libdill: Structured Concurrency for C


fdout - wait on file descriptor to become writable


#include <libdill.h>
int fdout(int fd, int64_t deadline);


Waits on a file descriptor (true OS file descriptor, not libdill socket handle) to either become readable 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.

deadline is a point in time when the operation should time out. 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 need be.


The function returns 0 on success. On error, it returns -1 and sets errno to one of the values below.



void sendbuf(int fd, const char *buf, size_t len) {
    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;