使用统一事件源的方式同时处理信号和 I/O
下面是一个服务器程序,他使用统一事件源的方式同时处理I/O和信号。
#include<sys/types.h>
#include<sys/socket.h>
#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<signal.h>
#include<fcntl.h>
#include<sys/epoll.h>
#include<pthread.h>
#include<errno.h>
#include<string.h>
#define MAX_EVENT_NUMBER 1024
static int pipefd[2];
int setnonblocking(int fd)
{
int old_option = fcntl(fd, F_GETFL);
int new_option = old_option | O_NONBLOCK;
fcntl(fd, F_SETFL, new_option);
return old_option;
}
void addfd(int epollfd, int fd)
{
epoll_event event;
event.events = EPOLLIN | EPOLLET;
event.data.fd = fd;
epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
setnonblocking(fd);
}
/* 信号处理函数 */
void sig_handler(int sig)
{
/* 保留原来的 errno,在函数最后恢复,以保证函数的可重入性 */
int save_errno = errno;
int msg = sig;
send(pipefd[1], (char*)&msg, 1, 0); /* 将信号值写入管道,以通知主循环 */
errno = save_errno;
}
/* 设置信号的处理函数 */
void addsig(int sig)
{
struct sigaction sa;
memset(&sa, '\0', sizeof(sa));
sa.sa_handler = sig_handler;
sa.sa_flags |= SA_RESTART; /* 重新调用被该信号终止的系统调用 */
sigfillset(&sa.sa_mask); /* 处理该信号过程中,阻塞所有其他信号 */
assert(sigaction(sig, &sa, NULL) != -1); /* 注册该信号的处理动作 */
}
int main(int argc, char* argv[])
{
if (argc <= 2)
{
return 1;
}
const char* ip = argv[1];
int port = atoi(argv[2]);
int ret = 0;
struct sockaddr_in address;
bzero(&address, sizeof(address));
address.sin_family = AF_INET;
address.sin_port = htons(port);
inet_pton(AF_INET, ip, &address.sin_addr);
int listenfd = socket(PF_INET, SOCK_STREAM, 0);
assert(listenfd >= 0);
ret = bind(listenfd, (struct sockaddr*)&address, sizeof(address));
if (ret == -1)
{
printf("errno is: %d\n", errno);
return 1;
}
ret = listen(listenfd, 5);
assert(ret != -1);
epoll_event events[MAX_EVENT_NUMBER];
int epollfd = epoll_create(10);
assert(epollfd != -1);
addfd(epollfd, listenfd);
/* 使用 socketpair 创建管道,注册 pipefd[0] 上的可读事件 */
ret = socketpair(PF_UNIX, SOCK_STREAM, 0, pipefd);
assert(ret != -1);
setnonblocking(pipefd[1]);
addfd(epollfd, pipefd[0]);
/* 设置(注册)一些信号的处理函数 */
addsig(SIGHUP);
addsig(SIGCHLD);
addsig(SIGTERM);
addsig(SIGINT);
bool stop_server = false;
while (!stop_server)
{
int number = epoll_wait(epollfd, events, MAX_EVENT_NUMBER, -1);
if (number < 0 && errno == EINTR)
{
break;
}
for (int i = 0; i < number; i++)
{
int sockfd = events[i].data.fd;
if (sockfd == listenfd) /* 如果文件描述符是 listenfd,则处理新连接 */
{
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);
int connfd = accept(sockfd, (struct sockaddr*)&client_address, &client_addrlength);
addfd(epollfd, connfd);
}
else if (sockfd == pipefd[0] && (events[i].events & EPOLLIN))
{
int sig;
char signals[1024];
ret = recv(pipefd[0], signals, sizeof(signals), 0);
if (ret == -1)
{
continue;
}
else if (ret == 0)
{
continue;
}
else
{
/* 因为每个信号值占1字节,所以按字节许来逐个接受信号。我们以 SIGTERM 为例,说明如何安全的终止服务器主循环 */
for (int i = 0; i < ret; i++)
{
switch(signals[i])
{
case SIGCHLD:
{
/* 执行自己性执行的操作 */
}
case SIGHUP:
{
continue;
}
case SIGTERM:
{
/* 执行自己性执行的操作 */
}
case SIGINT:
{
stop_server = true;
}
}
}
}
}
else
{
}
}
}
printf("close fds\n");
close(listenfd);
close(pipefd[1]);
close(pipefd[0]);
return 0;
}