c++实如今同一台主机两个步伐实实际时通信
c++代码实现同一台主机两个步伐实实际时通信对于历程间通信方式有很多种，对于本机两个步伐中可以实时通信那么应该选择哪个呢？很多人最快想到的就是socket通信。
套接字适用于跨网络的历程间通信，具有网络透明性、机动性和安全性高的优点，但性能开销较大，延迟较高！
共享内存适用于同一台呆板上的历程间通信，具有高性能、低延迟和高吞吐量的优点，但需要手动管理同步机制，安全性较低。以是我们优先使用共享内存来实现，在智能驾驶等工业场景中使用非常多。
共享内存实现
历程A：
#include <cstring>
#include <iostream>
#include <sys/shm.h>
#include <thread>
#include <unistd.h>
#define SHM_KEY_A 12345
#define SHM_KEY_B 67890
#define SHM_SIZE 1024
void send_messages(char* send_data)
{
std::string message;
while (std::getline(std::cin, message)) {
if (message == "exit") {
break;
}
strncpy(send_data, message.c_str(), SHM_SIZE - 1);
send_data = '\0';
while (std::strlen(send_data) > 0) {
usleep(100000); // 等待 100 毫秒
}
}
}
void receive_messages(char* recv_data)
{
while (true) {
while (std::strlen(recv_data) == 0) {
usleep(100000); // 等待 100 毫秒
}
std::cout << "Received message: " << recv_data << std::endl;
std::memset(recv_data, 0, SHM_SIZE);
}
}
int main()
{
// 创建共享内存A（用于接收消息）
int shmid_a = shmget(SHM_KEY_A, SHM_SIZE, 0666);
if (shmid_a == -1) {
std::cerr << "Failed to get shared memory A" << std::endl;
return 1;
}
// 创建共享内存B（用于发送消息）
int shmid_b = shmget(SHM_KEY_B, SHM_SIZE, 0666);
if (shmid_b == -1) {
std::cerr << "Failed to get shared memory B" << std::endl;
return 1;
}
// 将共享内存连接到当前进程
char* recv_data = (char*)shmat(shmid_a, nullptr, 0);
char* send_data = (char*)shmat(shmid_b, nullptr, 0);
if (recv_data == (char*)-1 || send_data == (char*)-1) {
std::cerr << "Failed to attach shared memory" << std::endl;
return 1;
}
std::thread sender(send_messages, send_data);
std::thread receiver(receive_messages, recv_data);
sender.join();
receiver.join();
// 清理共享内存
shmdt(recv_data);
shmdt(send_data);
shmctl(shmid_a, IPC_RMID, nullptr);
shmctl(shmid_b, IPC_RMID, nullptr);
return 0;
}
历程B：
#include <cstring>
#include <iostream>
#include <sys/shm.h>
#include <thread>
#include <unistd.h>
#define SHM_KEY_A 12345
#define SHM_KEY_B 67890
#define SHM_SIZE 1024
void send_messages(char* send_data)
{
std::string message;
while (std::getline(std::cin, message)) {
if (message == "exit") {
break;
}
strncpy(send_data, message.c_str(), SHM_SIZE - 1);
send_data = '\0';
while (std::strlen(send_data) > 0) {
usleep(100000); // 等待 100 毫秒
}
}
}
void receive_messages(char* recv_data)
{
while (true) {
while (std::strlen(recv_data) == 0) {
usleep(100000); // 等待 100 毫秒
}
std::cout << "Received message: " << recv_data << std::endl;
std::memset(recv_data, 0, SHM_SIZE);
}
}
int main()
{
// 获取共享内存A（用于发送消息）
int shmid_a = shmget(SHM_KEY_A, SHM_SIZE, IPC_CREAT | 0666);
if (shmid_a == -1) {
std::cerr << "Failed to create shared memory A" << std::endl;
return 1;
}
// 获取共享内存B（用于接收消息）
int shmid_b = shmget(SHM_KEY_B, SHM_SIZE, IPC_CREAT | 0666);
if (shmid_b == -1) {
std::cerr << "Failed to create shared memory B" << std::endl;
return 1;
}
// 将共享内存连接到当前进程
char* send_data = (char*)shmat(shmid_a, nullptr, 0);
char* recv_data = (char*)shmat(shmid_b, nullptr, 0);
if (send_data == (char*)-1 || recv_data == (char*)-1) {
std::cerr << "Failed to attach shared memory" << std::endl;
return 1;
}
std::thread sender(send_messages, send_data);
