xpcom/glue/Mutex.h
author Chris Jones <jones.chris.g@gmail.com>
Sat, 02 May 2009 21:13:57 -0700
changeset 27952 e902d43f10f26d623d6b46e6de320cd9d6860d1f
parent 27951 3deeb3c83c7795f7a19a7126aa874dfcd63c09e4
child 27982 b78e21f29c5128608cb5f133661267160aa373e1
permissions -rw-r--r--
Backed out changeset 3deeb3c83c77

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: sw=4 ts=4 et :
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#ifndef mozilla_Mutex_h
#define mozilla_Mutex_h

#include "prlock.h"

#include "mozilla/BlockingResourceBase.h"

//
// Provides:
//
//  - Mutex, a non-recursive mutex
//  - MutexAutoLock, an RAII class for ensuring that Mutexes are properly 
//    locked and unlocked
//  - MutexAutoUnlock, complementary sibling to MutexAutoLock
//
// Using MutexAutoLock/MutexAutoUnlock is MUCH preferred to making bare
// calls to Mutex.Lock and Unlock.
//
namespace mozilla {


/**
 * Mutex
 * When possible, use MutexAutoLock/MutexAutoUnlock to lock/unlock this
 * mutex within a scope, instead of calling Lock/Unlock directly.
 **/

class NS_COM_GLUE Mutex : BlockingResourceBase
{
public:
    /**
     * Mutex
     * @param name A name which can reference this lock
     * @returns If failure, nsnull
     *          If success, a valid Mutex* which must be destroyed
     *          by Mutex::DestroyMutex()
     **/
    Mutex(const char* name) {
        mLock = PR_NewLock();
        if (!mLock)
            NS_RUNTIMEABORT("Can't allocate mozilla::Mutex");
        Init(mLock, name, eMutex);
    }

    /**
     * ~Mutex
     **/
    ~Mutex() {
        NS_ASSERTION(mLock,
                     "improperly constructed Lock or double free");
        // NSPR does consistency checks for us
        PR_DestroyLock(mLock);
        mLock = 0;
    }

#ifndef DEBUG
    /**
     * Lock
     * @see prlock.h
     **/
    void Lock() {
        PR_Lock(mLock);
    }

    /**
     * Unlock
     * @see prlock.h
     **/
    void Unlock() {
        PR_Unlock(mLock);
    }

    /**
     * AssertCurrentThreadOwns
     * @see prlock.h
     **/
    void AssertCurrentThreadOwns () { }

    /**
     * AssertNotCurrentThreadOwns
     * @see prlock.h
     **/
    void AssertNotCurrentThreadOwns () { }

#else
    void Lock();
    void Unlock();

    void AssertCurrentThreadOwns () {
        PR_ASSERT_CURRENT_THREAD_OWNS_LOCK(mLock);
    }

    void AssertNotCurrentThreadOwns () {
        // TODO
    }

#endif  // ifndef DEBUG

private:
    Mutex();
    Mutex(const Mutex&);
    Mutex& operator=(const Mutex&);

    PRLock* mLock;

    friend class CondVar;
};


/**
 * MutexAutoLock
 * Acquires the Mutex when it enters scope, and releases it when it leaves 
 * scope.
 *
 * MUCH PREFERRED to bare calls to Mutex.Lock and Unlock.
 */ 
class NS_COM_GLUE NS_STACK_CLASS MutexAutoLock
{
public:
    /**
     * Constructor
     * The constructor aquires the given lock.  The destructor
     * releases the lock.
     * 
     * @param aLock A valid mozilla::Mutex* returned by 
     *              mozilla::Mutex::NewMutex. 
     **/
    MutexAutoLock(mozilla::Mutex& aLock)
        : mLock(&aLock) {
        NS_ASSERTION(mLock, "null mutex");
        mLock->Lock();
    }
    
    ~MutexAutoLock(void) {
        mLock->Unlock();
    }
 
private:
    MutexAutoLock();
    MutexAutoLock(MutexAutoLock&);
    MutexAutoLock& operator=(MutexAutoLock&);
    static void* operator new(size_t) CPP_THROW_NEW;
    static void operator delete(void*);

    mozilla::Mutex* mLock;
};


/**
 * MutexAutoUnlock
 * Releases the Mutex when it enters scope, and re-acquires it when it leaves 
 * scope.
 *
 * MUCH PREFERRED to bare calls to Mutex.Unlock and Lock.
 */ 
class NS_COM_GLUE NS_STACK_CLASS MutexAutoUnlock 
{
public:
    MutexAutoUnlock(mozilla::Mutex& aLock) 
        : mLock(&aLock) {
        NS_ASSERTION(mLock, "null lock");
        mLock->Unlock();
    }

    ~MutexAutoUnlock() 
    {
        mLock->Lock();
    }

private:
    MutexAutoUnlock();
    MutexAutoUnlock(MutexAutoUnlock&);
    MutexAutoUnlock& operator =(MutexAutoUnlock&);
    static void* operator new(size_t) CPP_THROW_NEW;
    static void operator delete(void*);
     
    mozilla::Mutex* mLock;
};


} // namespace mozilla


#endif // ifndef mozilla_Mutex_h