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pub struct ChunkedVec<T> {
chunks: Vec<Vec<T>>,
}
impl<T> Default for ChunkedVec<T> {
fn default() -> Self {
Self::new()
}
}
impl<T> ChunkedVec<T> {
pub fn new() -> Self {
Self { chunks: Vec::new() }
}
pub fn len(&self) -> usize {
for (i, chunk) in self.chunks.iter().enumerate().rev() {
if !chunk.is_empty() {
let free = chunk.capacity() - chunk.len();
return cumulative_chunk_size(i) - free;
}
}
0
}
pub fn push(&mut self, item: T) {
if let Some(chunk) = self.chunks.last_mut()
&& chunk.len() < chunk.capacity()
{
chunk.push(item);
return;
}
let mut chunk = Vec::with_capacity(chunk_size(self.chunks.len()));
chunk.push(item);
self.chunks.push(chunk);
}
pub fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
for item in iter {
self.push(item);
}
}
pub fn iter(&self) -> impl Iterator<Item = &T> {
ExactSizeIter {
iter: self.chunks.iter().flat_map(|chunk| chunk.iter()),
len: self.len(),
}
}
pub fn is_empty(&self) -> bool {
self.chunks.first().is_none_or(|chunk| chunk.is_empty())
}
}
impl<T> IntoIterator for ChunkedVec<T> {
type Item = T;
type IntoIter = ExactSizeIter<std::iter::Flatten<std::vec::IntoIter<Vec<T>>>>;
fn into_iter(self) -> Self::IntoIter {
let len = self.len();
ExactSizeIter {
iter: self.chunks.into_iter().flatten(),
len,
}
}
}
impl<T> Extend<T> for ChunkedVec<T> {
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
for item in iter {
self.push(item);
}
}
}
fn chunk_size(chunk_index: usize) -> usize {
8 << chunk_index
}
fn cumulative_chunk_size(chunk_index: usize) -> usize {
(8 << (chunk_index + 1)) - 8
}
pub struct ExactSizeIter<I: Iterator> {
iter: I,
len: usize,
}
impl<I: Iterator> Iterator for ExactSizeIter<I> {
type Item = I::Item;
fn next(&mut self) -> Option<Self::Item> {
self.iter.next().inspect(|_| self.len -= 1)
}
fn size_hint(&self) -> (usize, Option<usize>) {
(self.len, Some(self.len))
}
}
impl<I: Iterator> ExactSizeIterator for ExactSizeIter<I> {
fn len(&self) -> usize {
self.len
}
}
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