.TH io_fd_flags 3
.SH NAME
io_fd_flags \- prepare descriptor for io_wait
.SH SYNTAX
.B #include <libowfat/io.h>

int \fBio_fd\fP(int64 fd);

#ifdef HAVE_IO_FD_FLAGS

int \fBio_fd_flags\fP(int64 fd);
.SH DESCRIPTION
io_fd_flags behaves just like io_fd, but certain flags can be
bitwise-ORed to it to alter its behavior:

.RS 0
.IP IO_FD_CANWRITE
tell io_fd that the descriptor is writable.  This is useful so
io_wantwrite can queue the descriptor immediately and there is no need
to query the operating system event reporting mechanism.
.IP IO_FD_BLOCK
tell io_fd that the descriptor is blocking.
.IP IO_FD_NONBLOCK
tell io_fd that the descriptor is non-blocking.
.RE

Normally, io_fd calls fcntl to ask the operating system whether the
descriptor is blocking or not.  The frameworks needs to know because it
alters how io_tryread and io_trywrite handle the socket.  Never pass
both IO_FD_BLOCK and IO_FD_NONBLOCK at the same time.

Newly connected stream sockets are always writable if the connection is
established, so it is usually safe to pass IO_FD_CANWRITE.  The main
exception case where IO_FD_CANWRITE should not be passed is on a
non-blocking socket where a connect() is pending.  Then you need to poll
for writability to get notified when the connection is established.
.SH "RETURN VALUE"
io_fd_flags returns 1 on success, 0 on error.
.SH "SEE ALSO"
io_fd(3), io_fd_canwrite(3)