Symbian进程间通信 消息队列

核心提示：Contents* 1 Introduction* 2 Usage of Message Queue* 3 Creating a Queue* 4 Sending data to the Queue* 5 Receiving Messages from the Queue* 6 Other Queue Properti

Contents

* 1 Introduction

* 2 Usage of Message Queue

* 3 Creating a Queue

* 4 Sending data to the Queue

* 5 Receiving Messages from the Queue

* 6 Other Queue Properties

Introduction

Message Queues are one of the better and comfortable ways to send/receive messages/data between threads within a process(or a separate process).You can see other ways at Inter-Process Data Transfer and Inter-Thread Communication.

A queue is generally created to handle messages of a given type of defined(fixed) length. The size of a queue, ie, maximum number of messages, or slots, it can contain is defined and fixed when the queue is created. The size of message for which a queue is created, and the size of the queue is arbitrary, being limited only by system resources.

A Message Queue can be :

--A global queue, which is visible to all processes

--A local queue, which is local to the current process and not visible to any other process

Usage of Message Queue

The member functions defined in RMsgQueue are:

CreateGlobal(), CreateLocal(), Receive(), ReceiveBlocking(), Send(), SendBlocking()

Following are the neccessary steps to make use of a message queue:

* Create a queue

* Send data to the queue

* Receive message from the queue

* Other queue properites

Creating a Queue

RMsgQueue is the handle to a message queue.

class RMsgQueue : public RMsgQueueBase;

Here, RMsgQueueBase provides implementation for managing an asynchronous message queue, and is a base class for the RMsgQueue templated class.

class TMsgClass

{

public:

TInt iTemp1;

TInt iTemp2;

}

The following code shows how to create a global message queue with message