Working with Bencodex

Working with Bencodex

Bencodex is a serialization/deserialization format that Libplanet-based games use for serializing the game transactions, actions and more.

Why Bencodex

This section is a summary of the README of Bencodex repository.

Bencodex makes sure there is only one valid way to represent any value. This property makes checking equality between two values trivial; there is no way to have multiple same Bencodex values with different representations.

Data Types

The data types used in Bencodex are similar to what you would find in a normal JSON, with some differences like:

  • byte strings
  • replaced numbers with integers – meaning no floating numbers can be stored

This also means that as long as your JSON data contains no decimal points, you can convert them to Bencodex without a loss of data.

The complex data can be stored in arrays and dictionaries (corresponding to objects in JSON). Unlike JSON, you can choose to have byte string as a key.

Transmit over Text-based Channels

Bencodex is a binary-encoded format, so the data is usually encoded as hexadecimal when packed inside JSON or GraphQL. The 0x prefix is not used.

You’ll typically see this when working with GraphQL APIs of Nine Chronicles.

Bindings

C#

The C# bindings provide basic Encode and Decode methods for working with Bencodex data.

TODO: Fill this section.

JavaScript/TypeScript

There’s a third-party implementation for Bencodex which is also used within some of Planetarium’s products, such as the Nine Chronicles launcher.

To get a copy, you can install it on npm:

npm install bencodex

The API is fairly simple: it has encode for serializing the value into Bencodex or decode for vice-versa.

Note that the library decodes dictionaries into Map. You can use them via its methods or convert them to plain JavaScript object using Object.fromEntries.

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can you please give some examples about this?

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Well, I’m curious too. Mixed key types in the same dictionary are technically possible and I tested it with javascript implementation.
Example 1:

decode(Buffer.from(‘d3:cowu3:moou3:cow4:eggse’))
Map(2) { <Buffer 63 6f 77> => ‘moo’, ‘cow’ => <Buffer 65 67 67 73> }

I think what @Basix might tried to say was, you can’t mix byte-string based keys and “NON-UNICODE” based string (which is actually byte-string), as they’re indistinguishable in original bencodex format.

From that aside, I generally disencourage mixing the key type when using a dictionary, I mean you ‘can’ generate key type mixed bencodex string as d3:cowu3:moou3:cow4:eggse has 3:cow byte-string key and u3:cow Unicode-string key but most of the libraries will have a hard time when deserializing them and typing it as Dictionary<KeyType, ValueType>.

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Turns out it was my misinterpretation of the documentation :sweat:

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