akka.util.BoundedBlockingQueue.scala Maven / Gradle / Ivy
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/**
* Copyright (C) 2009-2016 Lightbend Inc.
*/
package akka.util
import java.util.concurrent.locks.ReentrantLock
import java.util.concurrent.{ TimeUnit, BlockingQueue }
import java.util.{ AbstractQueue, Queue, Collection, Iterator }
import annotation.tailrec
/**
* BoundedBlockingQueue wraps any Queue and turns the result into a BlockingQueue with a limited capacity.
* @param maxCapacity - the maximum capacity of this Queue, needs to be > 0
* @param backing - the backing Queue
*/
class BoundedBlockingQueue[E <: AnyRef](
val maxCapacity: Int, private val backing: Queue[E]) extends AbstractQueue[E] with BlockingQueue[E] {
backing match {
case null ⇒ throw new IllegalArgumentException("Backing Queue may not be null")
case b: BlockingQueue[_] ⇒
require(maxCapacity > 0)
require(b.size() == 0)
require(b.remainingCapacity >= maxCapacity)
case b: Queue[_] ⇒
require(b.size() == 0)
require(maxCapacity > 0)
}
protected val lock = new ReentrantLock(false)
private val notEmpty = lock.newCondition()
private val notFull = lock.newCondition()
def put(e: E) { //Blocks until not full
if (e eq null) throw new NullPointerException
lock.lockInterruptibly()
try {
@tailrec def putElement() {
if (backing.size() < maxCapacity) {
require(backing.offer(e))
notEmpty.signal()
} else {
notFull.await()
putElement()
}
}
putElement()
} finally lock.unlock()
}
def take(): E = { //Blocks until not empty
lock.lockInterruptibly()
try {
@tailrec def takeElement(): E = {
if (!backing.isEmpty()) {
val e = backing.poll()
require(e ne null)
notFull.signal()
e
} else {
notEmpty.await()
takeElement()
}
}
takeElement()
} finally lock.unlock()
}
def offer(e: E): Boolean = { //Tries to do it immediately, if fail return false
if (e eq null) throw new NullPointerException
lock.lock()
try {
if (backing.size() == maxCapacity) false
else {
require(backing.offer(e)) //Should never fail
notEmpty.signal()
true
}
} finally lock.unlock()
}
def offer(e: E, timeout: Long, unit: TimeUnit): Boolean = { //Tries to do it within the timeout, return false if fail
if (e eq null) throw new NullPointerException
lock.lockInterruptibly()
try {
@tailrec def offerElement(remainingNanos: Long): Boolean = {
if (backing.size() < maxCapacity) {
require(backing.offer(e)) //Should never fail
notEmpty.signal()
true
} else if (remainingNanos <= 0) false
else offerElement(notFull.awaitNanos(remainingNanos))
}
offerElement(unit.toNanos(timeout))
} finally lock.unlock()
}
def poll(timeout: Long, unit: TimeUnit): E = { //Tries to do it within the timeout, returns null if fail
lock.lockInterruptibly()
try {
@tailrec def pollElement(remainingNanos: Long): E = {
backing.poll() match {
case null if remainingNanos <= 0 ⇒ null.asInstanceOf[E]
case null ⇒ pollElement(notEmpty.awaitNanos(remainingNanos))
case e ⇒ {
notFull.signal()
e
}
}
}
pollElement(unit.toNanos(timeout))
} finally lock.unlock()
}
def poll(): E = { //Tries to remove the head of the queue immediately, if fail, return null
lock.lock()
try {
backing.poll() match {
case null ⇒ null.asInstanceOf[E]
case e ⇒
notFull.signal()
e
}
} finally lock.unlock()
}
override def remove(e: AnyRef): Boolean = { //Tries to do it immediately, if fail, return false
if (e eq null) throw new NullPointerException
lock.lock()
try {
if (backing remove e) {
notFull.signal()
true
} else false
} finally lock.unlock()
}
override def contains(e: AnyRef): Boolean = {
if (e eq null) throw new NullPointerException
lock.lock()
try backing.contains(e) finally lock.unlock()
}
override def clear() {
lock.lock()
try {
backing.clear()
notFull.signalAll()
} finally lock.unlock()
}
def remainingCapacity(): Int = {
lock.lock()
try {
maxCapacity - backing.size()
} finally lock.unlock()
}
def size(): Int = {
lock.lock()
try backing.size() finally lock.unlock()
}
def peek(): E = {
lock.lock()
try backing.peek() finally lock.unlock()
}
def drainTo(c: Collection[_ >: E]): Int = drainTo(c, Int.MaxValue)
def drainTo(c: Collection[_ >: E], maxElements: Int): Int = {
if (c eq null) throw new NullPointerException
if (c eq this) throw new IllegalArgumentException
if (c eq backing) throw new IllegalArgumentException
if (maxElements <= 0) 0
else {
lock.lock()
try {
@tailrec def drainOne(n: Int = 0): Int = {
if (n < maxElements) {
backing.poll() match {
case null ⇒ n
case e ⇒ c add e; drainOne(n + 1)
}
} else n
}
val n = drainOne()
if (n > 0) notFull.signalAll()
n
} finally lock.unlock()
}
}
override def containsAll(c: Collection[_]): Boolean = {
lock.lock()
try backing.containsAll(c) finally lock.unlock()
}
override def removeAll(c: Collection[_]): Boolean = {
lock.lock()
try {
if (backing.removeAll(c)) {
val sz = backing.size()
if (sz < maxCapacity) notFull.signal()
if (sz > 0) notEmpty.signal()
true
} else false
} finally lock.unlock()
}
override def retainAll(c: Collection[_]): Boolean = {
lock.lock()
try {
if (backing.retainAll(c)) {
val sz = backing.size()
if (sz < maxCapacity) notFull.signal()
if (sz > 0) notEmpty.signal()
true
} else false
} finally lock.unlock()
}
def iterator(): Iterator[E] = {
lock.lock
try {
val elements = backing.toArray
new Iterator[E] {
var at = 0
var last = -1
def hasNext(): Boolean = at < elements.length
def next(): E = {
if (at >= elements.length) throw new NoSuchElementException
last = at
at += 1
elements(last).asInstanceOf[E]
}
override def remove() {
if (last < 0) throw new IllegalStateException
val target = elements(last)
last = -1 //To avoid 2 subsequent removes without a next in between
lock.lock()
try {
@tailrec def removeTarget(i: Iterator[E] = backing.iterator()): Unit =
if (i.hasNext) {
if (i.next eq target) {
i.remove()
notFull.signal()
} else removeTarget(i)
}
removeTarget()
} finally lock.unlock()
}
}
} finally lock.unlock()
}
override def toArray(): Array[AnyRef] = {
lock.lock()
try backing.toArray finally lock.unlock()
}
override def isEmpty(): Boolean = {
lock.lock()
try backing.isEmpty() finally lock.unlock()
}
override def toArray[X](a: Array[X with AnyRef]) = {
lock.lock()
try backing.toArray[X](a) finally lock.unlock()
}
}