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module Make (S : Abstract.Storage.STORAGE) = struct
(* A branch state holds its multigroups and a backlink to the state it
succeeded, each multigroup its relations:
\system\branch\master\multigroup\universe\relation\planet
\system\branch\master\previous\multigroup\universe\relation\planet
*)
module SI = Storage.Make (S)
module M = Multigroup.Make (S)
module MultigroupM = Merkle.Interface (S) (Merkle.StringKey) (M)
module MMDirectory = Prototype.Directory.OfTree (S) (Merkle.StringKey) (M)
module MMAssociative = Prototype.Associative.OfTree (S) (Merkle.StringKey)
module MMAddressable = Prototype.Addressable.OfTree (S) (Merkle.StringKey)
module Error = struct
open Concepts.Condition
let incomplete_branch addr =
condition "incomplete-branch"
"A stored branch is missing part of its expected structure. Is your storage corrupted?"
("address" |=| Concepts.Value.String (Concepts.Hash.to_hum_string addr))
end
type t = {multigroups: MultigroupM.address; previous: t SI.Pointer.t option}
module rec Representation : (Concepts.Encoding.Record.S with type t = t) =
Concepts.Encoding.Record.Make (Body)
and Body : Concepts.Encoding.Record.BODY = struct
type nonrec t = t
let tag = 'Y'
let malformed () =
Concepts.Condition.(
condition "malformed-branch"
"The on-disk representation of a branch did not conform to what was expected. Is your \
database corrupted?"
empty )
let fields {multigroups; previous} =
let open Concepts.Encoding in
[ "multigroups", Value.bencode_of_hash multigroups;
( "previous",
Value.bencode_of_option
(fun v -> SI.Pointer.address_of v |> SI.as_hash |> Value.bencode_of_hash)
previous ) ]
let of_fields fields =
let open Utilities.Result in
let open Concepts.Encoding in
let* multigroups = Bencode.field "multigroups" fields |>> Value.hash_of_bencode in
let* previous =
Bencode.field "previous" fields
|>> Value.option_of_bencode (fun v ->
Value.hash_of_bencode v
|> Result.map (fun hash -> S.Hash hash)
|> Result.map (SI.Pointer.make Loader.load) )
in
Ok {multigroups; previous}
end
and Loader : sig
val load : S.transaction -> S.address -> (t, Concepts.Condition.condition) result
end = struct
let load tx addr = Utilities.Result.(SI.get_req tx addr |>> Representation.of_blob)
end
let pointer_of hash = SI.Pointer.make Loader.load (S.Hash hash)
let node_of tx branch =
let open Utilities.Result in
MultigroupM.find tx branch.multigroups
|>> Option.to_result ~none:(Error.incomplete_branch branch.multigroups)
(* Given [root], the stored programs of this state run through the
evaluators registered under it, against this very state, so an
earlier state reads as it was. *)
class branch ?root storage value node =
object (self)
inherit Lifecycle.null
method to_string = "branch"
val storage : S.connection = storage
val branch : t = value
val node = node (* FIXME: can we not place this inside `t`? *)
method deriving branch' =
let open Utilities.Result in
let branch'' = {branch' with previous= self#address |> pointer_of |> Option.some} in
let* node' =
SI.with_transaction storage (fun tx ->
let* _ = SI.store_blob tx (Representation.to_blob branch'') in
node_of tx branch' )
in
new branch ?root storage branch'' node' |> Protocols.Handle.make |> Result.ok
method private previous =
match branch.previous with
| None -> Ok None
| Some pointer ->
SI.with_read storage (fun tx ->
let open Utilities.Result in
let* previous = SI.Pointer.deref tx pointer in
let* node = node_of tx previous in
Ok (Some (Protocols.Handle.make {<branch = previous; node>})) )
method protocols : Protocols.Handle.protocol list =
let bind =
Option.map
(fun root -> {EphemeralRelation.root; within= Protocols.Handle.make {<>}})
root
in
let multigroups =
Prototype.mixture_of node (fun make node ->
[ MMAddressable.make ~node:(MultigroupM.into node);
MMDirectory.make ~storage ~node ~constructor:(M.load ?bind storage);
MMAssociative.make ~admit:M.admit ~storage ~node:(MultigroupM.into node)
~constructor:(fun node' -> MultigroupM.from node' |> make |> Result.ok ) ] )
in
let open Utilities.Result in
let admits (m, multigroup) =
Protocols.Handle.releasing multigroup (fun () ->
let* admission = Protocols.Admission.require multigroup in
let* violations = Protocols.Admission.check admission in
Ok
(List.map
(fun (d, witness) ->
Path.(to_string ("multigroup" @/ m @/ "denial" @/ d @/ this)), witness )
violations ) )
in
Protocols.
[ Addressable.make self;
Admission.make
object
method check =
let* named = Prototype.Directory.children multigroups in
Utilities.List.concat_map admits named
end;
Prototype.Associative.(
of_properties
[ ( "multigroup",
update_only (fun node' ->
Handle.require Addressable.from node'
|> Result.map Addressable.address
|>> (fun addr -> self#deriving {branch with multigroups= addr}) ) ) ] );
Directory.make
object
method list =
Ok
(BatFingerTree.of_list
( "multigroup"
:: Option.fold ~none:[] ~some:(fun _ -> ["previous"]) branch.previous ) )
method find =
function
| "multigroup" -> Ok (Some multigroups)
| "previous" -> self#previous
| _ -> Ok None
end ]
method hash = Representation.to_blob branch |> Concepts.Hash.hash_of_blob
method address = self#hash
end
let load ?root tx conn addr =
let open Utilities.Result in
let* data = SI.get_req tx (S.Hash addr) in
let* branch = Representation.of_blob data in
let* node = node_of tx branch in
Ok (new branch ?root conn branch node |> Protocols.Handle.make)
let make conn =
let open Utilities.Result in
SI.with_transaction conn (fun tx ->
let* empty = MultigroupM.empty_under tx in
let branch = {multigroups= empty; previous= None} in
let* _ = SI.store_blob tx (Representation.to_blob branch) in
Ok (new branch conn branch MultigroupM.empty |> Protocols.Handle.make) )
end
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