akka.util.LockUtil.scala Maven / Gradle / Ivy
/**
* Copyright (C) 2009-2012 Typesafe Inc.
*/
package akka.util
import java.util.concurrent.locks.{ ReentrantLock }
import java.util.concurrent.atomic.{ AtomicBoolean }
final class ReentrantGuard {
final val lock = new ReentrantLock
@inline
final def withGuard[T](body: ⇒ T): T = {
lock.lock
try {
body
} finally {
lock.unlock
}
}
}
/**
* 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 ⇒
switch.compareAndSet(!from, from) // revert status
throw e
}
true
} else false
}
/**
* Executes the provided action if the lock is on under a lock, so be _very_ careful with longrunning/blocking operations in it
* Only executes the action if the switch is on, and switches it off immediately after obtaining the lock
* Will switch it back on if the provided action throws an exception
*/
def switchOff(action: ⇒ Unit): Boolean = transcend(from = true, action)
/**
* Executes the provided action if the lock is off under a lock, so be _very_ careful with longrunning/blocking operations in it
* Only executes the action if the switch is off, and switches it on immediately after obtaining the lock
* Will switch it back off if the provided action throws an exception
*/
def switchOn(action: ⇒ Unit): Boolean = transcend(from = false, action)
/**
* Switches the switch off (if on), uses locking
*/
def switchOff: Boolean = synchronized { switch.compareAndSet(true, false) }
/**
* Switches the switch on (if off), uses locking
*/
def switchOn: Boolean = synchronized { switch.compareAndSet(false, true) }
/**
* Executes the provided action and returns its value if the switch is IMMEDIATELY on (i.e. no lock involved)
*/
def ifOnYield[T](action: ⇒ T): Option[T] = {
if (switch.get) Some(action)
else None
}
/**
* Executes the provided action and returns its value if the switch is IMMEDIATELY off (i.e. no lock involved)
*/
def ifOffYield[T](action: ⇒ T): Option[T] = {
if (!switch.get) Some(action)
else None
}
/**
* Executes the provided action and returns if the action was executed or not, if the switch is IMMEDIATELY on (i.e. no lock involved)
*/
def ifOn(action: ⇒ Unit): Boolean = {
if (switch.get) {
action
true
} else false
}
/**
* Executes the provided action and returns if the action was executed or not, if the switch is IMMEDIATELY off (i.e. no lock involved)
*/
def ifOff(action: ⇒ Unit): Boolean = {
if (!switch.get) {
action
true
} else false
}
/**
* Executes the provided action and returns its value if the switch is on, waiting for any pending changes to happen before (locking)
* Be careful of longrunning or blocking within the provided action as it can lead to deadlocks or bad performance
*/
def whileOnYield[T](action: ⇒ T): Option[T] = synchronized {
if (switch.get) Some(action)
else None
}
/**
* Executes the provided action and returns its value if the switch is off, waiting for any pending changes to happen before (locking)
* Be careful of longrunning or blocking within the provided action as it can lead to deadlocks or bad performance
*/
def whileOffYield[T](action: ⇒ T): Option[T] = synchronized {
if (!switch.get) Some(action)
else None
}
/**
* Executes the provided action and returns if the action was executed or not, if the switch is on, waiting for any pending changes to happen before (locking)
* Be careful of longrunning or blocking within the provided action as it can lead to deadlocks or bad performance
*/
def whileOn(action: ⇒ Unit): Boolean = synchronized {
if (switch.get) {
action
true
} else false
}
/**
* Executes the provided action and returns if the action was executed or not, if the switch is off, waiting for any pending changes to happen before (locking)
* Be careful of longrunning or blocking within the provided action as it can lead to deadlocks or bad performance
*/
def whileOff(action: ⇒ Unit): Boolean = synchronized {
if (!switch.get) {
action
true
} else false
}
/**
* Executes the provided callbacks depending on if the switch is either on or off waiting for any pending changes to happen before (locking)
* Be careful of longrunning or blocking within the provided action as it can lead to deadlocks or bad performance
*/
def fold[T](on: ⇒ T)(off: ⇒ T) = synchronized {
if (switch.get) on else off
}
/**
* Executes the given code while holding this switch’s lock, i.e. protected from concurrent modification of the switch status.
*/
def locked[T](code: ⇒ T) = synchronized { code }
/**
* Returns whether the switch is IMMEDIATELY on (no locking)
*/
def isOn = switch.get
/**
* Returns whether the switch is IMMEDDIATELY off (no locking)
*/
def isOff = !isOn
}