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Table of contents
1.
Introduction
2.
What is a Message?
3.
What is Message Passing in C++?
4.
Example of Message Passing in C++?
4.1.
Implementation
4.2.
C++
5.
How does this work?
6.
Writing Framework for Inter Thread Message Passing in C++
7.
What are Message Queues in C++?
8.
Difference between Method Call and Message passing.
9.
Messaging Design Patterns
10.
Frequently Asked Questions
10.1.
What is dynamic binding in C++ with example?
10.2.
What are the advantages of message passing?
10.3.
What is message passing in OOP?
10.4.
What is message passing and dynamic binding in C++?
10.5.
What is the difference between message passing and function call in C++?
11.
Conclusion
Last Updated: May 4, 2024
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Message Passing in C++

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Introduction

Let's ensure we understand the foundational concepts before delving further into the subjects. Here is a brief introduction if you are unfamiliar with C++.

C++ is a high-level programming language widely used for developing software for various platforms, including Windows, Mac, and Linux. It is an extension of the C programming language and provides object-oriented programming capabilities and low-level memory manipulation. C++ is often used for developing large, complex software systems, such as operating systems, video games, and simulations.

Now let's get started learning further about message passing in C++.

Message passing in C++ is the process by which objects communicate by exchanging messages, typically in the form of method or function calls. This mechanism enables objects to interact and collaborate, facilitating the accomplishment of desired objectives.

message passing in c++

What is a Message?

A message typically refers to a packet or block of data that is sent between software components, processes, or systems to perform a specific task or exchange information. Messages can be sent over various communication channels, including local or remote networks, shared memory, or inter-process communication mechanisms. Messages can also be used to signal events, requests, or responses between components, as well as for synchronization and coordination purposes.

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What is Message Passing in C++?

Message passing in C++ refers to the process of passing a message, or data, between different objects or components in a program. This can be done in many ways, such as function calls, events, or inter-process communication. The specific implementation of message passing will depend on the program's design and the system's needs.

Example of Message Passing in C++?

Here is an example of message passing in c++, which is based on real life.

Implementation

  • C++

C++

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;
class Lucky_generator {
public:
int lucky_number;
void get_luckyNumber() {
lucky_number = rand() % 100;
cout << "Whose lucky Number is: " << lucky_number << endl;
}
};
class Ninja {
private:
string ninja_name;
int ninja_id;
public:
Ninja(string name, int id) {
ninja_name = name;
ninja_id = id;
}
void call_luckyNumber(Lucky_generator &Number) { // Pass by reference
cout << "Ninja name is: " << ninja_name << endl;
cout << "Ninja id: " << ninja_id << endl;
Number.get_luckyNumber();
}
};
int main() {
srand(time(0)); // Seed the random number generator only once
Ninja Abhi("Abhi", 23);
Lucky_generator Number;
Abhi.call_luckyNumber(Number);
return 0;
}

 

Output

In this example, the Lucky number generator used to generate a lucky number of ninjas is represented by the class Lucky_generator. The lucky generator has the function of providing a lucky number. The ninjas are represented by the Ninja class and have a ninja_name and ninja_id and a call_luckyNumber function which calls the function in the Lucky_generator class. The main function has the real-life instances of the class called objects for the ninja and lucky generator, which are used by the call_luckyNumber function to pass the message that the get_luckyNumber() function must be called to provide the lucky number to the ninja.

How does this work?

The following steps to implement message passing in c++.

  • Creating a class and its associated Object.
     
  • A message can be used to assist objects in communicating with one another.
     
  • An object that will invoke the function in another object receives a message.
     
  • Thus, a message is used to start a conversation between two things.

Writing Framework for Inter Thread Message Passing in C++

Inter-thread message passing is a mechanism that allows threads within a program to communicate with each other by exchanging messages. To implement this in C++, we can define a Message class to represent the data to be exchanged and a MessageQueue class to manage the queue of messages. The MessageQueue class should use synchronization mechanisms (e.g., mutexes, condition variables) to ensure thread safety. The threads can then use the MessageQueue to send and receive messages using appropriate methods such as push and pop. This framework can be extended to include features such as message prioritization, message filtering, and multi-threaded message handling.

