debian man page for iob_write

iob_write(3)						     Library Functions Manual						      iob_write(3)

NAME
       iob_write - send I/O batch through callback

SYNTAX
       #include <iob.h>

       typedef int64 (*io_write_callback)(int64 s,const void* buf,uint64 n);

       int64 iob_write(int64 s,io_batch* b,io_write_callback cb);

DESCRIPTION
       iob_write sends the (rest of) b through the callback cb, passing s as first argument.  cb is expected to behave like io_trywrite(2).

       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  perma-
       nent 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  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.

NOTE
       iob_write will continue to call your callback until it returns an error.  So if you are in a state machine, for example a web server  using
       this  for  SSL  support,  make  sure  to  write at most n bytes at a time (e.g. 64k) and the next time you are called return -1.  Otherwise
       iob_write might not return until the whole file is served.

SEE ALSO
       iob_send(3)

																      iob_write(3)