C++ 使用 mmap 和 epoll 实现文件读写

以下是使用 C++ 实现 mmap+epoll 的示例代码：

#include <iostream>
#include <cstring>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/epoll.h>

using namespace std;

int main()
{
    int fd = open('test.txt', O_RDWR);
    if (fd == -1) {
        cerr << 'Failed to open file.' << endl;
        return 1;
    }
    
    struct stat sb;
    if (fstat(fd, &sb) == -1) {
        cerr << 'Failed to get file size.' << endl;
        close(fd);
        return 1;
    }
    
    char* data = (char*) mmap(NULL, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    if (data == MAP_FAILED) {
        cerr << 'Failed to mmap file.' << endl;
        close(fd);
        return 1;
    }
    
    close(fd);
    
    int epoll_fd = epoll_create1(0);
    if (epoll_fd == -1) {
        cerr << 'Failed to create epoll.' << endl;
        munmap(data, sb.st_size);
        return 1;
    }
    
    struct epoll_event event;
    memset(&event, 0, sizeof(event));
    event.events = EPOLLIN | EPOLLOUT;
    event.data.ptr = data;
    
    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, fd, &event) == -1) {
        cerr << 'Failed to add file descriptor to epoll.' << endl;
        close(epoll_fd);
        munmap(data, sb.st_size);
        return 1;
    }
    
    struct epoll_event events[10];
    int n = epoll_wait(epoll_fd, events, 10, 1000);
    if (n == -1) {
        cerr << 'Failed to wait for events.' << endl;
        close(epoll_fd);
        munmap(data, sb.st_size);
        return 1;
    }
    
    for (int i = 0; i < n; i++) {
        if (events[i].events & EPOLLIN) {
            // handle read event
        } else if (events[i].events & EPOLLOUT) {
            // handle write event
        }
    }
    
    close(epoll_fd);
    munmap(data, sb.st_size);
    
    return 0;
}

这个示例程序打开一个文件 test.txt，并将其映射到内存中。然后，它创建一个 epoll 实例并将文件描述符添加到其中。最后，它使用 epoll_wait 等待事件，处理读写事件并关闭所有资源。