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/*
 * Copyright (c) [2016] [  ]
 * This file is part of the ethereumJ library.
 *
 * The ethereumJ library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * The ethereumJ 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the ethereumJ library. If not, see .
 */
/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.higgschain.trust.evmcontract.util;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * A thread-safe version of {@link Map} in which all operations that change the
 * Map are implemented by making a new copy of the underlying Map.
 * 
 * While the creation of a new Map can be expensive, this class is designed for
 * cases in which the primary function is to read data from the Map, not to
 * modify the Map.  Therefore the operations that do not cause a change to this
 * class happen quickly and concurrently.
 *
 * @param  the type parameter
 * @param  the type parameter
 * @author The Apache MINA Project ([email protected])
 * @version $Rev$, $Date$
 */
public class CopyOnWriteMap implements Map, Cloneable {
    private volatile Map internalMap;

    /**
     * Creates a new instance of CopyOnWriteMap.
     */
    public CopyOnWriteMap() {
        internalMap = new HashMap();
    }

    /**
     * Creates a new instance of CopyOnWriteMap with the specified initial size
     *
     * @param initialCapacity The initial size of the Map.
     */
    public CopyOnWriteMap(int initialCapacity) {
        internalMap = new HashMap(initialCapacity);
    }

    /**
     * Creates a new instance of CopyOnWriteMap in which the
     * initial data being held by this map is contained in
     * the supplied map.
     *
     * @param data A Map containing the initial contents to be placed into             this class.
     */
    public CopyOnWriteMap(Map data) {
        internalMap = new HashMap(data);
    }

    /**
     * Adds the provided key and value to this map.
     *
     * @see Map#put(Object, Object)
     */
    @Override
    public V put(K key, V value) {
        synchronized (this) {
            Map newMap = new HashMap(internalMap);
            V val = newMap.put(key, value);
            internalMap = newMap;
            return val;
        }
    }

    /**
     * Removed the value and key from this map based on the
     * provided key.
     *
     * @see Map#remove(Object)
     */
    @Override
    public V remove(Object key) {
        synchronized (this) {
            Map newMap = new HashMap(internalMap);
            V val = newMap.remove(key);
            internalMap = newMap;
            return val;
        }
    }

    /**
     * Inserts all the keys and values contained in the
     * provided map to this map.
     *
     * @see Map#putAll(Map)
     */
    @Override
    public void putAll(Map newData) {
        synchronized (this) {
            Map newMap = new HashMap(internalMap);
            newMap.putAll(newData);
            internalMap = newMap;
        }
    }

    /**
     * Removes all entries in this map.
     *
     * @see Map#clear()
     */
    @Override
    public void clear() {
        synchronized (this) {
            internalMap = new HashMap();
        }
    }

    //
    //  Below are methods that do not modify
    //          the internal Maps

    /**
     * Returns the number of key/value pairs in this map.
     *
     * @see Map#size()
     */
    @Override
    public int size() {
        return internalMap.size();
    }

    /**
     * Returns true if this map is empty, otherwise false.
     *
     * @see Map#isEmpty()
     */
    @Override
    public boolean isEmpty() {
        return internalMap.isEmpty();
    }

    /**
     * Returns true if this map contains the provided key, otherwise
     * this method return false.
     *
     * @see Map#containsKey(Object)
     */
    @Override
    public boolean containsKey(Object key) {
        return internalMap.containsKey(key);
    }

    /**
     * Returns true if this map contains the provided value, otherwise
     * this method returns false.
     *
     * @see Map#containsValue(Object)
     */
    @Override
    public boolean containsValue(Object value) {
        return internalMap.containsValue(value);
    }

    /**
     * Returns the value associated with the provided key from this
     * map.
     *
     * @see Map#get(Object)
     */
    @Override
    public V get(Object key) {
        return internalMap.get(key);
    }

    /**
     * This method will return a read-only {@link Set}.
     */
    @Override
    public Set keySet() {
        return internalMap.keySet();
    }

    /**
     * This method will return a read-only {@link Collection}.
     */
    @Override
    public Collection values() {
        return internalMap.values();
    }

    /**
     * This method will return a read-only {@link Set}.
     */
    @Override
    public Set> entrySet() {
        return internalMap.entrySet();
    }

    @Override
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            throw new InternalError();
        }
    }
}