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

*                                                                      *

*               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"

/*	Push/pop streams

**

**	Written by Kiem-Phong Vo.

*/

#define STKMTXLOCK(f1,f2) \

	{ if(f1) SFMTXLOCK(f1); \

	  if(f2) SFMTXLOCK(f2); \

	}

#define STKMTXRETURN(f1,f2,rv) \

	{ if(f1) SFMTXUNLOCK(f1); \

	  if(f2) SFMTXUNLOCK(f2); \

	  return(rv); \

	}

#if __STD_C

Sfio_t* sfstack(Sfio_t* f1, Sfio_t* f2)

#else

Sfio_t* sfstack(f1,f2)

Sfio_t*	f1;	/* base of stack	*/

Sfio_t*	f2;	/* top of stack	*/

#endif

{

	reg int		n;

	reg Sfio_t*	rf;

	reg Sfrsrv_t*	rsrv;

	reg Void_t*	mtx;

	STKMTXLOCK(f1,f2);

	if(f1 && (f1->mode&SF_RDWR) != f1->mode && _sfmode(f1,0,0) < 0)

		STKMTXRETURN(f1,f2, NIL(Sfio_t*));

	if(f2 && (f2->mode&SF_RDWR) != f2->mode && _sfmode(f2,0,0) < 0)

		STKMTXRETURN(f1,f2, NIL(Sfio_t*));

	if(!f1)

		STKMTXRETURN(f1,f2, f2);

	/* give access to other internal functions */

	_Sfstack = sfstack;

	if(f2 == SF_POPSTACK)

	{	if(!(f2 = f1->push))

			STKMTXRETURN(f1,f2, NIL(Sfio_t*));

		f2->mode &= ~SF_PUSH;

	}

	else

	{	if(f2->push)

			STKMTXRETURN(f1,f2, NIL(Sfio_t*));

		if(f1->pool && f1->pool != &_Sfpool && f1->pool != f2->pool &&

		   f1 == f1->pool->sf[0])

		{	/* get something else to pool front since f1 will be locked */

			for(n = 1; n < f1->pool->n_sf; ++n)

			{	if(SFFROZEN(f1->pool->sf[n]) )

					continue;

				(*_Sfpmove)(f1->pool->sf[n],0);

				break;

			}

		}

	}

	if(f2->pool && f2->pool != &_Sfpool && f2 != f2->pool->sf[0])

		(*_Sfpmove)(f2,0);

	/* swap streams */

	sfswap(f1,f2);

	/* but the reserved buffer and mutex must remain the same */

	rsrv = f1->rsrv; f1->rsrv = f2->rsrv; f2->rsrv = rsrv;

	mtx = f1->mutex; f1->mutex = f2->mutex; f2->mutex = mtx;

	SFLOCK(f1,0);

	SFLOCK(f2,0);

	if(f2->push != f2)

	{	/* freeze the pushed stream */

		f2->mode |= SF_PUSH;

		f1->push = f2;

		rf = f1;

	}

	else

	{	/* unfreeze the just exposed stream */

		f1->mode &= ~SF_PUSH;

		f2->push = NIL(Sfio_t*);

		rf = f2;

	}

	SFOPEN(f1,0);

	SFOPEN(f2,0);

	STKMTXRETURN(f1,f2, rf);

}