jiff/util/
sync.rs

1/*!
2This module re-exports `Arc`.
3
4That is, it provides some indirection for the case when `alloc::sync::Arc` is
5unavailable.
6
7It also defines a "dumb" `Arc` in core-only mode that doesn't actually do
8anything (no indirection, no reference counting).
9*/
10
11#[cfg(all(feature = "alloc", not(target_has_atomic = "ptr")))]
12pub(crate) use portable_atomic_util::Arc;
13
14#[cfg(all(feature = "alloc", target_has_atomic = "ptr"))]
15pub(crate) use alloc::sync::Arc;
16
17/// A "fake" `Arc`.
18///
19/// Basically, it exposes the `Arc` APIs we use in Jiff, but doesn't
20/// actually introduce indirection or reference counting. It's only used
21/// in core-only mode and in effect results in inlining all data into its
22/// container.
23///
24/// Not ideal, but we use `Arc` in very few places. One is `TimeZone`,
25/// which ends up being pretty small in core-only mode since it doesn't
26/// support carrying TZif data.
27#[cfg(not(feature = "alloc"))]
28#[derive(Clone, Debug, Eq, PartialEq)]
29pub(crate) struct Arc<T>(T);
30
31#[cfg(not(feature = "alloc"))]
32impl<T> Arc<T> {
33    pub(crate) fn new(t: T) -> Arc<T> {
34        Arc(t)
35    }
36
37    pub(crate) fn get_mut(this: &mut Arc<T>) -> Option<&mut T> {
38        Some(&mut this.0)
39    }
40}
41
42#[cfg(not(feature = "alloc"))]
43impl<T> core::ops::Deref for Arc<T> {
44    type Target = T;
45    fn deref(&self) -> &T {
46        &self.0
47    }
48}