The QMutex class provides access serialization between threads. More...
#include <qthread.h>
Inherits Qt.
The purpose of a QMutex is to protect an object, data structure or section of code so that only one thread can access it at a time (In Java terms, this is similar to the synchronized keyword). For example, say there is a method which prints a message to the user on two lines:
void someMethod() { qDebug("Hello"); qDebug("World"); }
If this method is called simultaneously from two threads then the following sequence could result:
Hello Hello World World
If we add a mutex:
QMutex mutex; void someMethod() { mutex.lock(); qDebug("Hello"); qDebug("World"); mutex.unlock(); }
In Java terms this would be:
void someMethod() { synchronized { qDebug("Hello"); qDebug("World"); } }
Then only one thread can execute someMethod at a time and the order of messages is always correct. This is a trivial example, of course, but applies to any other case where things need to happen in a particular sequence.
Constructs a new mutex. The mutex is created in an unlocked state. A recursive mutex is created if recursive is TRUE; a normal mutex is created if recursive is FALSE (default argument). With a recursive mutex, a thread can lock the same mutex multiple times and it will not be unlocked until a corresponding number of unlock() calls have been made.
[virtual]
Destroys the mutex.
Attempt to lock the mutex. If another thread has locked the mutex then this call will block until that thread has unlocked it.
See also unlock().
Returns TRUE if the mutex is locked by another thread.
Unlocks the mutex. Attempting to unlock a mutex in a different thread to the one that locked it results in an error. Unlocking a mutex that is not locked results in undefined behaviour (varies between different Operating Systems' thread implementations).
See also lock().
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