num_threads/
lib.rs

1//! Minimum supported Rust version: 1.28
2
3use std::num::NonZeroUsize;
4
5#[cfg_attr(any(target_os = "linux", target_os = "android"), path = "linux.rs")]
6#[cfg_attr(target_os = "freebsd", path = "freebsd.rs")]
7#[cfg_attr(any(target_os = "macos", target_os = "ios"), path = "apple.rs")]
8mod imp;
9
10/// Obtain the number of threads currently part of the active process. Returns `None` if the number
11/// of threads cannot be determined.
12pub fn num_threads() -> Option<NonZeroUsize> {
13    imp::num_threads()
14}
15
16/// Determine if the current process is single-threaded. Returns `None` if the number of threads
17/// cannot be determined.
18pub fn is_single_threaded() -> Option<bool> {
19    num_threads().map(|n| n.get() == 1)
20}
21
22#[cfg(test)]
23mod test {
24    use std::num::NonZeroUsize;
25
26    // Run each expression in its own thread.
27    macro_rules! threaded {
28        ($first:expr;) => {
29            $first;
30        };
31        ($first:expr; $($rest:expr;)*) => {
32            $first;
33            ::std::thread::spawn(|| {
34                threaded!($($rest;)*);
35            })
36            .join()
37            .unwrap();
38        };
39    }
40
41    #[test]
42    fn num_threads() {
43        threaded! {
44            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(1));
45            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(2));
46            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(3));
47            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(4));
48            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(5));
49            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(6));
50        }
51    }
52
53    #[test]
54    fn is_single_threaded() {
55        threaded! {
56            assert_eq!(super::is_single_threaded(), Some(true));
57            assert_eq!(super::is_single_threaded(), Some(false));
58            assert_eq!(super::is_single_threaded(), Some(false));
59            assert_eq!(super::is_single_threaded(), Some(false));
60            assert_eq!(super::is_single_threaded(), Some(false));
61            assert_eq!(super::is_single_threaded(), Some(false));
62        }
63    }
64}
num_threads/lib.rs

num_threads/
lib.rs
