contributors, this list of conditions, and the
disclaimer that follows these conditions in the documentation
and/or other materials provided with the distribution.
3. The name "Egothor" must not be used to endorse or promote products
derived from this software without prior written permission. For
written permission, please contact [email protected]
4. Products derived from this software may not be called "Egothor",
nor may "Egothor" appear in their name, without prior written
permission from [email protected].
In addition, we request that you include in the end-user documentation
provided with the redistribution and/or in the software itself an
acknowledgement equivalent to the following:
"This product includes software developed by the Egothor Project.
http://egothor.sf.net/"
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 THE EGOTHOR PROJECT OR ITS CONTRIBUTORS 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
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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 software consists of voluntary contributions made by many
individuals on behalf of the Egothor Project and was originally
created by Leo Galambos ([email protected]).
*/
package org.egothor.stemmer;
/**
* The Diff object generates a patch string.
*
* A patch string is actually a command to a stemmer telling it how to reduce a word to its root.
* For example, to reduce the word teacher to its root teach the patch string Db would be generated.
* This command tells the stemmer to delete the last 2 characters from the word teacher to reach the
* stem (the patch commands are applied starting from the last character in order to save
*/
public class Diff {
int sizex = 0;
int sizey = 0;
int[][] net;
int[][] way;
int INSERT;
int DELETE;
int REPLACE;
int NOOP;
/** Constructor for the Diff object. */
public Diff() {
this(1, 1, 1, 0);
}
/**
* Constructor for the Diff object
*
* @param ins Description of the Parameter
* @param del Description of the Parameter
* @param rep Description of the Parameter
* @param noop Description of the Parameter
*/
public Diff(int ins, int del, int rep, int noop) {
INSERT = ins;
DELETE = del;
REPLACE = rep;
NOOP = noop;
}
/**
* Apply the given patch string diff to the given string
* dest.
*
* @param dest Destination string
* @param diff Patch string
*/
public static void apply(StringBuilder dest, CharSequence diff) {
try {
if (diff == null) {
return;
}
int pos = dest.length() - 1;
if (pos < 0) {
return;
}
// orig == ""
for (int i = 0; i < diff.length() / 2; i++) {
char cmd = diff.charAt(2 * i);
char param = diff.charAt(2 * i + 1);
int par_num = (param - 'a' + 1);
switch (cmd) {
case '-':
pos = pos - par_num + 1;
break;
case 'R':
dest.setCharAt(pos, param);
break;
case 'D':
int o = pos;
pos -= par_num - 1;
/*
* delete par_num chars from index pos
*/
// String s = orig.toString();
// s = s.substring( 0, pos ) + s.substring( o + 1 );
// orig = new StringBuffer( s );
dest.delete(pos, o + 1);
break;
case 'I':
dest.insert(pos += 1, param);
break;
}
pos--;
}
} catch (
@SuppressWarnings("unused")
StringIndexOutOfBoundsException x) {
// x.printStackTrace();
} catch (
@SuppressWarnings("unused")
ArrayIndexOutOfBoundsException x) {
// x.printStackTrace();
}
}
/**
* Construct a patch string that transforms a to b.
*
* @param a String 1st string
* @param b String 2nd string
* @return String
*/
public synchronized String exec(String a, String b) {
if (a == null || b == null) {
return null;
}
int x;
int y;
int maxx;
int maxy;
int[] go = new int[4];
final int X = 1;
final int Y = 2;
final int R = 3;
final int D = 0;
/*
* setup memory if needed => processing speed up
*/
maxx = a.length() + 1;
maxy = b.length() + 1;
if ((maxx >= sizex) || (maxy >= sizey)) {
sizex = maxx + 8;
sizey = maxy + 8;
net = new int[sizex][sizey];
way = new int[sizex][sizey];
}
/*
* clear the network
*/
for (x = 0; x < maxx; x++) {
for (y = 0; y < maxy; y++) {
net[x][y] = 0;
}
}
/*
* set known persistent values
*/
for (x = 1; x < maxx; x++) {
net[x][0] = x;
way[x][0] = X;
}
for (y = 1; y < maxy; y++) {
net[0][y] = y;
way[0][y] = Y;
}
for (x = 1; x < maxx; x++) {
for (y = 1; y < maxy; y++) {
go[X] = net[x - 1][y] + DELETE;
// way on x costs 1 unit
go[Y] = net[x][y - 1] + INSERT;
// way on y costs 1 unit
go[R] = net[x - 1][y - 1] + REPLACE;
go[D] = net[x - 1][y - 1] + ((a.charAt(x - 1) == b.charAt(y - 1)) ? NOOP : 100);
// diagonal costs 0, when no change
short min = D;
if (go[min] >= go[X]) {
min = X;
}
if (go[min] > go[Y]) {
min = Y;
}
if (go[min] > go[R]) {
min = R;
}
way[x][y] = min;
net[x][y] = (short) go[min];
}
}
// read the patch string
StringBuilder result = new StringBuilder();
final char base = 'a' - 1;
char deletes = base;
char equals = base;
for (x = maxx - 1, y = maxy - 1; x + y != 0; ) {
switch (way[x][y]) {
case X:
if (equals != base) {
result.append('-').append(equals);
equals = base;
}
deletes++;
x--;
break;
// delete
case Y:
if (deletes != base) {
result.append('D').append(deletes);
deletes = base;
}
if (equals != base) {
result.append('-').append(equals);
equals = base;
}
result.append('I');
result.append(b.charAt(--y));
break;
// insert
case R:
if (deletes != base) {
result.append('D').append(deletes);
deletes = base;
}
if (equals != base) {
result.append('-').append(equals);
equals = base;
}
result.append('R');
result.append(b.charAt(--y));
x--;
break;
// replace
case D:
if (deletes != base) {
result.append('D').append(deletes);
deletes = base;
}
equals++;
x--;
y--;
break;
// no change
}
}
if (deletes != base) {
result.append('D').append(deletes);
deletes = base;
}
return result.toString();
}
}