/*
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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 java.util.concurrent.Executor;
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import java.util.concurrent.ScheduledExecutorService;
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import java.util.concurrent.ScheduledFuture;
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import java.util.concurrent.TimeUnit;
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/**
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* An executor which executes with a delay, discarding pending executions such
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* that at most one task is queued at any time.
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*/
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public class ResettingDelayedExecutor implements Executor, SafeCloseable {
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private final ScheduledExecutorService mExecutor;
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private final long mDelay;
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private final TimeUnit mDelayUnit;
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/**
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* Lock for all mutable state: {@link #mLatestRunRequest} and
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* {@link #mClosed}.
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*/
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private final Object mLock;
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private ScheduledFuture<?> mLatestRunRequest;
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private boolean mClosed;
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public ResettingDelayedExecutor(ScheduledExecutorService executor, long delay, TimeUnit
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delayUnit) {
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mExecutor = executor;
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mDelay = delay;
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mDelayUnit = delayUnit;
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mLock = new Object();
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mClosed = false;
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}
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/**
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* Resets any pending executions.
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*/
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public void reset() {
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synchronized (mLock) {
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// Cancel any existing, queued task before scheduling another.
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if (mLatestRunRequest != null) {
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mLatestRunRequest.cancel(false /* mayInterruptIfRunning */);
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}
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}
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}
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@Override
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public void execute(Runnable runnable) {
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synchronized (mLock) {
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if (mClosed) {
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return;
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}
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reset();
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mLatestRunRequest = mExecutor.schedule(runnable, mDelay, mDelayUnit);
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}
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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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if (mClosed) {
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return;
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}
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mClosed = true;
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mExecutor.shutdownNow();
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}
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}
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}
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