284 lines
9.2 KiB
ReStructuredText
284 lines
9.2 KiB
ReStructuredText
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.. _handle:
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:c:type:`uv_handle_t` --- Base handle
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=====================================
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`uv_handle_t` is the base type for all libuv handle types.
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Structures are aligned so that any libuv handle can be cast to `uv_handle_t`.
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All API functions defined here work with any handle type.
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Libuv handles are not movable. Pointers to handle structures passed to
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functions must remain valid for the duration of the requested operation. Take
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care when using stack allocated handles.
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Data types
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----------
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.. c:type:: uv_handle_t
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The base libuv handle type.
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.. c:enum:: uv_handle_type
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The kind of the libuv handle.
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::
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typedef enum {
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UV_UNKNOWN_HANDLE = 0,
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UV_ASYNC,
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UV_CHECK,
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UV_FS_EVENT,
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UV_FS_POLL,
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UV_HANDLE,
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UV_IDLE,
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UV_NAMED_PIPE,
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UV_POLL,
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UV_PREPARE,
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UV_PROCESS,
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UV_STREAM,
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UV_TCP,
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UV_TIMER,
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UV_TTY,
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UV_UDP,
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UV_SIGNAL,
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UV_FILE,
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UV_HANDLE_TYPE_MAX
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} uv_handle_type;
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.. c:type:: uv_any_handle
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Union of all handle types.
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.. c:type:: void (*uv_alloc_cb)(uv_handle_t* handle, size_t suggested_size, uv_buf_t* buf)
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Type definition for callback passed to :c:func:`uv_read_start` and
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:c:func:`uv_udp_recv_start`. The user must allocate memory and fill the supplied
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:c:type:`uv_buf_t` structure. If NULL is assigned as the buffer's base or 0 as its length,
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a ``UV_ENOBUFS`` error will be triggered in the :c:type:`uv_udp_recv_cb` or the
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:c:type:`uv_read_cb` callback.
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Each buffer is used only once and the user is responsible for freeing it in the
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:c:type:`uv_udp_recv_cb` or the :c:type:`uv_read_cb` callback.
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A suggested size (65536 at the moment in most cases) is provided, but it's just an indication,
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not related in any way to the pending data to be read. The user is free to allocate the amount
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of memory they decide.
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As an example, applications with custom allocation schemes such as using freelists, allocation
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pools or slab based allocators may decide to use a different size which matches the memory
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chunks they already have.
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Example:
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::
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static void my_alloc_cb(uv_handle_t* handle, size_t suggested_size, uv_buf_t* buf) {
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buf->base = malloc(suggested_size);
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buf->len = suggested_size;
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}
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.. c:type:: void (*uv_close_cb)(uv_handle_t* handle)
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Type definition for callback passed to :c:func:`uv_close`.
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Public members
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^^^^^^^^^^^^^^
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.. c:member:: uv_loop_t* uv_handle_t.loop
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Pointer to the :c:type:`uv_loop_t` the handle is running on. Readonly.
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.. c:member:: uv_handle_type uv_handle_t.type
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The :c:type:`uv_handle_type`, indicating the type of the underlying handle. Readonly.
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.. c:member:: void* uv_handle_t.data
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Space for user-defined arbitrary data. libuv does not use this field.
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API
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---
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.. c:macro:: UV_HANDLE_TYPE_MAP(iter_macro)
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Macro that expands to a series of invocations of `iter_macro` for
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each of the handle types. `iter_macro` is invoked with two
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arguments: the name of the `uv_handle_type` element without the
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`UV_` prefix, and the name of the corresponding structure type
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without the `uv_` prefix and `_t` suffix.
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.. c:function:: int uv_is_active(const uv_handle_t* handle)
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Returns non-zero if the handle is active, zero if it's inactive. What
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"active" means depends on the type of handle:
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- A uv_async_t handle is always active and cannot be deactivated, except
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by closing it with uv_close().
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- A uv_pipe_t, uv_tcp_t, uv_udp_t, etc. handle - basically any handle that
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deals with i/o - is active when it is doing something that involves i/o,
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like reading, writing, connecting, accepting new connections, etc.
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- A uv_check_t, uv_idle_t, uv_timer_t, etc. handle is active when it has
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been started with a call to uv_check_start(), uv_idle_start(), etc.
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Rule of thumb: if a handle of type `uv_foo_t` has a `uv_foo_start()`
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function, then it's active from the moment that function is called.
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Likewise, `uv_foo_stop()` deactivates the handle again.
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.. c:function:: int uv_is_closing(const uv_handle_t* handle)
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Returns non-zero if the handle is closing or closed, zero otherwise.
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.. note::
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This function should only be used between the initialization of the handle and the
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arrival of the close callback.
