Class Channel

java.lang.Object
   |
   +----Channel

class Channel
extends Object

Channel extends an occam CHAN for multiple readers and writers. There is full synchronisation between a reading and writing thread. Any thread may read or write on this channel. Readers and writers are queued separately. A reader only completes when it gets to the front of its queue and finds a writer. A writer only completes when it gets to the front of its queue and finds a reader.

There is no logical buffering of data in the channel. The object passed into the channel is not cloned, but rather a reference is passed to the reader. Therefore, care must be taken that the object supplied by a writer does not then have its content modified asynchronously by the writer. This can be done by setting the reference to null, e.g. in a writer,

  String s = "Hello World";    // create a new string
  chan.write(s);               // send the string
  s = null;                    // delete writer's reference to string

or alternatively, a clone can be supplied, e.g.

  StringBuffer s = "Hello World";    // create a new string
  chan.write(s.clone());             // send the string
  s.reverse();                       // does not affect the reader's copy

Version:: $Revision: 1.1 $
Author:: Peter Welch, P.H.Welch@ukc.ac.uk, Dave Beckett, D.J.Beckett@ukc.ac.uk, with annotations by Richard Beton

Method Index

o is_empty(): is_empty method: determine whether a thread is waiting at the other end of the channel.
o read(): read method: read a message from the channel.
o write(Object): write method: write a message to the channel.

Methods

o read

  public Object read() throws InterruptedException

read method: read a message from the channel. This method blocks until a corresponding thread calls the write method, at which point a rendezvous is formed and the data is passed.

Returns:: the object sent from the writing thread.
Throws: InterruptedException: Occurs if the wait methods are interrupted.

o write

  public void write(Object o) throws InterruptedException

write method: write a message to the channel. This method blocks until a corresponding thread calls the read method, at which point a rendezvous is formed and the data is passed.

Parameters:: o - the object to be sent to the reading thread.
Throws: InterruptedException: Occurs if the wait methods are interrupted.

o is_empty

  public boolean is_empty()

is_empty method: determine whether a thread is waiting at the other end of the channel. This can be used either at the writing or the reading end of the channel.

Returns:: true iff no thread is waiting at the other end.