QReadLocker Class Reference

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

#include <qreadwritelock.h>

Public Functions
	QReadLocker (QReadWriteLock *readWriteLock)
	Constructs a QReadLocker and locks lock for reading. 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...
	~QReadLocker ()
	Destroys the QReadLocker and unlocks the lock that was passed to the constructor. More...

Properties
quintptr	q_val

Detailed Description

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

Note

This class or function is threadsafe.

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

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

QReadWriteLock lock;

QByteArray readData()
{
    QReadLocker locker(&lock);
    ...
    return data;
}

It is equivalent to the following code:

QReadWriteLock lock;

QByteArray readData()
{
    lock.lockForRead();
    ...
    lock.unlock();
    return data;
}

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

See also

QWriteLocker, QReadWriteLock

Definition at line 89 of file qreadwritelock.h.

Constructors and Destructors

QReadLocker()

QReadLocker::QReadLocker ( QReadWriteLock *  lock )

inline

Constructs a QReadLocker and locks lock for reading.

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

See also

QReadWriteLock::lockForRead()

Definition at line 125 of file qreadwritelock.h.

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

~QReadLocker()

QReadLocker::~QReadLocker ( )

inline

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

See also

QReadWriteLock::unlock()

Definition at line 94 of file qreadwritelock.h.

    { unlock(); }

Functions

readWriteLock()

QReadWriteLock * QReadLocker::readWriteLock ( ) const

inline

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

Definition at line 117 of file qreadwritelock.h.

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

relock()

void QReadLocker::relock ( )

inline

Relocks an unlocked lock.

See also

unlock()

Definition at line 107 of file qreadwritelock.h.

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

unlock()

void QReadLocker::unlock ( )

inline

Unlocks the lock associated with this locker.

See also

QReadWriteLock::unlock()

Definition at line 97 of file qreadwritelock.h.

Referenced by QDeclarativeMetaType::interfaceIId().

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

Properties

q_val

quintptr QReadLocker::q_val

private

Definition at line 122 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