runguard.cc

#include "runguard.h"

#include <QCryptographicHash>


namespace {
  QString generateKeyHash(const QString& key, const QString& salt)
  {
    const QByteArray data(key.toUtf8().append(salt.toUtf8()));
    return QCryptographicHash::hash(data, QCryptographicHash::Sha1).toHex();
  }
}

RunGuard::RunGuard( const QString& key )
  : m_key(key)
  , m_memLockKey(generateKeyHash(key, "_memLockKey"))
  , m_sharedmemKey(generateKeyHash(key, "_sharedmemKey"))
  , m_sharedMem(m_sharedmemKey)
  , m_memLock(m_memLockKey, 1)
{
  m_memLock.acquire();
  {
    QSharedMemory fix(m_sharedmemKey);  // Fix for *nix: http://habrahabr.ru/post/173281/
    fix.attach();
  }
  m_memLock.release();
}

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

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

  m_memLock.acquire();
  const bool isRunning = m_sharedMem.attach();
  if (isRunning)
    m_sharedMem.detach();
  m_memLock.release();

  return isRunning;
}

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

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

  return true;
}

void RunGuard::release()
{
  m_memLock.acquire();
  if (m_sharedMem.isAttached())
    m_sharedMem.detach();
  m_memLock.release();
}