iob_send man page
iob_send — send I/O batch
int64 iob_send(int64 s,io_batch* b);
iob_send sends the (rest of) b over the socket s.
iob_send 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_send until it returns 0, -1 or -3.
If it returns 0, terminate the loop (everything was written OK). If it returns -1, call io_wait again. If it returned -3, signal an error and close the socket.
The benefit of the I/O batch API is that it exploits platform specific APIs like FreeBSD's sendfile. The file contents will always be sent in a way that allows the operating systems to perform zero copy TCP, and the buffers will always be sent using as few syscalls as possible and avoiding unnecessary copying (using writev).
iob_reset(3), iob_send(3), iob_addbuf(3), iob_adds_free(3), iob_addfile(3), iob_prefetch(3)
iob_addbuf(3), iob_addbuf_free(3), iob_addfile(3), iob_addfile_close(3), iob_adds(3), iob_adds_free(3), iob_bytesleft(3), iob_new(3), iob_prefetch(3), iob_write(3), io_canwrite(3).