type decode = [ | `Field of Field.field Location.with_location| `Await| `End of string| `Malformed of string ]val decoder : ?p:Field.witness Field_name.Map.t -> Bigstringaf.t -> decoderdecoder ?p buf returns a decoder with a set of field-name binded with expected kind of value. When the decoder will decode value of a given field-name, it will try to extract expected value describe by the given Field.witness or it returns a Unstructured.t.
decode decoder is:
`Field field when extracted a field.`Await when the decoder wants more input.`End trailer when we reach end of the header. trailer is what the user gaves which is not the part of the header.`Malformed err we we reach an error while decoding.val src : decoder -> string -> int -> int -> (unit, [> Rresult.R.msg ]) resultsrc decoder src off len gives more input to decoder. The function can fail when given input is bigger than internal buffer of decoder (see decoder).