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= nng_aio_alloc(3)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt). A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//
== NAME
nng_aio_alloc - allocate asynchronous I/O handle
== SYNOPSIS
[source, c]
-----------
#include <nng/nng.h>
int nng_aio_alloc(nng_aio **aiop, void (*callb)(void *), void *arg);
-----------
== DESCRIPTION
The `nng_aio_alloc()` function allocates a handle for asynchronous I/O
operations, and stores a pointer to it in __aiop__. The handle is initialized
with a completion callback of _callb_, which will be executed when an
associated asynchronous operation finishes. It will be called with the
argument _arg_.
NOTE: The callback _callb_ must not perform any blocking operations, and
must complete it's execution quickly. If _callb_ does block, this can
lead ultimately to an apparent "hang" or deadlock in the application.
Asynchronous I/O operations all take an _aio_ handle such as allocated by
this function. Such operations are usually started by a function that returns
immediately. The operation is then run asynchronously, and completes sometime
later. When that operation is complete, the callback supplied here is called,
and that callback is able to determine the result of the operation using
<<nng_aio_result#,nng_aio_result(3)>>, <<nng_aio_count#,nng_aio_count(3)>>,
and <<nng_aio_get_output#,nng_aio_get_output(3)>>.
It is possible to wait synchronously for an otherwise asynchronous operation
by using the function <<nng_aio_wait#,nng_aio_wait(3)>>. In that case,
it is permissible for _callb_ and _arg_ to both be `NULL`. Note that if
these are `NULL`, then it will not be possible to determine when the
operation is complete except by calling the aforementioned
<<nng_aio_wait#,nng_aio_wait(3)>>.
== RETURN VALUES
This function returns 0 on success, and non-zero otherwise.
== ERRORS
`NNG_ENOMEM`:: Insufficient free memory to perform the operation.
== SEE ALSO
<<nng_aio_abort#,nng_aio_abort(3)>>,
<<nng_aio_cancel#,nng_aio_cancel(3)>>,
<<nng_aio_count#,nng_aio_count(3)>>,
<<nng_aio_free#,nng_aio_free(3)>>,
<<nng_aio_get_input#,nng_aio_get_input(3)>>,
<<nng_aio_get_msg#,nng_aio_get_msg(3)>>,
<<nng_aio_get_output#,nng_aio_get_output(3)>>,
<<nng_aio_result#,nng_aio_result(3)>>,
<<nng_aio_set_input#,nng_aio_set_input(3)>>,
<<nng_aio_set_iov#,nng_aio_set_iov(3)>>,
<<nng_aio_set_msg#,nng_aio_set_msg(3)>>,
<<nng_aio_set_timeout#,nng_aio_set_timeout(3)>>,
<<nng_aio_stop#,nng_aio_stop(3)>>,
<<nng_aio_wait#,nng_aio_wait(3)>>,
<<nng_strerror#,nng_strerror(3)>>,
<<nng#,nng(7)>>
|
