gustav

A helper library for two use-cases:

1. To help pack-up and un-pack data
2. To help with writing a udp-server

Examples

Imagine that you have a state #{a => 1, b => 2, c => 3, d => 4}. You need to pack-up this data (serialize) and send it over the wire. Your protocol specifies that:

Which can be described compactly as [{a, 8}, {b, 16}, {c, 32}, {d, 8}].

When using Gustav, packing up the dictionary into a binary payload:

Dictionary = #{a => 1, b => 2, c => 3, d => 4},
Packer = packer(Dictionary),
Payload = Packer([{a, 8}, {b, 16}, {c, 32}, {d, 8}]),
Payload.
<<1:8, 2:16, 3:32, 4:8>>

To unpack the binary payload is similar. We describe the binary protocol [{a, 8}, {b, 16}, {c, 32}, {d, 8}] and use a unpacker function.

Normally we only want to unpack the data into an empty map #{}. However, in some cases it is convenient to allow some "other" data in the map (state).

Using Gustav, to unpacking a binary payload into a dictionary:

Payload = <<1:8, 2:16, 3:32, 4:8>>,
UnPacker = unpacker(#{}, Payload),
NewDictionary = UnPacker([{a, 8}, {b, 16}, {c, 32}, {d, 8}]),
NewDictionary.
#{a => 1, b => 2, c => 3, d => 4}

Or if you already have some data you want to preserve #{q => 42}:

OrgDictionary = #{q => 42}  %% q => 42 is mapping we want to
Payload = <<1:8, 2:16, 3:32, 4:8>>,
UnPacker = unpacker(OrgDictionary, Payload),
NewDictionary = UnPacker([{a, 8}, {b, 16}, {c, 32}, {d, 8}]),
NewDictionary.
#{a => 1, b => 2, c => 3, d => 4, q => 42}

Build

$ rebar3 compile