└── main.cc


/main.cc:
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  1 | #include <sys/socket.h>
  2 | #include <sys/epoll.h>
  3 | #include <netinet/in.h>
  4 | #include <arpa/inet.h>
  5 | #include <fcntl.h>
  6 | #include <unistd.h>
  7 | #include <stdio.h>
  8 | #include <errno.h>
  9 | #include <string.h>
 10 | #include <stdlib.h>
 11 | 
 12 | #define exit_if(r, ...) if(r) {printf(__VA_ARGS__); printf("error no: %d error msg %s\n", errno, strerror(errno)); exit(1);}
 13 | 
 14 | void setNonBlock(int fd) {
 15 |     int flags = fcntl(fd, F_GETFL, 0);
 16 |     exit_if(flags<0, "fcntl failed");
 17 |     int r = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
 18 |     exit_if(r<0, "fcntl failed");
 19 | }
 20 | 
 21 | void updateEvents(int efd, int fd, int events, int op) {
 22 |     struct epoll_event ev;
 23 |     memset(&ev, 0, sizeof(ev));
 24 |     ev.events = events;
 25 |     ev.data.fd = fd;
 26 |     printf("%s fd %d events read %d write %d\n",
 27 |            op==EPOLL_CTL_MOD?"mod":"add", fd, ev.events & EPOLLIN, ev.events & EPOLLOUT);
 28 |     int r = epoll_ctl(efd, op, fd, &ev);
 29 |     exit_if(r, "epoll_ctl failed");
 30 | }
 31 | 
 32 | void handleAccept(int efd, int fd) {
 33 |     struct sockaddr_in raddr;
 34 |     socklen_t rsz = sizeof(raddr);
 35 |     int cfd = accept(fd,(struct sockaddr *)&raddr,&rsz);
 36 |     exit_if(cfd<0, "accept failed");
 37 |     sockaddr_in peer, local;
 38 |     socklen_t alen = sizeof(peer);
 39 |     int r = getpeername(cfd, (sockaddr*)&peer, &alen);
 40 |     exit_if(r<0, "getpeername failed");
 41 |     printf("accept a connection from %s\n", inet_ntoa(raddr.sin_addr));
 42 |     setNonBlock(cfd);
 43 |     updateEvents(efd, cfd, EPOLLIN|EPOLLOUT, EPOLL_CTL_ADD);
 44 | }
 45 | 
 46 | void handleRead(int efd, int fd) {
 47 |     char buf[4096];
 48 |     int n = 0;
 49 |     while ((n=::read(fd, buf, sizeof buf)) > 0) {
 50 |         printf("read %d bytes\n", n);
 51 |         int r = ::write(fd, buf, n); //写出读取的数据
 52 |         //实际应用中，写出数据可能会返回EAGAIN，此时应当监听可写事件，当可写时再把数据写出
 53 |         exit_if(r<=0, "write error");
 54 |     }
 55 |     if (n<0 && (errno == EAGAIN || errno == EWOULDBLOCK))
 56 |         return;
 57 |     exit_if(n<0, "read error"); //实际应用中，n<0应当检查各类错误，如EINTR
 58 |     printf("fd %d closed\n", fd);
 59 |     close(fd);
 60 | }
 61 | 
 62 | void handleWrite(int efd, int fd) {
 63 |     //实际应用应当实现可写时写出数据，无数据可写才关闭可写事件
 64 |     updateEvents(efd, fd, EPOLLIN, EPOLL_CTL_MOD);
 65 | }
 66 | 
 67 | void loop_once(int efd, int lfd, int waitms) {
 68 |     const int kMaxEvents = 20;
 69 |     struct epoll_event activeEvs[100];
 70 |     int n = epoll_wait(efd, activeEvs, kMaxEvents, waitms);
 71 |     printf("epoll_wait return %d\n", n);
 72 |     for (int i = 0; i < n; i ++) {
 73 |         int fd = activeEvs[i].data.fd;
 74 |         int events = activeEvs[i].events;
 75 |         if (events & (EPOLLIN | EPOLLERR)) {
 76 |             if (fd == lfd) {
 77 |                 handleAccept(efd, fd);
 78 |             } else {
 79 |                 handleRead(efd, fd);
 80 |             }
 81 |         } else if (events & EPOLLOUT) {
 82 |             handleWrite(efd, fd);
 83 |         } else {
 84 |             exit_if(1, "unknown event");
 85 |         }
 86 |     }
 87 | }
 88 | 
 89 | int main() {
 90 |     short port = 99;
 91 |     int epollfd = epoll_create(1);
 92 |     exit_if(epollfd < 0, "epoll_create failed");
 93 |     int listenfd = socket(AF_INET, SOCK_STREAM, 0);
 94 |     exit_if(listenfd < 0, "socket failed");
 95 |     struct sockaddr_in addr;
 96 |     memset(&addr, 0, sizeof addr);
 97 |     addr.sin_family = AF_INET;
 98 |     addr.sin_port = htons(port);
 99 |     addr.sin_addr.s_addr = INADDR_ANY;
100 |     int r = ::bind(listenfd,(struct sockaddr *)&addr, sizeof(struct sockaddr));
101 |     exit_if(r, "bind to 0.0.0.0:%d failed %d %s", port, errno, strerror(errno));
102 |     r = listen(listenfd, 20);
103 |     exit_if(r, "listen failed %d %s", errno, strerror(errno));
104 |     printf("fd %d listening at %d\n", listenfd, port);
105 |     setNonBlock(listenfd);
106 |     updateEvents(epollfd, listenfd, EPOLLIN, EPOLL_CTL_ADD);
107 |     for (;;) { //实际应用应当注册信号处理函数，退出时清理资源
108 |         loop_once(epollfd, listenfd, 10000);
109 |     }
110 |     return 0;
111 | }


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