xref: /libuv/docs/src/request.rst (revision 3e1733a0) 
1
2.. _request:
3
4:c:type:`uv_req_t` --- Base request
5===================================
6
7`uv_req_t` is the base type for all libuv request types.
8
9Structures are aligned so that any libuv request can be cast to `uv_req_t`.
10All API functions defined here work with any request type.
11
12
13Data types
14----------
15
16.. c:type:: uv_req_t
17
18    The base libuv request structure.
19
20.. c:type:: uv_any_req
21
22    Union of all request types.
23
24.. c:enum:: uv_req_type
25
26    The kind of the libuv request.
27
28    ::
29
30        typedef enum {
31            UV_UNKNOWN_REQ = 0,
32            UV_REQ,
33            UV_CONNECT,
34            UV_WRITE,
35            UV_SHUTDOWN,
36            UV_UDP_SEND,
37            UV_FS,
38            UV_WORK,
39            UV_GETADDRINFO,
40            UV_GETNAMEINFO,
41            UV_REQ_TYPE_MAX,
42        } uv_req_type;
43
44
45Public members
46^^^^^^^^^^^^^^
47
48.. c:member:: void* uv_req_t.data
49
50    Space for user-defined arbitrary data. libuv does not use this field.
51
52.. c:member:: uv_req_type uv_req_t.type
53
54    The :c:enum:`uv_req_type`, indicating the type of the request. Readonly.
55
56
57API
58---
59
60.. c:macro:: UV_REQ_TYPE_MAP(iter_macro)
61
62    Macro that expands to a series of invocations of `iter_macro` for
63    each of the request types. `iter_macro` is invoked with two
64    arguments: the name of the `uv_req_type` element without the `UV_`
65    prefix, and the name of the corresponding structure type without the
66    `uv_` prefix and `_t` suffix.
67
68.. c:function:: int uv_cancel(uv_req_t* req)
69
70    Cancel a pending request. Fails if the request is executing or has finished
71    executing.
72
73    Returns 0 on success, or an error code < 0 on failure.
74
75    Only cancellation of :c:type:`uv_fs_t`, :c:type:`uv_getaddrinfo_t`,
76    :c:type:`uv_getnameinfo_t`, :c:type:`uv_random_t` and :c:type:`uv_work_t`
77    requests is currently supported.
78
79    Cancelled requests have their callbacks invoked some time in the future.
80    It's **not** safe to free the memory associated with the request until the
81    callback is called.
82
83    Here is how cancellation is reported to the callback:
84
85    * A :c:type:`uv_fs_t` request has its req->result field set to `UV_ECANCELED`.
86
87    * A :c:type:`uv_work_t`, :c:type:`uv_getaddrinfo_t`,
88      :c:type:`uv_getnameinfo_t` or :c:type:`uv_random_t` request has its
89      callback invoked with status == `UV_ECANCELED`.
90
91.. c:function:: size_t uv_req_size(uv_req_type type)
92
93    Returns the size of the given request type. Useful for FFI binding writers
94    who don't want to know the structure layout.
95
96.. c:function:: void* uv_req_get_data(const uv_req_t* req)
97
98    Returns `req->data`.
99
100    .. versionadded:: 1.19.0
101
102.. c:function:: void uv_req_set_data(uv_req_t* req, void* data)
103
104    Sets `req->data` to `data`.
105
106    .. versionadded:: 1.19.0
107
108.. c:function:: uv_req_type uv_req_get_type(const uv_req_t* req)
109
110    Returns `req->type`.
111
112    .. versionadded:: 1.19.0
113
114.. c:function:: const char* uv_req_type_name(uv_req_type type)
115
116    Returns the name for the equivalent struct for a given request type,
117    e.g. `"connect"` (as in :c:type:`uv_connect_t`) for `UV_CONNECT`.
118
119    If no such request type exists, this returns `NULL`.
120
121    .. versionadded:: 1.19.0
122