#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>

void die(const char *msg) 
{fprintf(stderr, "%s: %s\n",msg,strerror(errno)); exit(1);}

void timer_expired(int sig) {}

int main(void)
{
	int fd1, fd2, i, err;
	char data[2048];
	pid_t pid;

	/* Create a fifo. Open one reader and two writers.
	   Make one writer non-blocking. */
	if (mkfifo("testpipe", 0666))
		if (errno!=EEXIST) die("mknod");
	if ((fd1=open("testpipe", O_RDWR))==-1) die("open");
	if ((fd2=open("testpipe", O_RDWR))==-1) die("open");
	if (unlink("testpipe")) die("unlink");
	if (fcntl(fd1, F_SETFL, O_NONBLOCK)==-1) die("fcntl");

	/* Fill the tty buffer until full */
	memset(data, 0, 2048);
	for (i=0; i<10; i++)
	{
		if (write(fd1, data, 2048)==-1) {
			if (errno==EINTR) continue;
			if (errno==EAGAIN) break;
			die("write");
		}
	}

	/* Fork, and do a blocking write in the child */
	if ((pid=fork())==-1) die("fork");
	if (!pid)
	{
		if (write(fd2, data, 2048)==-1)
			die("write");
		_exit(0);
	}
	sleep(1);
	alarm(0);
	signal(SIGALRM, timer_expired);
	alarm(1);
	errno=0;

	/* In the parent, do a non-blocking write while the atomic_write
	   semaphore is held. */
	if (write(fd1, data, 2048)==-1) {
		if (errno!=EINTR && errno!=EAGAIN) die("write");
	}
	err=errno;
	if (kill(pid, SIGTERM)) die("kill");
		
	switch(errno)
	{
	case EAGAIN:
		printf("pipe write failed with EAGAIN. Good.\n");
		return 0;
	case 0:
		printf("pipe write completed sucessfully. "
			"Bug test failed - run program again.\n");
		return 1;
	case EINTR:
		printf("pipe write failed with EINTR.\n"
			"write blocked despite file descriptor being "
			"non-blocking!\n");
		return 2;
	}
	return 1; /* NOTREACHED */
}