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use core::ops::{Index, IndexMut};
#[cfg(feature = "alloc")]
extern crate alloc;
#[cfg(feature = "alloc")]
use alloc::vec::Vec;
use core::iter::FromIterator;
/// `RingBuffer` is a trait defining the standard interface for all RingBuffer
/// implementations ([`AllocRingBuffer`](crate::AllocRingBuffer), [`ConstGenericRingBuffer`](crate::ConstGenericRingBuffer))
///
/// This trait is not object safe, so can't be used dynamically. However it is possible to
/// define a generic function over types implementing `RingBuffer`.
///
/// Most actual functionality of ringbuffers is contained in the extension traits [`RingBufferExt`], [`RingBufferRead`] and [`RingBufferWrite`]
pub trait RingBuffer<T>: Sized {
/// Returns the length of the internal buffer.
/// This length grows up to the capacity and then stops growing.
/// This is because when the length is reached, new items are appended at the start.
fn len(&self) -> usize;
/// Returns true if the buffer is entirely empty.
#[inline]
fn is_empty(&self) -> bool {
self.len() == 0
}
/// Returns true when the length of the ringbuffer equals the capacity. This happens whenever
/// more elements than capacity have been pushed to the buffer.
#[inline]
fn is_full(&self) -> bool {
self.len() == self.capacity()
}
/// Returns the capacity of the buffer.
fn capacity(&self) -> usize;
}
/// Defines behaviour for ringbuffers which allow for writing to the end of them (as a queue).
/// For arbitrary buffer access however, [`RingBufferExt`] is necessary.
pub trait RingBufferWrite<T>: RingBuffer<T> + Extend<T> {
/// Pushes a value onto the buffer. Cycles around if capacity is reached.
fn push(&mut self, value: T);
}
/// Defines behaviour for ringbuffers which allow for reading from the start of them (as a queue).
/// For arbitrary buffer access however, [`RingBufferExt`] is necessary.
pub trait RingBufferRead<T>: RingBuffer<T> {
/// dequeues the top item off the ringbuffer, and moves this item out.
fn dequeue(&mut self) -> Option<T>;
/// dequeues the top item off the queue, but does not return it. Instead it is dropped.
/// If the ringbuffer is empty, this function is a nop.
fn skip(&mut self);
/// Returns an iterator over the elements in the ringbuffer,
/// dequeueing elements as they are iterated over.
///
/// ```
/// use ringbuffer::{AllocRingBuffer, RingBufferWrite, RingBufferRead, RingBuffer};
///
/// let mut rb = AllocRingBuffer::with_capacity(16);
/// for i in 0..8 {
/// rb.push(i);
/// }
///
/// assert_eq!(rb.len(), 8);
///
/// for i in rb.drain() {
/// // prints the numbers 0 through 8
/// println!("{}", i);
/// }
///
/// // No elements remain
/// assert_eq!(rb.len(), 0);
///
/// ```
fn drain(&mut self) -> RingBufferDrainingIterator<T, Self> {
RingBufferDrainingIterator::new(self)
}
}
/// Defines behaviour for ringbuffers which allow them to be used as a general purpose buffer.
/// With this trait, arbitrary access of elements in the buffer is possible.
pub trait RingBufferExt<T>:
RingBuffer<T>
+ RingBufferRead<T>
+ RingBufferWrite<T>
+ Index<isize, Output = T>
+ IndexMut<isize>
+ FromIterator<T>
{
/// Sets every element in the ringbuffer to the value returned by f.
fn fill_with<F: FnMut() -> T>(&mut self, f: F);
/// Sets every element in the ringbuffer to it's default value
fn fill_default(&mut self)
where
T: Default,
{
self.fill_with(Default::default)
}
/// Sets every element in the ringbuffer to `value`
fn fill(&mut self, value: T)
where
T: Clone,
{
self.fill_with(|| value.clone())
}
/// Empties the buffer entirely. Sets the length to 0 but keeps the capacity allocated.
fn clear(&mut self);
/// Gets a value relative to the current index. 0 is the next index to be written to with push.
/// -1 and down are the last elements pushed and 0 and up are the items that were pushed the longest ago.
fn get(&self, index: isize) -> Option<&T>;
/// Gets a value relative to the current index mutably. 0 is the next index to be written to with push.
