#include <sys/select.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define BIG_PIPE_SIZE  64*1024 /* From sys/pipe.h */

/*
 * Test for the non-blocking big pipe bug (write(2) returning
 * EAGAIN while select(2) returns the descriptor as ready for write).
 */

static void
write_frame(int fd, char *buf, unsigned long buflen)
{
        fd_set wfd;
        int i;

        while (buflen) {
                FD_ZERO(&wfd);
                FD_SET(fd, &wfd);
                i = select(fd+1, NULL, &wfd, NULL, NULL);
                if (i < 0)
                        err(1, "select failed");
                if (i != 1) {
                        errx(1, "select returned unexpected value %d\n", i);
                        exit(1);
                }
                i = write(fd, buf, buflen);
                if (i < 0) {
                        if (errno != EAGAIN)
                                warn("write failed");
                        exit(1);
                }
                buf += i;
                buflen -= i;
        }
}

int
main(void)
{
        /* any value over PIPE_SIZE should do */
        char buf[BIG_PIPE_SIZE];
        int i, flags, fd[2];

        if (pipe(fd) < 0)
                errx(1, "pipe failed");

        flags = fcntl(fd[1], F_GETFL);
        if (flags == -1 || fcntl(fd[1], F_SETFL, flags|O_NONBLOCK) == -1) {
                printf("fcntl failed: %s\n", strerror(errno));
                exit(1);
        }

        switch (fork()) {
        case -1:
                err(1, "fork failed: %s\n", strerror(errno));
                break;
        case 0:
                close(fd[1]);
                for (;;) {
                        /* Any small size should do */
                        i = read(fd[0], buf, 256);
                        if (i == 0)
                                break;
                        if (i < 0)
                                err(1, "read");
                }
                exit(0);
        default:
                break;
        }

        close(fd[0]);
        memset(buf, 0, sizeof buf);
        for (i = 0; i < 1000; i++)
                write_frame(fd[1], buf, sizeof buf);

        printf("ok\n");
        exit(0);
}