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/* ps_alloc.c - allocate a presentation stream */
/*
* isode/psap/ps_alloc.c
*/
/*
* NOTICE
*
* Acquisition, use, and distribution of this module and related
* materials are subject to the restrictions of a license agreement.
* Consult the Preface in the User's Manual for the full terms of
* this agreement.
*
*/
/* LINTLIBRARY */
#include <stdio.h>
#include "psap.h"
/* A Presentatation Stream (or PStream) is the second generation of
"generic" I/O stream-based handling. (For the first attempt,
take a look at the prototype implementation of the TTI Trusted Mail
Agent.) The idea is to present a common, simple I/O paradigm (i.e.,
the UNIX v7 philosophy) to protocol-translation entities regardless of
the underlying medium (files, pipes, sockets, or strings).
New streams are created by a call to ps_alloc(). It allocates memory
and calls an open routine. This routine fills in the dispatch vectors
for read/write and (optionally) close. It can also fill in any other
part of the stream's structure it likes.
Once created, I/O is done using the macros ps_read/ps_write. These
return either NOTOK or OK; depending on how things went. The read/write
routines are invoked as:
int iofunc (ps, data, n, in_line)
PS ps;
PElementData data;
PElementLen n;
int in_line;
They should read/write upto len bytes, starting at data, and return the
number of bytes processed, or NOTOK on error. The routine ps_io() will
make successive calls to fill/flush the data. If the read/write routine
returns NOTOK, it should set ps_errno as well.
Streams are removed by a call to ps_free (). It calls the close
routine, if any, which should de-commission any parts of the stream's
structure that are in use. ps_free() will then free the allocated
memory.
*/
/* */
PS ps_alloc (io)
register IFP io;
{
register PS ps;
if ((ps = (PS) calloc (1, sizeof *ps)) == NULLPS)
return NULLPS;
if ((*io) (ps) == NOTOK) {
ps_free (ps);
return NULLPS;
}
return ps;
}
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