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pub use self::owned::{SliceBox, SlicePool, Sliceable};
use std::sync::Mutex;
use Chunk;
mod owned;
enum Order {
Preceding,
Following,
}
struct ChunkChain(Mutex<Vec<Chunk>>);
impl ChunkChain {
pub fn new(size: usize) -> Self {
ChunkChain(Mutex::new(vec![Chunk::new(size)]))
}
pub fn allocate(&self, size: usize) -> Option<Chunk> {
let mut chunks = self.0.lock().expect("poisoned chain");
let (index, _) = chunks
.iter()
.enumerate()
.filter(|(_, chunk)| chunk.free && chunk.size >= size)
.min_by_key(|(_, chunk)| chunk.size)?;
let delta = chunks[index].size - size;
if delta > 0 {
chunks[index].size -= delta;
if Self::has_free_adjacent(&chunks, index, Order::Preceding) {
chunks[index - 1].size += delta;
chunks[index].offset += delta;
} else if Self::has_free_adjacent(&chunks, index, Order::Following) {
chunks[index + 1].offset -= delta;
chunks[index + 1].size += delta;
} else {
let offset = chunks[index].offset + size;
chunks.insert(index + 1, Chunk::with_offset(delta, offset));
chunks[index].free = false;
}
} else {
chunks[index].free = false;
}
Some(chunks[index])
}
pub fn release(&self, offset: usize) {
let mut chunks = self.0.lock().expect("poisoned chain");
let index = chunks
.binary_search_by_key(&offset, |chunk| chunk.offset)
.expect("releasing chunk");
let size = chunks[index].size;
if Self::has_free_adjacent(&chunks, index, Order::Preceding) {
chunks[index - 1].size += size;
} else if Self::has_free_adjacent(&chunks, index, Order::Following) {
chunks[index + 1].offset -= size;
chunks[index + 1].size += size;
} else {
chunks[index].free = true;
return;
}
chunks.remove(index);
}
fn has_free_adjacent(chunks: &[Chunk], index: usize, order: Order) -> bool {
match order {
Order::Preceding => index > 0 && chunks[index - 1].free,
Order::Following => index + 1 < chunks.len() && chunks[index + 1].free,
}
}
}