csp.lang
Class LinkDriver

java.lang.Object
  |
  +--csp.lang.LinkDriver

Direct Known Subclasses:

ActionListenerDriver, BoundedBuffer, Buffer, ChannelListenerDriver, LowerBoundedBuffer, OverSamplingBuffer, OverwriteBuffer, Port, Rendezvous, SubSamplingBuffer, TCPIP, Timer, UDP, UpperBoundedBuffer

public abstract class LinkDriver

extends java.lang.Object

A link driver determines the actual way of communication and its subclass is the only hardware dependent part of the csp package. It can provide internal (e.g. via memory such as a rendezvous or buffered mechanism) or external (e.g. by peripherals such as RS232, PCI or TCP/IP) communication. The link driver can be plugged into a channel and provides a protocol of data-transfer via hardware (e.g. memory or peripherals). The channel provides the necessary synchronization and scheduling. The combination of channels and link drivers is powerful in that the concept provides a general framework for communication between two or more threads in the same address space (i.e. same memory) or for communication between systems (e.g. distributed systems). As a result, processes will become highly independent of their physical location on the total system. This enlarges the portability of enormously.

Each link driver class must extend the LinkDriver class. The LinkDriver class is an abstract class which provides an abstract read() and write() method. Furtermore, the LinkDriver implements a state variable, three static constants to set the state of the link driver, and a copy(..) method for copying source objects into destination objects. A link driver extends the LinkDriver class and must implement the read() and write() methods. The state variable must be set NONEMPTUFULL, EMPTY, or FULL according the state of the buffer used in the link driver. The initiate method can be overridden to initiate the state variable. The state variable is set to EMPTY by default.

Link driver states:
EMPTY : buffer reached empty state
FULL : buffer reached full state
NONEMPTYFULL : buffer is not empty and not full

Three basic mechanisms can be created by these constants, i.e. synchronous, quasi-synchronous, and asynchronous. Examples of these mechanisms are respectively the rendezvous communication, buffered communication, and a timer. The type of synchronization is the choice of the programmer, however the synchronous (i.e. rendezvous) mechanism is preferred according to the CSP concept.

Copyright © 1996-1999 University of Twente. All Rights Reserved.

Version:

December 1999, version 0.9, revision 16.

Author:

Gerald H. Hilderink, G.H.Hilderink@el.utwente.nl

Constructor Summary

LinkDriver()

Method Summary

abstract void	read(java.lang.Object object) Read an object.
abstract void	write(java.lang.Object object) Write specified object.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LinkDriver

public LinkDriver()

Method Detail

read

public abstract void read(java.lang.Object object)
                   throws IOException

Read an object.

Parameters:

object - the object to copy the message in when receiving

Throws:

IOException - if an I/O error occurs

write

public abstract void write(java.lang.Object object)
                    throws IOException

Write specified object.

Parameters:

object - the object to send

Throws:

IOException - if an I/O error occurs.