/**
* @param key Key to lock.
* @return Sync object that should be passed to {@link #unlock(Object, Object)} method.
*/
public <T> Object lock(T key) {
assert key != null;
boolean interrupted = false;
Sync t = new Sync();
try {
while (true) {
Sync old = locks.putIfAbsent(key, t);
if (old != null) {
while (true) {
try {
old.await();
break;
} catch (InterruptedException ignored) {
interrupted = true;
}
}
} else return t;
}
} finally {
if (interrupted) Thread.currentThread().interrupt();
}
}
/**
* @param key Key to lock.
* @return Sync object that should be passed to {@link #unlock(Object, Object)} method.
* @throws InterruptedException If interrupted while acquiring lock.
*/
public <T> Object lockInterruptibly(T key) throws InterruptedException {
assert key != null;
Sync t = new Sync();
while (true) {
Sync old = locks.putIfAbsent(key, t);
if (old != null) old.await();
else return t;
}
}
/**
* @param key Key.
* @param sync Sync that got from {@link #lockInterruptibly(Object)} call.
*/
public <T> void unlock(T key, Object sync) {
if (!locks.remove(key, sync))
throw new IllegalStateException("Lock has not been acquired for key: " + key);
((Sync) sync).finish();
}