Aeternity data serialization library

Usage no npm install needed!

<script type="module">
  import aeternityAeppCalldata from 'https://cdn.skypack.dev/@aeternity/aepp-calldata';


Aeternity data serialization

Aeternity contract calldata encoding and results decoding standalone library.

This is Javascript imeplemtnation of data serialization specified in aeternity protocol.

While the only purpose of the library at the moment of this writing is solely to provide ecnoding and decoding respectively of contracts calldata and return data it may evolve to full fledged serialization library of the full protocol specification.


npm install -P @aeternity/aepp-calldata

Quick Start

There is single module Encoder that should be imported and instanciated. The constructor takes a single argument - Sophia ACI as string.

The encode method is used to encode calldata taking the contract name as first argument, then function name and list of contract call arguments as last argument.

The decode method is used to decode contract call results while the first two arguments are the same as the encoding method the last one is the actuall result to be decoded.

NodeJS example:

const {Encoder} = require('@aeternity/aepp-calldata')
const ACI = require('./Test.json')
const CONTRACT = 'Test'

const encoder = new Encoder(ACI)

const encoded = encoder.encode(CONTRACT, 'test_string', ["whoolymoly"])
console.log(`Encoded data: ${encoded}`)

const decoded = encoder.decode(CONTRACT, 'test_string', 'cb_KXdob29seW1vbHlGazSE')
console.log(`Decoded data: ${decoded}`)

Expected output:

Encoded data: cb_KxHwzCuVGyl3aG9vbHltb2x5zwMSnw==
Decoded data: whoolymoly

Contract call errors

FATE contract call error message is represented as cb_ prefixed base64check encoded string, to get the error as string one can use decodeString shorthand method instead of doing it in their codebase. However, revert messages are FATE string encoded, so a different helper method decodeFateString should be used.


const {Encoder} = require('@aeternity/aepp-calldata')
const ACI = require('./Test.json')

const encoder = new Encoder(ACI)

// error message
const error = encoder.decodeString('cb_VHlwZSBlcnJvciBvbiBjYWxsOiBbe2J5dGVzLDw8MjQwLDIsLi4uPj59XSBpcyBub3Qgb2YgdHlwZSBbe2J5dGVzLDMyfV3EtJjU')
// note that decodeString returns a Buffer that has to be converted to string
console.log('Error: ' + error.toString())

// revert message
const revert = encoder.decodeFateString('cb_OXJlcXVpcmUgZmFpbGVkarP9mg==')
console.log('Revert: ' + revert)

Expected output:

Error: Type error on call: [{bytes,<<240,2,...>>}] is not of type [{bytes,32}]
Revert: require failed

Data types

Using the library involves data types and their mappings from Sophia to JavaScript and vice versa.

Sophia Type Sophia Example Javascript type Javascript Example
int 63, -63 BigInt 63n, -63n
bool true, false Boolean true, false
string "whoolymoly" String "whoolymoly"
bytes #beef BigInt BigInt("0xbeef")
list [1, 2, 3, 5, 8, 13, 21] Array [1,2,3,5,8,13,21]
tuple (true, false) Array [true, false]
map {[7] = false} Map new Map([[7, false]])
record {x = 0, y = 0} Object (POJO) {x: 0, y: 0}
variant Some(404), None Object (POJO) {'Some': [404]}, {'None': []}, 404, undefined
bits Bits.none, Bits.all Bits.set(Bits.none, 0) BigInt 0b0n, -1n, 0b00000001n
hash #001234d BigInt BigInt("0x001234d")
signature #001234d BigInt BigInt("0x001234d")
address ak_2gx9MEFxKvY9vMG5YnqnXWv1hCsX7rgnfvBLJS4aQurustR1rt String ak_2gx9MEFxKvY9vMG5YnqnXWv1hCsX7rgnfvBLJS4aQurustR1rt
  • note the fixed structure of variant object with a single key - the variant constructor (i.e. Some) and array of variant arguments as it's value.
  • while Javascript Number and primitive int types can be used as well when BigInt type is expected it's not recommended because of it's Number.MAX_SAFE_INTEGER limitation.


This project follows the semantic versioning guidelines. Refer to the CHANGELOG for more information about releases.

Public API

The backward compatibility promise signaled with semantic versioning above is only applied to public API of this library, that is only the module exports and data types listed above.

The public API namely consist of:

  • encode(contractName: string, functionName: string, arguments: Array<Data>): string
  • decode(contractName: string, functionName: string, encodedData: string): Data
  • decodeString(data: string): Buffer
  • decodeFateString(data: string): string

where Data: Boolean | BigInt | String | Array | Map | Object


Please make sure you get familiar with Contributing Guidelines first.


npm install


make tests

Verify browser compatibility with:

make browser-tests

To see the test coverage run:

make coverage