/*******************************************************************
*                                                                  *
*             This software is part of the ast package             *
*                Copyright (c) 1985-2003 AT&T Corp.                *
*        and it may only be used by you under license from         *
*                       AT&T Corp. ("AT&T")                        *
*         A copy of the Source Code Agreement is available         *
*                at the AT&T Internet web site URL                 *
*                                                                  *
*       http://www.research.att.com/sw/license/ast-open.html       *
*                                                                  *
*    If you have copied or used this software without agreeing     *
*        to the terms of the license you are infringing on         *
*           the license and copyright and are violating            *
*               AT&T's intellectual property rights.               *
*                                                                  *
*            Information and Software Systems Research             *
*                        AT&T Labs 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"

/*	Set some control flags or file descript for the stream
**
**	Written by Kiem-Phong Vo.
*/

#if __STD_C
int sfset(reg Sfio_t* f, reg int flags, reg int set)
#else
int sfset(f,flags,set)
reg Sfio_t*	f;
reg int		flags;
reg int		set;
#endif
{
	reg int	oflags;

	SFMTXSTART(f,0);

	if(flags == 0 && set == 0)
		SFMTXRETURN(f, (f->flags&SF_FLAGS));

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

	if(flags == 0)
		SFMTXRETURN(f, (f->flags&SF_FLAGS));

	SFLOCK(f,0);

	/* preserve at least one rd/wr flag */
	oflags = f->flags;
	if(!(f->bits&SF_BOTH) || (flags&SF_RDWR) == SF_RDWR )
		flags &= ~SF_RDWR;

	/* set the flag */
	if(set)
		f->flags |=  (flags&SF_SETS);
	else	f->flags &= ~(flags&SF_SETS);

	/* must have at least one of read/write */
	if(!(f->flags&SF_RDWR))
		f->flags |= (oflags&SF_RDWR);

	if(f->extent < 0)
		f->flags &= ~SF_APPENDWR;

	/* turn to appropriate mode as necessary */
	if((flags &= SF_RDWR) )
	{	if(!set)
		{	if(flags == SF_READ)
				flags = SF_WRITE;
			else	flags = SF_READ;
		}
		if((flags == SF_WRITE && !(f->mode&SF_WRITE)) ||
		   (flags == SF_READ && !(f->mode&(SF_READ|SF_SYNCED))) )
			(void)_sfmode(f,flags,1);
	}

	/* if not shared or unseekable, public means nothing */
	if(!(f->flags&SF_SHARE) || f->extent < 0)
		f->flags &= ~SF_PUBLIC;

	SFOPEN(f,0);
	SFMTXRETURN(f, (oflags&SF_FLAGS));
}
