| // 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(); |
| } |
| } |
| } |