QWriteLocker Class Reference

The QWriteLocker class is a convenience class that simplifies locking and unlocking read-write locks for write access. More...

#include <qreadwritelock.h>

Public Functions
	QWriteLocker (QReadWriteLock *readWriteLock)
	Constructs a QWriteLocker and locks lock for writing. More...
QReadWriteLock *	readWriteLock () const
	Returns a pointer to the read-write lock that was passed to the constructor. More...
void	relock ()
	Relocks an unlocked lock. More...
void	unlock ()
	Unlocks the lock associated with this locker. More...
	~QWriteLocker ()
	Destroys the QWriteLocker and unlocks the lock that was passed to the constructor. More...

Properties
quintptr	q_val

Detailed Description

The QWriteLocker class is a convenience class that simplifies locking and unlocking read-write locks for write access.

Note

This class or function is threadsafe.

The purpose of QWriteLocker (and QReadLocker is to simplify QReadWriteLock locking and unlocking. Locking and unlocking statements or in exception handling code is error-prone and difficult to debug. QWriteLocker can be used in such situations to ensure that the state of the lock is always well-defined.

Here's an example that uses QWriteLocker to lock and unlock a read-write lock for writing:

QReadWriteLock lock;

void writeData(const QByteArray &data)
{
    QWriteLocker locker(&lock);
    ...
}

It is equivalent to the following code:

QReadWriteLock lock;

void writeData(const QByteArray &data)
{
    lock.lockForWrite();
    ...
    lock.unlock();
}

The QMutexLocker documentation shows examples where the use of a locker object greatly simplifies programming.

See also

QReadLocker, QReadWriteLock

Definition at line 133 of file qreadwritelock.h.

Constructors and Destructors

QWriteLocker()

QWriteLocker::QWriteLocker ( QReadWriteLock *  lock )

inline

Constructs a QWriteLocker and locks lock for writing.

The lock will be unlocked when the QWriteLocker is destroyed. If lock is zero, QWriteLocker does nothing.

See also

QReadWriteLock::lockForWrite()

Definition at line 170 of file qreadwritelock.h.

    : q_val(reinterpret_cast<quintptr>(areadWriteLock))
{
    Q_ASSERT_X((q_val & quintptr(1u)) == quintptr(0),
               "QWriteLocker", "QReadWriteLock pointer is misaligned");
    relock();
}

~QWriteLocker()

QWriteLocker::~QWriteLocker ( )

inline

Destroys the QWriteLocker and unlocks the lock that was passed to the constructor.

See also

QReadWriteLock::unlock()

Definition at line 138 of file qreadwritelock.h.

    { unlock(); }

Functions

readWriteLock()

QReadWriteLock * QWriteLocker::readWriteLock ( ) const

inline

Returns a pointer to the read-write lock that was passed to the constructor.

Definition at line 161 of file qreadwritelock.h.

    { return reinterpret_cast<QReadWriteLock *>(q_val & ~quintptr(1u)); }

relock()

void QWriteLocker::relock ( )

inline

Relocks an unlocked lock.

See also

unlock()

Definition at line 151 of file qreadwritelock.h.

    {
        if (q_val) {
            if ((q_val & quintptr(1u)) == quintptr(0u)) {
                readWriteLock()->lockForWrite();
                q_val |= quintptr(1u);
            }
        }
    }

unlock()

void QWriteLocker::unlock ( )

inline

Unlocks the lock associated with this locker.

See also

QReadWriteLock::unlock()

Definition at line 141 of file qreadwritelock.h.

Referenced by QDeclarativeTypePrivate::init().

    {
        if (q_val) {
            if ((q_val & quintptr(1u)) == quintptr(1u)) {
                q_val &= ~quintptr(1u);
                readWriteLock()->unlock();
            }
        }
    }

Properties

q_val

quintptr QWriteLocker::q_val

private

Definition at line 167 of file qreadwritelock.h.

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The documentation for this class was generated from the following files:

• /src/corelib/thread/qreadwritelock.h
• /src/corelib/thread/qreadwritelock.cpp