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/*******************************************************************************
 *
 * Copyright (c) 2010, CloudBees, Inc.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:       
 *
 *******************************************************************************/ 

/*
 * The MIT License
 *
 * Copyright (c) 2010, CloudBees, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package hudson.util;

import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.converters.collections.MapConverter;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.mapper.Mapper;

import java.util.AbstractList;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

/**
 * Read-only map implementation that uses less memory than {@link HashMap}/{@link TreeMap}.
 *
 * 
 * The implementation is backed by a single exact-length array, so this implementation has the following
 * performance characteristics.
 *
 * 

 * iteration is fast (but creates a lot of short-lived objects.)
 * 
lookup is O(N)
 * 
memory consumption is low
 * 
 *
 * @author Kohsuke Kawaguchi
 */
@SuppressWarnings({"unchecked"})
public final class PackedMap extends AbstractMap {
    private Object[] kvpairs;

    /**
     *
     * @param src
     *      Map to copy contents from. Iteration order is preserved.
     */
    public static  PackedMap of(Map src) {
        return new PackedMap(src);
    }

    private PackedMap(Map src) {
        kvpairs = new Object[src.size()*2];
        int i=0;
        for (Entry e : src.entrySet()) {
            kvpairs[i++] = e.getKey();
            kvpairs[i++] = e.getValue();
        }
    }

    private final Set> entrySet = new AbstractSet>() {
        @Override
        public Iterator> iterator() {
            return new Iterator>() {
                int index=0;
                public boolean hasNext() {
                    return index next() {
                    final K k = (K)kvpairs[index++];
                    final V v = (V)kvpairs[index++];
                    return new Entry() {
                        public K getKey() {
                            return k;
                        }

                        public V getValue() {
                            return v;
                        }

                        public V setValue(V value) {
                            throw new UnsupportedOperationException();
                        }
                    };
                }

                public void remove() {
                    throw new UnsupportedOperationException();
                }
            };
        }

        @Override
        public int size() {
            return kvpairs.length/2;
        }
    };

    @Override
    public Set> entrySet() {
        return entrySet;
    }

    @Override
    public boolean containsKey(Object key) {
        for (int i=0; i values() {
        return new AbstractList() {
            @Override
            public V get(int index) {
                return (V)kvpairs[index*2];
            }

            @Override
            public int size() {
                return PackedMap.this.size();
            }
        };
    }

    /**
     * Should persist like a regular map.
     */
    public static class ConverterImpl extends MapConverter {
        public ConverterImpl(Mapper mapper) {
            super(mapper);
        }

        @Override
        public boolean canConvert(Class type) {
            return type==PackedMap.class;
        }

        @Override
        protected Object createCollection(Class type) {
            return new LinkedHashMap();
        }

        @Override
        public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
            return PackedMap.of((Map)super.unmarshal(reader, context));
        }
    }
}