/*
* Copyright 2011 Google Inc.
*
* 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.ipc.invalidation.ticl;
import com.google.common.base.Preconditions;
import com.google.ipc.invalidation.util.Marshallable;
import com.google.protos.ipc.invalidation.Client.RunStateP;
/**
* An abstraction that keeps track of whether the caller is started or stopped and only allows
* the following transitions NOT_STARTED -> STARTED -> STOPPED. This class is thread-safe.
*
*
*/
public class RunState implements Marshallable<RunStateP> {
/** Current run state. */
private RunStateP.State currentState;
private Object lock = new Object();
/** Constructs a new instance in the {@code NOT_STARTED} state. */
public RunState() {
currentState = RunStateP.State.NOT_STARTED;
}
/** Constructs a new instance with the state given in {@code runState}. */
RunState(RunStateP runState) {
this.currentState = runState.getState();
}
/**
* Marks the current state to be STARTED.
* <p>
* REQUIRES: Current state is NOT_STARTED.
*/
public void start() {
synchronized (lock) {
Preconditions.checkState(currentState == RunStateP.State.NOT_STARTED,
"Cannot start: %s", currentState);
currentState = RunStateP.State.STARTED;
}
}
/**
* Marks the current state to be STOPPED.
* <p>
* REQUIRES: Current state is STARTED.
*/
public void stop() {
synchronized (lock) {
Preconditions.checkState(currentState == RunStateP.State.STARTED,
"Cannot stop: %s", currentState);
currentState = RunStateP.State.STOPPED;
}
}
/**
* Returns true iff {@link #start} has been called on this but {@link #stop} has not been called.
*/
public boolean isStarted() {
synchronized (lock) {
return currentState == RunStateP.State.STARTED;
}
}
/** Returns true iff {@link #start} and {@link #stop} have been called on this object. */
public boolean isStopped() {
synchronized (lock) {
return currentState == RunStateP.State.STOPPED;
}
}
@Override
public RunStateP marshal() {
return RunStateP.newBuilder().setState(currentState).build();
}
@Override
public String toString() {
return "<RunState: " + currentState + ">";
}
}