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 #include "qtlockedfile.h"
 
 /*!
     \class QtLockedFile
 
     \brief The QtLockedFile class extends QFile with advisory locking
     functions.
 
     A file may be locked in read or write mode. Multiple instances of
     \e QtLockedFile, created in multiple processes running on the same
     machine, may have a file locked in read mode. Exactly one instance
     may have it locked in write mode. A read and a write lock cannot
     exist simultaneously on the same file.
 
     The file locks are advisory. This means that nothing prevents
     another process from manipulating a locked file using QFile or
     file system functions offered by the OS. Serialization is only
     guaranteed if all processes that access the file use
     QLockedFile. Also, while holding a lock on a file, a process
     must not open the same file again (through any API), or locks
     can be unexpectedly lost.
 
     The lock provided by an instance of \e QtLockedFile is released
     whenever the program terminates. This is true even when the
     program crashes and no destructors are called.
 */
 
 /*! \enum QtLockedFile::LockMode
 
     This enum describes the available lock modes.
 
     \value ReadLock A read lock.
     \value WriteLock A write lock.
     \value NoLock Neither a read lock nor a write lock.
 */
 
 /*!
     Constructs an unlocked \e QtLockedFile object. This constructor
     behaves in the same way as \e QFile::QFile().
 
     \sa QFile::QFile()
 */
 QtLockedFile::QtLockedFile()
     : QFile()
 {
 #ifdef Q_OS_WIN
     wmutex = 0;
     rmutex = 0;
 #endif
     m_lock_mode = NoLock;
 }
 
 /*!
     Constructs an unlocked QtLockedFile object with file \a name. This
     constructor behaves in the same way as \e QFile::QFile(const
     QString&).
 
     \sa QFile::QFile()
 */
 QtLockedFile::QtLockedFile(const QString &name)
     : QFile(name)
 {
 #ifdef Q_OS_WIN
     wmutex = 0;
     rmutex = 0;
 #endif
     m_lock_mode = NoLock;
 }
 
 /*!
   Opens the file in OpenMode \a mode.
 
   This is identical to QFile::open(), with the one exception that the
   Truncate mode flag is disallowed. Truncation would conflict with the
   advisory file locking, since the file would be modified before the
   write lock is obtained. If truncation is required, use resize(0)
   after obtaining the write lock.
 
   Returns true if successful; otherwise false.
 
   \sa QFile::open(), QFile::resize()
 */
 bool QtLockedFile::open(OpenMode mode)
 {
     if (mode & QIODevice::Truncate) {
         qWarning("QtLockedFile::open(): Truncate mode not allowed.");
         return false;
     }
     return QFile::open(mode);
 }
 
 /*!
     Returns \e true if this object has a in read or write lock;
     otherwise returns \e false.
 
     \sa lockMode()
 */
 bool QtLockedFile::isLocked() const
 {
     return m_lock_mode != NoLock;
 }
 
 /*!
     Returns the type of lock currently held by this object, or \e
     QtLockedFile::NoLock.
 
     \sa isLocked()
 */
 QtLockedFile::LockMode QtLockedFile::lockMode() const
 {
     return m_lock_mode;
 }
 
 /*!
     \fn bool QtLockedFile::lock(LockMode mode, bool block = true)
 
     Obtains a lock of type \a mode. The file must be opened before it
     can be locked.
 
     If \a block is true, this function will block until the lock is
     acquired. If \a block is false, this function returns \e false
     immediately if the lock cannot be acquired.
 
     If this object already has a lock of type \a mode, this function
     returns \e true immediately. If this object has a lock of a
     different type than \a mode, the lock is first released and then a
     new lock is obtained.
 
     This function returns \e true if, after it executes, the file is
     locked by this object, and \e false otherwise.
 
     \sa unlock(), isLocked(), lockMode()
 */
 
 /*!
     \fn bool QtLockedFile::unlock()
 
     Releases a lock.
 
     If the object has no lock, this function returns immediately.
 
     This function returns \e true if, after it executes, the file is
     not locked by this object, and \e false otherwise.
 
     \sa lock(), isLocked(), lockMode()
 */
 
 /*!
     \fn QtLockedFile::~QtLockedFile()
 
     Destroys the \e QtLockedFile object. If any locks were held, they
     are released.
 */