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1
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2 .. _async:
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3
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4 :c:type:`uv_async_t` --- Async handle
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5 =====================================
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6
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7 Async handles allow the user to "wakeup" the event loop and get a callback
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8 called from another thread.
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9
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10
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11 Data types
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12 ----------
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13
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14 .. c:type:: uv_async_t
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15
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16 Async handle type.
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17
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18 .. c:type:: void (*uv_async_cb)(uv_async_t* handle)
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19
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20 Type definition for callback passed to :c:func:`uv_async_init`.
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21
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22
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23 Public members
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24 ^^^^^^^^^^^^^^
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25
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26 N/A
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27
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28 .. seealso:: The :c:type:`uv_handle_t` members also apply.
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29
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30
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31 API
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32 ---
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33
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34 .. c:function:: int uv_async_init(uv_loop_t* loop, uv_async_t* async, uv_async_cb async_cb)
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35
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36 Initialize the handle. A NULL callback is allowed.
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37
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38 :returns: 0 on success, or an error code < 0 on failure.
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39
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40 .. note::
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41 Unlike other handle initialization functions, it immediately starts the handle.
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42
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43 .. c:function:: int uv_async_send(uv_async_t* async)
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44
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45 Wake up the event loop and call the async handle's callback.
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46
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47 :returns: 0 on success, or an error code < 0 on failure.
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48
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49 .. note::
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50 It's safe to call this function from any thread. The callback will be called on the
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51 loop thread.
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52
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53 .. note::
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54 :c:func:`uv_async_send` is `async-signal-safe <https://man7.org/linux/man-pages/man7/signal-safety.7.html>`_.
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55 It's safe to call this function from a signal handler.
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56
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57 .. warning::
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58 libuv will coalesce calls to :c:func:`uv_async_send`, that is, not every call to it will
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59 yield an execution of the callback. For example: if :c:func:`uv_async_send` is called 5
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60 times in a row before the callback is called, the callback will only be called once. If
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61 :c:func:`uv_async_send` is called again after the callback was called, it will be called
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62 again.
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63
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64 .. seealso::
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65 The :c:type:`uv_handle_t` API functions also apply.
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