BufferedTCP- Buffered TCP/IP Network Stream
BufferedTCP class implements a communications stream which
buffers both input and output from and to a TCP/IP network connection.
When an application first attempts to
Read() from a buffered
stream, the stream object (i) allocates a single, large input buffer
and (ii) reads as much data as it can - up to the size of the buffer -
with a single call to the system
read(2) function. The stream
object then doles out from the input buffer the amounts of data requested by
the application in successive
Read() calls. When the input buffer
is exhausted, the stream object performs another large
refill the buffer, and so on.
Output buffering is controlled by the timeout argument to the
Write() method. Unbuffered output is achieved with a negative
timeout (e.g., -1.0): the
Write() method blocks until all the
data (including previously buffered output) has been written to the stream's
network connection. Buffered output, on the other hand, results from a zero
or positive timeout. For a zero timeout,
Write() simply appends
the caller's data to a queue of output buffers. In the case of a positive
Write() adds the caller's data to the queue and then
write(2) to the stream's network connection as much
of the buffered data as possible in the given time interval.
When buffering output, the buffered data must be flushed to the network
connection at some point. This can by accomplished in a polled manner by
periodic calls to
Flush(). More sophisticated applications,
operating in the context of an event loop (e.g., the X Toolkit or ERAL's
Dispatcher), can register the
stream's socket connection, returned by
Fd(), as an output source.
When the event loop signals that the connection is ready for output, the
application should call
Flush() with a zero timeout. After all
the buffered output data has been flushed to the network connection and
false, the application
should unregister the connection as an output source.
BufferedTCP can be used as a stand-alone class, it is
primarily intended as a parent class for streams which must efficiently exchange
application-specific messages (e.g., those consisting of a fixed-length header
and a variable-length body).
(In addition to those inherited from
BufferedTCP()- creates a buffered TCP/IP stream by service name.
BufferedTCP()- creates a buffered TCP/IP stream by port number.
~BufferedTCP()- destroys a buffered TCP/IP stream.
Close()- closes a stream.
IsReadable()- checks if data can be read from the stream.
PendingInput()- checks for buffered input.
PendingOutput()- checks for buffered output.
Flush()- flushes buffered output.
Read()- reads from a buffered stream.
Write()- writes to a buffered stream.