/***********************************************************************

*                                                                      *

*               This software is part of the ast package               *

*          Copyright (c) 1985-2011 AT&T Intellectual Property          *

*                      and is licensed under the                       *

*                 Eclipse Public License, Version 1.0                  *

*                    by AT&T Intellectual Property                     *

*                                                                      *

*                A copy of the License is available at                 *

*          http://www.eclipse.org/org/documents/epl-v10.html           *

*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *

*                                                                      *

*              Information and Software Systems Research               *

*                            AT&T Research                             *

*                           Florham Park NJ                            *

*                                                                      *

*                 Glenn Fowler <gsf@research.att.com>                  *

*                  David Korn <dgk@research.att.com>                   *

*                   Phong Vo <kpv@research.att.com>                    *

*                                                                      *

***********************************************************************/

#include	"sfhdr.h"

/*	Delete all pending data in the buffer

**

**	Written by Kiem-Phong Vo.

*/

#if __STD_C

int sfpurge(Sfio_t* f)

#else

int sfpurge(f)

Sfio_t*	f;

#endif

{

	reg int	mode;

	SFMTXDECL(f);

	SFMTXENTER(f,-1);

	if((mode = f->mode&SF_RDWR) != (int)f->mode && _sfmode(f,mode|SF_SYNCED,0) < 0)

		SFMTXRETURN(f, -1);

	if((f->flags&SF_IOCHECK) && f->disc && f->disc->exceptf)

		(void)(*f->disc->exceptf)(f,SF_PURGE,(Void_t*)((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);

	/* if memory map must be a read stream, pretend data is gone */

#ifdef MAP_TYPE

	if(f->bits&SF_MMAP)

	{	f->here -= f->endb - f->next;

		if(f->data)

		{	SFMUNMAP(f,f->data,f->endb-f->data);

			(void)SFSK(f,f->here,SEEK_SET,f->disc);

		}

		SFOPEN(f,0);

		SFMTXRETURN(f, 0);

	}

#endif

	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;

			(void)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_t*)((int)0),f->disc);

	SFMTXRETURN(f, 0);

}