BMessageQueue

Derived from: none

Declared in: be/app/MessageQueue.h

Library: libbe.so

[method summary]

The BMessageQueue class completes the implementation of BLooper by providing a first-in/first-out stack in which the looper can place in-coming BMessages. In general, the message dispatching mechanism of BLooper should suffice. However, if you ever need to manipulate a BMessage queue directly, you can do so.

Constructor and Destructor

BMessageQueue()

      BMessageQueue(void) 

Creates an empty BMessageQueue object.

~BMessageQueue()

      virtual ~BMessageQueue()

Deletes all the objects in the queue and all the data structures used to manage the queue.

Member Functions

AddMessage(), RemoveMessage()

      void AddMessage(BMessage *message)
      void RemoveMessage(BMessage *message)

AddMessage() adds message to the far end of the queue. RemoveMessage() removes a particular message from the queue and deletes it.

CountMessages(), IsEmpty()

      int32 CountMessages(void) const
      bool IsEmpty(void) const

CountMessages() returns the number of messages currently in the queue.

IsEmpty() returns true if the object doesn't contain any messages, and false otherwise.

FindMessage()

      BMessage *FindMessage(int32 index) const
      BMessage *FindMessage(uint32 what, int32 index = 0) const

FindMessage() returns a pointer to the index'th BMessage in the queue, where index 0 signifies the message that's been in the queue the longest. The second version lets you specify a what field value; in this case, only messages that match the what argument are counted. If no message matches the criteria, the functions return NULL.

The message is not removed from the message queue.

IsEmpty() see CountMessages()

Lock(), Unlock()

      bool Lock(void) 
      void Unlock(void) 

These functions lock and unlock the BMessageQueue, so that another thread won't alter the contents of the queue while it's being read. Lock() doesn't return until it has the queue locked; it always returns true. Unlock() releases the lock so that someone else can lock it. Calls to these functions can be nested.

See also: BLooper::Lock()

NextMessage()

      BMessage *NextMessage(void)

Removes and returns the oldest message from the queue. If the queue is empty, the function returns NULL.

See also: FindMessage()

RemoveMessage() see AddMessage()

Unlock() see Lock()

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Last modified May 27, 1998.