1/***********************************************************************
2*                                                                      *
3*               This software is part of the ast package               *
4*          Copyright (c) 1985-2010 AT&T Intellectual Property          *
5*                      and is licensed under the                       *
6*                  Common Public License, Version 1.0                  *
7*                    by AT&T Intellectual Property                     *
8*                                                                      *
9*                A copy of the License is available at                 *
10*            http://www.opensource.org/licenses/cpl1.0.txt             *
11*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
12*                                                                      *
13*              Information and Software Systems Research               *
14*                            AT&T Research                             *
15*                           Florham Park NJ                            *
16*                                                                      *
17*                 Glenn Fowler <gsf@research.att.com>                  *
18*                  David Korn <dgk@research.att.com>                   *
19*                   Phong Vo <kpv@research.att.com>                    *
20*                                                                      *
21***********************************************************************/
22#include	"sfhdr.h"
23
24/*	Swap two streams. If the second argument is NULL,
25**	a new stream will be created. Always return the second argument
26**	or the new stream. Note that this function will always work
27**	unless streams are locked by SF_PUSH.
28**
29**	Written by Kiem-Phong Vo.
30*/
31
32#if __STD_C
33Sfio_t* sfswap(reg Sfio_t* f1, reg Sfio_t* f2)
34#else
35Sfio_t* sfswap(f1,f2)
36reg Sfio_t*	f1;
37reg Sfio_t*	f2;
38#endif
39{
40	Sfio_t	tmp;
41	int	f1pool, f2pool, f1mode, f2mode, f1flags, f2flags;
42
43	if(!f1 || (f1->mode&SF_AVAIL) || (SFFROZEN(f1) && (f1->mode&SF_PUSH)) )
44		return NIL(Sfio_t*);
45	if(f2 && SFFROZEN(f2) && (f2->mode&SF_PUSH) )
46		return NIL(Sfio_t*);
47	if(f1 == f2)
48		return f2;
49
50	f1mode = f1->mode;
51	SFLOCK(f1,0);
52	f1->mode |= SF_PUSH;		/* make sure there is no recursion on f1 */
53
54	if(f2)
55	{	f2mode = f2->mode;
56		SFLOCK(f2,0);
57		f2->mode |= SF_PUSH;	/* make sure there is no recursion on f2 */
58	}
59	else
60	{	f2 = f1->file == 0 ? sfstdin :
61		     f1->file == 1 ? sfstdout :
62		     f1->file == 2 ? sfstderr : NIL(Sfio_t*);
63		if((!f2 || !(f2->mode&SF_AVAIL)) )
64		{	if(!(f2 = (Sfio_t*)malloc(sizeof(Sfio_t))) )
65			{	f1->mode = f1mode;
66				SFOPEN(f1,0);
67				return NIL(Sfio_t*);
68			}
69
70			SFCLEAR(f2,NIL(Vtmutex_t*));
71		}
72		f2->mode = SF_AVAIL|SF_LOCK;
73		f2mode = SF_AVAIL;
74	}
75
76	if(!f1->pool)
77		f1pool = -1;
78	else for(f1pool = f1->pool->n_sf-1; f1pool >= 0; --f1pool)
79		if(f1->pool->sf[f1pool] == f1)
80			break;
81	if(!f2->pool)
82		f2pool = -1;
83	else for(f2pool = f2->pool->n_sf-1; f2pool >= 0; --f2pool)
84		if(f2->pool->sf[f2pool] == f2)
85			break;
86
87	f1flags = f1->flags;
88	f2flags = f2->flags;
89
90	/* swap image and pool entries */
91	memcpy((Void_t*)(&tmp),(Void_t*)f1,sizeof(Sfio_t));
92	memcpy((Void_t*)f1,(Void_t*)f2,sizeof(Sfio_t));
93	memcpy((Void_t*)f2,(Void_t*)(&tmp),sizeof(Sfio_t));
94	if(f2pool >= 0)
95		f1->pool->sf[f2pool] = f1;
96	if(f1pool >= 0)
97		f2->pool->sf[f1pool] = f2;
98
99	if(f2flags&SF_STATIC)
100		f2->flags |= SF_STATIC;
101	else	f2->flags &= ~SF_STATIC;
102
103	if(f1flags&SF_STATIC)
104		f1->flags |= SF_STATIC;
105	else	f1->flags &= ~SF_STATIC;
106
107	if(f2mode&SF_AVAIL)	/* swapping to a closed stream */
108	{	if(!(f1->flags&SF_STATIC) )
109			free(f1);
110	}
111	else
112	{	f1->mode = f2mode;
113		SFOPEN(f1,0);
114	}
115
116	f2->mode = f1mode;
117	SFOPEN(f2,0);
118	return f2;
119}
120