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/**
* Copyright (C) 2009-2011 Scalable Solutions AB <http://scalablesolutions.se>
*/
package akka.util
import java.util.concurrent.locks.{ ReentrantReadWriteLock, ReentrantLock }
import java.util.concurrent.atomic.{ AtomicBoolean }
import akka.event.EventHandler
/**
* @author <a href="http://jonasboner.com">Jonas Bonér</a>
*/
final class ReentrantGuard {
val lock = new ReentrantLock
final def withGuard[T](body: => T): T = {
lock.lock
try {
body
} finally {
lock.unlock
}
}
final def tryWithGuard[T](body: => T): T = {
while (!lock.tryLock) { Thread.sleep(10) } // wait on the monitor to be unlocked
try {
body
} finally {
lock.unlock
}
}
}
/**
* @author <a href="http://jonasboner.com">Jonas Bonér</a>
*/
class ReadWriteGuard {
private val rwl = new ReentrantReadWriteLock
val readLock = rwl.readLock
val writeLock = rwl.writeLock
def withWriteGuard[T](body: => T): T = {
writeLock.lock
try {
body
} finally {
writeLock.unlock
}
}
def withReadGuard[T](body: => T): T = {
readLock.lock
try {
body
} finally {
readLock.unlock
}
}
}
/**
* A very simple lock that uses CCAS (Compare Compare-And-Swap)
* Does not keep track of the owner and isn't Reentrant, so don't nest and try to stick to the if*-methods
*/
class SimpleLock {
val acquired = new AtomicBoolean(false)
def ifPossible(perform: () => Unit): Boolean = {
if (tryLock()) {
try {
perform
} finally {
unlock()
}
true
} else false
}
def ifPossibleYield[T](perform: () => T): Option[T] = {
if (tryLock()) {
try {
Some(perform())
} finally {
unlock()
}
} else None
}
def ifPossibleApply[T, R](value: T)(function: (T) => R): Option[R] = {
if (tryLock()) {
try {
Some(function(value))
} finally {
unlock()
}
} else None
}
def tryLock() = {
if (acquired.get) false
else acquired.compareAndSet(false, true)
}
def tryUnlock() = {
acquired.compareAndSet(true, false)
}
def locked = acquired.get
def unlock() {
acquired.set(false)
}
}
/**
* An atomic switch that can be either on or off
*/
class Switch(startAsOn: Boolean = false) {
private val switch = new AtomicBoolean(startAsOn)
protected def transcend(from: Boolean, action: => Unit): Boolean = synchronized {
if (switch.compareAndSet(from, !from)) {
try {
action
} catch {
case e: Throwable =>
EventHandler.error(e, this, e.getMessage)
switch.compareAndSet(!from, from) // revert status
throw e
}
true
} else false
}
def switchOff(action: => Unit): Boolean = transcend(from = true, action)
def switchOn(action: => Unit): Boolean = transcend(from = false, action)
def switchOff: Boolean = synchronized { switch.compareAndSet(true, false) }
def switchOn: Boolean = synchronized { switch.compareAndSet(false, true) }
def ifOnYield[T](action: => T): Option[T] = {
if (switch.get) Some(action)
else None
}
def ifOffYield[T](action: => T): Option[T] = {
if (!switch.get) Some(action)
else None
}
def ifOn(action: => Unit): Boolean = {
if (switch.get) {
action
true
} else false
}
def ifOff(action: => Unit): Boolean = {
if (!switch.get) {
action
true
} else false
}
def whileOnYield[T](action: => T): Option[T] = synchronized {
if (switch.get) Some(action)
else None
}
def whileOffYield[T](action: => T): Option[T] = synchronized {
if (!switch.get) Some(action)
else None
}
def whileOn(action: => Unit): Boolean = synchronized {
if (switch.get) {
action
true
} else false
}
def whileOff(action: => Unit): Boolean = synchronized {
if (switch.get) {
action
true
} else false
}
def ifElseYield[T](on: => T)(off: => T) = synchronized {
if (switch.get) on else off
}
def isOn = switch.get
def isOff = !isOn
}
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