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/*
* Copyright (C) 2020 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.server.utils;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.util.SparseArray;
import java.util.ArrayList;
/**
* A watched variant of SparseArray. If a {@link Watchable} is stored in the array, the
* array registers with the {@link Watchable}. The array registers only once with each
* {@link Watchable} no matter how many times the {@link Watchable} is stored in the
* array.
* @param The element type, stored in the array.
*/
public class WatchedSparseArray extends WatchableImpl
implements Snappable {
// The storage
private final SparseArray mStorage;
// If true, the array is watching its children
private volatile boolean mWatching = false;
// The local observer
private final Watcher mObserver = new Watcher() {
@Override
public void onChange(@Nullable Watchable o) {
WatchedSparseArray.this.dispatchChange(o);
}
};
/**
* A private convenience function that notifies registered listeners that an element
* has been added to or removed from the array. The what parameter is the array itself.
*/
private void onChanged() {
dispatchChange(this);
}
/**
* A convenience function. Register the object if it is {@link Watchable} and if the
* array is currently watching. Note that the watching flag must be true if this
* function is to succeed.
*/
private void registerChild(Object o) {
if (mWatching && o instanceof Watchable) {
((Watchable) o).registerObserver(mObserver);
}
}
/**
* A convenience function. Unregister the object if it is {@link Watchable} and if
* the array is currently watching. Note that the watching flag must be true if this
* function is to succeed.
*/
private void unregisterChild(Object o) {
if (mWatching && o instanceof Watchable) {
((Watchable) o).unregisterObserver(mObserver);
}
}
/**
* A convenience function. Unregister the object if it is {@link Watchable}, if the array is
* currently watching, and if the storage does not contain the object. Note that the watching
* flag must be true if this function is to succeed. This must be called after an object has
* been removed from the storage.
*/
private void unregisterChildIf(Object o) {
if (mWatching && o instanceof Watchable) {
if (mStorage.indexOfValue((E) o) == -1) {
((Watchable) o).unregisterObserver(mObserver);
}
}
}
/**
* Register a {@link Watcher} with the array. If this is the first Watcher than any
* array values that are {@link Watchable} are registered to the array itself.
*/
@Override
public void registerObserver(@NonNull Watcher observer) {
super.registerObserver(observer);
if (registeredObserverCount() == 1) {
// The watching flag must be set true before any children are registered.
mWatching = true;
final int end = mStorage.size();
for (int i = 0; i < end; i++) {
registerChild(mStorage.valueAt(i));
}
}
}
/**
* Unregister a {@link Watcher} from the array. If this is the last Watcher than any
* array values that are {@link Watchable} are unregistered to the array itself.
*/
@Override
public void unregisterObserver(@NonNull Watcher observer) {
super.unregisterObserver(observer);
if (registeredObserverCount() == 0) {
final int end = mStorage.size();
for (int i = 0; i < end; i++) {
unregisterChild(mStorage.valueAt(i));
}
// The watching flag must be true while children are unregistered.
mWatching = false;
}
}
/**
* Creates a new WatchedSparseArray containing no mappings.
*/
public WatchedSparseArray() {
mStorage = new SparseArray();
}
/**
* Creates a new WatchedSparseArray containing no mappings that
* will not require any additional memory allocation to store the
* specified number of mappings. If you supply an initial capacity of
* 0, the sparse array will be initialized with a light-weight
* representation not requiring any additional array allocations.
*/
public WatchedSparseArray(int initialCapacity) {
mStorage = new SparseArray(initialCapacity);
}
/**
* Create a {@link WatchedSparseArray} from a {@link SparseArray}
*/
public WatchedSparseArray(@NonNull SparseArray c) {
mStorage = c.clone();
}
/**
* The copy constructor does not copy the watcher data.
*/
public WatchedSparseArray(@NonNull WatchedSparseArray r) {
mStorage = r.mStorage.clone();
}
/**
* Make a copy of src. Any data in is discarded.
*/
public void copyFrom(@NonNull SparseArray src) {
clear();
final int end = src.size();
for (int i = 0; i < end; i++) {
put(src.keyAt(i), src.valueAt(i));
}
}
/**
* Make dst a copy of . Any previous data in dst is discarded.
