bevy_utils/
lib.rs

1#![cfg_attr(docsrs, feature(doc_cfg))]
2#![doc(
3    html_logo_url = "https://bevy.org/assets/icon.png",
4    html_favicon_url = "https://bevy.org/assets/icon.png"
5)]
6#![no_std]
7
8//! General utilities for first-party [Bevy] engine crates.
9//!
10//! [Bevy]: https://bevy.org/
11
12/// Configuration information for this crate.
13pub mod cfg {
14    pub(crate) use bevy_platform::cfg::*;
15
16    pub use bevy_platform::cfg::{alloc, std};
17
18    define_alias! {
19        #[cfg(feature = "parallel")] => {
20            /// Indicates the `Parallel` type is available.
21            parallel
22        }
23    }
24}
25
26cfg::std! {
27    extern crate std;
28}
29
30cfg::alloc! {
31    extern crate alloc;
32
33    mod map;
34    pub use map::*;
35}
36
37cfg::parallel! {
38    mod parallel_queue;
39    pub use parallel_queue::*;
40}
41
42/// The utilities prelude.
43///
44/// This includes the most common types in this crate, re-exported for your convenience.
45pub mod prelude {
46    pub use crate::debug_info::DebugName;
47    pub use crate::default;
48    pub use disqualified::ShortName;
49}
50
51mod debug_info;
52mod default;
53mod once;
54
55#[doc(hidden)]
56pub use once::OnceFlag;
57
58pub use default::default;
59
60use core::mem::ManuallyDrop;
61
62/// A type which calls a function when dropped.
63/// This can be used to ensure that cleanup code is run even in case of a panic.
64///
65/// Note that this only works for panics that [unwind](https://doc.rust-lang.org/nomicon/unwinding.html)
66/// -- any code within `OnDrop` will be skipped if a panic does not unwind.
67/// In most cases, this will just work.
68///
69/// # Examples
70///
71/// ```
72/// # use bevy_utils::OnDrop;
73/// # fn test_panic(do_panic: bool, log: impl FnOnce(&str)) {
74/// // This will print a message when the variable `_catch` gets dropped,
75/// // even if a panic occurs before we reach the end of this scope.
76/// // This is similar to a `try ... catch` block in languages such as C++.
77/// let _catch = OnDrop::new(|| log("Oops, a panic occurred and this function didn't complete!"));
78///
79/// // Some code that may panic...
80/// // ...
81/// # if do_panic { panic!() }
82///
83/// // Make sure the message only gets printed if a panic occurs.
84/// // If we remove this line, then the message will be printed regardless of whether a panic occurs
85/// // -- similar to a `try ... finally` block.
86/// core::mem::forget(_catch);
87/// # }
88/// #
89/// # test_panic(false, |_| unreachable!());
90/// # let mut did_log = false;
91/// # std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
92/// #   test_panic(true, |_| did_log = true);
93/// # }));
94/// # assert!(did_log);
95/// ```
96pub struct OnDrop<F: FnOnce()> {
97    callback: ManuallyDrop<F>,
98}
99
100impl<F: FnOnce()> OnDrop<F> {
101    /// Returns an object that will invoke the specified callback when dropped.
102    pub fn new(callback: F) -> Self {
103        Self {
104            callback: ManuallyDrop::new(callback),
105        }
106    }
107}
108
109impl<F: FnOnce()> Drop for OnDrop<F> {
110    fn drop(&mut self) {
111        #![expect(
112            unsafe_code,
113            reason = "Taking from a ManuallyDrop requires unsafe code."
114        )]
115        // SAFETY: We may move out of `self`, since this instance can never be observed after it's dropped.
116        let callback = unsafe { ManuallyDrop::take(&mut self.callback) };
117        callback();
118    }
119}
bevy_utils/lib.rs

bevy_utils/
lib.rs
