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https://github.com/fluencelabs/rust-libp2p
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Add circular-buffer
This commit is contained in:
Vurich
693
circular-buffer/src/lib.rs
Normal file
693
circular-buffer/src/lib.rs
Normal file
@ -0,0 +1,693 @@
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#![warn(missing_docs)]
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//! # `circular-buffer`
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//!
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//! An optimized FIFO queue that allows safe access to the internal storage as a slice (i.e. not
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//! just element-by-element). This is useful for circular buffers of bytes. Since it uses
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//! `smallvec`'s `Array` trait it can only be backed by an array of static size, this may change in
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//! the future.
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extern crate smallvec;
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use std::ops::{Deref, DerefMut, Drop};
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use std::mem::ManuallyDrop;
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use smallvec::Array;
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/// A slice that owns its elements, but not their storage. This is useful for things like
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/// `Vec::retain` and `CircularBuffer::pop_slice`, since these functions can return a slice but the
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/// elements of these slices would be leaked after the slice goes out of scope. `OwnedSlice` simply
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/// manually drops all its elements when it goes out of scope.
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#[derive(Debug, Eq, PartialEq)]
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pub struct OwnedSlice<'a, T: 'a>(&'a mut [T]);
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impl<'a, T: 'a> OwnedSlice<'a, T> {
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/// Construct an owned slice from a mutable slice pointer.
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///
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/// # Unsafety
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/// You must ensure that the memory pointed to by `inner` will not be accessible after the
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/// lifetime of the `OwnedSlice`.
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pub unsafe fn new(inner: &'a mut [T]) -> Self {
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OwnedSlice(inner)
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}
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}
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impl<'a, T> AsRef<[T]> for OwnedSlice<'a, T> {
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fn as_ref(&self) -> &[T] {
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self.0
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}
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}
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impl<'a, T> AsMut<[T]> for OwnedSlice<'a, T> {
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fn as_mut(&mut self) -> &mut [T] {
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self.0
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}
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}
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impl<'a, T> Deref for OwnedSlice<'a, T> {
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type Target = [T];
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fn deref(&self) -> &Self::Target {
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self.0
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}
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}
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impl<'a, T> DerefMut for OwnedSlice<'a, T> {
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fn deref_mut(&mut self) -> &mut Self::Target {
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self.0
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}
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}
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impl<'a, T> Drop for OwnedSlice<'a, T> {
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fn drop(&mut self) {
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use std::ptr;
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for element in self.iter_mut() {
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unsafe {
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ptr::drop_in_place(element);
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}
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}
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}
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}
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/// A fixed-size FIFO queue with safe access to the backing storage.
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///
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/// This type allows access to slices of the backing storage, for efficient, safe circular buffers
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/// of bytes or other `Copy` types.
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#[derive(Debug)]
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pub struct CircularBuffer<B: Array> {
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// This must be manually dropped, as some or all of the elements may be uninitialized
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buffer: ManuallyDrop<B>,
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start: usize,
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len: usize,
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}
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impl<B: Array> PartialEq for CircularBuffer<B>
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where
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B::Item: PartialEq,
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{
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fn eq(&self, other: &Self) -> bool {
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if self.len() != other.len() {
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return false;
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}
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for (a, b) in self.iter().zip(other.iter()) {
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if a != b {
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return false;
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}
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}
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return true;
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}
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}
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impl<B: Array> CircularBuffer<B> {
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/// Create an empty `CircularBuffer`.
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer = CircularBuffer::<[usize; 4]>::new();
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///
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/// assert!(buffer.is_empty());
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/// ```
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pub fn new() -> Self {
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use std::mem;
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CircularBuffer {
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buffer: unsafe { mem::uninitialized() },
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start: 0,
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len: 0,
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}
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}
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/// Pop a slice containing the maximum possible contiguous number of elements. Since this buffer
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/// is circular it will take a maximum of two calls to this function to drain the buffer
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/// entirely.
