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
25/*	Push/pop streams
26**
27**	Written by Kiem-Phong Vo.
28*/
29
30#define STKMTXLOCK(f1,f2) \
31	{ if(f1) SFMTXLOCK(f1); \
32	  if(f2) SFMTXLOCK(f2); \
33	}
34#define STKMTXRETURN(f1,f2,rv) \
35	{ if(f1) SFMTXUNLOCK(f1); \
36	  if(f2) SFMTXUNLOCK(f2); \
37	  return(rv); \
38	}
39
40#if __STD_C
41Sfio_t* sfstack(Sfio_t* f1, Sfio_t* f2)
42#else
43Sfio_t* sfstack(f1,f2)
44Sfio_t*	f1;	/* base of stack	*/
45Sfio_t*	f2;	/* top of stack	*/
46#endif
47{
48	reg int		n;
49	reg Sfio_t*	rf;
50	reg Sfrsrv_t*	rsrv;
51	reg Void_t*	mtx;
52
53	STKMTXLOCK(f1,f2);
54
55	if(f1 && (f1->mode&SF_RDWR) != f1->mode && _sfmode(f1,0,0) < 0)
56		STKMTXRETURN(f1,f2, NIL(Sfio_t*));
57	if(f2 && (f2->mode&SF_RDWR) != f2->mode && _sfmode(f2,0,0) < 0)
58		STKMTXRETURN(f1,f2, NIL(Sfio_t*));
59	if(!f1)
60		STKMTXRETURN(f1,f2, f2);
61
62	/* give access to other internal functions */
63	_Sfstack = sfstack;
64
65	if(f2 == SF_POPSTACK)
66	{	if(!(f2 = f1->push))
67			STKMTXRETURN(f1,f2, NIL(Sfio_t*));
68		f2->mode &= ~SF_PUSH;
69	}
70	else
71	{	if(f2->push)
72			STKMTXRETURN(f1,f2, NIL(Sfio_t*));
73		if(f1->pool && f1->pool != &_Sfpool && f1->pool != f2->pool &&
74		   f1 == f1->pool->sf[0])
75		{	/* get something else to pool front since f1 will be locked */
76			for(n = 1; n < f1->pool->n_sf; ++n)
77			{	if(SFFROZEN(f1->pool->sf[n]) )
78					continue;
79				(*_Sfpmove)(f1->pool->sf[n],0);
80				break;
81			}
82		}
83	}
84
85	if(f2->pool && f2->pool != &_Sfpool && f2 != f2->pool->sf[0])
86		(*_Sfpmove)(f2,0);
87
88	/* swap streams */
89	sfswap(f1,f2);
90
91	/* but the reserved buffer and mutex must remain the same */
92	rsrv = f1->rsrv; f1->rsrv = f2->rsrv; f2->rsrv = rsrv;
93	mtx = f1->mutex; f1->mutex = f2->mutex; f2->mutex = mtx;
94
95	SFLOCK(f1,0);
96	SFLOCK(f2,0);
97
98	if(f2->push != f2)
99	{	/* freeze the pushed stream */
100		f2->mode |= SF_PUSH;
101		f1->push = f2;
102		rf = f1;
103	}
104	else
105	{	/* unfreeze the just exposed stream */
106		f1->mode &= ~SF_PUSH;
107		f2->push = NIL(Sfio_t*);
108		rf = f2;
109	}
110
111	SFOPEN(f1,0);
112	SFOPEN(f2,0);
113
114	STKMTXRETURN(f1,f2, rf);
115}
116