typedef int64 (*io_write_callback)(int64 s,const void* buf,uint64 n);
int64 iob_write(int64 s,io_batch* b,io_write_callback cb);
iob_write sends the (rest of) b through the callback cb,
passing s as first argument. cb is expected to behave like
This interface is intended to send an I/O batch through a filter, for
example to encrypt or compress it. If you just want to send an I/O
batch to a socket, use iob_send instead.
iob_write returns the number of bytes written, 0 if there were no more
bytes to be written in the batch, -1 for EAGAIN, or -3 for a permanent
error (for example "connection reset by peer").
The normal usage pattern is using io_wait to know when a descriptor is
writable, and then calling iob_write until it returns 0, -1 or -3.
If iob_write returns 0, terminate the loop (everything was written OK). If it
returns -1, call io_wait again. If it returned -3, signal an error.
The callback is supposed to behave like write(2), i.e. return the number
of bytes written, 0 for EOF, -1 for error (iob_write will return -3
then). Return -1 with errno==EAGAIN if using non-blocking I/O when we
need to wait for the next write event. iob_write will then return -1.