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sfmutex.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 1985-2009 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                A copy of the License is available at                 *
*            http://www.opensource.org/licenses/cpl1.0.txt             *
*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
*                                                                      *
*              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"

/*    Obtain/release exclusive use of a stream.
**
**    Written by Kiem-Phong Vo.
*/

/* the main locking/unlocking interface */
#if __STD_C
int sfmutex(Sfio_t* f, int type)
#else
int sfmutex(f, type)
Sfio_t*     f;
int   type;
#endif
{
#if !vt_threaded
      NOTUSED(f); NOTUSED(type);
      return 0;
#else

      SFONCE();

      if(!f)
            return -1;

      if(!f->mutex)
      {     if(f->bits&SF_PRIVATE)
                  return 0;

            vtmtxlock(_Sfmutex);
            f->mutex = vtmtxopen(NIL(Vtmutex_t*), VT_INIT);
            vtmtxunlock(_Sfmutex);
            if(!f->mutex)
                  return -1;
      }

      if(type == SFMTX_LOCK)
            return vtmtxlock(f->mutex);
      else if(type == SFMTX_TRYLOCK)
            return vtmtxtrylock(f->mutex);
      else if(type == SFMTX_UNLOCK)
            return vtmtxunlock(f->mutex);
      else if(type == SFMTX_CLRLOCK)
            return vtmtxclrlock(f->mutex);
      else  return -1;
#endif /*vt_threaded*/
}

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