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module Error = struct
open Concepts.Condition
let invalid_root head =
condition "invalid-root" "The root hash for the database state is missing from the backend. Either your storage is corrupted, or this is a bug in RNT!"
("hash" |=| (Concepts.Value.String (Concepts.Hash.to_hum_string head)))
let no_such_branch branch_name =
condition "no-such-branch" "A branch with the specified name was not found"
("branch" |=| Concepts.Value.String branch_name)
let comparison_failed branch_name reference head =
condition "comparison-failed" "The HEAD of the branch did not match what was expected"
("branch" |=| Concepts.Value.String branch_name &
"reference" |=| Concepts.Value.String (Concepts.Hash.to_hum_string reference) &
"head" |=| Concepts.Value.String (Concepts.Hash.to_hum_string head))
end
module Make (S : Abstract.Storage.STORAGE) = struct
module M = Merkle.Make (S) (Merkle.StringKey)
module SI = Storage.Make (S)
type manager = { storage: S.connection;
label : string;
head: M.node Atomic.t }
let root_for tx label =
let open Utilities.Result in
let* label = S.get tx (S.Label label) in
let label = Option.map Concepts.Hash.hash_of_blob label in
Ok label
let initialize storage label =
let open Utilities.Result in
SI.with_transaction storage (fun tx ->
let* addr = root_for tx label in
match addr with
| None -> failwith "TODO"
| Some addr ->
let* head = M.find tx addr in
let* head = Option.to_result ~none:(Error.invalid_root addr) head in
Ok { storage; label; head = Atomic.make head })
let fetch { storage; head; _ } branch_name =
SI.with_transaction storage (fun tx ->
let head = Atomic.get head in
M.lookup tx branch_name head)
let update { storage; head; label } branch_name reference new_branch =
let open Utilities.Result in
let* _ = SI.with_transaction storage (fun tx ->
Utilities.Atomic.mswap head (fun head ->
let* branch = M.lookup tx branch_name head
|> Result.map (Option.to_result ~none:(Error.no_such_branch branch_name))
|> Result.join in
if branch = reference then
let* new_head = M.insert tx label new_branch head in
Ok new_head
else
Error (Error.comparison_failed branch_name reference branch))) in
Ok ()
end
|
