How to implement asynchronous programming with C++ functions?
Apr 27, 2024 pm 09:09 PMSummary: Asynchronous programming in C allows multitasking without waiting for time-consuming operations. Use function pointers to create pointers to functions. The callback function is called when the asynchronous operation completes. Libraries such as boost::asio provide support for asynchronous programming. The practical case demonstrates how to use function pointers and boost::asio to implement asynchronous network requests.
Use C functions to implement asynchronous programming
Introduction
Asynchronous programming is a A programming paradigm that allows a program to perform other tasks while waiting for time-consuming operations (such as network requests) to complete. In this process, the callback function will be called after the operation is completed without the program explicitly waiting. In C, asynchronous programming can be implemented using function pointers and related libraries.
Function pointer
The function pointer in C is a pointer to a function. We can create a function pointer from the name of the function like this:
int add(int a, int b) { return a + b; } using AddFunction = int(*)(int, int); AddFunction addPtr = &add;
addPtr
is now a function pointer pointing to the add
function.
Callback function
The callback function is a function that is called when certain events occur. When an asynchronous operation completes, the system calls the corresponding callback function. For example, the following function will be called when the network request is completed:
void networkCallback(const std::string& data) { // 使用 data 進行處理 }
Asynchronous libraries
There are many libraries in C that support asynchronous programming. One popular choice is boost::asio
. This library provides many classes and functions for creating and managing asynchronous operations.
Practical Case
Let us create a simple example to demonstrate how to use function pointers and boost::asio
to implement asynchronous network requests:
#include <boost/asio.hpp> #include <iostream> using namespace boost::asio; // 回調(diào)函數(shù) void networkCallback(const boost::system::error_code& error, boost::array<char, 1024> data) { if (!error) { std::cout << data.data() << std::endl; } else { std::cout << "Error: " << error.message() << std::endl; } } int main() { using namespace std::placeholders; // 創(chuàng)建 IO 服務(wù) io_service service; // 創(chuàng)建 IP 協(xié)議套接字 ip::tcp::socket socket(service); // 連接到服務(wù)器 socket.connect( ip::tcp::endpoint(ip::address::from_string("127.0.0.1"), 8080)); // 發(fā)送請求 std::string request = "GET / HTTP/1.1\r\n\r\n"; std::async_write(socket, buffer(request), networkCallback, _1); service.run(); return 0; }
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