= nng_aio_set_iov(3)
:doctype: manpage
:manmanual: nng
:mansource: nng
:manvolnum: 3
:copyright: Copyright 2018 mailto:info@staysail.tech[Staysail Systems, Inc.] + \
            Copyright 2018 mailto:info@capitar.com[Capitar IT Group BV] + \
            {blank} + \
            This document is supplied under the terms of the \
            https://opensource.org/licenses/MIT[MIT License].

== NAME

nng_aio_set_iov - set scatter/gather vector

== SYNOPSIS

[source, c]
-----------
#include <nng/nng.h>

int nng_aio_set_iov(nng_aio *aio, unsigned int niov, nng_iov *iov);
-----------

== DESCRIPTION

The `nng_aio_set_iov()` function sets a scatter/gather vector _iov_ on the
handle _aio_. 

The _iov_ is a pointer to an array of _niov_ `nng_iov` structures, which have
the following definition:

[source, c]
----
    typedef struct nng_iov {
        void * iov_buf;
        size_t iov_len;
    };
----

The _iov_ is copied into storage in the _aio_ itself, so that callers
may use stack allocated `nng_iov` structures.  The values pointed to
by the `iov_buf` members are *not* copied by this function though.

Up to four `nng_iov` members may be supplied without causing any
allocations, and thus this operation is guaranteed to succeed for
values of _niov_ less than four.

More than four (4) `nng_iov` members may be supplied, but this may require
heap allocations, and so the operation may fail with `NNG_ENOMEM`.
Additionally, not every operation can support longer vectors; the
actual limit is determined by the system, but is generally at least
sixteen (16).  Furthermore, values for _niov_ larger than sixty-four (64) will
generally result in `NNG_EINVAL`.

== RETURN VALUES

This function returns 0 on success, and non-zero otherwise.

== ERRORS

`NNG_ENOMEM`:: Insufficient free memory to perform operation.
`NNG_EINVAL`:: Value of specified _niov_ is too large.

== SEE ALSO

<<nng_aio_alloc#,nng_aio_alloc(3)>>,
<<nng_aio_cancel#,nng_aio_cancel(3)>>,
<<nng_aio_count#,nng_aio_count(3)>>,
<<nng_aio_result#,nng_aio_result(3)>>,
<<nng#,nng(7)>>

== COPYRIGHT

{copyright}
