JUCE/modules/juce_core/threads/juce_InterProcessLock.h

/*
  ==============================================================================

   This file is part of the JUCE library - "Jules' Utility Class Extensions"
   Copyright 2004-11 by Raw Material Software Ltd.

  ------------------------------------------------------------------------------

   JUCE can be redistributed and/or modified under the terms of the GNU General
   Public License (Version 2), as published by the Free Software Foundation.
   A copy of the license is included in the JUCE distribution, or can be found
   online at www.gnu.org/licenses.

   JUCE 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 General Public License for more details.

  ------------------------------------------------------------------------------

   To release a closed-source product which uses JUCE, commercial licenses are
   available: visit www.rawmaterialsoftware.com/juce for more information.

  ==============================================================================
*/

#ifndef __JUCE_INTERPROCESSLOCK_JUCEHEADER__
#define __JUCE_INTERPROCESSLOCK_JUCEHEADER__

#include "../text/juce_String.h"
#include "../memory/juce_ScopedPointer.h"


//==============================================================================
/**
    Acts as a critical section which processes can use to block each other.

    @see CriticalSection
*/
class JUCE_API  InterProcessLock
{
public:
    //==============================================================================
    /** Creates a lock object.

        @param name     a name that processes will use to identify this lock object
    */
    explicit InterProcessLock (const String& name);

    /** Destructor.

        This will also release the lock if it's currently held by this process.
    */
    ~InterProcessLock();

    //==============================================================================
    /** Attempts to lock the critical section.

        @param timeOutMillisecs     how many milliseconds to wait if the lock
                                    is already held by another process - a value of
                                    0 will return immediately, negative values will wait
                                    forever
        @returns    true if the lock could be gained within the timeout period, or
                    false if the timeout expired.
    */
    bool enter (int timeOutMillisecs = -1);

    /** Releases the lock if it's currently held by this process.
    */
    void exit();

    //==============================================================================
    /**
        Automatically locks and unlocks an InterProcessLock object.

        This works like a ScopedLock, but using an InterprocessLock rather than
        a CriticalSection.

        @see ScopedLock
    */
    class ScopedLockType
    {
    public:
        //==============================================================================
        /** Creates a scoped lock.

            As soon as it is created, this will lock the InterProcessLock, and
            when the ScopedLockType object is deleted, the InterProcessLock will
            be unlocked.

            Note that since an InterprocessLock can fail due to errors, you should check
            isLocked() to make sure that the lock was successful before using it.

            Make sure this object is created and deleted by the same thread,
            otherwise there are no guarantees what will happen! Best just to use it
            as a local stack object, rather than creating one with the new() operator.
        */
        explicit ScopedLockType (InterProcessLock& lock)                    : lock_ (lock) { lockWasSuccessful = lock.enter(); }

        /** Destructor.

            The InterProcessLock will be unlocked when the destructor is called.

            Make sure this object is created and deleted by the same thread,
            otherwise there are no guarantees what will happen!
        */
        inline ~ScopedLockType()                                            { lock_.exit(); }

        /** Returns true if the InterProcessLock was successfully locked. */
        bool isLocked() const noexcept                                      { return lockWasSuccessful; }

    private:
        //==============================================================================
        InterProcessLock& lock_;
        bool lockWasSuccessful;

        JUCE_DECLARE_NON_COPYABLE (ScopedLockType);
    };

private:
    //==============================================================================
    class Pimpl;
    friend class ScopedPointer <Pimpl>;
    ScopedPointer <Pimpl> pimpl;

    CriticalSection lock;
    String name;

    JUCE_DECLARE_NON_COPYABLE (InterProcessLock);
};


#endif   // __JUCE_INTERPROCESSLOCK_JUCEHEADER__