/*
* Copyright 2016-present Facebook, 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.facebook.buck.util.concurrent;
import com.facebook.buck.log.Logger;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Makes it simple to assert that access to a piece of code should be done from one thread at a time
* in a non-reentrant manner.
*/
public class AssertScopeExclusiveAccess {
private static final Logger LOG = Logger.get(AssertScopeExclusiveAccess.class);
private final AtomicBoolean inScope;
private Optional<Throwable> inScopeStack;
public AssertScopeExclusiveAccess() {
inScope = new AtomicBoolean();
inScopeStack = Optional.empty();
}
public Scope scope() {
final boolean firstOneInScope = inScope.compareAndSet(false, true);
if (firstOneInScope && LOG.isVerboseEnabled()) {
inScopeStack = Optional.of(new Throwable());
}
if (!firstOneInScope) {
LOG.verbose(inScopeStack.get(), "Indicating previous access to single threaded scope.");
throw new IllegalStateException(
"More than one thread attempting access to single-threaded scope.");
}
return () -> {
if (firstOneInScope) {
inScope.set(false);
}
};
}
public interface Scope extends AutoCloseable {
@Override
void close();
}
}