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.. c:function:: void uv_close(uv_handle_t* handle, uv_close_cb close_cb)
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Request handle to be closed. `close_cb` will be called asynchronously after
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this call. This MUST be called on each handle before memory is released.
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Moreover, the memory can only be released in `close_cb` or after it has
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returned.
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Handles that wrap file descriptors are closed immediately but
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`close_cb` will still be deferred to the next iteration of the event loop.
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It gives you a chance to free up any resources associated with the handle.
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In-progress requests, like uv_connect_t or uv_write_t, are cancelled and
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have their callbacks called asynchronously with status=UV_ECANCELED.
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.. c:function:: void uv_ref(uv_handle_t* handle)
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Reference the given handle. References are idempotent, that is, if a handle
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is already referenced calling this function again will have no effect.
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See :ref:`refcount`.
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.. c:function:: void uv_unref(uv_handle_t* handle)
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Un-reference the given handle. References are idempotent, that is, if a handle
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is not referenced calling this function again will have no effect.
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See :ref:`refcount`.
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.. c:function:: int uv_has_ref(const uv_handle_t* handle)
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Returns non-zero if the handle referenced, zero otherwise.
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See :ref:`refcount`.
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.. c:function:: size_t uv_handle_size(uv_handle_type type)
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Returns the size of the given handle type. Useful for FFI binding writers
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who don't want to know the structure layout.
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Miscellaneous API functions
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---------------------------
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The following API functions take a :c:type:`uv_handle_t` argument but they work
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just for some handle types.
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.. c:function:: int uv_send_buffer_size(uv_handle_t* handle, int* value)
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Gets or sets the size of the send buffer that the operating
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system uses for the socket.
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If `*value` == 0, then it will set `*value` to the current send buffer size.
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If `*value` > 0 then it will use `*value` to set the new send buffer size.
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On success, zero is returned. On error, a negative result is
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returned.
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This function works for TCP, pipe and UDP handles on Unix and for TCP and
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UDP handles on Windows.
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.. note::
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Linux will set double the size and return double the size of the original set value.
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.. c:function:: int uv_recv_buffer_size(uv_handle_t* handle, int* value)
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Gets or sets the size of the receive buffer that the operating
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system uses for the socket.
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If `*value` == 0, then it will set `*value` to the current receive buffer size.
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If `*value` > 0 then it will use `*value` to set the new receive buffer size.
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On success, zero is returned. On error, a negative result is
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returned.
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This function works for TCP, pipe and UDP handles on Unix and for TCP and
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UDP handles on Windows.
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.. note::
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Linux will set double the size and return double the size of the original set value.
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.. c:function:: int uv_fileno(const uv_handle_t* handle, uv_os_fd_t* fd)
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Gets the platform dependent file descriptor equivalent.
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The following handles are supported: TCP, pipes, TTY, UDP and poll. Passing
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any other handle type will fail with `UV_EINVAL`.
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If a handle doesn't have an attached file descriptor yet or the handle
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itself has been closed, this function will return `UV_EBADF`.
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.. warning::
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Be very careful when using this function. libuv assumes it's in control of the file
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descriptor so any change to it may lead to malfunction.
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.. c:function:: uv_loop_t* uv_handle_get_loop(const uv_handle_t* handle)
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Returns `handle->loop`.
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.. versionadded:: 1.19.0
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.. c:function:: void* uv_handle_get_data(const uv_handle_t* handle)
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Returns `handle->data`.
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.. versionadded:: 1.19.0
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.. c:function:: void* uv_handle_set_data(uv_handle_t* handle, void* data)
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Sets `handle->data` to `data`.
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.. versionadded:: 1.19.0
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.. c:function:: uv_handle_type uv_handle_get_type(const uv_handle_t* handle)
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Returns `handle->type`.
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.. versionadded:: 1.19.0
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.. c:function:: const char* uv_handle_type_name(uv_handle_type type)
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Returns the name for the equivalent struct for a given handle type,
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e.g. `"pipe"` (as in :c:type:`uv_pipe_t`) for `UV_NAMED_PIPE`.
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If no such handle type exists, this returns `NULL`.
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.. versionadded:: 1.19.0
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.. _refcount:
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Reference counting
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------------------
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The libuv event loop (if run in the default mode) will run until there are no
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active `and` referenced handles left. The user can force the loop to exit early
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by unreferencing handles which are active, for example by calling :c:func:`uv_unref`
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after calling :c:func:`uv_timer_start`.
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A handle can be referenced or unreferenced, the refcounting scheme doesn't use
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a counter, so both operations are idempotent.
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All handles are referenced when active by default, see :c:func:`uv_is_active`
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for a more detailed explanation on what being `active` involves.
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