C++ concurrent programming: How to implement an event-driven concurrency model?

The event-driven concurrency model is a popular concurrent programming paradigm in C that uses event loops to handle events from different sources. The event loop is an infinite loop that retrieves and processes events from an event queue, typically by calling a callback function. In C, you can create an event loop using libevent or the operating system API. This model is suitable for handling a large number of events, such as network servers, GUI programs, and data processing.

C Concurrent Programming: Event-driven Concurrency Model

Introduction

Concurrent programming is a programming paradigm that allows multiple tasks or processes to be executed simultaneously. In C, the event-driven concurrency model is a popular programming model that utilizes event loops to handle events from different sources.

Event loop

The event loop is the core of the concurrency model. It is an infinite loop that continuously retrieves and processes events from the event queue. When an event occurs (for example, user input or network request), it is added to the queue. The event loop will read these events from the queue and process them, typically by calling the appropriate callback function.

Implementing event loop in C

In C, we can use libevent and other libraries or directly use the operating system API to create an event loop . The following is an example of using libevent to implement an event loop:

#include <event2/event.h>

void on_event(evutil_socket_t fd, short events, void *arg) {
  // 处理事件
}

int main() {
  struct event_base *base = event_base_new();
  event *ev = event_new(base, STDIN_FILENO, EV_READ | EV_PERSIST, on_event, NULL);
  event_add(ev, NULL);
  event_base_dispatch(base);
  event_free(ev);
  event_base_free(base);
  return 0;
}

This example creates an event loop (base) and then uses libevent Create an event (ev). This event listens for read events (EV_READ) on standard input and specifies a callback function (on_event) to be called when the event occurs. event_base_dispatch Starts an event loop that will continue to run until manually stopped or an error occurs.

Practical Case

The event-driven concurrency model is very suitable for handling a large number of events from multiple sources. The following are some common practical cases:

• Network server: Use an event loop to handle connections and requests from clients.
• GUI program: Listen for events from the user interface (clicks, mouse movements, etc.).
• Data processing: Process data streams from different sources concurrently.

Conclusion

The event-driven concurrency model provides a powerful and efficient way to manage concurrent tasks in C. By using the event loop, developers can create scalable, responsive and high-performance applications.

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