buffer_pool/
buffer.rs

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26
27use std::ops::Deref;
28use std::ops::DerefMut;
29
30use crate::Reuse;
31
32/// A convinience wrapper around Vec that allows to "consume" data from the
33/// front *without* shifting.
34///
35/// This is not unlike `VecDeque` but more ergonomic
36/// for the operations we require. Conceptually `VecDeque` is two slices, and
37/// this is one slice. Also there is no `set_len` for `VecDeque`, so it has to
38/// be converted to `Vec` and then back again.
39#[derive(Default, Debug)]
40pub struct ConsumeBuffer {
41    inner: Vec<u8>,
42    head: usize,
43}
44
45impl Deref for ConsumeBuffer {
46    type Target = [u8];
47
48    fn deref(&self) -> &Self::Target {
49        &self.inner[self.head..]
50    }
51}
52
53impl DerefMut for ConsumeBuffer {
54    fn deref_mut(&mut self) -> &mut Self::Target {
55        &mut self.inner[self.head..]
56    }
57}
58
59impl Reuse for ConsumeBuffer {
60    fn reuse(&mut self, val: usize) -> bool {
61        self.inner.clear();
62        self.inner.shrink_to(val);
63        self.head = 0;
64        self.inner.capacity() > 0
65    }
66}
67
68impl ConsumeBuffer {
69    pub fn from_vec(inner: Vec<u8>) -> Self {
70        ConsumeBuffer { inner, head: 0 }
71    }
72
73    pub fn into_vec(self) -> Vec<u8> {
74        let mut inner = self.inner;
75        inner.drain(0..self.head);
76        inner
77    }
78
79    pub fn pop_front(&mut self, count: usize) {
80        assert!(self.head + count <= self.inner.len());
81        self.head += count;
82    }
83
84    pub fn expand(&mut self, count: usize) {
85        self.inner.reserve_exact(count);
86        // SAFETY: u8 is always initialized and we reserved the capacity.
87        unsafe { self.inner.set_len(count) };
88    }
89
90    pub fn truncate(&mut self, count: usize) {
91        self.inner.truncate(self.head + count);
92    }
93
94    pub fn add_prefix(&mut self, prefix: &[u8]) -> bool {
95        if self.head < prefix.len() {
96            return false;
97        }
98
99        self.head -= prefix.len();
100        self.inner[self.head..self.head + prefix.len()].copy_from_slice(prefix);
101
102        true
103    }
104}
105
106impl<'a> Extend<&'a u8> for ConsumeBuffer {
107    fn extend<T: IntoIterator<Item = &'a u8>>(&mut self, iter: T) {
108        self.inner.extend(iter)
109    }
110}
buffer_pool/buffer.rs

buffer_pool/
buffer.rs
