usr/src/lib/libast/common/sfio/sfstack.c

   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
  41 Sfio_t* sfstack(Sfio_t* f1, Sfio_t* f2)
  42 #else
  43 Sfio_t* sfstack(f1,f2)
  44 Sfio_t* f1;     /* base of stack        */
  45 Sfio_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 }