diff options
Diffstat (limited to 'lib/concepts/Codec.ml')
| -rw-r--r-- | lib/concepts/Codec.ml | 182 |
1 files changed, 0 insertions, 182 deletions
diff --git a/lib/concepts/Codec.ml b/lib/concepts/Codec.ml deleted file mode 100644 index 758d718..0000000 --- a/lib/concepts/Codec.ml +++ /dev/null @@ -1,182 +0,0 @@ - module Error = struct - open Condition - - let unexpected_end = - condition "codec-unexpected-end" "Unexpected end of input while decoding" empty - - let malformed_integer digits = - condition "codec-malformed-integer" "A byte run is not a valid integer" - ("digits" |=| Value.String digits) - - let unexpected_byte c = - condition "codec-unexpected-byte" "Unexpected byte while decoding" - ("byte" |=| Value.String (String.make 1 c)) - - let string_out_of_bounds length = - condition "codec-string-out-of-bounds" "A string length runs past the end of input" - ("length" |=| Value.Integer length) - - let trailing_bytes = - condition "codec-trailing-bytes" "Bytes remain after a complete value" empty - - let tag_mismatch ~expected ~actual = - condition "codec-tag-mismatch" "A value with a different tag was expected" - ("expected" |=| Value.String (String.make 1 expected) & - "actual" |=| Value.String (String.make 1 actual)) - - let type_mismatch ~expected = - condition "codec-type-mismatch" "A Bencode value of a different shape was expected" - ("expected" |=| Value.String expected) - - let missing_field key = - condition "codec-missing-field" "A required field is absent" - ("field" |=| Value.String key) - - let unexpected_object ~expected ~actual = - condition "codec-unexpected-object" "The decoded object is not of the expected kind" - ("expected" |=| Value.String expected & "actual" |=| Value.String actual) -end - -(* A self-describing serialization used as the uniform wire format for - durable objects. Chosen over an ad-hoc key=value scheme because it - nests (a multigroup holds a map of relation hashes) and has a - single byte form for a given value (dict keys are emitted sorted), - which matters once these bytes are content-addressed. - - Grammar: - - Int "i" <decimal> "e" (negatives allowed) - - String <length> ":" <raw bytes> - - List "l" <element>* "e" - - Dict "d" (<String key> <value>)* "e" keys sorted on encode *) -module Bencode = struct - type t = Tagged of char * t | Int of int | String of string | List of t list | Dict of (string * t) list - - let rec encode buf = function - | Tagged (tag, value) -> - Buffer.add_char buf 't'; - Buffer.add_char buf tag; - encode buf value - | Int n -> - Buffer.add_char buf 'i'; - Buffer.add_string buf (string_of_int n); - Buffer.add_char buf 'e' - | String s -> - Buffer.add_string buf (string_of_int (String.length s)); - Buffer.add_char buf ':'; - Buffer.add_string buf s - | List xs -> - Buffer.add_char buf 'l'; - List.iter (encode buf) xs; - Buffer.add_char buf 'e' - | Dict kvs -> - Buffer.add_char buf 'd'; - List.iter - (fun (k, v) -> - encode buf (String k); - encode buf v ) - (List.sort (fun (a, _) (b, _) -> String.compare a b) kvs); - Buffer.add_char buf 'e' - - let to_bytes (value : t) : bytes = - let buf = Buffer.create 256 in - encode buf value; - Buffer.to_bytes buf - - let as_string = function String s -> Ok s | _ -> Error (Error.type_mismatch ~expected:"string") - let as_int = function Int n -> Ok n | _ -> Error (Error.type_mismatch ~expected:"integer") - let as_list = function List l -> Ok l | _ -> Error (Error.type_mismatch ~expected:"list") - let as_dict = function Dict d -> Ok d | _ -> Error (Error.type_mismatch ~expected:"dict") - - let of_bytes (bytes : bytes) : (t, Condition.condition) result = - let open Utilities.Result in - let s = Bytes.to_string bytes in - let n = String.length s in - let pos = ref 0 in - let peek () = if !pos >= n then Error (Error.unexpected_end) else Ok (s.[!pos]) in - let advance () = incr pos in - (* Read the decimal run up to (and consuming) [term]. *) - let read_int_from start term = - let rec scan () = - let* c = peek () in - if c = term then begin - let digits = String.sub s start (!pos - start) in - advance (); - match int_of_string_opt digits with - | Some i -> Ok i - | None -> Error (Error.malformed_integer digits) - end - else begin - advance (); - scan () - end - in - scan () - in - let read_int term = read_int_from !pos term in - let read_char () = - let* c = peek () in - advance (); - Ok c - in - let rec parse () = - let* c = peek () in - advance (); - match c with - | 't' -> - let* tag = read_char () in - let* data = parse () in - Ok (Tagged (tag, data)) - | 'i' -> - let* n = read_int 'e' in - Ok (Int n) - | 'l' -> parse_list [] - | 'd' -> parse_dict [] - | c when c >= '0' && c <= '9' -> parse_string_from (!pos - 1) - | c -> Error (Error.unexpected_byte c) - and parse_string () = - parse_string_from !pos - and parse_string_from start = - let* len = read_int_from start ':' in - if len < 0 || !pos + len > n then - Error (Error.string_out_of_bounds len) - else - let str = String.sub s !pos len in - pos := !pos + len; - Ok (String str) - and parse_list acc = - let* c = peek () in - if c = 'e' then (advance (); Ok (List (List.rev acc))) - else - let* result = parse () in - parse_list (result :: acc) - and parse_dict acc = - let* c = peek () in - if c = 'e' then (advance (); Ok (Dict (List.rev acc))) - else - let* key = parse_string () in - let* key = as_string key in - let* value = parse () in - parse_dict ((key, value) :: acc) - in - let* value = parse () in - if !pos <> n then Error Error.trailing_bytes else - Ok value - - let to_blob x = to_bytes x |> Representation.blob_of_bytes - let of_blob b = Representation.bytes_of_blob b |> of_bytes - - let with_tag t = function - | Tagged (t', v) -> - if t = t' then - Ok v - else - Error (Error.tag_mismatch ~expected:t ~actual:t') - | _ -> Error (Error.type_mismatch ~expected:"tagged") - - let field key = function - | Dict kvs -> ( - match List.assoc_opt key kvs with - | Some v -> Ok v - | None -> Error (Error.missing_field key) ) - | _ -> Error (Error.type_mismatch ~expected:"dict") -end |