std::thread receiver(receive_messages, recv_data);
sender.join();
receiver.join();
// 清理共享内存
shmdt(send_data);
shmdt(recv_data);
shmctl(shmid_a, IPC_RMID, nullptr);
shmctl(shmid_b, IPC_RMID, nullptr);
return 0;
}
代码简洁比较容易。有些捞仔可能会问了，除了共享内存另有没有其它方式呢？有！当然有，只不过性能不如共享内存啦。
命名管道实现
历程A：
#include <fstream>
#include <iostream>
#include <sys/stat.h>
#include <thread>
#include <unistd.h>
#define PIPE_NAME_A "pipe_a"
#define PIPE_NAME_B "pipe_b"
void send_messages(const std::string& pipe_name)
{
std::ofstream pipe(pipe_name);
if (!pipe) {
std::cerr << "Failed to open named pipe for writing" << std::endl;
return;
}
std::cout << "Enter messages to send (type 'exit' to quit):" << std::endl;
while (true) {
std::string message;
std::getline(std::cin, message);
if (message == "exit") {
break;
}
pipe << message << std::endl;
pipe.flush();
}
}
void receive_messages(const std::string& pipe_name)
{
std::ifstream pipe(pipe_name);
if (!pipe) {
std::cerr << "Failed to open named pipe for reading" << std::endl;
return;
}
std::cout << "Waiting for messages..." << std::endl;
while (true) {
std::string message;
std::getline(pipe, message);
// 处理程序在没有数据时不会频繁地检查管道，从而节省CPU资源，同时保持对新数据的响应
if (pipe.eof()) {
sleep(1);
pipe.clear();
pipe.seekg(0, std::ios::end);
} else {
std::cout << "Received message: " << message << std::endl;
}
}
}
int main()
{
// 创建命名管道
if (mkfifo(PIPE_NAME_A, 0666) == -1) {
std::cerr << "Failed to create named pipe A" << std::endl;
return 1;
}
if (mkfifo(PIPE_NAME_B, 0666) == -1) {
std::cerr << "Failed to create named pipe B" << std::endl;
return 1;
}
std::thread sender(send_messages, PIPE_NAME_A);
std::thread receiver(receive_messages, PIPE_NAME_B);
sender.join();
receiver.join();
return 0;
}
历程B：
#include <fstream>
#include <iostream>
#include <sys/stat.h>
#include <thread>
#include <unistd.h>
#define PIPE_NAME_A "pipe_a"
#define PIPE_NAME_B "pipe_b"
void send_messages(const std::string& pipe_name)
{
std::ofstream pipe(pipe_name);
if (!pipe) {
std::cerr << "Failed to open named pipe for writing" << std::endl;
return;
}
std::cout << "Enter messages to send (type 'exit' to quit):" << std::endl;
while (true) {
std::string message;
std::getline(std::cin, message);
if (message == "exit") {
break;
}
pipe << message << std::endl;
pipe.flush();
}
}
void receive_messages(const std::string& pipe_name)
{
std::ifstream pipe(pipe_name);
if (!pipe) {
std::cerr << "Failed to open named pipe for reading" << std::endl;
return;
}
std::cout << "Waiting for messages..." << std::endl;
while (true) {
std::string message;
std::getline(pipe, message);
if (pipe.eof()) {
sleep(1);
pipe.clear();
pipe.seekg(0, std::ios::end);
} else {
std::cout << "Received message: " << message << std::endl;
}
}
}
int main()
{
std::thread sender(send_messages, PIPE_NAME_B);
std::thread receiver(receive_messages, PIPE_NAME_A);
sender.join();
receiver.join();
return 0;
}
相对于共享内存的优缺点：
优点：
[*]简单易用：命名管道的实现相对简单，得当用于简单的历程间通信。
缺点：
[*]性能开销：命名管道的性能略低于共享内存，因为数据需要通过内核缓冲区传输。共享内存是所有历程间通信（IPC）机制中最快的，因为它不需要在历程之间复制数据。
[*]单向通信：命名管道通常是单向的，需要两个管道实现双向通信。
还可以使用消息队列实现（本人使用的是wsl2，微软不支持，故没有代码）
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