/* $Id$ $Revision$ */
/* vim:set shiftwidth=4 ts=8: */

/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: See CVS logs. Details at http://www.graphviz.org/
 *************************************************************************/

#include	"sfhdr.h"

/*	Delete all pending data in the buffer
**
**	Written by Kiem-Phong Vo.
*/

int sfpurge(reg Sfio_t * f)
{
    reg int mode;

    SFMTXSTART(f, -1);

    if ((mode = f->mode & SF_RDWR) != (int) f->mode
	&& _sfmode(f, mode, 0) < 0)
	SFMTXRETURN(f, -1);

    if ((f->flags & SF_IOCHECK) && f->disc && f->disc->exceptf)
	(void) (*f->disc->exceptf) (f, SF_PURGE, (void *) ((int) 1),
				    f->disc);

    if (f->disc == _Sfudisc)
	(void) sfclose((*_Sfstack) (f, NIL(Sfio_t *)));

    /* cannot purge read string streams */
    if ((f->flags & SF_STRING) && (f->mode & SF_READ))
	goto done;

    SFLOCK(f, 0);

    switch (f->mode & ~SF_LOCK) {
    default:
	SFOPEN(f, 0);
	SFMTXRETURN(f, -1);
    case SF_WRITE:
	f->next = f->data;
	if (!f->proc || !(f->flags & SF_READ) || !(f->mode & SF_WRITE))
	    break;

	/* 2-way pipe, must clear read buffer */
	(void) _sfmode(f, SF_READ, 1);
	/* fall through */
    case SF_READ:
	if (f->extent >= 0 && f->endb > f->next) {
	    f->here -= f->endb - f->next;
	    SFSK(f, f->here, SEEK_SET, f->disc);
	}
	f->endb = f->next = f->data;
	break;
    }

    SFOPEN(f, 0);

  done:
    if ((f->flags & SF_IOCHECK) && f->disc && f->disc->exceptf)
	(void) (*f->disc->exceptf) (f, SF_PURGE, (void *) ((int) 0),
				    f->disc);

    SFMTXRETURN(f, 0);
}
