.. _async:

:c:type:`uv_async_t` --- Async handle
=====================================

Async handles allow the user to "wakeup" the event loop and get a callback
called from another thread.


Data types
----------

.. c:type:: uv_async_t

    Async handle type.

.. c:type:: void (*uv_async_cb)(uv_async_t* handle)

    Type definition for callback passed to :c:func:`uv_async_init`.


Public members
^^^^^^^^^^^^^^

N/A

.. seealso:: The :c:type:`uv_handle_t` members also apply.


API
---

.. c:function:: int uv_async_init(uv_loop_t* loop, uv_async_t* async, uv_async_cb async_cb)

    Initialize the handle. A NULL callback is allowed.

    .. note::
        Unlike other handle initialization  functions, it immediately starts the handle.

.. c:function:: int uv_async_send(uv_async_t* async)

    Wakeup the event loop and call the async handle's callback.

    .. note::
        It's safe to call this function from any thread. The callback will be called on the
        loop thread.

    .. warning::
        libuv will coalesce calls to :c:func:`uv_async_send`, that is, not every call to it will
        yield an execution of the callback, the only guarantee is that it will be called at least
        once. Thus, calling this function may not wakeup the event loop if it was already called
        previously within a short period of time.

.. seealso::
    The :c:type:`uv_handle_t` API functions also apply.