Module Picos_rc.Make

Creates a new external reference counting table for a resource type.

An externally reference counted resource.

ℹī¸ This is intended for cases where a resource needs to be safely shared between multiple independent threads of control whether they are fibers, threads, or domains. In that use case you typically need to increment the reference count before handing the resource from one independent thread of control to another and the other independent thread of control then becomes responsible for decrementing the reference count after being done with the resource.

Parameters

Signature

module Resource = Resource

Resource type.

type t

Opaque type alias for the resource type.

val create : ?dispose:bool -> Resource.t -> t

create resource adds an entry for the resource with an initial reference count of 1 to the table for the resource and returns the resource as a value of the opaque alias type.

The optional dispose argument defaults to true. When explicitly specified as ~dispose:false, the resource will not be disposed when the reference count becomes zero. This is intended for special cases where a resource is e.g. managed outside of the control of the user program.

val unsafe_get : t -> Resource.t

unsafe_get opaque_resource casts the opaque alias type back to the resource type.

⚠ī¸ This should only be called and the resource used either after creating the reference counting entry or after incrementing the reference count and before the matching decrement.

val incr : t -> unit

incr opaque_resource tries to find the entry for the resource and increment the reference count.

  • raises Invalid_argument

    in case no entry is found for the resource or the reference count was zero or the resource was marked as closed previously by a decrement operation.

val decr : ?close:bool -> t -> unit

decr opaque_resource tries to find the entry for the resource and decrement the reference count. If the reference count becomes zero, the entry for the resource will be removed and the resource will be disposed, unless ~dispose:false was specified for create.

The optional close argument defaults to false. When explicitly specified as ~close:true the resource will be marked as closed and attempts to increment the reference could will fail.

  • raises Invalid_argument

    in case no entry is found for the resource or the reference count was zero.

type info = {
  1. resource : Resource.t;
    (*

    The resource.

    *)
  2. count : int;
    (*

    Reference count. This may be 0.

    *)
  3. closed : bool;
    (*

    Whether the resource has been closed, see decr.

    *)
  4. dispose : bool;
    (*

    Whether to dispose the resource, see create.

    *)
  5. bt : Stdlib.Printexc.raw_backtrace;
    (*

    Backtrace captured at create.

    *)
}

Information on a resource.

val infos : unit -> info Stdlib.Seq.t

infos () returns a sequence of entries in the reference counting table at the point in time of of calling infos ().