From cf7c5917c984a424af718863d2cf0574cd710651 Mon Sep 17 00:00:00 2001
From: Philipp Haller <hallerp@gmail.com>
Date: Sun, 21 Jan 2007 14:19:36 +0000
Subject: Added fast message queue implementation.

---
 src/actors/scala/actors/MessageQueue.scala | 86 ++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 src/actors/scala/actors/MessageQueue.scala

(limited to 'src/actors')

diff --git a/src/actors/scala/actors/MessageQueue.scala b/src/actors/scala/actors/MessageQueue.scala
new file mode 100644
index 0000000000..4503065d8a
--- /dev/null
+++ b/src/actors/scala/actors/MessageQueue.scala
@@ -0,0 +1,86 @@
+
+package scala.actors
+
+/**
+ * This class is used by our efficient message queue
+ * implementation.
+ *
+ * @version 0.9.2
+ * @author Philipp Haller
+ */
+class MessageQueueElement {
+  var msg: Any = _
+  var session: Channel[Any] = null
+  var next: MessageQueueElement = null
+}
+
+/**
+ * The class <code>MessageQueue</code> provides an efficient
+ * implementation of a message queue specialized for this actor
+ * library. Classes in this package are supposed to be the only
+ * clients of this class.
+ *
+ * @version 0.9.2
+ * @author Philipp Haller
+ */
+class MessageQueue {
+  var first: MessageQueueElement = null
+  // last == null iff list empty
+  var last: MessageQueueElement = null
+
+  def append(msg: Any, session: Channel[Any]) = {
+    if (null eq last) { // list empty
+      val el = new MessageQueueElement
+      el.msg = msg
+      el.session = session
+      first = el
+      last = el
+    }
+    else {
+      val el = new MessageQueueElement
+      el.msg = msg
+      el.session = session
+      last.next = el
+      last = el
+    }
+  }
+
+  def extractFirst(p: Any => boolean): MessageQueueElement = {
+    if (null eq last) null
+    else {
+      // test first element
+      if (p(first.msg)) {
+        val tmp = first
+        // remove first element
+        first = first.next
+
+        // might have to update last
+        if (tmp eq last) {
+          last = null
+        }
+
+        tmp
+      }
+      else {
+        var curr = first
+        var prev = curr
+        while(curr.next != null) {
+          prev = curr
+          curr = curr.next
+          if (p(curr.msg)) {
+            // remove curr
+            prev.next = curr.next
+
+            // might have to update last
+            if (curr eq last) {
+              last = prev
+            }
+
+            return curr
+          }
+        }
+        null
+      }
+    }
+  }
+}
-- 
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