Revision control
Copy as Markdown
Other Tools
use std::ops::{Bound, Range, RangeBounds};
/// A owned window around an underlying buffer.
///
/// Normally slices work great for considering sub-portions of a buffer, but
/// unfortunately a slice is a *borrowed* type in Rust which has an associated
/// lifetime. When working with future and async I/O these lifetimes are not
/// always appropriate, and are sometimes difficult to store in tasks. This
/// type strives to fill this gap by providing an "owned slice" around an
/// underlying buffer of bytes.
///
/// A `Window<T>` wraps an underlying buffer, `T`, and has configurable
/// start/end indexes to alter the behavior of the `AsRef<[u8]>` implementation
/// that this type carries.
///
/// This type can be particularly useful when working with the `write_all`
/// combinator in this crate. Data can be sliced via `Window`, consumed by
/// `write_all`, and then earned back once the write operation finishes through
/// the `into_inner` method on this type.
#[derive(Debug)]
pub struct Window<T> {
inner: T,
range: Range<usize>,
}
impl<T: AsRef<[u8]>> Window<T> {
/// Creates a new window around the buffer `t` defaulting to the entire
/// slice.
///
/// Further methods can be called on the returned `Window<T>` to alter the
/// window into the data provided.
pub fn new(t: T) -> Self {
Self { range: 0..t.as_ref().len(), inner: t }
}
/// Gets a shared reference to the underlying buffer inside of this
/// `Window`.
pub fn get_ref(&self) -> &T {
&self.inner
}
/// Gets a mutable reference to the underlying buffer inside of this
/// `Window`.
pub fn get_mut(&mut self) -> &mut T {
&mut self.inner
}
/// Consumes this `Window`, returning the underlying buffer.
pub fn into_inner(self) -> T {
self.inner
}
/// Returns the starting index of this window into the underlying buffer
/// `T`.
pub fn start(&self) -> usize {
self.range.start
}
/// Returns the end index of this window into the underlying buffer
/// `T`.
pub fn end(&self) -> usize {
self.range.end
}
/// Changes the range of this window to the range specified.
///
/// # Panics
///
/// This method will panic if `range` is out of bounds for the underlying
/// slice or if [`start_bound()`] of `range` comes after the [`end_bound()`].
///
/// [`start_bound()`]: std::ops::RangeBounds::start_bound
/// [`end_bound()`]: std::ops::RangeBounds::end_bound
pub fn set<R: RangeBounds<usize>>(&mut self, range: R) {
let start = match range.start_bound() {
Bound::Included(n) => *n,
Bound::Excluded(n) => *n + 1,
Bound::Unbounded => 0,
};
let end = match range.end_bound() {
Bound::Included(n) => *n + 1,
Bound::Excluded(n) => *n,
Bound::Unbounded => self.inner.as_ref().len(),
};
assert!(end <= self.inner.as_ref().len());
assert!(start <= end);
self.range.start = start;
self.range.end = end;
}
}
impl<T: AsRef<[u8]>> AsRef<[u8]> for Window<T> {
fn as_ref(&self) -> &[u8] {
&self.inner.as_ref()[self.range.start..self.range.end]
}
}
impl<T: AsMut<[u8]>> AsMut<[u8]> for Window<T> {
fn as_mut(&mut self) -> &mut [u8] {
&mut self.inner.as_mut()[self.range.start..self.range.end]
}
}