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#[cfg(test)]
extern crate quickcheck;
#[cfg(test)]
#[macro_use(quickcheck)]
extern crate quickcheck_macros;
use std::alloc::Layout;
use std::mem::{align_of, size_of};
use std::ptr::NonNull;
use std::slice;
use bumpalo::boxed::Box;
use bumpalo::Bump;
const INLINED_ELEMENTS: usize = 3;
const FIRST_CHUNK_SIZE: usize = 8;
pub struct Uell<'b, T> {
len: usize,
first_chunk: Option<NonNull<Chunk<T>>>,
last_chunk: Option<NonNull<Chunk<T>>>,
last_elem_chunk: Option<NonNull<T>>,
elems: [T; INLINED_ELEMENTS],
bump: &'b Bump,
}
impl<'b, T: Copy + Default> Uell<'b, T> {
pub fn new_in(bump: &'b Bump) -> Uell<T> {
Uell {
len: 0,
first_chunk: None,
last_chunk: None,
last_elem_chunk: None,
elems: [T::default(); INLINED_ELEMENTS],
bump,
}
}
pub fn from_iter_in<I>(iter: I, bump: &'b Bump) -> Uell<T>
where
I: IntoIterator<Item = T>,
{
let mut uell = Uell::new_in(bump);
iter.into_iter().for_each(|elem| uell.push(elem));
uell
}
pub fn len(&self) -> usize {
self.len
}
pub fn is_empty(&self) -> bool {
self.len() == 0
}
pub fn push(&mut self, elem: T) {
if self.len < INLINED_ELEMENTS {
unsafe { *self.elems.get_unchecked_mut(self.len) = elem };
} else {
match self.last_elem_chunk {
Some(ptr) if self.remaining_space() != 0 => {
let new_ptr = unsafe { ptr.as_ptr().offset(1) };
unsafe { new_ptr.write(elem) };
self.last_elem_chunk = NonNull::new(new_ptr);
}
_otherwise => {
let last_chunk = self.push_empty_chunk();
let new_ptr = unsafe { last_chunk.elems.get_unchecked_mut(0) };
*new_ptr = elem;
self.last_elem_chunk = NonNull::new(new_ptr);
}
}
}
self.len += 1;
}
fn remaining_space(&self) -> usize {
if self.len > INLINED_ELEMENTS {
let mut len = self.len - INLINED_ELEMENTS;
let mut next_chunk_size = FIRST_CHUNK_SIZE;
while len > next_chunk_size {
len -= next_chunk_size;
next_chunk_size *= 2;
}
next_chunk_size - len
} else {
INLINED_ELEMENTS - self.len
}
}
fn last_chunk_size(&self) -> Option<usize> {
self.last_chunk.map(|chunk| unsafe { chunk.as_ref().capacity() })
}
fn push_empty_chunk(&mut self) -> &mut Chunk<T> {
let size = self.last_chunk_size().map(|size| size * 2).unwrap_or(FIRST_CHUNK_SIZE);
let last_chunk = Box::leak(Chunk::new(self.bump, size));
let last_chunk_ptr = NonNull::from(last_chunk);
if self.first_chunk.is_none() {
self.first_chunk = Some(last_chunk_ptr);
}
if let Some(mut last) = self.last_chunk {
unsafe { last.as_mut().next = Some(last_chunk_ptr) };
}
self.last_chunk = Some(last_chunk_ptr);
unsafe { &mut *last_chunk_ptr.as_ptr() }
}
}
impl<'b, T> Drop for Uell<'b, T> {
fn drop(&mut self) {
unsafe {
let mut current_chunk = self.first_chunk.take().map(|p| Box::from_raw(p.as_ptr()));
while let Some(mut chunk) = current_chunk.take() {
current_chunk = chunk.next.take().map(|p| Box::from_raw(p.as_ptr()));
}
}
}
}
impl<'b, T: 'b + Copy> IntoIterator for Uell<'b, T> {
type Item = T;
type IntoIter = IntoIter<'b, T>;
fn into_iter(self) -> Self::IntoIter {
IntoIter::new(self)
}
}
struct IntoChunkIter<'b, T> {
chunk: Option<Box<'b, Chunk<T>>>,
}
impl<'b, T> IntoChunkIter<'b, T> {
fn new(chunk: Option<NonNull<Chunk<T>>>) -> IntoChunkIter<'b, T> {
IntoChunkIter { chunk: chunk.map(|p| unsafe { Box::from_raw(p.as_ptr()) }) }
}
}
impl<'b, T> Iterator for IntoChunkIter<'b, T> {
type Item = Box<'b, Chunk<T>>;
fn next(&mut self) -> Option<Self::Item> {
match self.chunk.take() {
Some(mut chunk) => {
let next_chunk = chunk.next.take().map(|p| unsafe { Box::from_raw(p.as_ptr()) });
self.chunk = next_chunk;
Some(chunk)
}
None => None,
}
}
}
pub struct IntoIter<'b, T> {
inner: InnerIntoIter<'b, T>,
}
enum InnerIntoIter<'b, T> {
Inline {
elems: [T; INLINED_ELEMENTS],
inline_offset: usize,
chunks: Option<NonNull<Chunk<T>>>,
len: usize,
},
Chunks {
current_chunk: Option<Box<'b, Chunk<T>>>,
chunk_offset: usize,
chunk_iter: IntoChunkIter<'b, T>,
