1 use crate::BufMut;
2
3 use core::{cmp, mem::MaybeUninit};
4
5 /// A `BufMut` adapter which limits the amount of bytes that can be written
6 /// to an underlying buffer.
7 #[derive(Debug)]
8 pub struct Limit<T> {
9 inner: T,
10 limit: usize,
11 }
12
new<T>(inner: T, limit: usize) -> Limit<T>13 pub(super) fn new<T>(inner: T, limit: usize) -> Limit<T> {
14 Limit { inner, limit }
15 }
16
17 impl<T> Limit<T> {
18 /// Consumes this `Limit`, returning the underlying value.
into_inner(self) -> T19 pub fn into_inner(self) -> T {
20 self.inner
21 }
22
23 /// Gets a reference to the underlying `BufMut`.
24 ///
25 /// It is inadvisable to directly write to the underlying `BufMut`.
get_ref(&self) -> &T26 pub fn get_ref(&self) -> &T {
27 &self.inner
28 }
29
30 /// Gets a mutable reference to the underlying `BufMut`.
31 ///
32 /// It is inadvisable to directly write to the underlying `BufMut`.
get_mut(&mut self) -> &mut T33 pub fn get_mut(&mut self) -> &mut T {
34 &mut self.inner
35 }
36
37 /// Returns the maximum number of bytes that can be written
38 ///
39 /// # Note
40 ///
41 /// If the inner `BufMut` has fewer bytes than indicated by this method then
42 /// that is the actual number of available bytes.
limit(&self) -> usize43 pub fn limit(&self) -> usize {
44 self.limit
45 }
46
47 /// Sets the maximum number of bytes that can be written.
48 ///
49 /// # Note
50 ///
51 /// If the inner `BufMut` has fewer bytes than `lim` then that is the actual
52 /// number of available bytes.
set_limit(&mut self, lim: usize)53 pub fn set_limit(&mut self, lim: usize) {
54 self.limit = lim
55 }
56 }
57
58 impl<T: BufMut> BufMut for Limit<T> {
remaining_mut(&self) -> usize59 fn remaining_mut(&self) -> usize {
60 cmp::min(self.inner.remaining_mut(), self.limit)
61 }
62
bytes_mut(&mut self) -> &mut [MaybeUninit<u8>]63 fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
64 let bytes = self.inner.bytes_mut();
65 let end = cmp::min(bytes.len(), self.limit);
66 &mut bytes[..end]
67 }
68
advance_mut(&mut self, cnt: usize)69 unsafe fn advance_mut(&mut self, cnt: usize) {
70 assert!(cnt <= self.limit);
71 self.inner.advance_mut(cnt);
72 self.limit -= cnt;
73 }
74 }
75