/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.camera.async;
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import com.google.common.annotations.VisibleForTesting;
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import com.google.common.base.Preconditions;
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/**
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* Wraps an object with reference counting. When the reference count goes to 0
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* for the first time, the object is closed.
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*/
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public class RefCountBase<T extends SafeCloseable> implements SafeCloseable {
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private final Object mLock;
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private final T mObject;
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private int mRefCount;
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private boolean mObjectClosed;
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public RefCountBase(T object) {
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this(object, 1);
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}
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public RefCountBase(T object, int initialReferenceCount) {
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Preconditions.checkState(
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initialReferenceCount > 0, "initialReferenceCount is not greater than 0.");
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mLock = new Object();
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mObject = object;
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mRefCount = initialReferenceCount;
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mObjectClosed = false;
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}
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public void addRef() {
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synchronized (mLock) {
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Preconditions.checkState(!mObjectClosed,
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"addRef on an object which has been closed.");
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mRefCount++;
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}
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}
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public T get() {
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return mObject;
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}
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@Override
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public void close() {
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synchronized (mLock) {
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// A SafeCloseable must tolerate multiple calls to close().
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if (mObjectClosed) {
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return;
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}
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mRefCount--;
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if (mRefCount > 0) {
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return;
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}
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mObjectClosed = true;
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}
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// Do this outside of the mLock critical section for speed and to avoid
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// deadlock.
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mObject.close();
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}
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@VisibleForTesting
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public int getRefCount() {
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synchronized (mLock) {
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return mRefCount;
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}
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}
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}
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