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use crate::ffi;
use crate::pyclass::{tp_free_fallback, PyClassAlloc};
use crate::type_object::{PyLayout, PyTypeInfo};
use crate::Python;
use std::mem;
use std::os::raw::c_void;
pub trait PyClassWithFreeList {
fn get_free_list() -> &'static mut FreeList<*mut ffi::PyObject>;
}
pub enum Slot<T> {
Empty,
Filled(T),
}
pub struct FreeList<T> {
entries: Vec<Slot<T>>,
split: usize,
capacity: usize,
}
impl<T> FreeList<T> {
pub fn with_capacity(capacity: usize) -> FreeList<T> {
let entries = (0..capacity).map(|_| Slot::Empty).collect::<Vec<_>>();
FreeList {
entries,
split: 0,
capacity,
}
}
pub fn pop(&mut self) -> Option<T> {
let idx = self.split;
if idx == 0 {
None
} else {
match mem::replace(&mut self.entries[idx - 1], Slot::Empty) {
Slot::Filled(v) => {
self.split = idx - 1;
Some(v)
}
_ => panic!("FreeList is corrupt"),
}
}
}
pub fn insert(&mut self, val: T) -> Option<T> {
let next = self.split + 1;
if next < self.capacity {
self.entries[self.split] = Slot::Filled(val);
self.split = next;
None
} else {
Some(val)
}
}
}
impl<T> PyClassAlloc for T
where
T: PyTypeInfo + PyClassWithFreeList,
{
unsafe fn alloc(_py: Python) -> *mut Self::Layout {
if let Some(obj) = <Self as PyClassWithFreeList>::get_free_list().pop() {
ffi::PyObject_Init(obj, <Self as PyTypeInfo>::type_object() as *const _ as _);
obj as _
} else {
crate::pyclass::default_alloc::<Self>() as _
}
}
unsafe fn dealloc(py: Python, self_: *mut Self::Layout) {
(*self_).py_drop(py);
let obj = self_ as _;
if ffi::PyObject_CallFinalizerFromDealloc(obj) < 0 {
return;
}
if let Some(obj) = <Self as PyClassWithFreeList>::get_free_list().insert(obj) {
match Self::type_object().tp_free {
Some(free) => free(obj as *mut c_void),
None => tp_free_fallback(obj),
}
}
}
}