bytes/buf/limit.rs
1use crate::buf::UninitSlice;
2use crate::BufMut;
3
4use core::cmp;
5
6/// A `BufMut` adapter which limits the amount of bytes that can be written
7/// to an underlying buffer.
8#[derive(Debug)]
9pub struct Limit<T> {
10 inner: T,
11 limit: usize,
12}
13
14pub(super) fn new<T>(inner: T, limit: usize) -> Limit<T> {
15 Limit { inner, limit }
16}
17
18impl<T> Limit<T> {
19 /// Consumes this `Limit`, returning the underlying value.
20 pub fn into_inner(self) -> T {
21 self.inner
22 }
23
24 /// Gets a reference to the underlying `BufMut`.
25 ///
26 /// It is inadvisable to directly write to the underlying `BufMut`.
27 pub fn get_ref(&self) -> &T {
28 &self.inner
29 }
30
31 /// Gets a mutable reference to the underlying `BufMut`.
32 ///
33 /// It is inadvisable to directly write to the underlying `BufMut`.
34 pub fn get_mut(&mut self) -> &mut T {
35 &mut self.inner
36 }
37
38 /// Returns the maximum number of bytes that can be written
39 ///
40 /// # Note
41 ///
42 /// If the inner `BufMut` has fewer bytes than indicated by this method then
43 /// that is the actual number of available bytes.
44 pub fn limit(&self) -> usize {
45 self.limit
46 }
47
48 /// Sets the maximum number of bytes that can be written.
49 ///
50 /// # Note
51 ///
52 /// If the inner `BufMut` has fewer bytes than `lim` then that is the actual
53 /// number of available bytes.
54 pub fn set_limit(&mut self, lim: usize) {
55 self.limit = lim
56 }
57}
58
59unsafe impl<T: BufMut> BufMut for Limit<T> {
60 fn remaining_mut(&self) -> usize {
61 cmp::min(self.inner.remaining_mut(), self.limit)
62 }
63
64 fn chunk_mut(&mut self) -> &mut UninitSlice {
65 let bytes = self.inner.chunk_mut();
66 let end = cmp::min(bytes.len(), self.limit);
67 &mut bytes[..end]
68 }
69
70 unsafe fn advance_mut(&mut self, cnt: usize) {
71 assert!(cnt <= self.limit);
72 self.inner.advance_mut(cnt);
73 self.limit -= cnt;
74 }
75}