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use crate::buf::UninitSlice;
use crate::BufMut;
use core::cmp;
/// A `BufMut` adapter which limits the amount of bytes that can be written
/// to an underlying buffer.
#[derive(Debug)]
pub struct Limit<T> {
inner: T,
limit: usize,
}
pub(super) fn new<T>(inner: T, limit: usize) -> Limit<T> {
Limit { inner, limit }
}
impl<T> Limit<T> {
/// Consumes this `Limit`, returning the underlying value.
pub fn into_inner(self) -> T {
self.inner
}
/// Gets a reference to the underlying `BufMut`.
///
/// It is inadvisable to directly write to the underlying `BufMut`.
pub fn get_ref(&self) -> &T {
&self.inner
}
/// Gets a mutable reference to the underlying `BufMut`.
///
/// It is inadvisable to directly write to the underlying `BufMut`.
pub fn get_mut(&mut self) -> &mut T {
&mut self.inner
}
/// Returns the maximum number of bytes that can be written
///
/// # Note
///
/// If the inner `BufMut` has fewer bytes than indicated by this method then
/// that is the actual number of available bytes.
pub fn limit(&self) -> usize {
self.limit
}
/// Sets the maximum number of bytes that can be written.
///
/// # Note
///
/// If the inner `BufMut` has fewer bytes than `lim` then that is the actual
/// number of available bytes.
pub fn set_limit(&mut self, lim: usize) {
self.limit = lim
}
}
unsafe impl<T: BufMut> BufMut for Limit<T> {
fn remaining_mut(&self) -> usize {
cmp::min(self.inner.remaining_mut(), self.limit)
}
fn chunk_mut(&mut self) -> &mut UninitSlice {
let bytes = self.inner.chunk_mut();
let end = cmp::min(bytes.len(), self.limit);
&mut bytes[..end]
}
unsafe fn advance_mut(&mut self, cnt: usize) {
assert!(cnt <= self.limit);
self.inner.advance_mut(cnt);
self.limit -= cnt;
}
}