@substrate-system/bencode/test/specifications.md

Bencode de/encoder

_Strings_ are length-prefixed base ten followed by a colon and the string. For example 4:spam corresponds to 'spam'.

_Integers_ are represented by an 'i' followed by the number in base 10 followed by an 'e'. For example i3e corresponds to 3 and i-3e corresponds to -3. Integers have no size limitation. i-0e is invalid. All encodings with a leading zero, such as i03e, are invalid, other than i0e, which of course corresponds to 0.

_Lists_ are encoded as an 'l' followed by their elements (also bencoded) followed by an 'e'. For example l4:spam4:eggse corresponds to ['spam', 'eggs'].

_Dictionaries_ are encoded as a 'd' followed by a list of alternating keys and their corresponding values followed by an 'e'. For example, d3:cow3:moo4:spam4:eggse corresponds to {'cow': 'moo', 'spam': 'eggs'} and d4:spaml1:a1:bee corresponds to {'spam': ['a', 'b']}.
Keys must be strings and appear in sorted order (sorted as raw strings, not alphanumerics).