Qt：单实例应用保护的最佳做法

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问题描述

QSingleApplication ？ QMutex ？ QSharedMemory ？我正在寻找的东西，将在Windows，OSX和Linux（Ubuntu）中顺利工作。使用Qt 4.7.1

QSingleApplication? QMutex? QSharedMemory? I'm looking for something that will work smoothly in Windows, OSX and Linux (Ubuntu). Using Qt 4.7.1

推荐答案

简单的解决方案，这是你想要的。没有网络依赖（ QtSingleApplication ）且没有任何开销。

Simple solution, that does what you want. Without network dependency (as QtSingleApplication) and without any overhead.

用法：

int main()
{
    RunGuard guard( "some_random_key" );
    if ( !guard.tryToRun() )
        return 0;

    QAppplication a(/*...*/);
    // ...
}

RunGuard.h

#ifndef RUNGUARD_H
#define RUNGUARD_H

#include <QObject>
#include <QSharedMemory>
#include <QSystemSemaphore>


class RunGuard
{

public:
    RunGuard( const QString& key );
    ~RunGuard();

    bool isAnotherRunning();
    bool tryToRun();
    void release();

private:
    const QString key;
    const QString memLockKey;
    const QString sharedmemKey;

    QSharedMemory sharedMem;
    QSystemSemaphore memLock;

    Q_DISABLE_COPY( RunGuard )
};


#endif // RUNGUARD_H

RunGuard.cpp

#include "RunGuard.h"

#include <QCryptographicHash>


namespace
{

QString generateKeyHash( const QString& key, const QString& salt )
{
    QByteArray data;

    data.append( key.toUtf8() );
    data.append( salt.toUtf8() );
    data = QCryptographicHash::hash( data, QCryptographicHash::Sha1 ).toHex();

    return data;
}

}


RunGuard::RunGuard( const QString& key )
    : key( key )
    , memLockKey( generateKeyHash( key, "_memLockKey" ) )
    , sharedmemKey( generateKeyHash( key, "_sharedmemKey" ) )
    , sharedMem( sharedmemKey )
    , memLock( memLockKey, 1 )
{
    memLock.acquire();
    {
        QSharedMemory fix( sharedmemKey );    // Fix for *nix: http://habrahabr.ru/post/173281/
        fix.attach();
    }
    memLock.release();
}

RunGuard::~RunGuard()
{
    release();
}

bool RunGuard::isAnotherRunning()
{
    if ( sharedMem.isAttached() )
        return false;

    memLock.acquire();
    const bool isRunning = sharedMem.attach();
    if ( isRunning )
        sharedMem.detach();
    memLock.release();

    return isRunning;
}

bool RunGuard::tryToRun()
{
    if ( isAnotherRunning() )   // Extra check
        return false;

    memLock.acquire();
    const bool result = sharedMem.create( sizeof( quint64 ) );
    memLock.release();
    if ( !result )
    {
        release();
        return false;
    }

    return true;
}

void RunGuard::release()
{
    memLock.acquire();
    if ( sharedMem.isAttached() )
        sharedMem.detach();
    memLock.release();
}

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