libdill: Structured Concurrency for C

NAME

fdout - wait on file descriptor to become writable

SYNOPSIS

#include <libdill.h>

int fdout(
    int fd,
    int64_t deadline);

DESCRIPTION

Waits on a file descriptor (true OS file descriptor, not libdill socket handle) to either become writeable or get into an error state. Either case leads to a successful return from the function. To distinguish the two outcomes, follow up with a write operation on the file descriptor.

fd: file descriptor (OS-level one, not a libdill handle)

deadline: A point in time when the operation should time out, in milliseconds. Use the now function to get your current point in time. 0 means immediate timeout, i.e., perform the operation if possible or return without blocking if not. -1 means no deadline, i.e., the call will block forever if the operation cannot be performed.

RETURN VALUE

In case of success the function returns 0. In case of error it returns -1 and sets errno to one of the values below.

ERRORS

EBADF: Not a file descriptor.
EBUSY: Another coroutine already blocked on fdout with this file descriptor.
ECANCELED: Current coroutine was canceled.
ETIMEDOUT: Deadline was reached.

EXAMPLE

int result = fcntl(fd, F_SETFL, O_NONBLOCK);
assert(result == 0);
while(len) {
    result = fdout(fd, -1);
    assert(result == 0);
    ssize_t sent = send(fd, buf, len, 0);
    assert(len > 0);
    buf += sent;
    len -= sent;
}