diff --git a/com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/RChannel.java b/com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/RChannel.java
new file mode 100644
index 0000000000000000000000000000000000000000..49b668807d232a7ca5ae852b949339f271501be2
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+++ b/com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/RChannel.java
@@ -0,0 +1,165 @@
+/*
+ * Copyright (c) 2015, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.truffle.r.runtime;
+
+import java.util.concurrent.*;
+
+import com.oracle.truffle.r.runtime.data.*;
+
+/**
+ * Implementation of a channel abstraction used for communication between parallel contexts in
+ * shared memory space.
+ */
+public class RChannel {
+
+ private final static int INITIAL_CHANNEL_NUM = 4;
+ private final static int CHANNEL_NUM_GROW_FACTOR = 2;
+ private final static int QUEUE_CAPACITY = 1;
+
+ private static int[] keys = new int[INITIAL_CHANNEL_NUM];
+ private static RChannel[] channels = new RChannel[INITIAL_CHANNEL_NUM];
+
+ /*
+ * Used to mediate access to the semaphore instances
+ */
+ private final static Semaphore create = new Semaphore(1, true);
+
+ private final ArrayBlockingQueue<Object> masterToClient = new ArrayBlockingQueue<>(QUEUE_CAPACITY);
+ private final ArrayBlockingQueue<Object> clientToMaster = new ArrayBlockingQueue<>(QUEUE_CAPACITY);
+
+ public static int createChannel(int key) {
+ if (key == 0) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "channel's key must be non-zero");
+ }
+ try {
+ create.acquire();
+ while (true) {
+ int freeSlot = -1;
+ // start from one as we need slots that have distinguishable positive and negative
+ // value
+ for (int i = 1; i < keys.length; i++) {
+ if (keys[i] == key) {
+ create.release();
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "channel with specified key already exists");
+ }
+ if (keys[i] == 0 && freeSlot == -1) {
+ freeSlot = i;
+ }
+
+ }
+ if (freeSlot != -1) {
+ keys[freeSlot] = key;
+ channels[freeSlot] = new RChannel();
+ create.release();
+ return freeSlot;
+ } else {
+ int[] keysTmp = new int[keys.length * CHANNEL_NUM_GROW_FACTOR];
+ RChannel[] channelsTmp = new RChannel[channels.length * CHANNEL_NUM_GROW_FACTOR];
+ for (int i = 1; i < keys.length; i++) {
+ keysTmp[i] = keys[i];
+ channelsTmp[i] = channels[i];
+ }
+ keys = keysTmp;
+ channels = channelsTmp;
+ }
+ }
+ } catch (InterruptedException x) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "error creating a channel");
+ }
+ }
+
+ public static int getChannel(int key) {
+ try {
+ create.acquire();
+ for (int i = 1; i < keys.length; i++) {
+ if (keys[i] == key) {
+ create.release();
+ return -i;
+ }
+ }
+ create.release();
+ } catch (InterruptedException x) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "error accessing channel");
+ }
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "channel does not exist");
+ }
+
+ public static void closeChannel(int id) {
+ int actualId = Math.abs(id);
+ try {
+ create.acquire();
+ if (actualId == 0 || actualId >= channels.length || channels[actualId] == null) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "channel with specified id does not exist");
+ }
+ keys[actualId] = 0;
+ channels[actualId] = null;
+ create.release();
+ } catch (InterruptedException x) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "error closing channel");
+ }
+ }
+
+ private static RChannel getChannelFromId(int id) {
+ int actualId = Math.abs(id);
+ try {
+ create.acquire();
+ if (actualId == 0 || actualId >= channels.length || channels[actualId] == null) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "channel with specified id does not exist");
+ }
+ RChannel channel = channels[actualId];
+ create.release();
+ return channel;
+ } catch (InterruptedException x) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "error transmitting through channel");
+ }
+ }
+
+ public static void send(int id, Object data) {
+ RChannel channel = getChannelFromId(id);
+ if (data instanceof RShareable) {
+ // make sure that what's passed through the channel will be copied on the first update
+ RShareable shareable = (RShareable) data;
+ if (FastROptions.NewStateTransition) {
+ shareable.incRefCount();
+ shareable.incRefCount();
+ } else {
+ shareable.makeShared();
+ }
+ }
+ try {
+ (id > 0 ? channel.masterToClient : channel.clientToMaster).put(data);
+ } catch (InterruptedException x) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "error sending through the channel");
+ }
+ }
+
+ public static Object receive(int id) {
+ RChannel channel = getChannelFromId(id);
+ try {
+ return (id < 0 ? channel.masterToClient : channel.clientToMaster).take();
+ } catch (InterruptedException x) {
+ throw RError.error(RError.NO_NODE, RError.Message.GENERIC, "error receiving from the channel");
+ }
+ }
+
+}