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer = CircularBuffer::from_array([1, 2, 3, 4]);
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///
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/// assert_eq!(buffer.pop(), Some(1));
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/// assert!(buffer.push(1).is_none());
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///
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/// assert_eq!(
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/// buffer.pop_slice().as_ref().map(|s| &s[..]),
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/// Some(&[2, 3, 4][..])
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/// );
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/// assert_eq!(buffer.pop_slice().as_ref().map(|s| &s[..]), Some(&[1][..]));
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/// assert!(buffer.pop_slice().is_none());
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///
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/// assert_eq!(buffer.len(), 0);
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/// ```
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///
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/// This returns an `OwnedSlice`, which owns the items but not the storage (you cannot have two
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/// slices returned from `pop_slice` alive at once, but the elements will be have `drop` called
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/// when the slice goes out of scope), if you're using non-`Drop` types you can use
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/// `pop_slice_leaky`.
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pub fn pop_slice(&mut self) -> Option<OwnedSlice<B::Item>> {
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self.pop_slice_leaky().map(OwnedSlice)
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}
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/// Pop a slice containing the maximum possible contiguous number of elements. Since this buffer
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/// is circular it will take a maximum of two calls to this function to drain the buffer
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/// entirely. This returns a slice and so any `Drop` types returned from this function will be
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/// leaked.
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer = CircularBuffer::from_array([1, 2, 3, 4]);
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///
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/// assert_eq!(buffer.pop(), Some(1));
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/// assert!(buffer.push(1).is_none());
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///
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/// assert_eq!(
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/// buffer.pop_slice_leaky(),
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/// Some(&mut [2, 3, 4][..])
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/// );
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/// assert_eq!(buffer.pop_slice_leaky(), Some(&mut [1][..]));
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/// assert!(buffer.pop_slice_leaky().is_none());
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///
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/// assert_eq!(buffer.len(), 0);
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/// ```
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pub fn pop_slice_leaky(&mut self) -> Option<&mut [B::Item]> {
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use std::slice;
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if self.is_empty() {
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None
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} else {
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let (start, out_length) = (self.start, self.len.min(B::size() - self.start));
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self.advance(out_length);
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unsafe {
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Some(slice::from_raw_parts_mut(
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self.buffer.ptr_mut().offset(start as isize),
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out_length,
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))
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}
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}
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}
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/// A borrowed iterator of this buffer's elements
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// assert_eq!(
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/// CircularBuffer::from_array([1, 2, 3, 4]).iter().cloned().collect::<Vec<_>>(),
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/// vec![1, 2, 3, 4]
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/// );
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/// ```
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pub fn iter(&self) -> Iter<B> {
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self.into_iter()
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}
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/// Iterate over slices of the buffer (of arbitrary size, but in order).
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer = CircularBuffer::from_array([1, 2, 3, 4]);
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///
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/// assert_eq!(buffer.pop(), Some(1));
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/// assert!(buffer.push(1).is_none());
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///
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/// let mut iter = buffer.slices();
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///
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/// assert_eq!(
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/// iter.collect::<Vec<_>>(),
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/// vec![&[2, 3, 4][..], &[1]]
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/// );
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/// ```
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pub fn slices(&self) -> SlicesIter<B> {
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SlicesIter {
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buffer: self,
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start: self.start,
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len: self.len,
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}
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}
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/// Whether the buffer is empty.
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer = CircularBuffer::<[usize; 4]>::new();
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///
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/// assert!(buffer.is_empty());
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/// ```
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pub fn is_empty(&self) -> bool {
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self.len == 0
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}
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/// Whether the buffer is full (i.e. it is no longer possible to push new elements without
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/// popping old ones first).
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer = CircularBuffer::from_array([1, 2, 3, 4]);
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///
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/// assert!(buffer.is_full());
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/// ```
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pub fn is_full(&self) -> bool {
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self.len == B::size()
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}
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/// The number of elements in the buffer.
