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