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/*
* Copyright (C) 2015 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.android.tv.util;
import android.support.annotation.VisibleForTesting;
import android.util.ArraySet;
import android.util.LongSparseArray;
import java.util.Collections;
import java.util.Set;
/**
* Uses a {@link LongSparseArray} to hold sets of {@code T}.
*
* <p>This has the same memory and performance trade offs listed in {@link LongSparseArray}.
*/
public class MultiLongSparseArray<T> {
@VisibleForTesting
static final int DEFAULT_MAX_EMPTIES_KEPT = 4;
private final LongSparseArray<Set<T>> mSparseArray;
private final Set<T>[] mEmptySets;
private int mEmptyIndex = -1;
public MultiLongSparseArray() {
mSparseArray = new LongSparseArray<>();
mEmptySets = new Set[DEFAULT_MAX_EMPTIES_KEPT];
}
public MultiLongSparseArray(int initialCapacity, int emptyCacheSize) {
mSparseArray = new LongSparseArray<>(initialCapacity);
mEmptySets = new Set[emptyCacheSize];
}
/**
* Adds a mapping from the specified key to the specified value,
* replacing the previous mapping from the specified key if there
* was one.
*/
public void put(long key, T value) {
Set<T> values = mSparseArray.get(key);
if (values == null) {
values = getEmptySet();
mSparseArray.put(key, values);
}
values.add(value);
}
/**
* Removes the value at the specified index.
*/
public void remove(long key, T value) {
Set<T> values = mSparseArray.get(key);
if (values != null) {
values.remove(value);
if (values.isEmpty()) {
mSparseArray.remove(key);
cacheEmptySet(values);
}
}
}
/**
* Gets the set of Objects mapped from the specified key, or an empty set
* if no such mapping has been made.
*/
public Iterable<T> get(long key) {
Set<T> values = mSparseArray.get(key);
return values == null ? Collections.EMPTY_SET : values;
}
/**
* Clears cached empty sets.
*/
public void clearEmptyCache() {
while (mEmptyIndex >= 0) {
mEmptySets[mEmptyIndex--] = null;
}
}
@VisibleForTesting
int getEmptyCacheSize() {
return mEmptyIndex + 1;
}
private void cacheEmptySet(Set<T> emptySet) {
if (mEmptyIndex < DEFAULT_MAX_EMPTIES_KEPT - 1) {
mEmptySets[++mEmptyIndex] = emptySet;
}
}
private Set<T> getEmptySet() {
if (mEmptyIndex < 0) {
return new ArraySet<>();
}
Set<T> emptySet = mEmptySets[mEmptyIndex];
mEmptySets[mEmptyIndex--] = null;
return emptySet;
}
@Override
public String toString() {
return mSparseArray.toString() + "(emptyCacheSize=" + getEmptyCacheSize() + ")";
}
}
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