/// -1 and down are the last elements pushed and 0 and up are the items that were pushed the longest ago.
fn get_mut(&mut self, index: isize) -> Option<&mut T>;
/// Gets a value relative to the start of the array (rarely useful, usually you want [`Self::get`])
fn get_absolute(&self, index: usize) -> Option<&T>;
/// Gets a value mutably relative to the start of the array (rarely useful, usually you want [`Self::get_mut`])
fn get_absolute_mut(&mut self, index: usize) -> Option<&mut T>;
/// Returns the value at the current index.
/// This is the value that will be overwritten by the next push and also the value pushed
/// the longest ago. (alias of [`Self::front`])
#[inline]
fn peek(&self) -> Option<&T> {
self.front()
}
/// Returns the value at the front of the queue.
/// This is the value that will be overwritten by the next push and also the value pushed
/// the longest ago.
/// (alias of peek)
#[inline]
fn front(&self) -> Option<&T> {
self.get(0)
}
/// Returns a mutable reference to the value at the back of the queue.
/// This is the value that will be overwritten by the next push.
/// (alias of peek)
#[inline]
fn front_mut(&mut self) -> Option<&mut T> {
self.get_mut(0)
}
/// Returns the value at the back of the queue.
/// This is the item that was pushed most recently.
#[inline]
fn back(&self) -> Option<&T> {
self.get(-1)
}
/// Returns a mutable reference to the value at the back of the queue.
/// This is the item that was pushed most recently.
#[inline]
fn back_mut(&mut self) -> Option<&mut T> {
self.get_mut(-1)
}
/// Creates a mutable iterator over the buffer starting from the item pushed the longest ago,
/// and ending at the element most recently pushed.
#[inline]
fn iter_mut(&mut self) -> RingBufferMutIterator<T, Self> {
RingBufferMutIterator::new(self)
}
/// Creates an iterator over the buffer starting from the item pushed the longest ago,
/// and ending at the element most recently pushed.
#[inline]
fn iter(&self) -> RingBufferIterator<T, Self> {
RingBufferIterator::new(self)
}
/// Converts the buffer to a vector. This Copies all elements in the ringbuffer.
#[cfg(feature = "alloc")]
fn to_vec(&self) -> Vec<T>
where
T: Clone,
{
self.iter().cloned().collect()
}
/// Returns true if elem is in the ringbuffer.
fn contains(&self, elem: &T) -> bool
where
T: PartialEq,
{
self.iter().any(|i| i == elem)
}
}
mod iter {
use crate::{RingBufferExt, RingBufferRead};
use core::iter::FusedIterator;
use core::marker::PhantomData;
/// RingBufferIterator holds a reference to a `RingBufferExt` and iterates over it. `index` is the
/// current iterator position.
pub struct RingBufferIterator<'rb, T, RB: RingBufferExt<T>> {
obj: &'rb RB,
len: usize,
index: usize,
phantom: PhantomData<T>,
}
impl<'rb, T, RB: RingBufferExt<T>> RingBufferIterator<'rb, T, RB> {
#[inline]
pub fn new(obj: &'rb RB) -> Self {
Self {
obj,
len: obj.len(),
index: 0,
phantom: PhantomData::default(),
}
}
}
impl<'rb, T: 'rb, RB: RingBufferExt<T>> Iterator for RingBufferIterator<'rb, T, RB> {
type Item = &'rb T;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
if self.index < self.len {
let res = self.obj.get(self.index as isize);
self.index += 1;
res
} else {
None
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(self.len, Some(self.len))
}
}
impl<'rb, T: 'rb, RB: RingBufferExt<T>> FusedIterator for RingBufferIterator<'rb, T, RB> {}
impl<'rb, T: 'rb, RB: RingBufferExt<T>> ExactSizeIterator for RingBufferIterator<'rb, T, RB> {}
impl<'rb, T: 'rb, RB: RingBufferExt<T>> DoubleEndedIterator for RingBufferIterator<'rb, T, RB> {
#[inline]
fn next_back(&mut self) -> Option<Self::Item> {
if self.len > 0 && self.index < self.len {
let res = self.obj.get((self.len - 1) as isize);
self.len -= 1;
res
} else {
None
}
}
}
/// `RingBufferMutIterator` holds a reference to a `RingBufferExt` and iterates over it. `index` is the
/// current iterator position.