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer: CircularBuffer<[usize; 4]> = CircularBuffer::from_slice(&[1, 2]).unwrap();
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///
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/// assert_eq!(buffer.len(), 2);
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///
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/// assert!(buffer.push(1).is_none());
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/// assert!(buffer.push(2).is_none());
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///
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/// assert_eq!(buffer.len(), 4);
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/// ```
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pub fn len(&self) -> usize {
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self.len
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}
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/// The maximum number of elements this buffer can take.
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer: CircularBuffer<[usize; 4]> = CircularBuffer::new();
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///
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/// assert_eq!(buffer.capacity(), 4);
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/// ```
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pub fn capacity(&self) -> usize {
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B::size()
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}
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/// Append a single element to the end of the buffer, returning it if it could not be added.
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer: CircularBuffer<[usize; 4]> = CircularBuffer::new();
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///
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/// assert_eq!(buffer.len(), 0);
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///
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/// assert!(buffer.push(1).is_none());
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/// assert!(buffer.push(2).is_none());
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/// assert!(buffer.push(3).is_none());
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/// assert!(buffer.push(4).is_none());
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///
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/// assert!(buffer.push(5).is_some());
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///
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/// assert_eq!(buffer.len(), 4);
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/// ```
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pub fn push(&mut self, element: B::Item) -> Option<B::Item> {
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use std::ptr;
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debug_assert!(self.len <= B::size());
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if self.is_full() {
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Some(element)
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} else {
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let dest = (self.start + self.len) % B::size();
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unsafe {
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ptr::write(self.buffer.ptr_mut().offset(dest as isize), element);
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}
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self.len += 1;
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None
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}
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}
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/// Remove a single element from the start of the buffer.
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///
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/// ```rust
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/// use circular_buffer::CircularBuffer;
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///
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/// let mut buffer = CircularBuffer::from_array([1, 2, 3, 4]);
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///
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/// assert_eq!(buffer.pop(), Some(1));
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/// ```
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pub fn pop(&mut self) -> Option<B::Item> {
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use std::ptr;
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if self.is_empty() {
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None
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} else {
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let offset = self.start;
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self.advance(1);
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unsafe { Some(ptr::read(self.buffer.ptr_mut().offset(offset as _))) }
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}
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}
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/// Get a borrow to an element at an index safely (if the index is out of bounds, return
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/// `None`).
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pub fn get(&self, index: usize) -> Option<&B::Item> {
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if index < self.len {
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unsafe { Some(self.get_unchecked(index)) }
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} else {
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None
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}
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}
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/// Get a borrow to an element at an index unsafely (causes undefined behaviour if the index is
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/// out of bounds).
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pub unsafe fn get_unchecked(&self, index: usize) -> &B::Item {
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use std::mem;
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mem::transmute(self.buffer.ptr().offset(
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((index + self.start) % B::size()) as isize,
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))
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}
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// This is not unsafe because it can only leak data, not cause uninit to be read.
