org.egothor.stemmer.Trie 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
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 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;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.List;
/**
* A Trie is used to store a dictionary of words and their stems.
*
* Actually, what is stored are words with their respective patch commands. A trie can be termed
* forward (keys read from left to right) or backward (keys read from right to left). This property
* will vary depending on the language for which a Trie is constructed.
*/
public class Trie {
List rows = new ArrayList<>();
List cmds = new ArrayList<>();
int root;
boolean forward;
/**
* Constructor for the Trie object.
*
* @param is the input stream
* @exception IOException if an I/O error occurs
*/
public Trie(DataInput is) throws IOException {
forward = is.readBoolean();
root = is.readInt();
for (int i = is.readInt(); i > 0; i--) {
cmds.add(is.readUTF());
}
for (int i = is.readInt(); i > 0; i--) {
rows.add(new Row(is));
}
}
/**
* Constructor for the Trie object.
*
* @param forward set to true
*/
public Trie(boolean forward) {
rows.add(new Row());
root = 0;
this.forward = forward;
}
/**
* Constructor for the Trie object.
*
* @param forward true if read left to right, false if read right to
* left
* @param root index of the row that is the root node
* @param cmds the patch commands to store
* @param rows a Vector of Vectors. Each inner Vector is a node of this Trie
*/
public Trie(boolean forward, int root, List cmds, List rows) {
this.rows = rows;
this.cmds = cmds;
this.root = root;
this.forward = forward;
}
/**
* Gets the all attribute of the Trie object
*
* @param key Description of the Parameter
* @return The all value
*/
public CharSequence[] getAll(CharSequence key) {
int[] res = new int[key.length()];
int resc = 0;
Row now = getRow(root);
int w;
StrEnum e = new StrEnum(key, forward);
boolean br = false;
for (int i = 0; i < key.length() - 1; i++) {
char ch = e.next();
w = now.getCmd(ch);
if (w >= 0) {
int n = w;
for (int j = 0; j < resc; j++) {
if (n == res[j]) {
n = -1;
break;
}
}
if (n >= 0) {
res[resc++] = n;
}
}
w = now.getRef(ch);
if (w >= 0) {
now = getRow(w);
} else {
br = true;
break;
}
}
if (br == false) {
w = now.getCmd(e.next());
if (w >= 0) {
int n = w;
for (int j = 0; j < resc; j++) {
if (n == res[j]) {
n = -1;
break;
}
}
if (n >= 0) {
res[resc++] = n;
}
}
}
if (resc < 1) {
return null;
}
CharSequence[] R = new CharSequence[resc];
for (int j = 0; j < resc; j++) {
R[j] = cmds.get(res[j]);
}
return R;
}
/**
* Return the number of cells in this Trie object.
*
* @return the number of cells
*/
public int getCells() {
int size = 0;
for (Row row : rows) size += row.getCells();
return size;
}
/**
* Gets the cellsPnt attribute of the Trie object
*
* @return The cellsPnt value
*/
public int getCellsPnt() {
int size = 0;
for (Row row : rows) size += row.getCellsPnt();
return size;
}
/**
* Gets the cellsVal attribute of the Trie object
*
* @return The cellsVal value
*/
public int getCellsVal() {
int size = 0;
for (Row row : rows) size += row.getCellsVal();
return size;
}
/**
* Return the element that is stored in a cell associated with the given key.
*
* @param key the key
* @return the associated element
*/
public CharSequence getFully(CharSequence key) {
Row now = getRow(root);
int w;
Cell c;
int cmd = -1;
StrEnum e = new StrEnum(key, forward);
char ch;
for (int i = 0; i < key.length(); ) {
ch = e.next();
i++;
c = now.at(ch);
if (c == null) {
return null;
}
cmd = c.cmd;
for (int skip = c.skip; skip > 0; skip--) {
if (i < key.length()) {
e.next();
} else {
return null;
}
i++;
}
w = now.getRef(ch);
if (w >= 0) {
now = getRow(w);
} else if (i < key.length()) {
return null;
}
}
return (cmd == -1) ? null : cmds.get(cmd);
}
/**
* Return the element that is stored as last on a path associated with the given key.
*
* @param key the key associated with the desired element
* @return the last on path element
*/
public CharSequence getLastOnPath(CharSequence key) {
Row now = getRow(root);
int w;
CharSequence last = null;
StrEnum e = new StrEnum(key, forward);
for (int i = 0; i < key.length() - 1; i++) {
char ch = e.next();
w = now.getCmd(ch);
if (w >= 0) {
last = cmds.get(w);
}
w = now.getRef(ch);
if (w >= 0) {
now = getRow(w);
} else {
return last;
}
}
w = now.getCmd(e.next());
return (w >= 0) ? cmds.get(w) : last;
}
/**
* Return the Row at the given index.
*
* @param index the index containing the desired Row
* @return the Row
*/
private Row getRow(int index) {
if (index < 0 || index >= rows.size()) {
return null;
}
return rows.get(index);
}
/**
* Write this Trie to the given output stream.
*
* @param os the output stream
* @exception IOException if an I/O error occurs
*/
public void store(DataOutput os) throws IOException {
os.writeBoolean(forward);
os.writeInt(root);
os.writeInt(cmds.size());
for (CharSequence cmd : cmds) os.writeUTF(cmd.toString());
os.writeInt(rows.size());
for (Row row : rows) row.store(os);
}
/**
* Add the given key associated with the given patch command. If either parameter is null this
* method will return without executing.
*
* @param key the key
* @param cmd the patch command
*/
void add(CharSequence key, CharSequence cmd) {
if (key == null || cmd == null) {
return;
}
if (cmd.length() == 0) {
return;
}
int id_cmd = cmds.indexOf(cmd);
if (id_cmd == -1) {
id_cmd = cmds.size();
cmds.add(cmd);
}
int node = root;
Row r = getRow(node);
StrEnum e = new StrEnum(key, forward);
for (int i = 0; i < e.length() - 1; i++) {
char ch = e.next();
node = r.getRef(ch);
if (node >= 0) {
r = getRow(node);
} else {
node = rows.size();
Row n;
rows.add(n = new Row());
r.setRef(ch, node);
r = n;
}
}
r.setCmd(e.next(), id_cmd);
}
/**
* Remove empty rows from the given Trie and return the newly reduced Trie.
*
* @param by the Trie to reduce
* @return the newly reduced Trie
*/
public Trie reduce(Reduce by) {
return by.optimize(this);
}
/** writes debugging info to the printstream */
public void printInfo(PrintStream out, CharSequence prefix) {
out.println(
prefix
+ "nds "
+ rows.size()
+ " cmds "
+ cmds.size()
+ " cells "
+ getCells()
+ " valcells "
+ getCellsVal()
+ " pntcells "
+ getCellsPnt());
}
/** This class is part of the Egothor Project */
class StrEnum {
CharSequence s;
int from;
int by;
/**
* Constructor for the StrEnum object
*
* @param s Description of the Parameter
* @param up Description of the Parameter
*/
StrEnum(CharSequence s, boolean up) {
this.s = s;
if (up) {
from = 0;
by = 1;
} else {
from = s.length() - 1;
by = -1;
}
}
int length() {
return s.length();
}
char next() {
char ch = s.charAt(from);
from += by;
return ch;
}
}
}