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A library jar that provides APIs for Applications written for the Google Android Platform.
/*
* 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 android.util;
import android.os.SystemClock;
import com.android.internal.annotations.GuardedBy;
import java.util.concurrent.TimeoutException;
/**
* This is a helper class for making an async one way call and
* its async one way response response in a sync fashion within
* a timeout. The key idea is to call the remote method with a
* sequence number and a callback and then starting to wait for
* the response. The remote method calls back with the result and
* the sequence number. If the response comes within the timeout
* and its sequence number is the one sent in the method invocation,
* then the call succeeded. If the response does not come within
* the timeout then the call failed.
*
* Typical usage is:
*
*
* public class MyMethodCaller extends TimeoutRemoteCallHelper
*
* @param The type of the expected result.
*
* @hide
*/
public abstract class TimedRemoteCaller {
public static final long DEFAULT_CALL_TIMEOUT_MILLIS = 5000;
private final Object mLock = new Object();
private final long mCallTimeoutMillis;
/** The callbacks we are waiting for, key == sequence id, value == 1 */
@GuardedBy("mLock")
private final SparseIntArray mAwaitedCalls = new SparseIntArray(1);
/** The callbacks we received but for which the result has not yet been reported */
@GuardedBy("mLock")
private final SparseArray mReceivedCalls = new SparseArray<>(1);
@GuardedBy("mLock")
private int mSequenceCounter;
/**
* Create a new timed caller.
*
* @param callTimeoutMillis The time to wait in {@link #getResultTimed} before a timed call will
* be declared timed out
*/
public TimedRemoteCaller(long callTimeoutMillis) {
mCallTimeoutMillis = callTimeoutMillis;
}
/**
* Indicate that a timed call will be made.
*
* @return The sequence id for the call
*/
protected final int onBeforeRemoteCall() {
synchronized (mLock) {
int sequenceId;
do {
sequenceId = mSequenceCounter++;
} while (mAwaitedCalls.get(sequenceId) != 0);
mAwaitedCalls.put(sequenceId, 1);
return sequenceId;
}
}
/**
* Indicate that the timed call has returned.
*
* @param result The result of the timed call
* @param sequence The sequence id of the call (from {@link #onBeforeRemoteCall()})
*/
protected final void onRemoteMethodResult(T result, int sequence) {
synchronized (mLock) {
// Do nothing if we do not await the call anymore as it must have timed out
boolean containedSequenceId = mAwaitedCalls.get(sequence) != 0;
if (containedSequenceId) {
mAwaitedCalls.delete(sequence);
mReceivedCalls.put(sequence, result);
mLock.notifyAll();
}
}
}
/**
* Wait until the timed call has returned.
*
* @param sequence The sequence id of the call (from {@link #onBeforeRemoteCall()})
*
* @return The result of the timed call (set in {@link #onRemoteMethodResult(Object, int)})
*/
protected final T getResultTimed(int sequence) throws TimeoutException {
final long startMillis = SystemClock.uptimeMillis();
while (true) {
try {
synchronized (mLock) {
if (mReceivedCalls.indexOfKey(sequence) >= 0) {
return mReceivedCalls.removeReturnOld(sequence);
}
final long elapsedMillis = SystemClock.uptimeMillis() - startMillis;
final long waitMillis = mCallTimeoutMillis - elapsedMillis;
if (waitMillis <= 0) {
mAwaitedCalls.delete(sequence);
throw new TimeoutException("No response for sequence: " + sequence);
}
mLock.wait(waitMillis);
}
} catch (InterruptedException ie) {
/* ignore */
}
}
}
}