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/*
* Copyright 2014 Higher Frequency Trading http://www.higherfrequencytrading.com
*
* 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 net.openhft.chronicle.algo.locks;
import net.openhft.chronicle.algo.bytes.Access;
import net.openhft.chronicle.core.threads.ThreadHints;
import java.util.concurrent.TimeUnit;
public final class AcquisitionStrategies {
private AcquisitionStrategies() {
}
public static
AcquisitionStrategy spinLoop(long duration, TimeUnit unit) {
return new SpinLoopAcquisitionStrategy<>(duration, unit);
}
public static
AcquisitionStrategy spinLoopOrFail(long duration, TimeUnit unit) {
return new SpinLoopOrFailAcquisitionStrategy<>(duration, unit);
}
public static
AcquisitionStrategy spinLoopRegisteringWaitOrFail(
long duration, TimeUnit unit) {
return new SpinLoopWriteWithWaitsAcquisitionStrategy<>(duration, unit);
}
private static class SpinLoopAcquisitionStrategy
implements AcquisitionStrategy {
private final long durationNanos;
private SpinLoopAcquisitionStrategy(long duration, TimeUnit unit) {
durationNanos = unit.toNanos(duration);
}
@Override
public boolean acquire(TryAcquireOperation operation, S strategy,
Access access, T t, long offset) {
if (operation.tryAcquire(strategy, access, t, offset))
return true;
long deadLineNanos = System.nanoTime() + durationNanos;
beforeLoop(strategy, access, t, offset);
do {
if (operation.tryAcquire(strategy, access, t, offset))
return true;
ThreadHints.onSpinWait();
} while (deadLineNanos - System.nanoTime() >= 0L); // overflow-cautious
afterLoop(strategy, access, t, offset);
return end();
}
void beforeLoop(S strategy, Access access, T t, long offset) {
}
void afterLoop(S strategy, Access access, T t, long offset) {
}
boolean end() {
return false;
}
}
private static class SpinLoopOrFailAcquisitionStrategy
extends SpinLoopAcquisitionStrategy {
private SpinLoopOrFailAcquisitionStrategy(long duration, TimeUnit unit) {
super(duration, unit);
}
@Override
boolean end() {
throw new IllegalStateException("Failed to acquire the lock");
}
}
private static class SpinLoopWriteWithWaitsAcquisitionStrategy<
S extends ReadWriteWithWaitsLockingStrategy>
extends SpinLoopOrFailAcquisitionStrategy {
private SpinLoopWriteWithWaitsAcquisitionStrategy(long duration, TimeUnit unit) {
super(duration, unit);
}
@Override
void beforeLoop(S strategy, Access access, T t, long offset) {
strategy.registerWait(access, t, offset);
}
@Override
void afterLoop(S strategy, Access access, T t, long offset) {
strategy.deregisterWait(access, t, offset);
}
}
}
