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BoundedBlockingQueue.scala
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BoundedBlockingQueue.scala
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package gakesson.util.concurrent.scala
import java.util.AbstractQueue
import java.util.concurrent.BlockingQueue
import java.util.concurrent.locks.ReentrantLock
import java.util.concurrent.TimeUnit
import java.util.Queue
import java.util.Collection
import java.util.Iterator
import java.util.concurrent.locks.Condition
import scala.annotation.tailrec
class BoundedBlockingQueue[E <: AnyRef](private val backingQueue: Queue[E], private val capacity: Int, private val fair: Boolean)
extends AbstractQueue[E] with BlockingQueue[E] {
backingQueue match {
case null => throw new IllegalArgumentException
case b: Queue[_] => {
require(b.size() <= capacity)
require(capacity > 0)
}
}
private val lock = new ReentrantLock(fair)
private val notEmpty = lock.newCondition()
private val notFull = lock.newCondition()
@throws[InterruptedException]
def put(e: E) {
if (e eq null) throw new NullPointerException
lock.lockInterruptibly()
try {
@tailrec def putOne(e: E) {
if (backingQueue.size() < capacity) {
backingQueue.add(e)
notEmpty.signal()
} else {
notFull.await()
putOne(e)
}
}
putOne(e)
} finally lock.unlock();
}
def offer(e: E): Boolean = {
if (e eq null) throw new NullPointerException
lock.lock()
try {
if (backingQueue.size() < capacity) {
backingQueue.add(e)
notEmpty.signal()
true
} else false
} finally lock.unlock()
}
@throws[InterruptedException]
def offer(e: E, timeout: Long, unit: TimeUnit): Boolean = {
if (e eq null) throw new NullPointerException
val timeoutNanos = unit.toNanos(timeout)
lock.lockInterruptibly()
try {
@tailrec def offerOne(e: E, timeoutNanos: Long): Boolean = {
if (backingQueue.size() < capacity) {
backingQueue.add(e)
notEmpty.signal()
true
} else if (timeoutNanos > 0) offerOne(e, notFull.awaitNanos(timeoutNanos))
else false
}
offerOne(e, timeoutNanos)
} finally lock.unlock()
}
@throws[InterruptedException]
def take(): E = {
lock.lockInterruptibly()
try {
@tailrec def takeOne(): E = {
if (!backingQueue.isEmpty()) {
val e = backingQueue.remove()
notFull.signal()
e
} else {
notEmpty.await()
takeOne()
}
}
takeOne()
} finally lock.unlock()
}
def poll(): E = {
lock.lock()
try {
backingQueue.poll() match {
case null => null.asInstanceOf[E]
case e =>
notFull.signal()
e
}
} finally lock.unlock()
}
@throws[InterruptedException]
def poll(timeout: Long, unit: TimeUnit): E = {
val timeoutNanos = unit.toNanos(timeout)
lock.lockInterruptibly()
try {
@tailrec def pollOne(timeoutNanos: Long): E = {
if (!backingQueue.isEmpty()) {
backingQueue.poll() match {
case null => null.asInstanceOf[E]
case e =>
notFull.signal()
e
}
} else if (timeoutNanos > 0) pollOne(notEmpty.awaitNanos(timeoutNanos))
else null.asInstanceOf[E]
}
pollOne(timeoutNanos)
} finally lock.unlock()
}
def peek(): E = {
lock.lock()
try {
backingQueue.peek()
} finally lock.unlock()
}
def remainingCapacity(): Int = {
lock.lock()
try {
capacity - size()
} finally lock.unlock()
}
override def remove(o: AnyRef): Boolean = {
if (o eq null) throw new NullPointerException
lock.lock()
try {
backingQueue.remove(o) match {
case false => false
case true =>
notFull.signal()
true
}
} finally lock.unlock()
}
override def contains(o: AnyRef): Boolean = {
if (o eq null) throw new NullPointerException
lock.lock()
try {
backingQueue.contains(o)
} finally lock.unlock()
}
def size(): Int = {
lock.lock()
try {
backingQueue.size()
} finally lock.unlock()
}
override def clear() {
lock.lock()
try {
backingQueue.clear()
notFull.signalAll()
} 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
require(c ne this)
require(c ne backingQueue)
lock.lock()
try {
@tailrec def drainOne(n: Int = 0): Int = {
if (n < maxElements && !backingQueue.isEmpty()) {
c.add(backingQueue.remove())
drainOne(n + 1)
} else n
}
val n = drainOne()
if (n > 0) notFull.signalAll()
n
} finally lock.unlock()
}
def iterator(): Iterator[E] = {
lock.lock()
try {
val queueElements = backingQueue.toArray()
new Iterator[E] {
private def NO_INDEX: Int = { -1 }
private var currentIndex = 0
private var lastReturnedIndex = NO_INDEX
def hasNext(): Boolean = {
currentIndex < queueElements.length
}
def next(): E = {
if (!hasNext()) throw new NoSuchElementException
val element = queueElements(currentIndex)
lastReturnedIndex = currentIndex
currentIndex = currentIndex + 1
element.asInstanceOf[E]
}
def remove() {
if (lastReturnedIndex == NO_INDEX) throw new IllegalStateException
val removeIndex = lastReturnedIndex
lastReturnedIndex = NO_INDEX
def removeElementByIdentity(o: AnyRef) {
lock.lock()
try {
@tailrec def removeTarget(queueIterator: Iterator[E] = backingQueue.iterator()) {
if (queueIterator.hasNext()) {
if (queueIterator.next() eq o) {
queueIterator.remove()
notFull.signal()
} else removeTarget(queueIterator)
}
}
removeTarget()
} finally lock.unlock()
}
removeElementByIdentity(queueElements(removeIndex))
}
}
} finally lock.unlock()
}
}