h2/proto/streams/
buffer.rs

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1use slab::Slab;
2
3/// Buffers frames for multiple streams.
4#[derive(Debug)]
5pub struct Buffer<T> {
6    slab: Slab<Slot<T>>,
7}
8
9/// A sequence of frames in a `Buffer`
10#[derive(Debug)]
11pub struct Deque {
12    indices: Option<Indices>,
13}
14
15/// Tracks the head & tail for a sequence of frames in a `Buffer`.
16#[derive(Debug, Default, Copy, Clone)]
17struct Indices {
18    head: usize,
19    tail: usize,
20}
21
22#[derive(Debug)]
23struct Slot<T> {
24    value: T,
25    next: Option<usize>,
26}
27
28impl<T> Buffer<T> {
29    pub fn new() -> Self {
30        Buffer { slab: Slab::new() }
31    }
32}
33
34impl Deque {
35    pub fn new() -> Self {
36        Deque { indices: None }
37    }
38
39    pub fn is_empty(&self) -> bool {
40        self.indices.is_none()
41    }
42
43    pub fn push_back<T>(&mut self, buf: &mut Buffer<T>, value: T) {
44        let key = buf.slab.insert(Slot { value, next: None });
45
46        match self.indices {
47            Some(ref mut idxs) => {
48                buf.slab[idxs.tail].next = Some(key);
49                idxs.tail = key;
50            }
51            None => {
52                self.indices = Some(Indices {
53                    head: key,
54                    tail: key,
55                });
56            }
57        }
58    }
59
60    pub fn push_front<T>(&mut self, buf: &mut Buffer<T>, value: T) {
61        let key = buf.slab.insert(Slot { value, next: None });
62
63        match self.indices {
64            Some(ref mut idxs) => {
65                buf.slab[key].next = Some(idxs.head);
66                idxs.head = key;
67            }
68            None => {
69                self.indices = Some(Indices {
70                    head: key,
71                    tail: key,
72                });
73            }
74        }
75    }
76
77    pub fn pop_front<T>(&mut self, buf: &mut Buffer<T>) -> Option<T> {
78        match self.indices {
79            Some(mut idxs) => {
80                let mut slot = buf.slab.remove(idxs.head);
81
82                if idxs.head == idxs.tail {
83                    assert!(slot.next.is_none());
84                    self.indices = None;
85                } else {
86                    idxs.head = slot.next.take().unwrap();
87                    self.indices = Some(idxs);
88                }
89
90                Some(slot.value)
91            }
92            None => None,
93        }
94    }
95}
h2/proto/streams/buffer.rs

h2/proto/streams/
buffer.rs
