smart_mutex.h

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/*
 * smart_mutex.h
 *
 * Copyright (C) 2007,2010  Thomas A. Vaughan
 * All rights reserved.
 *
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the <organization> nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THOMAS A. VAUGHAN ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THOMAS A. VAUGHAN BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * Simple smart mutex object.
 */

#ifndef WAVEPACKET_THREADSAFE_SMART_MUTEX_H__
#define WAVEPACKET_THREADSAFE_SMART_MUTEX_H__

// includes --------------------------------------------------------------------
#include "common/common.h"

#ifdef WIN32
typedef CRITICAL_SECTION        mutex_t;
#else   // WIN32
#include <pthread.h>
typedef pthread_mutex_t         mutex_t;
#endif  // WIN32

/// \ingroup threading
/*@{*/

/// \defgroup threadsafe Threadsafe Collection API
///
/// A set of objects and collection for threadsafe C++ code.
/// Abstracts lower-level threadsafe objects.
/*@{*/


/// class that automatically creates and destroys mutexes
class smart_mutex {
public:
        /// constructor will automatically create mutex
        smart_mutex(void) {
#ifdef WIN32
                        // use spin count, can help multi-proc
                        // (spin count is ignored on single-proc machines)
                        InitializeCriticalSectionAndSpinCount(&m_mutex, 4096);
#else   // WIN32
                        ASSERT(!pthread_mutex_init(&m_mutex, NULL),
                            "Failed to initialize mutex");
#endif  // WIN32
                }

        /// destructor will automatically destroy mutex
        ~smart_mutex(void) {
#ifdef WIN32
                        DeleteCriticalSection(&m_mutex);
#else   // WIN32
                        pthread_mutex_destroy(&m_mutex);
#endif  // WIN32
                }

        /// operating-system-dependent accessor
        mutex_t * getMutex(void) { return &m_mutex; }

private:
        // private member data
        mutex_t         m_mutex;
};



/// class that automatically locks and unlocks pthread mutexes
/// To use mlocks in code:
///   - create smart_mutex that will be locked
///   - create an mlock object and pass the mutex in the constructor
///   - on destruction, the mlock will automatically unlock the mutex
///
/// Example:
///\code
///     void threadsafeFunction(void)
///     {
///             smart_mutex my_mutex;
///
///             mlock lock(my_mutex);   // blocks until mutex is acquired
///
///             // some stuff that needs to be protected happens here
///             ...
///
///     }  <--- mutex is unlocked here as mlock destructor is called
///\endcode
class mlock {
public:
        /// constructor that accepts smart_mutex
        mlock(IN smart_mutex& sm) {
                        mutex_t * pm = sm.getMutex();
                        if (pm) {
                                m_pMutex = pm;
#ifdef WIN32
                                EnterCriticalSection(pm);
#else   // WIN32
                                pthread_mutex_lock(pm);
#endif  // WIN32
                        }
                }

        /// destructor automatically unlocks
        ~mlock(void) {
                        if (m_pMutex) {
#ifdef WIN32
                                LeaveCriticalSection(m_pMutex);
#else   // WIN32
                                pthread_mutex_unlock(m_pMutex);
#endif  // WIN32
                        }
                }

private:
        // private helper methods
        mlock(void);
        mlock(IN const mlock&);

        // private member data -------------------------------------------------
        mutex_t *       m_pMutex;
};



#endif  // WAVEPACKET_THREADSAFE_SMART_MUTEX_H__