*/
public void copyTo(@NonNull SparseArray dst) {
dst.clear();
final int end = size();
for (int i = 0; i < end; i++) {
dst.put(keyAt(i), valueAt(i));
}
}
/**
* Return the underlying storage. This breaks the wrapper but is necessary when
* passing the array to distant methods.
*/
public SparseArray untrackedStorage() {
return mStorage;
}
/**
* Returns true if the key exists in the array. This is equivalent to
* {@link #indexOfKey(int)} >= 0.
*
* @param key Potential key in the mapping
* @return true if the key is defined in the mapping
*/
public boolean contains(int key) {
return mStorage.contains(key);
}
/**
* Gets the Object mapped from the specified key, or null
* if no such mapping has been made.
*/
public E get(int key) {
return mStorage.get(key);
}
/**
* Gets the Object mapped from the specified key, or the specified Object
* if no such mapping has been made.
*/
public E get(int key, E valueIfKeyNotFound) {
return mStorage.get(key, valueIfKeyNotFound);
}
/**
* Removes the mapping from the specified key, if there was any.
*/
public void delete(int key) {
final E child = mStorage.get(key);
mStorage.delete(key);
unregisterChildIf(child);
onChanged();
}
/**
* @hide
* Removes the mapping from the specified key, if there was any, returning the old value.
*/
public E removeReturnOld(int key) {
final E result = mStorage.removeReturnOld(key);
unregisterChildIf(result);
return result;
}
/**
* Alias for {@link #delete(int)}.
*/
public void remove(int key) {
delete(key);
}
/**
* Removes the mapping at the specified index.
*
* For indices outside of the range 0...size()-1, an
* {@link ArrayIndexOutOfBoundsException} is thrown.
*/
public void removeAt(int index) {
final E child = mStorage.valueAt(index);
mStorage.removeAt(index);
unregisterChildIf(child);
onChanged();
}
/**
* Remove a range of mappings as a batch.
*
* @param index Index to begin at
* @param size Number of mappings to remove
*
* For indices outside of the range 0...size()-1,
* the behavior is undefined.
*/
public void removeAtRange(int index, int size) {
final ArrayList children = new ArrayList<>();
try {
for (int i = 0; i < size; i++) {
children.add(mStorage.valueAt(i + index));
}
} catch (Exception e) {
// Ignore any exception and proceed with removal.
}
try {
mStorage.removeAtRange(index, size);
} finally {
// Even on exception, make sure to deregister children that have been
// removed.
for (int i = 0; i < size; i++) {
unregisterChildIf(children.get(i));
}
}
onChanged();
}
/**
* 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(int key, E value) {
final E old = mStorage.get(key);
mStorage.put(key, value);
unregisterChildIf(old);
registerChild(value);
onChanged();
}
/**
* Returns the number of key-value mappings that this SparseArray
* currently stores.
*/
public int size() {
return mStorage.size();
}
/**
* Given an index in the range 0...size()-1, returns
* the key from the indexth key-value mapping that this
* SparseArray stores.
*
* The keys corresponding to indices in ascending order are guaranteed to
* be in ascending order, e.g., keyAt(0) will return the
* smallest key and keyAt(size()-1) will return the largest
* key.
*
* For indices outside of the range 0...size()-1,
* the behavior is undefined for apps targeting {@link android.os.Build.VERSION_CODES#P} and
* earlier, and an {@link ArrayIndexOutOfBoundsException} is thrown for apps targeting
* {@link android.os.Build.VERSION_CODES#Q} and later.
*/
public int keyAt(int index) {
return mStorage.keyAt(index);
}
/**
* Given an index in the range 0...size()-1, returns
* the value from the indexth key-value mapping that this
* SparseArray stores.
*
* The values corresponding to indices in ascending order are guaranteed
* to be associated with keys in ascending order, e.g.,
* valueAt(0) will return the value associated with the
* smallest key and valueAt(size()-1) will return the value
* associated with the largest key.
*
* For indices outside of the range 0...size()-1,
* the behavior is undefined for apps targeting {@link android.os.Build.VERSION_CODES#P} and
* earlier, and an {@link ArrayIndexOutOfBoundsException} is thrown for apps targeting
* {@link android.os.Build.VERSION_CODES#Q} and later.
