akka.util.BoundedBlockingQueue.scala Maven / Gradle / Ivy
/*
* Copyright (C) 2009-2020 Lightbend Inc.
*/
package akka.util
import java.util.{ AbstractQueue, Collection, Iterator, Queue }
import java.util.concurrent.{ BlockingQueue, TimeUnit }
import java.util.concurrent.locks.{ Condition, ReentrantLock }
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 = createLock()
protected val notEmpty = createNotEmptyCondition()
protected val notFull = createNotFullCondition()
protected def createLock(): ReentrantLock = new ReentrantLock(false)
protected def createNotEmptyCondition(): Condition = lock.newCondition()
protected def createNotFullCondition(): Condition = lock.newCondition()
def put(e: E): Unit = { //Blocks until not full
if (e eq null) throw new NullPointerException
lock.lockInterruptibly()
try {
@tailrec def putElement(): Unit = {
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(): Unit = {
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(): Unit = {
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()
}
}