First of all, this looks great. But is there a reason to use this custom BinaryPack format, over another binary JSON-alike such as msgpack, which already has a lot of bindings in other languages?
I'm glad you asked! BinaryPack is actually a extended version of msgpack. Specifically msgpack doesn't differentiate between binary and string types. This is fine for most dynamic languages as "strings" can hold both string and binary data. However Javascript has very distinct binary types and thus we need separate types within the serialization format.