*/
public E valueAt(int index) {
return mStorage.valueAt(index);
}
/**
* Given an index in the range 0...size()-1, sets a new
* value for the indexth key-value mapping that this
* SparseArray stores.
*
* For indices outside of the range 0...size()-1, the behavior is undefined for
* apps targeting {@link android.os.Build.VERSION_CODES#P} and earlier, and an
* {@link ArrayIndexOutOfBoundsException} is thrown for apps targeting
* {@link android.os.Build.VERSION_CODES#Q} and later.
*/
public void setValueAt(int index, E value) {
final E old = mStorage.valueAt(index);
mStorage.setValueAt(index, value);
if (value != old) {
unregisterChildIf(old);
registerChild(value);
onChanged();
}
}
/**
* Returns the index for which {@link #keyAt} would return the
* specified key, or a negative number if the specified
* key is not mapped.
*/
public int indexOfKey(int key) {
return mStorage.indexOfKey(key);
}
/**
* Returns an index for which {@link #valueAt} would return the
* specified value, or a negative number if no keys map to the
* specified value.
* Beware that this is a linear search, unlike lookups by key,
* and that multiple keys can map to the same value and this will
* find only one of them.
*
Note also that unlike most collections' {@code indexOf} methods,
* this method compares values using {@code ==} rather than {@code equals}.
*/
public int indexOfValue(E value) {
return mStorage.indexOfValue(value);
}
/**
* Returns an index for which {@link #valueAt} would return the
* specified value, or a negative number if no keys map to the
* specified value.
*
Beware that this is a linear search, unlike lookups by key,
* and that multiple keys can map to the same value and this will
* find only one of them.
*
Note also that this method uses {@code equals} unlike {@code indexOfValue}.
* @hide
*/
public int indexOfValueByValue(E value) {
return mStorage.indexOfValueByValue(value);
}
/**
* Removes all key-value mappings from this SparseArray.
*/
public void clear() {
// The storage cannot be simply cleared. Each element in the storage must be
// unregistered. Deregistration is only needed if the array is actually
// watching.
if (mWatching) {
final int end = mStorage.size();
for (int i = 0; i < end; i++) {
unregisterChild(mStorage.valueAt(i));
}
}
mStorage.clear();
onChanged();
}
/**
* Puts a key/value pair into the array, optimizing for the case where
* the key is greater than all existing keys in the array.
*/
public void append(int key, E value) {
mStorage.append(key, value);
registerChild(value);
onChanged();
}
@Override
public int hashCode() {
return mStorage.hashCode();
}
@Override
public boolean equals(@Nullable Object o) {
if (o instanceof WatchedSparseArray) {
WatchedSparseArray w = (WatchedSparseArray) o;
return mStorage.equals(w.mStorage);
} else {
return false;
}
}
/**
*
This implementation composes a string by iterating over its mappings. If
* this map contains itself as a value, the string "(this Map)"
* will appear in its place.
*/
@Override
public String toString() {
return mStorage.toString();
}
/**
* Create a copy of the array. If the element is a subclass of Snapper then the copy
* contains snapshots of the elements. Otherwise the copy contains references to the
* elements. The returned snapshot is immutable.
* @return A new array whose elements are the elements of .
*/
public WatchedSparseArray snapshot() {
WatchedSparseArray l = new WatchedSparseArray<>(size());
snapshot(l, this);
return l;
}
/**
* Make a snapshot of the argument. Note that is immutable when the
* method returns. must be empty when the function is called.
* @param r The source array, which is copied into
*/
public void snapshot(@NonNull WatchedSparseArray r) {
snapshot(this, r);
}
/**
* Make the destination a copy of the source. If the element is a subclass of Snapper then the
* copy contains snapshots of the elements. Otherwise the copy contains references to the
* elements. The destination must be initially empty. Upon return, the destination is
* immutable.
* @param dst The destination array. It must be empty.
* @param src The source array. It is not modified.
*/
public static void snapshot(@NonNull WatchedSparseArray dst,
@NonNull WatchedSparseArray src) {
if (dst.size() != 0) {
throw new IllegalArgumentException("snapshot destination is not empty");
}
final int end = src.size();
for (int i = 0; i < end; i++) {
final E val = Snapshots.maybeSnapshot(src.valueAt(i));
final int key = src.keyAt(i);
dst.put(key, val);
}
dst.seal();
}
}