1 use crate::runtime::context;
2
3 use std::fmt;
4
5 /// An opaque ID that uniquely identifies a task relative to all other currently
6 /// running tasks.
7 ///
8 /// # Notes
9 ///
10 /// - Task IDs are unique relative to other *currently running* tasks. When a
11 /// task completes, the same ID may be used for another task.
12 /// - Task IDs are *not* sequential, and do not indicate the order in which
13 /// tasks are spawned, what runtime a task is spawned on, or any other data.
14 /// - The task ID of the currently running task can be obtained from inside the
15 /// task via the [`task::try_id()`](crate::task::try_id()) and
16 /// [`task::id()`](crate::task::id()) functions and from outside the task via
17 /// the [`JoinHandle::id()`](crate::task::JoinHandle::id()) function.
18 ///
19 /// **Note**: This is an [unstable API][unstable]. The public API of this type
20 /// may break in 1.x releases. See [the documentation on unstable
21 /// features][unstable] for details.
22 ///
23 /// [unstable]: crate#unstable-features
24 #[cfg_attr(docsrs, doc(cfg(all(feature = "rt", tokio_unstable))))]
25 #[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
26 #[derive(Clone, Copy, Debug, Hash, Eq, PartialEq)]
27 pub struct Id(u64);
28
29 /// Returns the [`Id`] of the currently running task.
30 ///
31 /// # Panics
32 ///
33 /// This function panics if called from outside a task. Please note that calls
34 /// to `block_on` do not have task IDs, so the method will panic if called from
35 /// within a call to `block_on`. For a version of this function that doesn't
36 /// panic, see [`task::try_id()`](crate::runtime::task::try_id()).
37 ///
38 /// **Note**: This is an [unstable API][unstable]. The public API of this type
39 /// may break in 1.x releases. See [the documentation on unstable
40 /// features][unstable] for details.
41 ///
42 /// [task ID]: crate::task::Id
43 /// [unstable]: crate#unstable-features
44 #[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
45 #[track_caller]
id() -> Id46 pub fn id() -> Id {
47 context::current_task_id().expect("Can't get a task id when not inside a task")
48 }
49
50 /// Returns the [`Id`] of the currently running task, or `None` if called outside
51 /// of a task.
52 ///
53 /// This function is similar to [`task::id()`](crate::runtime::task::id()), except
54 /// that it returns `None` rather than panicking if called outside of a task
55 /// context.
56 ///
57 /// **Note**: This is an [unstable API][unstable]. The public API of this type
58 /// may break in 1.x releases. See [the documentation on unstable
59 /// features][unstable] for details.
60 ///
61 /// [task ID]: crate::task::Id
62 /// [unstable]: crate#unstable-features
63 #[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
64 #[track_caller]
try_id() -> Option<Id>65 pub fn try_id() -> Option<Id> {
66 context::current_task_id()
67 }
68
69 impl fmt::Display for Id {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result70 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
71 self.0.fmt(f)
72 }
73 }
74
75 impl Id {
next() -> Self76 pub(crate) fn next() -> Self {
77 use crate::loom::sync::atomic::{Ordering::Relaxed, StaticAtomicU64};
78
79 static NEXT_ID: StaticAtomicU64 = StaticAtomicU64::new(1);
80
81 Self(NEXT_ID.fetch_add(1, Relaxed))
82 }
83
as_u64(&self) -> u6484 pub(crate) fn as_u64(&self) -> u64 {
85 self.0
86 }
87 }
88