From c5d1362bfa759c818beebf8e7fd38bb96404a6ba Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gustav=20=C3=85kesson?= <gustav.r.akesson@gmail.com>
Date: Tue, 30 Jul 2013 20:22:42 +0200
Subject: [PATCH] =act #3557 Improved semantics for BoundedBlockingQueue

- Blocking methods lock interruptibly
- drainTo can no longer drain to the backing
- drainTo/clear now calls signalAll instead of signal

Also made some other changes to make the code nicer (I hope!).
---
 .../akka/util/BoundedBlockingQueue.scala      | 103 +++++++++---------
 1 file changed, 50 insertions(+), 53 deletions(-)

diff --git a/akka-actor/src/main/scala/akka/util/BoundedBlockingQueue.scala b/akka-actor/src/main/scala/akka/util/BoundedBlockingQueue.scala
index ccfa1cc408..e079b83bbc 100644
--- a/akka-actor/src/main/scala/akka/util/BoundedBlockingQueue.scala
+++ b/akka-actor/src/main/scala/akka/util/BoundedBlockingQueue.scala
@@ -10,7 +10,7 @@ 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
+ * 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
  * @tparam E - The type of the contents of this Queue
@@ -36,24 +36,36 @@ class BoundedBlockingQueue[E <: AnyRef](
 
   def put(e: E) { //Blocks until not full
     if (e eq null) throw new NullPointerException
-    lock.lock()
+    lock.lockInterruptibly()
     try {
-      while (backing.size() == maxCapacity)
-        notFull.await()
-      require(backing.offer(e))
-      notEmpty.signal()
+      @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 {
-      while (backing.size() == 0)
-        notEmpty.await()
-      val e = backing.poll()
-      require(e ne null)
-      notFull.signal()
-      e
+      @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()
   }
 
@@ -72,50 +84,34 @@ class BoundedBlockingQueue[E <: AnyRef](
 
   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 {
-      @tailrec def awaitNotFull(ns: Long): Boolean =
-        if (backing.size() == maxCapacity) {
-          if (ns > 0) awaitNotFull(notFull.awaitNanos(ns))
-          else false
-        } else true
-
-      if (awaitNotFull(nanos)) {
-        require(backing.offer(e)) //Should never fail
-        notEmpty.signal()
-        true
-      } else false
+      @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
-    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 ⇒
+      @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()
-            result = e
-            true
+            e
+          }
         }
       }
-      result
+      pollElement(unit.toNanos(timeout))
     } finally lock.unlock()
   }
 
@@ -124,7 +120,7 @@ class BoundedBlockingQueue[E <: AnyRef](
     try {
       backing.poll() match {
         case null ⇒ null.asInstanceOf[E]
-        case e ⇒
+        case e    ⇒
           notFull.signal()
           e
       }
@@ -152,7 +148,7 @@ class BoundedBlockingQueue[E <: AnyRef](
     lock.lock()
     try {
       backing.clear()
-      notFull.signal()
+      notFull.signalAll()
     } finally lock.unlock()
   }
 
@@ -178,21 +174,22 @@ class BoundedBlockingQueue[E <: AnyRef](
   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): Int =
+        @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 {
-            notFull.signal()
-            n
-          }
-        drainOne(0)
+          } else n
+        }
+        val n = drainOne()
+        if (n > 0) notFull.signalAll()
+        n
       } finally lock.unlock()
     }
   }