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

*                                                                      *

*               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"

/*	Obtain/release exclusive use of a stream.

**

**	Written by Kiem-Phong Vo.

*/

/* the main locking/unlocking interface */

#if __STD_C

int sfmutex(Sfio_t* f, int type)

#else

int sfmutex(f, type)

Sfio_t*	f;

int	type;

#endif

{

#if !vt_threaded

	NOTUSED(f); NOTUSED(type);

	return 0;

#else

	SFONCE();

	if(!f)

		return -1;

	if(!f->mutex)

	{	if(f->bits&SF_PRIVATE)

			return 0;

		vtmtxlock(_Sfmutex);

		f->mutex = vtmtxopen(NIL(Vtmutex_t*), VT_INIT);

		vtmtxunlock(_Sfmutex);

		if(!f->mutex)

			return -1;

	}

	if(type == SFMTX_LOCK)

		return vtmtxlock(f->mutex);

	else if(type == SFMTX_TRYLOCK)

		return vtmtxtrylock(f->mutex);

	else if(type == SFMTX_UNLOCK)

		return vtmtxunlock(f->mutex);

	else if(type == SFMTX_CLRLOCK)

		return vtmtxclrlock(f->mutex);

	else	return -1;

#endif /*vt_threaded*/

}