Let us look at a simple example of inter-thread message passing using a queue and mutexes:

#include <iostream>
#include <thread>
#include <mutex>
#include <queue>
#include <chrono>
std::mutex mtx; // Mutex for protecting the shared queue
std::queue<int> messageQueue; // Shared queue for passing messages between threads
// Function for sending messages to the queue
void sendMessage(int message) {
   // Lock the mutex before accessing the shared queue
   std::lock_guard<std::mutex> lock(mtx);
   messageQueue.push(message);
}
// Function for receiving messages from the queue
void receiveMessage() {
   while (true) {
       // Lock the mutex before accessing the shared queue
       std::lock_guard<std::mutex> lock(mtx);
       // Check if the queue is not empty
       if (!messageQueue.empty()) {
           int message = messageQueue.front();
           messageQueue.pop();
           std::cout << "Received message: " << message << std::endl;
       }
   }
}
int main() {
   // Create a thread for receiving messages
   std::thread receiverThread(receiveMessage);
   // Send messages from the main thread
   for (int i = 0; i < 5; ++i) {
       sendMessage(i);
       std::this_thread::sleep_for(std::chrono::seconds(1)); // Simulate some work
   }
   // Wait for the receiver thread to finish
   receiverThread.join();
   return 0;
}

Explanation:

We include necessary C++ standard library headers for thread management (<thread>), mutexes (<mutex>), queues (<queue>), and input/output (<iostream>). We declare a mutex mtx to protect the shared queue messageQueue from concurrent access by multiple threads. We define two functions: sendMessage() and receiveMessage(). sendMessage() is responsible for adding messages to the queue, and receiveMessage() continuously checks the queue for incoming messages and processes them. In the main() function, we create a separate thread receiverThread for executing the receiveMessage() function. In the main thread, we send five messages to the shared queue with a delay of 1 second between each message to simulate some work. Finally, we wait for the receiverThread to finish its execution by calling join() on it.

What are Message Queues in C++?

Message queues are data structures that allows multiple threads or processes to communicate with each other by passing messages. It is usually implemented using the standard library's std::queue or a third-party library.

Difference between Method Call and Message passing.

The following table summarises the significant difference between Method call and Message passing.

ParametersMethod CallMessage Passing
DefinitionMethod call is a specific type of message passing in which one object calls a member function of another object.Message passing refers to any mechanism that allows objects to communicate with each other.
RangeMethod call is a specific, concrete way of passing a message between objects.Message passing is a more general concept that encompasses different types of communication mechanisms.
Nature of CommunicationMethod call is a direct communication between two objects.Message passing can involve various forms of communication such as events, signals, and slots.
Handling of MessageThe sender knows the receiver object, and the message is passed through a function call.The sender raises an event, the receiver subscribes to that event, and the message is passed when the event is raised.
Message Handling FlexibilityThe receiver object will have a specific function to handle the message.The receiver object may handle the message in various ways, and even multiple objects can handle the same message.
Specificity of TerminologyA method call is a specific form of message passing involving calling a member function of another object.Message passing is a broader term referring to any mechanism allowing objects to communicate with each other.
Inclusion of ParametersParameters are typically passed along with the method call to provide necessary data for the function invocation.Parameters can also be passed along with the message, providing necessary data for handling by the receiving object.

Messaging Design Patterns

Messaging design patterns provide solutions to common communication challenges in distributed systems or systems involving multiple components. These patterns facilitate effective message exchange between components, promoting loose coupling and scalability. Here are some messaging design patterns commonly used in software development:

  • Publish-Subscribe Pattern: Facilitates broadcasting messages to multiple subscribers without direct coupling.
  • Message Queue Pattern: Decouples message producers from consumers, ensuring reliable and asynchronous message processing.
  • Request-Reply Pattern: Enables synchronous communication between components by sending requests and receiving responses.
  • Message Broker Pattern: Mediates message exchange between producers and consumers, offering features like routing, filtering, and transformation.
  • Command Pattern: Encapsulates requests as objects, supporting queuing, parameterization, and undo mechanisms.

Frequently Asked Questions

What is dynamic binding in C++ with example?

In C++, Dynamic binding means when you have different versions of a function in a class hierarchy, the correct version gets used when you call it, depending on the actual object's type. This helps with polymorphism. For example, if you have a base class with a particular function and different classes that inherit from it each have their versions of that function, dynamic binding and make sure that when you call the function on an object, it uses the correct version from the specific class that object belongs to, all while your program is running.

What are the advantages of message passing?

Multiple processes can read and write data to the message queue using the message-passing technique without being connected. Messages are kept in the queue until their intended receiver picks them up. Most operating systems use message queues, which are highly useful for interprocess communication.

What is message passing in OOP?

Message passing in OOP is a mechanism for objects to communicate and interact with each other by sending messages. It involves invoking methods on objects, which can lead to the exchange of information, execution of a specific behaviour, or modification of an object's state.

What is message passing and dynamic binding in C++?

Message passing in C++ is invoking a function or method of an object using a pointer or reference. Dynamic binding is a mechanism where the correct function or method is selected at runtime based on the type of object being pointed to or referenced.

What is the difference between message passing and function call in C++?

Message passing in C++ involves invoking methods on objects to communicate and interact with each other, while function call involves invoking a function or method with specific arguments to perform a task. Message passing supports dynamic binding, while function call uses static binding by default.

Conclusion

In this article, we have extensively discussed the details of message passing in C++.

Along with an example of how it works and the difference between a method call and message passing in C++.

We hope the blog has helped you enhance your knowledge of What message passing is in C++. For more about C++, you can refer to these articles: 

 

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