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

*                                                                      *

*               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"

/*	Swap two streams. If the second argument is NULL,

**	a new stream will be created. Always return the second argument

**	or the new stream. Note that this function will always work

**	unless streams are locked by SF_PUSH.

**

**	Written by Kiem-Phong Vo.

*/

#if __STD_C

Sfio_t* sfswap(reg Sfio_t* f1, reg Sfio_t* f2)

#else

Sfio_t* sfswap(f1,f2)

reg Sfio_t*	f1;

reg Sfio_t*	f2;

#endif

{

	Sfio_t	tmp;

	int	f1pool, f2pool, f1mode, f2mode, f1flags, f2flags;

	if(!f1 || (f1->mode&SF_AVAIL) || (SFFROZEN(f1) && (f1->mode&SF_PUSH)) )

		return NIL(Sfio_t*);

	if(f2 && SFFROZEN(f2) && (f2->mode&SF_PUSH) )

		return NIL(Sfio_t*);

	if(f1 == f2)

		return f2;

	f1mode = f1->mode;

	SFLOCK(f1,0);

	f1->mode |= SF_PUSH;		/* make sure there is no recursion on f1 */

	if(f2)

	{	f2mode = f2->mode;

		SFLOCK(f2,0);

		f2->mode |= SF_PUSH;	/* make sure there is no recursion on f2 */

	}

	else

	{	f2 = f1->file == 0 ? sfstdin :

		     f1->file == 1 ? sfstdout :

		     f1->file == 2 ? sfstderr : NIL(Sfio_t*);

		if((!f2 || !(f2->mode&SF_AVAIL)) )

		{	if(!(f2 = (Sfio_t*)malloc(sizeof(Sfio_t))) )

			{	f1->mode = f1mode;

				SFOPEN(f1,0);

				return NIL(Sfio_t*);

			}

			SFCLEAR(f2,NIL(Vtmutex_t*));

		}

		f2->mode = SF_AVAIL|SF_LOCK;

		f2mode = SF_AVAIL;

	}

	if(!f1->pool)

		f1pool = -1;

	else for(f1pool = f1->pool->n_sf-1; f1pool >= 0; --f1pool)

		if(f1->pool->sf[f1pool] == f1)

			break;

	if(!f2->pool)

		f2pool = -1;

	else for(f2pool = f2->pool->n_sf-1; f2pool >= 0; --f2pool)

		if(f2->pool->sf[f2pool] == f2)

			break;

	f1flags = f1->flags;

	f2flags = f2->flags;

	/* swap image and pool entries */

	memcpy((Void_t*)(&tmp),(Void_t*)f1,sizeof(Sfio_t));

	memcpy((Void_t*)f1,(Void_t*)f2,sizeof(Sfio_t));

	memcpy((Void_t*)f2,(Void_t*)(&tmp),sizeof(Sfio_t));

	if(f2pool >= 0)

		f1->pool->sf[f2pool] = f1;

	if(f1pool >= 0)

		f2->pool->sf[f1pool] = f2;

	if(f2flags&SF_STATIC)

		f2->flags |= SF_STATIC;

	else	f2->flags &= ~SF_STATIC;

	if(f1flags&SF_STATIC)

		f1->flags |= SF_STATIC;

	else	f1->flags &= ~SF_STATIC;

	if(f2mode&SF_AVAIL)	/* swapping to a closed stream */

	{	if(!(f1->flags&SF_STATIC) )

			free(f1);

	}

	else

	{	f1->mode = f2mode;

		SFOPEN(f1,0);

	}

	f2->mode = f1mode;

	SFOPEN(f2,0);

	return f2;

}