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();
        {
                // Fix for *nix: http://habrahabr.ru/post/173281/
                QSharedMemory fix(sharedmemKey);
                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()
{
        // Extra check
        if (isAnotherRunning())
                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();
}