usr/src/lib/libast/common/sfio/sfmutex.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 /*      Obtain/release exclusive use of a stream.
  25 **
  26 **      Written by Kiem-Phong Vo.
  27 */
  28
  29 /* the main locking/unlocking interface */
  30 #if __STD_C
  31 int sfmutex(Sfio_t* f, int type)
  32 #else
  33 int sfmutex(f, type)
  34 Sfio_t* f;
  35 int     type;
  36 #endif
  37 {
  38 #if !vt_threaded
  39         NOTUSED(f); NOTUSED(type);
  40         return 0;
  41 #else
  42
  43         SFONCE();
  44
  45         if(!f)
  46                 return -1;
  47
  48         if(!f->mutex)
  49         {       if(f->bits&SF_PRIVATE)
  50                         return 0;
  51
  52                 vtmtxlock(_Sfmutex);
  53                 f->mutex = vtmtxopen(NIL(Vtmutex_t*), VT_INIT);
  54                 vtmtxunlock(_Sfmutex);
  55                 if(!f->mutex)
  56                         return -1;
  57         }
  58
  59         if(type == SFMTX_LOCK)
  60                 return vtmtxlock(f->mutex);
  61         else if(type == SFMTX_TRYLOCK)
  62                 return vtmtxtrylock(f->mutex);
  63         else if(type == SFMTX_UNLOCK)
  64                 return vtmtxunlock(f->mutex);
  65         else if(type == SFMTX_CLRLOCK)
  66                 return vtmtxclrlock(f->mutex);
  67         else    return -1;
  68 #endif /*vt_threaded*/
  69 }