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fn advance(&mut self, by: usize) {
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assert!(by <= self.len);
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self.start = (self.start + by) % B::size();
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self.len -= by;
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}
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}
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impl<B: Array> Drop for CircularBuffer<B> {
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fn drop(&mut self) {
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while self.pop_slice().is_some() {}
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}
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}
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impl<B: Array> IntoIterator for CircularBuffer<B> {
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type Item = B::Item;
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type IntoIter = IntoIter<B>;
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fn into_iter(self) -> Self::IntoIter {
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IntoIter { buffer: self }
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}
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}
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impl<'a, B: Array + 'a> IntoIterator for &'a CircularBuffer<B> {
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type Item = &'a B::Item;
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type IntoIter = Iter<'a, B>;
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fn into_iter(self) -> Self::IntoIter {
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Iter {
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buffer: self,
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remaining: self.len(),
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}
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}
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}
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/// The iteration type returning owned elements of the buffer
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pub struct IntoIter<B: Array> {
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buffer: CircularBuffer<B>,
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}
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impl<B: Array> Iterator for IntoIter<B> {
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type Item = B::Item;
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fn next(&mut self) -> Option<Self::Item> {
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self.buffer.pop()
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}
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}
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/// The iteration type returning borrows to elements of the buffer
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pub struct Iter<'a, B: Array + 'a> {
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buffer: &'a CircularBuffer<B>,
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remaining: usize,
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}
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impl<'a, B: Array + 'a> Iterator for Iter<'a, B> {
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type Item = &'a B::Item;
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fn next(&mut self) -> Option<Self::Item> {
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if self.remaining == 0 {
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None
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} else {
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let remaining = self.remaining;
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self.remaining -= 1;
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||||
self.buffer.get(self.buffer.len() - remaining)
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||||
}
|
||||
}
|
||||
}
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||||
|
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/// The iteration type for immutable slices of the circular buffer. See `CircularBuffer::slices`.
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||||
pub struct SlicesIter<'a, B: Array + 'a> {
|
||||
buffer: &'a CircularBuffer<B>,
|
||||
start: usize,
|
||||
len: usize,
|
||||
}
|
||||
|
||||
impl<'a, B: Array + 'a> Iterator for SlicesIter<'a, B> {
|
||||
type Item = &'a [B::Item];
|
||||
|
||||
fn next(&mut self) -> Option<Self::Item> {
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||||
use std::slice;
|
||||
|
||||
if self.len == 0 {
|
||||
None
|
||||
} else {
|
||||
let (start, out_length) = (self.start, self.len.min(B::size() - self.start));
|
||||
|
||||
self.start = (self.start + out_length) % B::size();
|
||||
self.len -= out_length;
|
||||
|
||||
unsafe {
|
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Some(slice::from_raw_parts(
|
||||
self.buffer.buffer.ptr().offset(start as isize),
|
||||
out_length,
|
||||
))
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl<B: Array> CircularBuffer<B>
|
||||
where
|
||||
B::Item: Copy,
|
||||
{
|
||||
/// Create a `CircularBuffer` from a slice of elements, returning `None` if not all the elements
|
||||
/// can fit in the buffer.
|
||||
///
|
||||
/// ```rust
|
||||
/// use circular_buffer::CircularBuffer;
|
||||
///
|
||||
/// assert!(CircularBuffer::<[usize; 5]>::from_slice(&[1, 2, 3, 4, 5, 6]).is_none());
|
||||
/// assert!(CircularBuffer::<[usize; 5]>::from_slice(&[1, 2, 3, 4]).is_some());
|
||||
/// ```
|
||||
pub fn from_slice(slice: &[B::Item]) -> Option<Self> {
|
||||
let mut out = Self::new();
|
||||
if out.extend_from_slice(slice) {
|
||||
Some(out)
|
||||
} else {
|
||||
None
|
||||
}
|
||||
}
|
||||
|
||||
/// Create a `CircularBuffer` from a slice of elements, returning the number of elements copied.
