added one-time channel

Author: rssh

src/main/scala/gopher/channels/OneTimeChannel.scala

@@ -0,0 +1,47 @@
+package gopher.channels
+
+import scala.concurrent._
+import gopher._
+import java.util.concurrent.atomic._
+
+/**
+ * channel, in which only one message can be written,
+ * after which it is automatically closed
+ */
+class OneTimeChannel[T](override val api:GopherAPI) extends Channel[T]
+{
+  val p = Promise[T]()
+  val readed = new AtomicBoolean(false)
+
+  def cbread[B](f: ContRead[T,B] => Option[ContRead.In[T] => Future[Continuated[B]]],ft: FlowTermination[B]): Unit = 
+  {
+   p.future.foreach{ a =>
+       f(ContRead(f,this,ft)) foreach { g =>
+            if (readed.compareAndSet(false,true)) {
+                api.continue(g(ContRead.Value(a)),ft)
+            } else{
+                api.continue(g(ContRead.Skip),ft)
+            }
+       }
+   }(api.executionContext)
+  }
+   
+  def cbwrite[B](f: ContWrite[T,B] => Option[(T, Future[Continuated[B]])],ft: FlowTermination[B]): Unit = 
+  {
+    if (p.isCompleted) {
+       throw new ChannelClosedException()
+    } else {
+       f(ContWrite(f,this,ft)) foreach { case (a, next) =>
+           if (!p.trySuccess(a)) {
+             throw new ChannelClosedException()
+           }
+           api.continue(next,ft)
+       }
+    }
+  }
+
+
+  def close(): Unit = 
+       p failure new ChannelClosedException()
+
+}