rippled/modules/beast_core/threads/beast_InterProcessLock.h

//------------------------------------------------------------------------------
/*
    This file is part of Beast: https://github.com/vinniefalco/Beast
    Copyright 2013, Vinnie Falco <vinnie.falco@gmail.com>

    Portions of this file are from JUCE.
    Copyright (c) 2013 - Raw Material Software Ltd.
    Please visit http://www.juce.com

    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#ifndef BEAST_INTERPROCESSLOCK_BEASTHEADER
#define BEAST_INTERPROCESSLOCK_BEASTHEADER

#include "../text/beast_String.h"
#include "../memory/beast_ScopedPointer.h"


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

    @see CriticalSection
*/
class BEAST_API InterProcessLock : Uncopyable
{
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 : Uncopyable
    {
    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& l)        : ipLock (l) { lockWasSuccessful = l.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()                             { ipLock.exit(); }

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

    private:
        //==============================================================================
        InterProcessLock& ipLock;
        bool lockWasSuccessful;
    };

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

    CriticalSection lock;
    String name;
};


#endif   // BEAST_INTERPROCESSLOCK_BEASTHEADER