diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 19:33:14 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 19:33:14 +0000 |
commit | 36d22d82aa202bb199967e9512281e9a53db42c9 (patch) | |
tree | 105e8c98ddea1c1e4784a60a5a6410fa416be2de /third_party/rust/chunky-vec/src | |
parent | Initial commit. (diff) | |
download | firefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.tar.xz firefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.zip |
Adding upstream version 115.7.0esr.upstream/115.7.0esr
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/rust/chunky-vec/src')
-rw-r--r-- | third_party/rust/chunky-vec/src/lib.rs | 343 |
1 files changed, 343 insertions, 0 deletions
diff --git a/third_party/rust/chunky-vec/src/lib.rs b/third_party/rust/chunky-vec/src/lib.rs new file mode 100644 index 0000000000..dc81552553 --- /dev/null +++ b/third_party/rust/chunky-vec/src/lib.rs @@ -0,0 +1,343 @@ +//! This crate provides a pin-safe, append-only vector which guarantees never +//! to move the storage for an element once it has been allocated. + +use std::{ + ops::{Index, IndexMut}, + slice, +}; + +struct Chunk<T> { + /// The elements of this chunk. + elements: Vec<T>, +} + +impl<T> Chunk<T> { + fn with_capacity(capacity: usize) -> Self { + let elements = Vec::with_capacity(capacity); + assert_eq!(elements.capacity(), capacity); + Self { elements } + } + + fn len(&self) -> usize { + self.elements.len() + } + + /// Returns the number of available empty elements. + fn available(&self) -> usize { + self.elements.capacity() - self.elements.len() + } + + /// Returns a shared reference to the element at the given index. + /// + /// # Panics + /// + /// Panics if the index is out of bounds. + pub fn get(&self, index: usize) -> Option<&T> { + self.elements.get(index) + } + + /// Returns an exclusive reference to the element at the given index. + /// + /// # Panics + /// + /// Panics if the index is out of bounds. + pub fn get_mut(&mut self, index: usize) -> Option<&mut T> { + self.elements.get_mut(index) + } + + /// Pushes a new value into the fixed capacity entry. + /// + /// # Panics + /// + /// If the entry is already at its capacity. + /// Note that this panic should never happen since the entry is only ever + /// accessed by its outer chunk vector that checks before pushing. + pub fn push(&mut self, new_value: T) { + if self.available() == 0 { + panic!("No available elements.") + } + self.elements.push(new_value); + } + + pub fn push_get(&mut self, new_value: T) -> &mut T { + self.push(new_value); + unsafe { + let last = self.elements.len() - 1; + self.elements.get_unchecked_mut(last) + } + } + + /// Returns an iterator over the elements of the chunk. + pub fn iter(&self) -> slice::Iter<T> { + self.elements.iter() + } + + /// Returns an iterator over the elements of the chunk. + pub fn iter_mut(&mut self) -> slice::IterMut<T> { + self.elements.iter_mut() + } +} + +impl<T> Index<usize> for Chunk<T> { + type Output = T; + + fn index(&self, index: usize) -> &Self::Output { + self.get(index).expect("index out of bounds") + } +} + +impl<T> IndexMut<usize> for Chunk<T> { + fn index_mut(&mut self, index: usize) -> &mut Self::Output { + self.get_mut(index).expect("index out of bounds") + } +} + +/// Pin safe vector +/// +/// An append only vector that never moves the backing store for each element. +pub struct ChunkyVec<T> { + /// The chunks holding elements + chunks: Vec<Chunk<T>>, +} + +impl<T> Default for ChunkyVec<T> { + fn default() -> Self { + Self { + chunks: Vec::default(), + } + } +} + +impl<T> Unpin for ChunkyVec<T> {} + +impl<T> ChunkyVec<T> { + const DEFAULT_CAPACITY: usize = 32; + + pub fn len(&self) -> usize { + if self.chunks.is_empty() { + 0 + } else { + // # Safety - There is at least one chunk here. + (self.chunks.len() - 1) * Self::DEFAULT_CAPACITY + self.chunks.last().unwrap().len() + } + } + + pub fn is_empty(&self) -> bool { + // # Safety - Since it's impossible to pop, at least one chunk means we're not empty. + self.chunks.is_empty() + } + + /// Returns an iterator that yields shared references to the elements of the bucket vector. + pub fn iter(&self) -> Iter<T> { + Iter::new(self) + } + + /// Returns an iterator that yields exclusive reference to the elements of the bucket vector. + pub fn iter_mut(&mut self) -> IterMut<T> { + IterMut::new(self) + } + + /// Returns a shared reference to the element at the given index if any. + pub fn get(&self, index: usize) -> Option<&T> { + let (x, y) = ( + index / Self::DEFAULT_CAPACITY, + index % Self::DEFAULT_CAPACITY, + ); + self.chunks.get(x).and_then(|chunk| chunk.get(y)) + } + + /// Returns an exclusive reference to the element at the given index if any. + pub fn get_mut(&mut self, index: usize) -> Option<&mut T> { + let (x, y) = ( + index / Self::DEFAULT_CAPACITY, + index % Self::DEFAULT_CAPACITY, + ); + self.chunks.get_mut(x).and_then(|chunk| chunk.get_mut(y)) + } + + /// Pushes a new element onto the bucket vector. + /// + /// # Note + /// + /// This operation will never move other elements, reallocates or otherwise + /// invalidate pointers of elements contained by the bucket vector. + pub fn push(&mut self, new_value: T) { + self.push_get(new_value); + } + + pub fn push_get(&mut self, new_value: T) -> &mut T { + if self.chunks.last().map(Chunk::available).unwrap_or_default() == 0 { + self.chunks.push(Chunk::with_capacity(Self::DEFAULT_CAPACITY)); + } + // Safety: Guaranteed to have a chunk with available elements + unsafe { + let last = self.chunks.len() - 1; + self.chunks.get_unchecked_mut(last).push_get(new_value) + } + } +} + +impl<T> Index<usize> for ChunkyVec<T> { + type Output = T; + + fn index(&self, index: usize) -> &Self::Output { + self.get(index).expect("index out of bounds") + } +} + +impl<T> IndexMut<usize> for ChunkyVec<T> { + fn index_mut(&mut self, index: usize) -> &mut Self::Output { + self.get_mut(index).expect("index out of bounds") + } +} + +/// An iterator yielding shared references to the elements of a ChunkyVec. +#[derive(Clone)] +pub struct Iter<'a, T> { + /// Chunks iterator. + chunks: slice::Iter<'a, Chunk<T>>, + /// Forward iterator for `next`. + iter: Option<slice::Iter<'a, T>>, + /// Number of elements that are to be yielded by the iterator. + len: usize, +} + +impl<'a, T> Iter<'a, T> { + /// Creates a new iterator over the ChunkyVec + pub(crate) fn new(vec: &'a ChunkyVec<T>) -> Self { + let len = vec.len(); + Self { + chunks: vec.chunks.iter(), + iter: None, + len, + } + } +} + +impl<'a, T> Iterator for Iter<'a, T> { + type Item = &'a T; + + fn next(&mut self) -> Option<Self::Item> { + loop { + if let Some(ref mut iter) = self.iter { + if let front @ Some(_) = iter.next() { + self.len -= 1; + return front; + } + } + self.iter = Some(self.chunks.next()?.iter()); + } + } + + fn size_hint(&self) -> (usize, Option<usize>) { + (self.len(), Some(self.len())) + } +} + +impl<'a, T> ExactSizeIterator for Iter<'a, T> { + fn len(&self) -> usize { + self.len + } +} + +/// An iterator yielding exclusive references to the elements of a ChunkVec. +pub struct IterMut<'a, T> { + /// Chunks iterator. + chunks: slice::IterMut<'a, Chunk<T>>, + /// Forward iterator for `next`. + iter: Option<slice::IterMut<'a, T>>, + /// Number of elements that are to be yielded by the iterator. + len: usize, +} + +impl<'a, T> IterMut<'a, T> { + /// Creates a new iterator over the bucket vector. + pub(crate) fn new(vec: &'a mut ChunkyVec<T>) -> Self { + let len = vec.len(); + Self { + chunks: vec.chunks.iter_mut(), + iter: None, + len, + } + } +} + +impl<'a, T> Iterator for IterMut<'a, T> { + type Item = &'a mut T; + + fn next(&mut self) -> Option<Self::Item> { + loop { + if let Some(ref mut iter) = self.iter { + if let front @ Some(_) = iter.next() { + self.len -= 1; + return front; + } + } + self.iter = Some(self.chunks.next()?.iter_mut()); + } + } + + fn size_hint(&self) -> (usize, Option<usize>) { + (self.len(), Some(self.len())) + } +} + +impl<'a, T> ExactSizeIterator for IterMut<'a, T> { + fn len(&self) -> usize { + self.len + } +} +impl<'a, T> IntoIterator for &'a ChunkyVec<T> { + type Item = &'a T; + type IntoIter = Iter<'a, T>; + + fn into_iter(self) -> Iter<'a, T> { + self.iter() + } +} + +impl<'a, T> IntoIterator for &'a mut ChunkyVec<T> { + type Item = &'a mut T; + type IntoIter = IterMut<'a, T>; + + fn into_iter(self) -> IterMut<'a, T> { + self.iter_mut() + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn iterate_empty() { + let v = ChunkyVec::<usize>::default(); + for i in &v { + println!("{:?}", i); + } + } + + #[test] + fn iterate_multiple_chunks() { + let mut v = ChunkyVec::<usize>::default(); + for i in 0..33 { + v.push(i); + } + let mut iter = v.iter(); + for _ in 0..32 { + iter.next(); + } + assert_eq!(iter.next(), Some(&32)); + assert_eq!(iter.next(), None); + } + + #[test] + fn index_multiple_chunks() { + let mut v = ChunkyVec::<usize>::default(); + for i in 0..33 { + v.push(i); + } + assert_eq!(v.get(32), Some(&32)); + assert_eq!(v[32], 32); + } +} |