3 files changed, 124 insertions, 0 deletions
diff --git a/src/main/java/derms/net/tomulticast/Message.java b/src/main/java/derms/net/tomulticast/Message.java
new file mode 100644
index 0000000..035e968
--- /dev/null
+++ b/src/main/java/derms/net/tomulticast/Message.java
@@ -0,0 +1,40 @@
+package derms.net.tomulticast;
+
+import derms.net.rmulticast.MessagePayload;
+
+class Message<T extends MessagePayload> implements MessagePayload {
+    long seq; // Sequence number.
+    T payload;
+
+    Message(long seq, T payload) {
+        this.seq = seq;
+        this.payload = payload;
+    }
+
+    @Override
+    public int hash() {
+        return (int) seq * payload.hash();
+    }
+
+    @Override
+    public int hashCode() {
+        return hash();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == null)
+            return false;
+        if (obj.getClass() != this.getClass())
+            return false;
+        Message<?> other = (Message<?>) obj;
+        if (other.payload.getClass() != this.payload.getClass())
+            return false;
+        return other.seq == this.seq && other.hash() == this.hash();
+    }
+
+    @Override
+    public String toString() {
+        return getClass().getSimpleName() + "{" + seq + ", " + payload + "}";
+    }
+}
diff --git a/src/main/java/derms/net/tomulticast/TotalOrderMulticast.java b/src/main/java/derms/net/tomulticast/TotalOrderMulticast.java
new file mode 100644
index 0000000..d83a34d
--- /dev/null
+++ b/src/main/java/derms/net/tomulticast/TotalOrderMulticast.java
@@ -0,0 +1,53 @@
+package derms.net.tomulticast;
+
+import derms.net.rmulticast.MessagePayload;
+import derms.net.rmulticast.ReliableMulticast;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.util.logging.Logger;
+
+/**
+ * <p>A single-sender, multiple-receiver multicast group that enforces a total order on
+ * received messages. If a process delivers message <i>A</i> before message <i>B</i>,
+ * then all other processes will deliver <i>A</i> and <i>B</i> in the same order
+ * (<i>A</i> before <i>B</i>).</p>
+ *
+ * <p>Additionally, the protocol guarantees reliable delivery of messages. If the sender
+ * crashes while sending a message, either all processes will receive the message, or
+ * none of them will.</p>
+ *
+ * <p><b>Only one sender is allowed per multicast group</b>, but a group may have multiple
+ * receivers. Use {@link derms.net.tomulticast.TotalOrderMulticastSender} to send
+ * messages, and {@link derms.net.tomulticast.TotalOrderMulticastReceiver} to receive
+ * them.</p>
+ */
+public abstract class TotalOrderMulticast<T extends MessagePayload> {
+    final ReliableMulticast<Message<T>> sock;
+    protected final InetSocketAddress group;
+    protected Long seq; // Sequence number.
+    protected final Logger log;
+
+    protected TotalOrderMulticast(InetSocketAddress group, InetAddress laddr) throws IOException {
+        this.sock = new ReliableMulticast<Message<T>>(group, laddr);
+        this.group = group;
+        this.seq = (long) 0;
+        this.log = Logger.getLogger(this.getClass().getName());
+    }
+
+    /** Close the underlying socket. */
+    public void close() {
+        sock.close();
+    }
+
+    /** Increment the sequence number. */
+    protected void incSeq() {
+        if (seq < seq.MAX_VALUE) {
+            seq++;
+        } else {
+            log.warning("Sequence number overflow. Wrapping to 0.");
+            seq = (long) 0;
+        }
+    }
+}
diff --git a/src/main/java/derms/net/tomulticast/TotalOrderMulticastSender.java b/src/main/java/derms/net/tomulticast/TotalOrderMulticastSender.java
new file mode 100644
index 0000000..63498a6
--- /dev/null
+++ b/src/main/java/derms/net/tomulticast/TotalOrderMulticastSender.java
@@ -0,0 +1,31 @@
+package derms.net.tomulticast;
+
+import derms.net.rmulticast.MessagePayload;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+
+/**
+ * The single sending process in a {@link TotalOrderMulticast} group. <b>Only one sender is
+ *  allowed per group.</b>
+ */
+public class TotalOrderMulticastSender<T extends MessagePayload> extends TotalOrderMulticast<T> {
+    /**
+     * Join the specified totally-ordered multicast group as its lone sender.
+     *
+     * @param group The IP address and port of the multicast group to join.
+     * @param laddr The IP address of the local process.
+     */
+    public TotalOrderMulticastSender(InetSocketAddress group, InetAddress laddr) throws IOException {
+        super(group, laddr);
+    }
+
+    /** Send a message to the group. */
+    public void send(T payload) throws IOException {
+        Message<T> msg = new Message<T>(seq, payload);
+        sock.send(msg);
+        incSeq();
+        log.info("Sent " + msg + " from " + sock + " to " + group);
+    }
+}