/*
* Copyright (C) 2013 The Android Open Source Project
*
* 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.glview.support.v4.util;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
/**
* ArrayMap is a generic key->value mapping data structure that is
* designed to be more memory efficient than a traditional {@link java.util.HashMap},
* this implementation is a version of the platform's
* {@link android.util.ArrayMap} that can be used on older versions of the platform.
* It keeps its mappings in an array data structure -- an integer array of hash
* codes for each item, and an Object array of the key/value pairs. This allows it to
* avoid having to create an extra object for every entry put in to the map, and it
* also tries to control the growth of the size of these arrays more aggressively
* (since growing them only requires copying the entries in the array, not rebuilding
* a hash map).
*
* <p>If you don't need the standard Java container APIs provided here (iterators etc),
* consider using {@link SimpleArrayMap} instead.</p>
*
* <p>Note that this implementation is not intended to be appropriate for data structures
* that may contain large numbers of items. It is generally slower than a traditional
* HashMap, since lookups require a binary search and adds and removes require inserting
* and deleting entries in the array. For containers holding up to hundreds of items,
* the performance difference is not significant, less than 50%.</p>
*
* <p>Because this container is intended to better balance memory use, unlike most other
* standard Java containers it will shrink its array as items are removed from it. Currently
* you have no control over this shrinking -- if you set a capacity and then remove an
* item, it may reduce the capacity to better match the current size. In the future an
* explicit call to set the capacity should turn off this aggressive shrinking behavior.</p>
*/
public class ArrayMap<K, V> extends SimpleArrayMap<K, V> implements Map<K, V> {
MapCollections<K, V> mCollections;
public ArrayMap() {
super();
}
/**
* Create a new ArrayMap with a given initial capacity.
*/
public ArrayMap(int capacity) {
super(capacity);
}
/**
* Create a new ArrayMap with the mappings from the given ArrayMap.
*/
public ArrayMap(SimpleArrayMap map) {
super(map);
}
private MapCollections<K, V> getCollection() {
if (mCollections == null) {
mCollections = new MapCollections<K, V>() {
@Override
protected int colGetSize() {
return mSize;
}
@Override
protected Object colGetEntry(int index, int offset) {
return mArray[(index<<1) + offset];
}
@Override
protected int colIndexOfKey(Object key) {
return indexOfKey(key);
}
@Override
protected int colIndexOfValue(Object value) {
return indexOfValue(value);
}
@Override
protected Map<K, V> colGetMap() {
return ArrayMap.this;
}
@Override
protected void colPut(K key, V value) {
put(key, value);
}
@Override
protected V colSetValue(int index, V value) {
return setValueAt(index, value);
}
@Override
protected void colRemoveAt(int index) {
removeAt(index);
}
@Override
protected void colClear() {
clear();
}
};
}
return mCollections;
}
/**
* Determine if the array map contains all of the keys in the given collection.
* @param collection The collection whose contents are to be checked against.
* @return Returns true if this array map contains a key for every entry
* in <var>collection</var>, else returns false.
*/
public boolean containsAll(Collection<?> collection) {
return MapCollections.containsAllHelper(this, collection);
}
/**
* Perform a {@link #put(Object, Object)} of all key/value pairs in <var>map</var>
* @param map The map whose contents are to be retrieved.
*/
@Override
public void putAll(Map<? extends K, ? extends V> map) {
ensureCapacity(mSize + map.size());
for (Map.Entry<? extends K, ? extends V> entry : map.entrySet()) {
put(entry.getKey(), entry.getValue());
}
}
/**
* Remove all keys in the array map that exist in the given collection.
* @param collection The collection whose contents are to be used to remove keys.
* @return Returns true if any keys were removed from the array map, else false.
*/
public boolean removeAll(Collection<?> collection) {
return MapCollections.removeAllHelper(this, collection);
}
/**
* Remove all keys in the array map that do <b>not</b> exist in the given collection.
* @param collection The collection whose contents are to be used to determine which
* keys to keep.
* @return Returns true if any keys were removed from the array map, else false.
*/
public boolean retainAll(Collection<?> collection) {
return MapCollections.retainAllHelper(this, collection);
}
/**
* Return a {@link java.util.Set} for iterating over and interacting with all mappings
* in the array map.
*
* <p><b>Note:</b> this is a very inefficient way to access the array contents, it
* requires generating a number of temporary objects.</p>
*
* <p><b>Note:</b></p> the semantics of this
* Set are subtly different than that of a {@link java.util.HashMap}: most important,
* the {@link java.util.Map.Entry Map.Entry} object returned by its iterator is a single
* object that exists for the entire iterator, so you can <b>not</b> hold on to it
* after calling {@link java.util.Iterator#next() Iterator.next}.</p>
*/
@Override
public Set<Entry<K, V>> entrySet() {
return getCollection().getEntrySet();
}
/**
* Return a {@link java.util.Set} for iterating over and interacting with all keys
* in the array map.
*
* <p><b>Note:</b> this is a fairly inefficient way to access the array contents, it
* requires generating a number of temporary objects.</p>
*/
@Override
public Set<K> keySet() {
return getCollection().getKeySet();
}
/**
* Return a {@link java.util.Collection} for iterating over and interacting with all values
* in the array map.
*
* <p><b>Note:</b> this is a fairly inefficient way to access the array contents, it
* requires generating a number of temporary objects.</p>
*/
@Override
public Collection<V> values() {
return getCollection().getValues();
}
}