// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.google.devtools.build.lib.shell;
/**
* <p>A simple implementation of {@link KillableObserver} which can be told
* explicitly to kill its {@link Killable} by calling {@link #kill()}. This
* is the sort of functionality that callers might expect to find available
* on the {@link Command} class.</p>
*
* <p>Note that this class can only observe one {@link Killable} at a time;
* multiple instances should be used for concurrent calls to
* {@link Command#execute(byte[], KillableObserver, boolean)}.</p>
*/
public final class SimpleKillableObserver implements KillableObserver {
private Killable killable;
/**
* Does nothing except store a reference to the given {@link Killable}.
*
* @param killable {@link Killable} to kill
*/
@Override
public synchronized void startObserving(final Killable killable) {
this.killable = killable;
}
/**
* Forgets reference to {@link Killable} provided to
* {@link #startObserving(Killable)}
*/
@Override
public synchronized void stopObserving(final Killable killable) {
if (!this.killable.equals(killable)) {
throw new IllegalStateException("start/stopObservering called with " +
"different Killables");
}
this.killable = null;
}
/**
* Calls {@link Killable#kill()} on the saved {@link Killable}.
*/
public synchronized void kill() {
if (killable != null) {
killable.kill();
}
}
}