Erlpack

Erlpack is a fast encoder and decoder for the Erlang Term Format (version 131) for Python and JavaScript.

JavaScript

Things that can be packed:

• [X] Null
• [X] Booleans
• [X] Strings
• [ ] Atoms
• [X] Unicode Strings
• [X] Floats
• [X] Integers
• [ ] Longs
• [ ] Longs over 64 bits
• [X] Objects
• [X] Arrays
• [ ] Tuples
• [ ] PIDs
• [ ] Ports
• [ ] Exports
• [ ] References

How to pack:

let erlpack = require("erlpack");

packed = erlpack.pack({'a': true, 'list': ['of', 3, 'things', 'to', 'pack']});

How to unpack:

Note: Unpacking requires the binary data be a Uint8Array or Buffer. For those using electron/libchromium see the gotcha below. ```js let erlpack = require("erlpack");

let unpacked = null; let packed = new Buffer('', 'binary'); try { unpacked = erlpack.unpack(packed); } catch (e) { // got an exception parsing } ```

Libchromium / Electron Gotcha

Some versions of libchromium replace the native data type backing TypedArrays with a custom data type called blink::WebArrayBuffer. To keep erlpack' dependencies simple this data type is not supported directly. If you're using Electron / Libchromium you need to convert the blink::WebArrayBuffer into a node::Buffer before passing to erlpack. You will need to add this code into your native package somewhere: ```cpp v8::Localv8::Value ConvertToNodeBuffer(const v8::Localv8::Object& blinkArray) { if (node::Buffer::HasInstance(blinkArray)) { return blinkArray; } else if (blinkArray->IsArrayBufferView()) { auto byteArray = v8::ArrayBufferView::Cast(blinkArray); return node::Buffer::Copy(v8::Isolate::GetCurrent(), (const char)byteArray->Buffer()->GetContents().Data(), byteArray->ByteLength()).ToLocalChecked(); }

return v8::Local<:primitive>(v8::Null(v8::Isolate::GetCurrent()));

} ```

Then in JavaScript something like:

let packed = NativeUtils.convertToNodeBuffer(new Uint8Array(binaryPayload));
// unpack now using erlpack.unpack(packed)

Python

Things that can be packed:

• [X] None
• [X] Booleans
• [X] Strings
• [X] Atoms
• [X] Unicode Strings
• [X] Floats
• [X] Integers
• [X] Longs
• [ ] Longs over 64 bits
• [X] Dictionaries
• [X] Lists
• [X] Tuples
• [X] User Types (via an encode hook)
• [ ] PIDs
• [ ] Ports
• [ ] Exports
• [ ] References

How to pack:

from erlpack import pack

packed = pack(["thing", "to", "pack"])

How to unpack:

from erlpack import unpack

unpacked = unpack(packed)

How to pack an atom:

from erlpack import Atom, pack

packed = pack(Atom('hello'))

How to use an encode hook.

from erlpack import ErlangTermEncoder

def encode_hook(obj):
    if isinstance(obj, datetime.datetime):
        return obj.isoformat()
encoder = ErlangTermEncoder(encode_hook=encode_hook)
packed = encoder.pack(datetime.datetime(2015, 12, 25, 12, 23, 55))

How to make custom types packable.

from erlpack import pack, Atom

class User(object):
    def init(self, name, age):
        self.name = name
        self.age = age
def __erlpack__(self):
    return {
        Atom('name'): self.name,
        Atom('age'): self.age
    }
u = User(name='Jake', age=23)
packed = pack(u)

Go (golang)

Discord has moved away from Go internally and so we do not maintain a version of erlpack in Go ourselves. However, all is not lost!, please check out: https://github.com/JakeMakesStuff/go-erlpack