1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
module A = Atomic_
type 'a list_ = Nil | Cons of int * 'a * 'a list_
type 'a t = {
mk_item: unit -> 'a;
clear: 'a -> unit;
max_size: int; (** Max number of items *)
items: 'a list_ A.t;
}
let create ?(clear = ignore) ~mk_item ?(max_size = 512) () : _ t =
{ mk_item; clear; max_size; items = A.make Nil }
let rec acquire_ self =
match A.get self.items with
| Nil -> self.mk_item ()
| Cons (_, x, tl) as l ->
if A.compare_and_set self.items l tl then
x
else
acquire_ self
let[@inline] size_ = function
| Cons (sz, _, _) -> sz
| Nil -> 0
let release_ self x : unit =
let rec loop () =
match A.get self.items with
| Cons (sz, _, _) when sz >= self.max_size ->
()
| l ->
if not (A.compare_and_set self.items l (Cons (size_ l + 1, x, l))) then
loop ()
in
self.clear x;
loop ()
let with_resource (self : _ t) f =
let x = acquire_ self in
try
let res = f x in
release_ self x;
res
with e ->
let bt = Printexc.get_raw_backtrace () in
release_ self x;
Printexc.raise_with_backtrace e bt