tracing_subscriber/registry/
stack.rs

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1pub(crate) use tracing_core::span::Id;
2
3#[derive(Debug)]
4struct ContextId {
5    id: Id,
6    duplicate: bool,
7}
8
9/// `SpanStack` tracks what spans are currently executing on a thread-local basis.
10///
11/// A "separate current span" for each thread is a semantic choice, as each span
12/// can be executing in a different thread.
13#[derive(Debug, Default)]
14pub(crate) struct SpanStack {
15    stack: Vec<ContextId>,
16}
17
18impl SpanStack {
19    #[inline]
20    pub(super) fn push(&mut self, id: Id) -> bool {
21        let duplicate = self.stack.iter().any(|i| i.id == id);
22        self.stack.push(ContextId { id, duplicate });
23        !duplicate
24    }
25
26    #[inline]
27    pub(super) fn pop(&mut self, expected_id: &Id) -> bool {
28        if let Some((idx, _)) = self
29            .stack
30            .iter()
31            .enumerate()
32            .rev()
33            .find(|(_, ctx_id)| ctx_id.id == *expected_id)
34        {
35            let ContextId { id: _, duplicate } = self.stack.remove(idx);
36            return !duplicate;
37        }
38        false
39    }
40
41    #[inline]
42    pub(crate) fn iter(&self) -> impl Iterator<Item = &Id> {
43        self.stack
44            .iter()
45            .rev()
46            .filter_map(|ContextId { id, duplicate }| if !*duplicate { Some(id) } else { None })
47    }
48
49    #[inline]
50    pub(crate) fn current(&self) -> Option<&Id> {
51        self.iter().next()
52    }
53}
54
55#[cfg(test)]
56mod tests {
57    use super::{Id, SpanStack};
58
59    #[test]
60    fn pop_last_span() {
61        let mut stack = SpanStack::default();
62        let id = Id::from_u64(1);
63        stack.push(id.clone());
64
65        assert!(stack.pop(&id));
66    }
67
68    #[test]
69    fn pop_first_span() {
70        let mut stack = SpanStack::default();
71        stack.push(Id::from_u64(1));
72        stack.push(Id::from_u64(2));
73
74        let id = Id::from_u64(1);
75        assert!(stack.pop(&id));
76    }
77}
tracing_subscriber/registry/stack.rs

tracing_subscriber/registry/
stack.rs
