feat pool: expose acquire/release

Author: c-cube

src/core/pool.ml

@@ -12,20 +12,20 @@ type '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 =
+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
+      acquire self
 
 let[@inline] size_ = function
   | Cons (sz, _, _) -> sz
   | Nil -> 0
 
-let release_ self x : unit =
+let release self x : unit =
   let rec loop () =
     match A.get self.items with
     | Cons (sz, _, _) when sz >= self.max_size ->
@@ -40,12 +40,17 @@ let release_ self x : unit =
   loop ()
 
 let with_resource (self : _ t) f =
-  let x = acquire_ self in
+  let x = acquire self in
   try
     let res = f x in
-    release_ self x;
+    release self x;
     res
   with e ->
     let bt = Printexc.get_raw_backtrace () in
-    release_ self x;
+    release self x;
     Printexc.raise_with_backtrace e bt
+
+module Raw = struct
+  let release = release
+  let acquire = acquire
+end

src/core/pool.mli

@@ -23,3 +23,12 @@ val with_resource : 'a t -> ('a -> 'b) -> 'b
 (** [with_resource pool f] runs [f x] with [x] a resource;
     when [f] fails or returns, [x] is returned to the pool for
     future reuse. *)
+
+(** Low level control over the pool.
+    This is easier to get wrong (e.g. releasing the same resource twice)
+    so use with caution.
+  @since NEXT_RELEASE *)
+module Raw : sig
+  val acquire : 'a t -> 'a
+  val release : 'a t -> 'a -> unit
+end