remaining_len: usize,
},
}
impl<'b, T: Copy> IntoIter<'b, T> {
fn new(mut uell: Uell<'b, T>) -> IntoIter<T> {
IntoIter {
inner: InnerIntoIter::Inline {
elems: uell.elems,
inline_offset: 0,
chunks: uell.first_chunk.take(),
len: uell.len,
},
}
}
fn new_from_chunks(len: usize, chunks: Option<NonNull<Chunk<T>>>) -> IntoIter<'b, T> {
let mut chunk_iter = IntoChunkIter::new(chunks);
IntoIter {
inner: InnerIntoIter::Chunks {
current_chunk: chunk_iter.next(),
chunk_offset: 0,
chunk_iter,
remaining_len: len - INLINED_ELEMENTS,
},
}
}
}
impl<'b, T: Copy> Iterator for IntoIter<'b, T> {
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
loop {
match &mut self.inner {
InnerIntoIter::Inline { elems, inline_offset, chunks, len } => {
if *inline_offset == elems.len() {
*self = IntoIter::new_from_chunks(*len, chunks.take());
} else if *inline_offset < *len {
let elem = elems[*inline_offset];
*inline_offset += 1;
return Some(elem);
} else {
return None;
}
}
InnerIntoIter::Chunks {
current_chunk,
chunk_iter,
chunk_offset,
remaining_len,
} => match current_chunk {
Some(chunk) => {
if *remaining_len == 0 {
return None;
} else if *chunk_offset == chunk.capacity() {
*current_chunk = chunk_iter.next();
*chunk_offset = 0;
} else {
let elem = chunk.elems[*chunk_offset];
*chunk_offset += 1;
*remaining_len -= 1;
return Some(elem);
}
}
None => return None,
},
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
match self.inner {
InnerIntoIter::Inline { inline_offset, len, .. } => {
let remaining_len = len - inline_offset;
(remaining_len, Some(remaining_len))
}
InnerIntoIter::Chunks { remaining_len, .. } => (remaining_len, Some(remaining_len)),
}
}
}
struct Chunk<T> {
next: Option<NonNull<Chunk<T>>>,
elems: [T],
}
impl<T: Copy + Default> Chunk<T> {
fn new(bump: &Bump, size: usize) -> Box<'_, Chunk<T>> {
let ptr = {
let elems_size = size * size_of::<T>();
let header_size = size_of::<Option<NonNull<Chunk<T>>>>();
let size = header_size + elems_size;
let align = align_of::<Option<Box<'_, Chunk<T>>>>();
let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
bump.alloc_layout(layout)
};
fn fatten<T>(data: NonNull<u8>, len: usize) -> *mut Chunk<T> {
let slice = unsafe { slice::from_raw_parts(data.as_ptr() as *mut (), len) };
slice as *const [()] as *mut Chunk<T>
}
let chunk_ptr = fatten::<T>(ptr, size);
let mut chunk = unsafe { Box::from_raw(chunk_ptr) };
chunk.next = None;
chunk
}
}
impl<T: Copy> Chunk<T> {
fn capacity(&self) -> usize {
self.elems.len()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn small_push() {
let bump = Bump::new();
let mut uell = Uell::new_in(&bump);
for i in 0..INLINED_ELEMENTS {
uell.push(i);
}
assert_eq!(uell.len(), INLINED_ELEMENTS);
}
#[test]
fn bigger_push() {
let bump = Bump::new();
let mut uell = Uell::new_in(&bump);
let count = INLINED_ELEMENTS + 10;
for i in 0..count {
uell.push(i);
}
assert_eq!(uell.len(), count);
}
#[test]
fn small_push_into_iter() {
let bump = Bump::new();
let mut uell = Uell::new_in(&bump);
for i in 0..(INLINED_ELEMENTS - 1) {
uell.push(i);
}
let mut iter = uell.into_iter();
assert_eq!(iter.next(), Some(0));
assert_eq!(iter.next(), Some(1));
assert_eq!(iter.next(), None);
}
#[test]
fn bigger_push_into_iter() {
let bump = Bump::new();
let mut uell = Uell::new_in(&bump);
for i in 0..(INLINED_ELEMENTS + 100) {
uell.push(i);
}
assert!(uell.into_iter().eq(0..INLINED_ELEMENTS + 100));
}
#[test]
fn chunk_iter() {
let bump = Bump::new();
let mut uell = Uell::new_in(&bump);
let len = INLINED_ELEMENTS + 100;
for i in 0..len {
uell.push(i);
}
let first_chunk = uell.first_chunk.take();
let iter = IntoChunkIter::new(first_chunk);
assert_eq!(iter.count(), 4);
}
#[quickcheck]
fn qc_simple_push_and_iter(xs: Vec<u32>) -> bool {
let bump = Bump::new();
let mut uell = Uell::new_in(&bump);
xs.iter().copied().for_each(|x| uell.push(x));
uell.into_iter().eq(xs)
}
}