///
/// WARNING: NEVER ACCESS THE `obj` FIELD. it's private on purpose, and can technically be accessed
/// in the same module. However, this breaks the safety of `next()`
pub struct RingBufferMutIterator<'rb, T, RB: RingBufferExt<T>> {
obj: &'rb mut RB,
index: usize,
phantom: PhantomData<T>,
}
impl<'rb, T, RB: RingBufferExt<T>> RingBufferMutIterator<'rb, T, RB> {
#[inline]
pub fn new(obj: &'rb mut RB) -> Self {
Self {
obj,
index: 0,
phantom: PhantomData::default(),
}
}
pub fn next(&mut self) -> Option<&mut T> {
if self.index < self.obj.len() {
let res = self.obj.get_mut(self.index as isize);
self.index += 1;
res
} else {
None
}
}
}
/// `RingBufferMutIterator` holds a reference to a `RingBufferRead` and iterates over it. `index` is the
/// current iterator position.
pub struct RingBufferDrainingIterator<'rb, T, RB: RingBufferRead<T>> {
obj: &'rb mut RB,
phantom: PhantomData<T>,
}
impl<'rb, T, RB: RingBufferRead<T>> RingBufferDrainingIterator<'rb, T, RB> {
#[inline]
pub fn new(obj: &'rb mut RB) -> Self {
Self {
obj,
phantom: PhantomData::default(),
}
}
}
impl<'rb, T, RB: RingBufferRead<T>> Iterator for RingBufferDrainingIterator<'rb, T, RB> {
type Item = T;
fn next(&mut self) -> Option<T> {
self.obj.dequeue()
}
}
}
pub use iter::{RingBufferDrainingIterator, RingBufferIterator, RingBufferMutIterator};
/// Implement various functions on implementors of RingBufferRead.
/// This is to avoid duplicate code.
macro_rules! impl_ringbuffer_read {
() => {
#[inline]
fn skip(&mut self) {
let _ = self.dequeue().map(drop);
}
};
}
/// Implement various functions on implementors of RingBuffer.
/// This is to avoid duplicate code.
macro_rules! impl_ringbuffer {
($readptr: ident, $writeptr: ident) => {
#[inline]
fn len(&self) -> usize {
self.$writeptr - self.$readptr
}
};
}
/// Implement various functions on implementors of RingBufferExt.
/// This is to avoid duplicate code.
macro_rules! impl_ringbuffer_ext {
($get_unchecked: ident, $get_unchecked_mut: ident, $readptr: ident, $writeptr: ident, $mask: expr) => {
#[inline]
fn get(&self, index: isize) -> Option<&T> {
use core::ops::Not;
self.is_empty().not().then(move || {
let index_from_readptr = if index >= 0 {
index
} else {
self.len() as isize + index
};
let normalized_index =
self.readptr as isize + index_from_readptr.rem_euclid(self.len() as isize);
unsafe {
// SAFETY: index has been modulo-ed to be within range
// to be within bounds
self.$get_unchecked($crate::mask(self.capacity(), normalized_index as usize))
}
})
}
#[inline]
fn get_mut(&mut self, index: isize) -> Option<&mut T> {
use core::ops::Not;
self.is_empty().not().then(move || {
let index_from_readptr = if index >= 0 {
index
} else {
self.len() as isize + index
};
let normalized_index =
self.readptr as isize + index_from_readptr.rem_euclid(self.len() as isize);
unsafe {
// SAFETY: index has been modulo-ed to be within range
// to be within bounds
self.$get_unchecked_mut($crate::mask(
self.capacity(),
normalized_index as usize,
))
}
})
}
#[inline]
fn get_absolute(&self, index: usize) -> Option<&T> {
let read = $mask(self.capacity(), self.$readptr);
let write = $mask(self.capacity(), self.$writeptr);
(index >= read && index < write).then(|| unsafe {
// SAFETY: index has been checked against $mask to be within bounds
self.$get_unchecked(index)
})
}
#[inline]
fn get_absolute_mut(&mut self, index: usize) -> Option<&mut T> {
(index >= $mask(self.capacity(), self.$readptr)
&& index < $mask(self.capacity(), self.$writeptr))
.then(move || unsafe {
// SAFETY: index has been checked against $mask to be within bounds
self.$get_unchecked_mut(index)
})
}
#[inline]
fn clear(&mut self) {
for i in self.drain() {
drop(i);
}
self.$readptr = 0;
self.$writeptr = 0;
}
};
}