Package org.jcsp.net2

Class Link

  • All Implemented Interfaces:
    CSProcess
    Direct Known Subclasses:
    TCPIPLink
    public abstract class Link
extends java.lang.Object
implements CSProcess
    Abstract class representing a Link. This class defines the two processes (Link TX, Link RX) where the network protocol is of key importance. Specific technology protocols (e.g. TCP/IP) must extend this class, providing the necessary streams for operation, and also overriding the methods connect, createResources and destroyResources, which will have specific implementations dependent on the underlying technology. Everything else should operate as defined in this class.
    See Also:
    NetworkProtocol

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      (package private) class  Link.RxLoop
      The RxLoop for the Link.
      (package private) class  Link.TxLoop
      The TxLoop for the Link.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected boolean connected
      A flag used to indicate whether the Link is connected or not.
      private java.util.Hashtable connectedBarriers
      This Hashtable is used to keep track of the current barriers that are connected to this Link.
      private java.util.Hashtable connectedOutputs
      This Hashtable is used to keep track of the current output channels that are connected to this Link.
      static int LINK_PRIORITY
      Link priority in the system.
      protected int priority
      Link priority for this Link.
      protected NodeID remoteID
      The NodeID of the opposite end of the connection.
      protected java.io.DataInputStream rxStream
      The incoming stream for the connection.
      private Any2OneChannel txChannel
      The channel connected to the Link Tx process.
      protected java.io.DataOutputStream txStream
      The outgoing stream for the connection.

    • Constructor Summary

      Constructors 
      Constructor Description
      Link()  

    • Field Detail

      • connected

        protected boolean connected
        A flag used to indicate whether the Link is connected or not. This flag is set normally during the connect operation, but may be done within the constructor. If not set during the constructor, and if connect is not called to set the flag to true, then when the process is run connect will be called.

      • rxStream

        protected java.io.DataInputStream rxStream
        The incoming stream for the connection. This must be created by the specific protocol implementation.

      • txStream

        protected java.io.DataOutputStream txStream
        The outgoing stream for the connection. This must be created by the specific protocol implementation.

      • txChannel

        private final Any2OneChannel txChannel
        The channel connected to the Link Tx process. This is used by channels, barriers, and the Link Rx to send messages to the node this Link is connected to.

      • remoteID

        protected NodeID remoteID
        The NodeID of the opposite end of the connection. This should be set either during construction, or during the connect method of a child class.

      • LINK_PRIORITY

        public static int LINK_PRIORITY
        Link priority in the system. This is a publicly accessible value that can be set by a user.

      • priority

        protected int priority
        Link priority for this Link. This is exposed to child classes to allow specific Link priorities for different Link types.

      • connectedOutputs

        private java.util.Hashtable connectedOutputs
        This Hashtable is used to keep track of the current output channels that are connected to this Link. In the outcome of a connection failure to the remote Node, the Link uses this table to notify all registered output ends, allowing them to throw an exception instead of deadlocking.

      • connectedBarriers

        private java.util.Hashtable connectedBarriers
        This Hashtable is used to keep track of the current barriers that are connected to this Link. In the outcome of a connection failure to the remote Node, the Link uses this table to notify all registered barriers, allowing them to throw an exception instead of deadlocking.

    • Constructor Detail

      • Link

        public Link()

    • Method Detail

      • getRemoteNodeID

        public final NodeID getRemoteNodeID()
        Returns the NodeID of the connected Link.
        Returns:
        NodeID of the connected Link.

      • getTxChannel

        protected final ChannelOutput getTxChannel()
        Gets the channel that is connected to the Link Tx process.
        Returns:
        The ChannelOutput used to communicate with the Link Tx.

      • connect

        public abstract boolean connect()
                         throws JCSPNetworkException
        Connects to the remote Node. This must be overridden by a child class implementation.
        Returns:
        True if the connection succeeds, false otherwise.
        Throws:
        JCSPNetworkException - Thrown if the connection fails.

      • createResources

        protected abstract boolean createResources()
                                    throws JCSPNetworkException
        Creates the resources (if any) required for the Node. These could be set up during construction, but if not, this method is called immediately after connect within the run method. Child implementations should override this method.
        Returns:
        True if resources were created OK, false otherwise.
        Throws:
        JCSPNetworkException - Thrown if a problem occurs creating the resources.

      • destroyResources

        protected abstract void destroyResources()
        Destroys any used resources. This is called whenever a Node fails. Particular implementations must overwrite this method.

      • registerLink

        public final boolean registerLink()
        Registers the Link with the LinkManager
        Returns:
        True if Link was registered, false otherwise.

      • lostLink

        protected final void lostLink()
        Marks the Link as lost within the LinkManager.

      • registerChannel

        void registerChannel​(ChannelData data)
        Register a channel with the Link.
        Parameters:
        data - The ChannelData object representing the channel

      • deRegisterChannel

        void deRegisterChannel​(ChannelData data)
        Unregisters and removes the channel from the Link.
        Parameters:
        data - The ChannelData object representing the channel.

      • registerBarrier

        void registerBarrier​(BarrierData data)
        Registers a barrier with the Link
        Parameters:
        data - The barrier to register with the Link

      • deRegisterBarrier

        void deRegisterBarrier​(BarrierData data)
        Unregisters a barrier with the Link
        Parameters:
        data - The BarrierData representing the Barrier to unregister

      • run

        public final void run()
        The run method for the process. This will connect the Link (if necessary) and then start the Tx and Rx Loops.
        Specified by:
        run in interface CSProcess