NAME

       nng_aio_alloc - allocate asynchronous I/O handle

SYNOPSIS

           #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 its
           execution quickly. If callb does block, this can lead ultimately to an apparent "hang"
           or deadlock in the application. This also means you should avoid operations such as
           allocating new objects, which also means opening or closing sockets, dialers, and so
           forth.

           Tip
           If more complex or blocking work needs to be performed by callb, a separate thread can
           be used, along with a condition variable which can be signaled by the callback.

       Asynchronous I/O operations all take an nng_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_count(), and nng_aio_get_output().

       It is possible to wait synchronously for an otherwise asynchronous operation by using the
       function nng_aio_wait(). 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().

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(3), nng_aio_cancel(3), nng_aio_count(3), nng_aio_free(3),
       nng_aio_get_input(3), nng_aio_get_msg(3), nng_aio_get_output(3), nng_aio_result(3),
       nng_aio_set_input(3), nng_aio_set_iov(3), nng_aio_set_msg(3), nng_aio_set_timeout(3),
       nng_aio_stop(3), nng_aio_wait(3), nng_strerror(3), nng_aio(5), nng(7)

                                            2024-10-11                           NNG_AIO_ALLOC(3)