src/rungaurd.cpp


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#include "rungaurd.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;
}

} // namespace

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();
}