#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

static void
showpoll(const char *title, int events)
{
	int n = 0;

	printf("%s=0x%x<", title, events);
	if (events & POLLIN)
		printf("%sPOLLIN", n++ ? "," : "");
	if (events & POLLRDNORM)
		printf("%sPOLLRDNORM", n++ ? "," : "");
	if (events & POLLRDBAND)
		printf("%sPOLLRDBAND", n++ ? "," : "");
	if (events & POLLOUT)
		printf("%sPOLLOUT", n++ ? "," : "");
	if (events & POLLWRNORM)
		printf("%sPOLLWRNORM", n++ ? "," : "");
	if (events & POLLWRBAND)
		printf("%sPOLLWRBAND", n++ ? "," : "");
	if (events & POLLHUP)
		printf("%sPOLLHUP", n++ ? "," : "");
	if (events & POLLERR)
		printf("%sPOLLERR", n++ ? "," : "");
	if (events & POLLNVAL)
		printf("%sPOLLNVAL", n++ ? "," : "");
	printf(">\n");
}

int
main(void)
{
	int rd0, wr, rd1;
	struct pollfd pfd[2];
	int nfds;
	char ch;
	ssize_t nread;
	int bzzt = 0;

	(void)unlink("fifo");
	if (mkfifo("fifo", 0600) == -1)
		err(EXIT_FAILURE, "mkfifo");

	printf("1. open rd0\n");
	fflush(stdout);

	if ((rd0 = open("fifo", O_RDONLY|O_NONBLOCK)) == -1)
		err(EXIT_FAILURE, "open rd0");
	memset(&pfd, 0, sizeof(pfd));
	pfd[0].fd = rd0;
	pfd[0].events = POLLIN;
	if ((nfds = poll(pfd, 1, 0)) == -1)
		err(EXIT_FAILURE, "poll");
	printf("nfds=%d\n", nfds);
	showpoll("pfd[0].revents", pfd[0].revents);
	fflush(stdout);
	if ((nread = read(rd0, &ch, 1)) == -1) {
		int error = errno;

		warn("read rd0");
		if (error == EAGAIN &&
		    (pfd[0].revents & POLLIN) != 0) {
			printf("*bzzt* poll said rd0 readable, why block?\n");
			bzzt = 1;
		}
	} else {
		printf("read rd0 returned %zd bytes\n", nread);
		if ((pfd[0].revents & POLLIN) == 0) {
			printf("*bzzt* poll said rd0 nonreadable, why read?\n");
			bzzt = 1;
		}
	}

	printf("2. open and close wr\n");
	fflush(stdout);
	if ((wr = open("fifo", O_WRONLY)) == -1)
		err(EXIT_FAILURE, "open wr");
	if (close(wr) == -1)
		err(EXIT_FAILURE, "close wr");
	memset(&pfd, 0, sizeof(pfd));
	pfd[0].fd = rd0;
	pfd[0].events = POLLIN;
	if ((nfds = poll(pfd, 1, 0)) == -1)
		err(EXIT_FAILURE, "poll");
	printf("nfds=%d\n", nfds);
	showpoll("pfd[0].revents", pfd[0].revents);
	fflush(stdout);
	if ((nread = read(rd0, &ch, 1)) == -1) {
		int error = errno;

		warn("read rd0");
		if (error == EAGAIN &&
		    (pfd[0].revents & POLLIN) != 0) {
			printf("*bzzt* poll said rd0 readable, why block?\n");
			bzzt = 1;
		}
	} else {
		printf("read rd0 returned %zd bytes\n", nread);
		if ((pfd[0].revents & POLLIN) == 0) {
			printf("*bzzt* poll said rd0 nonreadable, why read?\n");
			bzzt = 1;
		}
	}

	printf("3. open rd1\n");
	fflush(stdout);
	if ((rd1 = open("fifo", O_RDONLY|O_NONBLOCK)) == -1)
		err(EXIT_FAILURE, "open rd1");
	memset(&pfd, 0, sizeof(pfd));
	pfd[0].fd = rd0;
	pfd[0].events = POLLIN;
	pfd[1].fd = rd1;
	pfd[1].events = POLLIN;
	if ((nfds = poll(pfd, 2, 0)) == -1)
		err(EXIT_FAILURE, "poll");
	printf("nfds=%d\n", nfds);
	showpoll("pfd[0].revents", pfd[0].revents);
	showpoll("pfd[1].revents", pfd[1].revents);
	fflush(stdout);
	if ((nread = read(rd0, &ch, 1)) == -1) {
		int error = errno;

		warn("read rd0");
		if (error == EAGAIN &&
		    (pfd[0].revents & POLLIN) != 0) {
			printf("*bzzt* poll said rd0 readable, why block?\n");
			bzzt = 1;
		}
	} else {
		printf("read rd0 returned %zd bytes\n", nread);
		if ((pfd[0].revents & POLLIN) == 0) {
			printf("*bzzt* poll said rd0 nonreadable, why read?\n");
			bzzt = 1;
		}
	}
	fflush(stdout);
	if ((nread = read(rd1, &ch, 1)) == -1) {
		int error = errno;

		warn("read rd1");
		if (error == EAGAIN &&
		    (pfd[1].revents & POLLIN) != 0) {
			printf("*bzzt* poll said rd1 readable, why block?\n");
			bzzt = 1;
		}
	} else {
		printf("read rd1 returned %zd bytes\n", nread);
		if ((pfd[1].revents & POLLIN) == 0) {
			printf("*bzzt* poll said rd1 nonreadable, why read?\n");
			bzzt = 1;
		}
	}
	fflush(stdout);
	return bzzt | ferror(stdout);
}