|
||||
///
|
||||
/// ```rust
|
||||
/// use circular_buffer::CircularBuffer;
|
||||
///
|
||||
/// let result = CircularBuffer::<[usize; 5]>::from_slice_prefix(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 20]);
|
||||
/// assert_eq!(result, (CircularBuffer::from_array([1, 2, 3, 4, 5]), 5));
|
||||
/// ```
|
||||
pub fn from_slice_prefix(slice: &[B::Item]) -> (Self, usize) {
|
||||
let mut out = Self::new();
|
||||
let num_copied = out.extend_from_slice_prefix(slice);
|
||||
(out, num_copied)
|
||||
}
|
||||
|
||||
/// Create a circular buffer from a fixed-size array
|
||||
///
|
||||
/// ```rust
|
||||
/// use circular_buffer::CircularBuffer;
|
||||
///
|
||||
/// let result = CircularBuffer::from_array([1, 2, 3, 4, 5]);
|
||||
/// assert_eq!(result.into_iter().collect::<Vec<_>>(), vec![1, 2, 3, 4, 5]);
|
||||
/// ```
|
||||
pub fn from_array(slice: B) -> Self {
|
||||
CircularBuffer {
|
||||
buffer: ManuallyDrop::new(slice),
|
||||
start: 0,
|
||||
len: B::size(),
|
||||
}
|
||||
}
|
||||
|
||||
fn write_slice(&mut self, index: usize, slice: &[B::Item]) -> bool {
|
||||
use std::ptr;
|
||||
|
||||
let mut offset = 0;
|
||||
|
||||
assert!(index <= self.len);
|
||||
|
||||
if slice.len() > self.capacity() - index {
|
||||
return false;
|
||||
}
|
||||
|
||||
while offset < slice.len() {
|
||||
unsafe {
|
||||
let dest = (index + self.start + offset) % B::size();
|
||||
let copy_len = if dest < self.start {
|
||||
self.start - dest
|
||||
} else {
|
||||
B::size() - dest
|
||||
}.min(slice.len() - offset);
|
||||
|
||||
let slice_ptr = slice.as_ptr().offset(offset as isize);
|
||||
let ptr = self.buffer.ptr_mut().offset(dest as isize);
|
||||
|
||||
ptr::copy(slice_ptr, ptr, copy_len);
|
||||
|
||||
self.len = self.len.max(index + offset + copy_len);
|
||||
offset += copy_len;
|
||||
}
|
||||
}
|
||||
|
||||
true
|
||||
}
|
||||
|
||||
fn write_slice_prefix(&mut self, index: usize, slice: &[B::Item]) -> usize {
|
||||
use std::ptr;
|
||||
|
||||
let mut offset = 0;
|
||||
|
||||
assert!(index <= self.len);
|
||||
|
||||
while !self.is_full() && offset < slice.len() {
|
||||
unsafe {
|
||||
let dest = (index + self.start + offset) % B::size();
|
||||
let copy_len = if dest < self.start {
|
||||
self.start - dest
|
||||
} else {
|
||||
B::size() - dest
|
||||
}.min(slice.len() - offset);
|
||||
|
||||
let slice_ptr = slice.as_ptr().offset(offset as isize);
|
||||
let ptr = self.buffer.ptr_mut().offset(dest as isize);
|
||||
|
||||
ptr::copy(slice_ptr, ptr, copy_len);
|
||||
|
||||
self.len = self.len.max(index + offset + copy_len);
|
||||
offset += copy_len;
|
||||
}
|
||||
}
|
||||
|
||||
offset
|
||||
}
|
||||
|
||||
/// Append the elements from a slice to the buffer, returning the number of elements copied
|
||||
///
|
||||
/// ```rust
|
||||
/// use circular_buffer::CircularBuffer;
|
||||
///
|
||||
/// let mut buffer = CircularBuffer::<[usize; 5]>::from_slice(&[1, 2]).unwrap();
|
||||
///
|
||||
/// assert_eq!(buffer.iter().cloned().collect::<Vec<_>>(), vec![1, 2]);
|
||||
///
|
||||
/// let consumed = buffer.extend_from_slice_prefix(&[1, 2, 3, 4, 5]);
|
||||
///
|
||||
/// assert_eq!(consumed, 3);
