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use std::{mem, fmt};
use std::ops::{Deref, DerefMut};
use std::sync::{Arc, Mutex};
use super::Chunk;
pub trait Sliceable<T>: AsMut<[T]> + AsRef<[T]> { }
impl<T, V> Sliceable<T> for V where V: AsRef<[T]> + AsMut<[T]> { }
pub struct SlicePool<T>(Arc<Mutex<ChunkableInner<T>>>);
impl<T> SlicePool<T> {
pub fn new<Data: Sliceable<T> + 'static>(data: Data) -> Self {
SlicePool(Arc::new(Mutex::new(ChunkableInner {
values: vec![Chunk { size: data.as_ref().len(), offset: 0, free: true }],
memory: Box::new(data),
})))
}
pub fn allocate(&mut self, size: usize) -> Option<PoolVal<T>> {
(*self.0).lock()
.unwrap()
.allocate(size)
.map(|slice| PoolVal { inner: self.0.clone(), data: slice })
}
pub fn as_ptr(&self) -> *const T {
(*self.0).lock().unwrap().memory.deref().as_ref().as_ptr()
}
pub fn len(&self) -> usize {
(*self.0).lock().unwrap().memory.deref().as_ref().len()
}
}
pub struct PoolVal<T: 'static> {
inner: Arc<Mutex<ChunkableInner<T>>>,
data: &'static mut [T],
}
impl<T: fmt::Debug> fmt::Debug for PoolVal<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{:?}", self.deref())
}
}
impl<T> Deref for PoolVal<T> {
type Target = [T];
fn deref(&self) -> &Self::Target {
&self.data
}
}
impl<T> DerefMut for PoolVal<T> {
fn deref_mut<'b>(&'b mut self) -> &'b mut [T] {
self.data
}
}
impl<T> Drop for PoolVal<T> {
fn drop(&mut self) {
unsafe { (*self.inner).lock().unwrap().release(self.data) };
}
}
struct ChunkableInner<T> {
values: Vec<Chunk>,
memory: Box<Sliceable<T>>,
}
impl<T> ChunkableInner<T> {
fn allocate(&mut self, size: usize) -> Option<&'static mut [T]> {
if let Some(index) = self.values.iter().position(|chunk| chunk.free && chunk.size >= size) {
let mut chunk = self.values[index].clone();
let chunk_range = chunk.offset..(chunk.offset + size);
let delta_size = chunk.size - size;
chunk.size -= delta_size;
chunk.free = false;
self.values[index] = chunk;
if delta_size > 0 {
let adjacent_index = index + 1;
self.values.insert(adjacent_index, Chunk {
offset: chunk_range.end,
size: delta_size,
free: true
});
self.defragment(adjacent_index);
}
Some(unsafe {
mem::transmute(&mut self.memory.deref_mut().as_mut()[chunk_range])
})
} else {
None
}
}
unsafe fn release(&mut self, slice: &mut [T]) {
let index = self.values.iter().position(|chunk| {
self.memory.deref().as_ref().as_ptr().offset(chunk.offset as isize) == slice.as_ptr()
}).unwrap();
self.values[index].free = true;
self.defragment(index);
}
fn defragment(&mut self, index: usize) {
let adjacent_index = index + 1;
if self.values.get(adjacent_index).iter().any(|chunk| chunk.free) {
self.values[index].size += self.values[adjacent_index].size;
self.values.remove(adjacent_index);
}
if index > 0 && self.values[index - 1].free {
self.values[index - 1].size += self.values[index].size;
self.values.remove(index);
}
}
}
unsafe impl<T> Send for ChunkableInner<T> { }