epoll.c

#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#define MAXEVENTS 64

static const char reply[] =
    "HTTP/1.0 200 OK\r\n"
    "Content-type: text/html\r\n"
    "Connection: close\r\n"
    "Content-Length: 82\r\n"
    "\r\n"
    "test";

int main(int argc, char *argv[]) {
  if (argc != 2) return fprintf(stderr, "Usage: %s [port]\n", argv[0]), -1;

  int sfd = socket(AF_INET, SOCK_STREAM, 0);
  bind(sfd,
       (struct sockaddr *)&((struct sockaddr_in){
           .sin_family = AF_INET, htons(atoi(argv[1])), {}}),
       sizeof(struct sockaddr_in));
  fcntl(sfd, F_SETFL, fcntl(sfd, F_GETFL, 0) | O_NONBLOCK);
  listen(sfd, SOMAXCONN);
  int efd = epoll_create1(0);
  static struct epoll_event events[MAXEVENTS];
  struct epoll_event event = {.data.fd = sfd, .events = EPOLLIN | EPOLLET};
  int s = epoll_ctl(efd, EPOLL_CTL_ADD, sfd, &event);
  while (1) {
    int n = epoll_wait(efd, events, sizeof(events) / sizeof(*events), -1);
    for (int i = 0; i < n; i++) {
      if ((events[i].events & EPOLLERR) || (events[i].events & EPOLLHUP) || (!(events[i].events & EPOLLIN))) {
        close(events[i].data.fd);
      } else if (sfd == events[i].data.fd) {
        while (1) {
          struct sockaddr in_addr;
          socklen_t in_len = sizeof in_addr;
          int infd = accept(sfd, &in_addr, &in_len);
          if (infd == -1) {
            break;
          }
          fcntl(infd, F_SETFL, fcntl(infd, F_GETFL, 0) | O_NONBLOCK);
          event.data.fd = infd;
          event.events = EPOLLIN | EPOLLET;
          epoll_ctl(efd, EPOLL_CTL_ADD, infd, &event);
        }
      } else {
        int done = 0;
        while (1) {
          char buf[512];
          ssize_t count = read(events[i].data.fd, buf, sizeof buf);
          done = (count == -1 && errno != EAGAIN) || !count;
          if (count <= 0) break;
          write(events[i].data.fd, reply, sizeof(reply));
        }
        if (done) {
          close(events[i].data.fd);
        }
      }
    }
  }
  close(sfd);
  return EXIT_SUCCESS;
}