|
||||
/// assert_eq!(buffer.iter().cloned().collect::<Vec<_>>(), vec![1, 2, 1, 2, 3]);
|
||||
/// ```
|
||||
#[inline]
|
||||
pub fn extend_from_slice_prefix(&mut self, slice: &[B::Item]) -> usize {
|
||||
let len = self.len();
|
||||
self.write_slice_prefix(len, slice)
|
||||
}
|
||||
|
||||
/// Append the elements from a slice to the buffer iff there is enough space for all the
|
||||
/// elements
|
||||
///
|
||||
/// ```rust
|
||||
/// use circular_buffer::CircularBuffer;
|
||||
///
|
||||
/// let mut buffer = CircularBuffer::<[usize; 5]>::from_slice(&[1, 2]).unwrap();
|
||||
///
|
||||
/// assert_eq!(buffer.iter().cloned().collect::<Vec<_>>(), vec![1, 2]);
|
||||
///
|
||||
/// assert!(!buffer.extend_from_slice(&[1, 2, 3, 4, 5]));
|
||||
/// assert!(buffer.extend_from_slice(&[1, 2, 3]));
|
||||
///
|
||||
/// assert_eq!(buffer.iter().cloned().collect::<Vec<_>>(), vec![1, 2, 1, 2, 3]);
|
||||
/// ```
|
||||
#[inline]
|
||||
pub fn extend_from_slice(&mut self, slice: &[B::Item]) -> bool {
|
||||
let len = self.len();
|
||||
self.write_slice(len, slice)
|
||||
}
|
||||
}
|
||||
|
||||
#[cfg(test)]
|
||||
mod tests {
|
||||
use super::CircularBuffer;
|
||||
|
||||
#[test]
|
||||
fn push_pop() {
|
||||
let mut buffer: CircularBuffer<[usize; 4]> = CircularBuffer::new();
|
||||
|
||||
assert_eq!(buffer.len(), 0);
|
||||
|
||||
assert!(buffer.push(1).is_none());
|
||||
assert!(buffer.push(2).is_none());
|
||||
assert!(buffer.push(3).is_none());
|
||||
assert!(buffer.push(4).is_none());
|
||||
|
||||
assert!(buffer.push(5).is_some());
|
||||
|
||||
assert_eq!(buffer.len(), 4);
|
||||
|
||||
assert_eq!(buffer.pop(), Some(1));
|
||||
assert_eq!(buffer.pop(), Some(2));
|
||||
assert_eq!(buffer.pop(), Some(3));
|
||||
assert_eq!(buffer.pop(), Some(4));
|
||||
assert_eq!(buffer.pop(), None);
|
||||
|
||||
assert_eq!(buffer.len(), 0);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn pop_slice() {
|
||||
let mut buffer: CircularBuffer<[usize; 4]> = CircularBuffer::new();
|
||||
|
||||
assert_eq!(buffer.len(), 0);
|
||||
|
||||
assert!(buffer.push(1).is_none());
|
||||
assert!(buffer.push(2).is_none());
|
||||
assert!(buffer.push(3).is_none());
|
||||
assert!(buffer.push(4).is_none());
|
||||
|
||||
assert!(buffer.push(5).is_some());
|
||||
|
||||
assert_eq!(buffer.len(), 4);
|
||||
|
||||
assert_eq!(buffer.pop(), Some(1));
|
||||
assert!(buffer.push(1).is_none());
|
||||
|
||||
assert_eq!(
|
||||
buffer.pop_slice().as_ref().map(|s| &s[..]),
|
||||
Some(&[2, 3, 4][..])
|
||||
);
|
||||
assert_eq!(buffer.pop_slice().as_ref().map(|s| &s[..]), Some(&[1][..]));
|
||||
assert!(buffer.pop_slice().is_none());
|
||||
|
||||
assert_eq!(buffer.len(), 0);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn extend_from_slice() {
|
||||
let mut buffer: CircularBuffer<[usize; 4]> = CircularBuffer::from_slice(&[1, 2]).unwrap();
|
||||
|
||||
assert_eq!(buffer.pop(), Some(1));
|
||||
assert_eq!(buffer.pop(), Some(2));
|
||||
|
||||
assert!(buffer.extend_from_slice(&[1, 2, 3, 4]));
|
||||
|
||||
assert_eq!(buffer.iter().cloned().collect::<Vec<_>>(), vec![1, 2, 3, 4])
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user