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CharTrie.java
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CharTrie.java
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/*
* Copyright 2016 Ahmad Mozafarnia
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.t9.engine;
import com.esotericsoftware.kryo.Kryo;
import com.t9.util.serialization.KryoSerializer;
import java.io.*;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.function.BiConsumer;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
/**
* @author ahmad
*/
public final class CharTrie {
/**
* A KryoSerializer that is used for Serializing and Deserializing dictionaries.
*/
@SuppressWarnings("unchecked")
private static final KryoSerializer<List<Word>> WORD_LIST_SERIALIZER = new KryoSerializer<>(() -> {
Kryo kryo = new Kryo();
kryo.register(Word.class);
return kryo;
}, (Class<List<Word>>) (Class<?>) ArrayList.class);
/**
* Pointer to root Node
*/
private final Node root = new Node();
/**
* Puts the specified word in this CharTrie and increases its frequency.
*
* @param word word to put in this CharTrie
* @return the previous frequency of the specified word
*/
public int put(String word) {
if (word.isEmpty()) {
return 0;
}
Node current = root;
for (int i = 0; i < word.length(); i++) {
current = current.children.computeIfAbsent(word.charAt(i), ch -> new Node());
}
return current.getAndIncreaseFrequency();
}
/**
* @param word the word whose frequency is to be returned
* @return the current frequency of the specified word or -1 if there isn't such a word in this CharTrie
*/
public int frequency(String word) {
if (word.isEmpty()) {
return 0;
}
Node current = root;
for (int i = 0; i < word.length() && current != null; i++) {
current = current.children.get(word.charAt(i));
}
return current == null ? -1 : current.frequency;
}
/**
* @param word the word whose presence in this CharTrie is to be tested
* @return true if this CharTrie contains the specified word
*/
public boolean contains(String word) {
return frequency(word) > 0;
}
/**
* @return a CharTrie Iterator over the Nodes in this CharTrie, starting at the root Node.
*/
public Iterator iterator() {
return new Iterator(root);
}
/**
* Node in the CharTrie.
* frequency-children entry
*/
private static final class Node {
/**
* the number of occurrences of the character that is associated to this Node,
* at certain position in the CharTrie
*/
private volatile int frequency = 0;
private static final AtomicIntegerFieldUpdater<Node> frequencyUpdater
= AtomicIntegerFieldUpdater.newUpdater(Node.class, "frequency");
/**
* Children of this Node
*/
private final Map<Character, Node> children = new ConcurrentHashMap<>();
/**
* Atomically increments by one the current value of the frequency.
*
* @return the previous frequency
*/
private int getAndIncreaseFrequency() {
return frequencyUpdater.getAndIncrement(this);
}
}
/**
* Iterator over the Nodes in the CharTrie
*/
public static final class Iterator implements Cloneable {
/**
* Pointer to current Node
*/
private Node current;
private Iterator(Node current) {
this.current = current;
}
/**
* Returns true if the current Node contains the specified character in its children,
* then moves to the child Node.
* Otherwise, the current Node will not change.
*
* @param ch the character whose presence in the current Node's children is to be tested
* @return true if the current Node's children contains the specified character
*/
public boolean next(char ch) {
Node next = current.children.get(ch);
if (next == null) {
return false;
}
current = next;
return true;
}
/**
* @return the current frequency of the current Node
*/
public int frequency() {
return current.frequency;
}
/**
* @return the newly created CharTrie Iterator, starting at the current Node of this Iterator
*/
@Override
@SuppressWarnings("CloneDoesntCallSuperClone")
public Iterator clone() {
return new Iterator(current);
}
}
/**
* Exports this CharTrie's dictionary as binary object to the specified file.
*
* @param dest the output file
* @throws IOException
*/
public void exportBinary(Path dest) throws IOException {
List<Word> words = new ArrayList<>();
move(root, "", (v, f) -> words.add(new Word(v, f)));
try (GZIPOutputStream outputStream = new GZIPOutputStream(new BufferedOutputStream(new FileOutputStream(dest.toFile())))) {
WORD_LIST_SERIALIZER.write(words, outputStream);
}
}
/**
* Exports this CharTrie's dictionary as text to the specified file.
*
* @param dest the output file
* @throws IOException
*/
public void exportDictionary(Path dest) throws IOException {
try (final BufferedWriter writer = new BufferedWriter(new FileWriter(dest.toFile()))) {
move(root, "", (v, f) -> {
try {
for (int i = f; i > 0; i--) {
writer.write(v);
writer.newLine();
}
} catch (IOException e) {
throw new Error(e);
}
});
}
}
private static void move(Node node, String word, BiConsumer<String, Integer> action) {
if (node.frequency > 0) {
action.accept(word, node.frequency);
}
for (Map.Entry<Character, Node> e : node.children.entrySet()) {
move(e.getValue(), word + e.getKey(), action);
}
}
/**
* Imports dictionary from the specified binary file to this CharTrie.
*
* @param src the source file to be imported
* @throws IOException
*/
public void importBinary(Path src) throws IOException {
try (GZIPInputStream inputStream = new GZIPInputStream(new BufferedInputStream(new FileInputStream(src.toFile())))) {
for (Word word : WORD_LIST_SERIALIZER.read(inputStream)) {
for (int i = word.getFrequency(); i > 0; i--) {
put(word.getValue());
}
}
}
}
/**
* Imports dictionary from the specified text file to this CharTrie.
*
* @param src the source file to be imported
* @throws IOException
*/
public void importDictionary(Path src) throws IOException {
try (BufferedReader reader = new BufferedReader(new FileReader(src.toFile()))) {
String word;
while ((word = reader.readLine()) != null) {
put(word);
}
}
}
}