akka.util.LockUtil.scala Maven / Gradle / Ivy
/*
* Copyright (C) 2009-2019 Lightbend Inc.
*/
package akka.util
import java.util.concurrent.locks.ReentrantLock
import java.util.concurrent.atomic.AtomicBoolean
final class ReentrantGuard extends ReentrantLock {
@inline
final def withGuard[T](body: => T): T = {
lock()
try body
finally unlock()
}
}
/**
* An atomic switch that can be either on or off
*/
class Switch(startAsOn: Boolean = false) {
private val switch = new AtomicBoolean(startAsOn) // FIXME switch to AQS
protected def transcend(from: Boolean, action: => Unit): Boolean = synchronized {
if (switch.compareAndSet(from, !from)) {
try action
catch {
case t: Throwable =>
switch.compareAndSet(!from, from) // revert status
throw t
}
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): 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): T = synchronized { code }
/**
* Returns whether the switch is IMMEDIATELY on (no locking)
*/
def isOn: Boolean = switch.get
/**
* Returns whether the switch is IMMEDIATELY off (no locking)
*/
def isOff: Boolean = !isOn
}
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