@activeprospect/bert-elixir

BERT

Binary ERlang Term serialization library for Javascript. (An updated version of this repo )

Usage

---

Example Usage

When needing to consume data in Javascript from an Erlang system, the Erlang system can simply send encoded binary data:

Elixir/Erlang:

# This is Elixir code, but function calls will be very similar in Erlang

personData = %{
  name: "Bob",
  age: 32,
  eye_color: "Brown",
  personality_traits: [
    "Funny",
    "Inquisitive"
  ]
}

# Convert to binary
:erlang.term_to_binary(personData)

# .... Code that sends binary data to javascript

Javascript:

// ... Code that receives binary data from erlang/elixir and stores it
// to a variable, personData

const Bert = require('bert-elixir')

const decodedPerson = Bert.decode(personData)
/*
  => { age: 32,
      eye_color: 'Brown',
      name: 'Bob',
      personality_traits: [ 'Funny', 'Inquisitive' ]
    }
*/

Modifying this data and sending it back to Erlang/Elixir would be as simple as:

Javascript:

// ... Assuming we have a decodedPerson object

decodedPerson.age = 38
decodedPerson.name = 'Robert'

const reEncodedPerson = Bert.encode(decodedPerson)

// ... Send the binary

Elixir/Erlang:

# ... After having received binary data and setting it to variable modifiedPersonData:

decodedPerson = :erlang.binary_to_term(modifiedPersonData, [:safe])

# => %{ age: 38, eye_color: "Brown", name: "Robert", personality_traits: ["Funny", "Inquisitive"] }

safe option should be always used when decoding an untrusted input, make also sure to have already all required atoms in the atoms table.

Encoding

Maps (Elixir)

Javascript objects map directly to Maps in Erlang

const Bert = require('bert-elixir')

// To encode a javascript object to an elixir map:
const mapToEncode = { a: 1, b: "hello!", c: [1, 2, 3] }
const encodedMap = Bert.encode(mapToEncode)

// BinaryToList shows individual bytes as a javascript array
console.log(Bert.binaryToList(encodedMap))
// => [ 131, 116, 0, 0, 0, 3, 100, 0, 1, 97, 97, 1, 100, 0, 1, 98, 109, 0, 0, 0, 6, 104, 101, 108, 108, 111, 33, 100, 0, 1, 99, 108, 0, 0, 0, 3, 97, 1, 97, 2, 97, 3, 106 ]

Lists

Javascript arrays map to Erlang Lists

const Bert = require('bert-elixir')

const arrayToEncode = ['hello', 'world', 32, [{ key: "value" }]]
const encodedArray = Bert.encode(arrayToEncode)

console.log(Bert.binaryToList(encodedArray))

Todo:

• Write docs for rest of data types
• Return nil as null instead of 'nil'
• Add support for NEW_FLOAT_EXT

---

Decoding

Decoding is typically much simpler than encoding. Just pass the given Binary Erlang Term:

const Bert = require('bert-elixir')

// We're showing the term as an array of bytes here for clarity.
// You'll more likely have a string
const erlangTerm = [131, 116, 0, 0, 0, 3, 100, 0, 1, 97, 97, 1, 100, 0, 1, 98, 97, 2, 100, 0, 1, 99, 116, 0, 0, 0, 1, 100, 0, 4, 119, 111, 97, 104, 109, 0, 0, 0, 8, 97, 32, 115, 116, 114, 105, 110, 103]
.map(x => String.fromCharCode(x)).join('') // Convert the array to a string

const decoded = Bert.decode(erlangTerm)

console.log(decoded)
// => { a: 1, b: 2, c: { woah: 'a string' } }