slot_repr.ml
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type error += Invalid_slot of int
let () =
register_error_kind
`Permanent
~id:"slot.invalid_slot"
~title:"invalid slot"
~description:"Invalid slot"
~pp:(fun ppf x -> Format.fprintf ppf "invalid slot: %d" x)
Data_encoding.(obj1 (req "bad_slot" int31))
(function Invalid_slot x -> Some x | _ -> None)
(fun x -> Invalid_slot x)
include Compare.Int
(* TODO? should there be some assertions to verify that slots are
never too big ? Or do that in a storage module that depends on
constants ? *)
let encoding = Data_encoding.uint16
let pp = Format.pp_print_int
let zero = 0
let succ = succ
let to_int x = x
let max_value = (1 lsl 16) - 1
let of_int_do_not_use_except_for_parameters i = i
let of_int_exn i =
if Compare.Int.(i < 0 || i > max_value) then
invalid_arg
(Format.sprintf
"valid slot values are in the interval [0, %d] (%d given)"
max_value
i)
else i
module Map = Map.Make (Compare.Int)
module Set = Set.Make (Compare.Int)
module List = struct
(* Expected invariant: list of increasing values *)
(* TODO find a way to properly enforce this invariant *)
type nonrec t = t list
module Compressed = struct
type elt = {skip : int; take : int}
type encoded = elt list
let elt_encoding =
Data_encoding.(
conv
(fun {skip; take} -> (skip, take))
(fun (skip, take) -> {skip; take})
(obj2 (req "skip" uint16) (req "take" uint16)))
let encoding = Data_encoding.list elt_encoding
let encode l : encoded =
let rec loop_taking ~pos ~skipped ~taken l =
match l with
| [] -> if taken > 0 then [{skip = skipped; take = taken}] else []
| h :: t ->
if h = pos then
loop_taking ~pos:(pos + 1) ~skipped ~taken:(taken + 1) t
else
let elt = {skip = skipped; take = taken} in
let skipped = h - pos in
let taken = 1 in
let elts = loop_taking ~pos:(h + 1) ~skipped ~taken t in
elt :: elts
in
loop_taking ~pos:0 ~skipped:0 ~taken:0 l
let decode (elts : encoded) =
let rec loop ~pos elts =
match elts with
| [] -> Ok []
| elt :: elts -> (
let pos = pos + elt.skip in
match
List.init ~when_negative_length:() elt.take (fun i -> i + pos)
with
| Ok l -> (
let pos = pos + elt.take in
match loop ~pos elts with Ok t -> Ok (l @ t) | e -> e)
| Error () ->
Error "A compressed element contains a negative list size")
in
loop ~pos:0 elts
end
let encoding =
Data_encoding.conv_with_guard
Compressed.encode
Compressed.decode
Compressed.encoding
let slot_range ~min ~count =
error_when (min < 0) (Invalid_slot min) >>? fun () ->
error_when (min > max_value) (Invalid_slot min) >>? fun () ->
error_when (count < 1) (Invalid_slot count) >>? fun () ->
error_when (count > max_value) (Invalid_slot count) >>? fun () ->
let max = min + count - 1 in
error_when (max > max_value) (Invalid_slot max) >>? fun () ->
ok Misc.(min --> max)
end