rustc_ast_pretty/pp/
ring.rs

Help
1use std::collections::VecDeque;
2use std::ops::{Index, IndexMut};
3
4/// A view onto a finite range of an infinitely long sequence of T.
5///
6/// The Ts are indexed 0..infinity. A RingBuffer begins as a view of elements
7/// 0..0 (i.e. nothing). The user of the RingBuffer advances its left and right
8/// position independently, although only in the positive direction, and only
9/// with left <= right at all times.
10///
11/// Holding a RingBuffer whose view is elements left..right gives the ability to
12/// use Index and IndexMut to access elements i in the infinitely long queue for
13/// which left <= i < right.
14pub(super) struct RingBuffer<T> {
15    data: VecDeque<T>,
16    // Abstract index of data[0] in the infinitely sized queue.
17    offset: usize,
18}
19
20impl<T> RingBuffer<T> {
21    pub(super) fn new() -> Self {
22        RingBuffer { data: VecDeque::new(), offset: 0 }
23    }
24
25    pub(super) fn is_empty(&self) -> bool {
26        self.data.is_empty()
27    }
28
29    pub(super) fn push(&mut self, value: T) -> usize {
30        let index = self.offset + self.data.len();
31        self.data.push_back(value);
32        index
33    }
34
35    pub(super) fn clear(&mut self) {
36        self.data.clear();
37    }
38
39    pub(super) fn index_of_first(&self) -> usize {
40        self.offset
41    }
42
43    pub(super) fn first(&self) -> Option<&T> {
44        self.data.front()
45    }
46
47    pub(super) fn first_mut(&mut self) -> Option<&mut T> {
48        self.data.front_mut()
49    }
50
51    pub(super) fn pop_first(&mut self) -> Option<T> {
52        let first = self.data.pop_front()?;
53        self.offset += 1;
54        Some(first)
55    }
56
57    pub(super) fn last(&self) -> Option<&T> {
58        self.data.back()
59    }
60
61    pub(super) fn last_mut(&mut self) -> Option<&mut T> {
62        self.data.back_mut()
63    }
64}
65
66impl<T> Index<usize> for RingBuffer<T> {
67    type Output = T;
68    fn index(&self, index: usize) -> &Self::Output {
69        &self.data[index.checked_sub(self.offset).unwrap()]
70    }
71}
72
73impl<T> IndexMut<usize> for RingBuffer<T> {
74    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
75        &mut self.data[index.checked_sub(self.offset).unwrap()]
76    }
77}
rustc_ast_pretty/pp/ring.rs

rustc_ast_pretty/pp/
ring.rs
