52 lines
1.9 KiB
OCaml
52 lines
1.9 KiB
OCaml
open Types
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open Utils
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let parse_header reader =
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let max_size = 6 in
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match List.init max_size (fun offset -> unpack_short_be reader.data (offset * 2)) with
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| [ id; flags; num_questions; num_answers; num_authorities; num_additionals ] ->
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( { reader with pointer = reader.pointer + (max_size * 2) }
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, { id; flags; num_questions; num_answers; num_authorities; num_additionals } )
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| _ -> failwith "Invalid number of fields"
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;;
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let rec parse_question reader =
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let name, offset_name = decode_name reader in
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let data = bytes_forward reader.data (reader.pointer + offset_name) in
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let max_size = 2 in
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match List.init max_size (fun offset -> unpack_short_be data (offset * 2)) with
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| [ type_; class_ ] ->
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( { reader with pointer = reader.pointer + offset_name + (max_size * 2) }
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, { name; type_; class_ } )
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| _ -> failwith "Invalid number of fields"
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and decode_name reader =
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let rec read_parts parts pos =
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let length = int_of_char (Bytes.get reader.data (reader.pointer + pos)) in
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if length = 0
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then 1, parts
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else if length land 0b1100_0000 <> 0
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then (
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let decoded_name = decode_compressed_name reader length in
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2, decoded_name :: parts)
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else (
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let part = Bytes.sub_string reader.data (reader.pointer + pos + 1) length in
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let last_length, parts' = read_parts (parts @ [ part ]) (pos + 1 + length) in
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last_length + length + 1, parts')
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in
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let offset, parts = read_parts [] 0 in
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String.to_bytes (String.concat "." parts), offset
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and decode_compressed_name reader length =
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let pointer =
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(length land 0b0011_1111) + int_of_char (Bytes.get reader.data (reader.pointer + 1))
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in
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String.of_bytes (fst (decode_name { reader with pointer }))
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;;
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let parse_record reader =
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let name, _offset_name = decode_name reader in
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(* TODO *)
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let type_, class_, ttl, data = 0, 0, 0, Bytes.empty in
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{ name; type_; class_; ttl; data }
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;;
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