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s3_mutex.cc

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/*
 * Stone Three Foundation Class (s3fc) provides a number of utility classes.
 * Copyright (C) 2001 by Stone Three Signal Processing (Pty) Ltd.
 *
 * Authored by Stone Three Signal Processing (Pty) Ltd.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 * Please see the file 'COPYING' in the source root directory.
 */

#include <s3fc/s3_mutex.h>
#include <s3fc/s3_exception.h>
#include <sstream>
#include <errno.h>

#ifndef CONST_OVERRIDE_MUTEX_T
//#define CONST_OVERRIDE_MUTEX_T(x) const_cast<pthread_mutex_t*>(x)
#define CONST_OVERRIDE_MUTEX_T(x) (x)  
#endif

// init mutex
s3_mutex::s3_mutex()
{
   // default init (fast mutex)
   pthread_mutex_init(CONST_OVERRIDE_MUTEX_T(&mutex), 0);
}

// destroy mutex
s3_mutex::~s3_mutex()
{
   if ( pthread_mutex_destroy(CONST_OVERRIDE_MUTEX_T(&mutex)) != 0 )
   {
      // To throw an exception here would be naughty. we rather unlock and leave.
      s3_mutex::unlock();
 //     throw s3_generic_exception("s3_mutex::~s3_mutex()",
 //                                "Attempted to destroy locked mutex");
   }
}

// this should NEVER be called
s3_mutex::s3_mutex(const s3_mutex& src)
{
   throw s3_generic_exception("s3_mutex::s3_mutex(const s3_mutex&)",
                              "Function should *never* be called.");
}

// this should NEVER be called
s3_mutex& s3_mutex::operator=(const s3_mutex& src)
{
   throw s3_generic_exception("s3_mutex::operator=(const s3_mutex&)",
                              "Function should *never* be called.");
}

// call pthread_mutex_lock
void s3_mutex::lock() const
{
   if ( pthread_mutex_lock(CONST_OVERRIDE_MUTEX_T(&mutex)) != 0 )
   {
      throw s3_generic_exception("s3_mutex::lock()",
                                 "Mutex uninitialised.");
   }
}

// call pthread_mutex_trylock
bool s3_mutex::try_lock() const
{
   int ev = pthread_mutex_trylock(CONST_OVERRIDE_MUTEX_T(&mutex));
   bool rv = false;
   if ( ev == 0 )
   {
      rv  = true;    // lock succeeded
   }
   else if ( ev == EBUSY )
   {
      rv = false;    // could not acquire lock
   }
   else if ( ev == EINVAL )
   {
      throw s3_generic_exception("s3_mutex::trylock()",
                                 "Mutex uninitialised.");
   }
   else 
   {
      std::stringstream str;
      str << "Unknown error: '" << strerror(rv) << "'";
      throw s3_generic_exception("s3_mutex::trylock()",
                                 str.str());
   }
   
   return rv;
}

// call pthread_mutex_unlock
void s3_mutex::unlock() const
{
   if ( pthread_mutex_unlock(CONST_OVERRIDE_MUTEX_T(&mutex)) != 0 )
   {
      throw s3_generic_exception("s3_mutex::unlock()",
                                 "Mutex uninitialised.");
   }
}

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