Module Compact.Custom

This module can be used to write compact encoding for complex types without relying on the existing combinators.

type tag = int
val join_tags : (tag * int) list -> tag

Combine multiple tags; will throw an error if the total length of the tags is more than 16.

module type S = sig ... end
val make : (module S with type input = 'a) -> 'a t

make (module M) is a compact encoding for the type of M.input.

The JSON representation is entirely determined by M.json_encoding.

The binary representation is determined as follows.

  • A value v : M.input is classified into a layout l by M.classify v.
  • A tag M.tag l is used (which may be combined with the tags of other compact encodings as described before).
  • The payload is the same bytes as can be found in the string returned by Data_encoding.Binary.to_string (M.partial_encoding l) v.

In other words, the tag of a value is M.(tag (layout v)) and the payload of a value is M.(partial_encoding (layout v) v).

It is the user's responsibility to ensure that all the values of M follow the invariants documented in S.