/*
* 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}.
*
* <p>
* The implementation is backed by a single exact-length array, so this implementation has the following
* performance characteristics.
*
* <ul>
* <li>iteration is fast (but creates a lot of short-lived objects.)
* <li>lookup is O(N)
* <li>memory consumption is low
* </ul>
*
* @author Kohsuke Kawaguchi
*/
@SuppressWarnings({"unchecked"})
public final class PackedMap<K,V> extends AbstractMap<K,V> {
private Object[] kvpairs;
/**
*
* @param src
* Map to copy contents from. Iteration order is preserved.
*/
public static <K,V> PackedMap<K,V> of(Map<? extends K,? extends V> src) {
return new PackedMap<K, V>(src);
}
private PackedMap(Map<? extends K,? extends V> src) {
kvpairs = new Object[src.size()*2];
int i=0;
for (Entry<? extends K, ? extends V> e : src.entrySet()) {
kvpairs[i++] = e.getKey();
kvpairs[i++] = e.getValue();
}
}
private final Set<Entry<K,V>> entrySet = new AbstractSet<Entry<K, V>>() {
@Override
public Iterator<Entry<K, V>> iterator() {
return new Iterator<Entry<K, V>>() {
int index=0;
public boolean hasNext() {
return index<kvpairs.length;
}
@SuppressWarnings({"unchecked"})
public Entry<K, V> next() {
final K k = (K)kvpairs[index++];
final V v = (V)kvpairs[index++];
return new Entry<K, V>() {
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<Entry<K, V>> entrySet() {
return entrySet;
}
@Override
public boolean containsKey(Object key) {
for (int i=0; i<kvpairs.length; i+=2)
if (key.equals(kvpairs[i]))
return true;
return false;
}
@Override
public V get(Object key) {
for (int i=0; i<kvpairs.length; i+=2)
if (key.equals(kvpairs[i]))
return (V)kvpairs[i+1];
return null;
}
@Override
public Collection<V> values() {
return new AbstractList<V>() {
@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<String,String>();
}
@Override
public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
return PackedMap.of((Map)super.unmarshal(reader, context));
}
}
}