8-13 socketpairを利用したepoll_wait()の解除

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/epoll.h>

#define NEVENTS 16

int soc[2];

void
processA()
{
  sleep(3);

  printf("processA : send message\n");

  write(soc[0], "HOGE", 4);

  return;
}

void
processB()
{
  int epfd;
  struct epoll_event ev, ev_ret[NEVENTS];
  int nfds;
  int i;
  char buf[128];

  epfd = epoll_create(NEVENTS);
  if (epfd < 0) {
    perror("epoll_create");
    return;
  }

  memset(&ev, 0, sizeof(ev));
  ev.events = EPOLLIN;
  ev.data.fd = soc[1];
  if (epoll_ctl(epfd, EPOLL_CTL_ADD, soc[1], &ev) != 0) {
    perror("epoll_ctl");
    return;
  }

  memset(&ev, 0, sizeof(ev));
  ev.events = EPOLLIN;
  ev.data.fd = fileno(stdin);
  if (epoll_ctl(epfd, EPOLL_CTL_ADD, fileno(stdin), &ev) != 0) {
    perror("epoll_ctl");
    return;
  }

  while (1) {
    printf("before epoll_wait\n");
    nfds = epoll_wait(epfd, ev_ret, NEVENTS, -1);
    if (nfds < 0) {
      perror("epoll_wait");
      return;
    }

    printf("after epoll_wait\n");

    for (i=0; i<nfds; i++) {
      if (ev_ret[i].data.fd == soc[1]) {
        printf("processB: break message from socketpair\n");
        goto outofloop;
      } else if (ev_ret[i].data.fd == fileno(stdin)) {
        read(fileno(stdin), buf, sizeof(buf));
        printf("processB: input from stdin\n");
      }
    }
  }

  outofloop:

  printf("processB: outside of loop\n");

  return;
}

int
main()
{
  int ret;

  ret = socketpair(AF_UNIX, SOCK_STREAM, 0, soc);
  if (ret != 0) {
    perror("socketpair");
    return 1;
  }

  if (fork() == 0) {
    processA();
  } else {
    processB();
  }

  return 0;
}

拙著「Linuxネットワークプログラミング」の紹介