rustpython_common/
refcount.rs

1use crate::atomic::{Ordering::*, PyAtomic, Radium};
2
3/// from alloc::sync
4/// A soft limit on the amount of references that may be made to an `Arc`.
5///
6/// Going above this limit will abort your program (although not
7/// necessarily) at _exactly_ `MAX_REFCOUNT + 1` references.
8const MAX_REFCOUNT: usize = isize::MAX as usize;
9
10pub struct RefCount {
11    strong: PyAtomic<usize>,
12}
13
14impl Default for RefCount {
15    fn default() -> Self {
16        Self::new()
17    }
18}
19
20impl RefCount {
21    const MASK: usize = MAX_REFCOUNT;
22
23    pub fn new() -> Self {
24        RefCount {
25            strong: Radium::new(1),
26        }
27    }
28
29    #[inline]
30    pub fn get(&self) -> usize {
31        self.strong.load(SeqCst)
32    }
33
34    #[inline]
35    pub fn inc(&self) {
36        let old_size = self.strong.fetch_add(1, Relaxed);
37
38        if old_size & Self::MASK == Self::MASK {
39            std::process::abort();
40        }
41    }
42
43    /// Returns true if successful
44    #[inline]
45    pub fn safe_inc(&self) -> bool {
46        self.strong
47            .fetch_update(AcqRel, Acquire, |prev| (prev != 0).then_some(prev + 1))
48            .is_ok()
49    }
50
51    /// Decrement the reference count. Returns true when the refcount drops to 0.
52    #[inline]
53    pub fn dec(&self) -> bool {
54        if self.strong.fetch_sub(1, Release) != 1 {
55            return false;
56        }
57
58        PyAtomic::<usize>::fence(Acquire);
59
60        true
61    }
62}
63
64impl RefCount {
65    // move these functions out and give separated type once type range is stabilized
66
67    pub fn leak(&self) {
68        debug_assert!(!self.is_leaked());
69        const BIT_MARKER: usize = (isize::MAX as usize) + 1;
70        debug_assert_eq!(BIT_MARKER.count_ones(), 1);
71        debug_assert_eq!(BIT_MARKER.leading_zeros(), 0);
72        self.strong.fetch_add(BIT_MARKER, Relaxed);
73    }
74
75    pub fn is_leaked(&self) -> bool {
76        (self.strong.load(Acquire) as isize) < 0
77    }
78}
rustpython_common/refcount.rs

rustpython_common/
refcount.rs
