.  \"ident	"%W%"
.  \"Copyright (c) 1984 AT&T
.  \"All Rights Reserved
.  \"THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T
.  \"The copyright notice above does not evidence any
.  \"actual or intended publication of such source code.
.TH PIPEBUF 3I+ "C++ Stream Library" " "
.SH NAME
pipebuf \- streambuf specialized as circular queue
.SH SYNOPSIS
.nf
.ft B
.ta1i 2i
#include <iostream.h>
#include <pipestream.h>

class pipebuf :	streambuf {
		pipebuf();
	int 	empty();
	int	full();
	streambuf*	setbuf(char* ptr, int len);
} ;
.ft R
.fi
.SH DESCRIPTION
A \f(CWpipebuf\fR
uses its reserve area to support a circular
queue of characters.
In terms of the abstract notion of buffer a \f(CWpipebuf\fR
is a potentially infinite sequence in which the put pointer
and get pointer move independently.
The put pointer is always at the end of the sequence, and
puts extend the sequence.
As long as the get pointer remains behind the put pointer, but
not too far behind, fetching and storing can continue indefinitely.
Seeks are not supported.
.PP
Assume
.br
\(em \fBpb\fR is a \f(CWpipebuf\fR.
.br
\(em \fBptr\fR is a \f(CWchar*\fR.
.br
\(em \fBi\fR and \fBlen\fR are an \f(CWint\fR.
.br
\(em \fBsb\fR is \f(CWstreambuf*\fR.
.PP
Constructor:
.TP
\fBpipebuf()\fR
Constructs an empty buffer.
.PP
Members:
.TP
\fBi=pb.empty()\fR
Returns non-zero if the get pointer is at the end of the sequence,
and attempts to get characters will therefore fail.
.TP
\fBi=pb.full()\fR
Returns non-zero if there is no more room for putting
characters.  In the current implementation, the capacity of
the buffer is one less than the size of the reserve area.
.TP
\fBsb=pb.setbuf(ptr,len)\fR
Establishes the \fBlen\fR bytes starting at \fBptr\fR
as the reserve area.  Normally it will return \fB&pb\fR.  But
it will return a null pointer if it fails.  Failure occurs
if \fBpb.empty()\fR is zero, or if \fBlen\fR is less than 2.
.SH CAVEATS
There ought to be a version with an unbounded capacity.
.SH SEE ALSO
streambuf(3C++)
pipestream(3C++)