akka.util.BoundedBlockingQueue.scala Maven / Gradle / Ivy
/**
* Copyright (C) 2009-2012 Typesafe Inc.
*/
package akka.util
import java.util.concurrent.locks.ReentrantLock
import java.util.concurrent.{ TimeUnit, BlockingQueue }
import java.util.{ AbstractQueue, Queue, Collection, Iterator }
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.lock()
try {
while (backing.size() == maxCapacity)
notFull.await()
require(backing.offer(e))
notEmpty.signal()
} finally {
lock.unlock()
}
}
def take(): E = { //Blocks until not empty
lock.lockInterruptibly()
try {
while (backing.size() == 0)
notEmpty.await()
val e = backing.poll()
require(e ne null)
notFull.signal()
e
} 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
var nanos = unit.toNanos(timeout)
lock.lockInterruptibly()
try {
while (backing.size() == maxCapacity) {
if (nanos <= 0)
return false
else
nanos = notFull.awaitNanos(nanos)
}
require(backing.offer(e)) //Should never fail
notEmpty.signal()
true
} finally {
lock.unlock()
}
}
def poll(timeout: Long, unit: TimeUnit): E = { //Tries to do it within the timeout, returns null if fail
var nanos = unit.toNanos(timeout)
lock.lockInterruptibly()
try {
var result: E = null.asInstanceOf[E]
var hasResult = false
while (!hasResult) {
hasResult = backing.poll() match {
case null if nanos <= 0 ⇒
result = null.asInstanceOf[E]
true
case null ⇒
try {
nanos = notEmpty.awaitNanos(nanos)
} catch {
case ie: InterruptedException ⇒
notEmpty.signal()
throw ie
}
false
case e ⇒
notFull.signal()
result = e
true
}
}
result
} 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
} 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 (maxElements <= 0) 0
else {
lock.lock()
try {
var n = 0
var e: E = null.asInstanceOf[E]
while (n < maxElements) {
backing.poll() match {
case null ⇒ return n
case e ⇒
c add e
n += 1
}
}
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]
}
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 {
val i = backing.iterator()
while (i.hasNext) {
if (i.next eq target) {
i.remove()
notFull.signal()
return ()
}
}
} 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()
}
}
}
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