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Aeternity data serialization

Aeternity contract calldata encoding and results decoding standalone library.

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

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

Installation

npm install -P @aeternity/aepp-calldata

Quick Start

To work with contract calls with type information provided by ACI the AciContractCallEncoder class should be used. The constructor takes a single argument - Sophia ACI as string.

NodeJS example:

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

const encoder = new AciContractCallEncoder(ACI)

Encoding calldata

The encodeCall 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.

Example:

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

Expected output:

Encoded data: cb_KxHwzCuVGyl3aG9vbHltb2x5zwMSnw==

Decoding call result

The decodeResult method is used to decode contract call result based on it's type. While the first two arguments are the same as the encoding method, the third one is the actual result to be decoded and last one is the result type which defaults to 'ok'.

Example:

const decoded = encoder.decodeResult(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 encoded contract bytearray (cb_ prefixed string). However, revert messages are FATE string encoded, so the decodeResult method accepts forth argument with the result type.

Example:

// error message
const error = encoder.decodeResult(
    CONTRACT,
    'test_string',
    'cb_VHlwZSBlcnJvciBvbiBjYWxsOiBbe2J5dGVzLDw8MjQwLDIsLi4uPj59XSBpcyBub3Qgb2YgdHlwZSBbe2J5dGVzLDMyfV3EtJjU',
    'error'
)
console.log('Error: ' + error)

// revert message
const revert = encoder.decodeResult(CONTRACT, 'test_string', 'cb_OXJlcXVpcmUgZmFpbGVkarP9mg==', 'revert')
console.log('Revert: ' + revert)

Expected output:

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

Events

Example:

const data = encoder.decodeEvent('Test', 'cb_dHJpZ2dlcmVk1FYuYA==', [
    34853523142692495808479485503424878684430196596020091237715106250497712463899n,
    17n
])
console.log(data)

Expected output:

{EventTwo: [17n, 'triggered']}

Byte Arrays

Any contract bytearray can be decocded using the ContractByteArrayEncoder class.

Node that FATE does not carry some of the type informaton with the data:

• Record keys are lost
• Variant constructor names are lost
• Any user type information is lost
• STL type information is lost: i.e. Chain, AENS, Set, BLS12_381

Example:

const {ContractByteArrayEncoder} = require('@aeternity/aepp-calldata')

const decodedString = encoder.decode('cb_KXdob29seW1vbHlGazSE')
console.log(`Decoded string: ${decodedString}`)

const decodedMap = encoder.decode('cb_LwEOfzGit9U')
console.log('Decoded map:', decodedMap)

Expected output:

Decoded string: whoolymoly
Decoded map: Map(1) { 7n => false }

The encoder could also work with explicit type information:

Example:

const {ContractByteArrayEncoder, TypeResolver} = require('@aeternity/aepp-calldata')

const encoder = new ContractByteArrayEncoder()
const resolver = new TypeResolver()

const decodedString = encoder.decodeWithType('cb_KXdob29seW1vbHlGazSE', resolver.resolveType('string'))
console.log(`Decoded string: ${decodedString}`)

const type = resolver.resolveType({map: ['int', 'bool']})
const encodedMap = encoder.encodeWithType(new Map([[7n, false]]), type)
console.log('Encoded map:', encodedMap)

Expected output:

Decoded string: whoolymoly
Decoded map: Map(1) { 7n => false }

FATE API Encoder

Any of the following FATE API data types can be encoded and decoded:

• key_block_hash
• micro_block_hash
• block_pof_hash
• block_tx_hash
• block_state_hash
• contract_bytearray
• contract_pubkey
• account_pubkey
• account_seckey
• channel
• oracle_pubkey
• oracle_query_id
• peer_pubkey
• name
• tx_hash
• signature
• commitment
• bytearray

Example:

const {FateApiEncoder} = require('@aeternity/aepp-calldata')
const encoder = new FateApiEncoder()

const encoded = encoder.encode('contract_bytearray', new Uint8Array())
console.log(`Encoded: ${encoded}`)

const decoded = encoder.decode('cb_Xfbg4g==')
console.log('Decoded:', decoded)

Expected output:

Encoded: cb_Xfbg4g==
Decoded: Uint8Array(0) []

Note that the encoder work with binary data, so that strings has to be encoded as Uint8Array.

String Example:

const textEncoder = new TextEncoder()
const textDecoder = new TextDecoder()

const encoded = encoder.encode('contract_bytearray', textEncoder.encode('whoolymoly'))
console.log(`Encoded: ${encoded}`)

const decoded = textDecoder.decode(encoder.decode('cb_d2hvb2x5bW9seeO2SW0='))
console.log('Decoded:', decoded)

Excepted output:

Encoded: cb_d2hvb2x5bW9seeO2SW0=
Decoded: whoolymoly

Contract Encoder

Decodes contract metadata including bytecode.

Example:

const {ContractEncoder} = require('@aeternity/aepp-calldata')
const encoder = new ContractEncoder()

const testContract = fs.readFileSync(path.resolve(__dirname, '../build/contracts/Test.aeb'))
const contract = encoder.decode(testContract.toString())

console.log('Contract:', contract)

Expected output (trimmed):

{
  tag: 70n,
  vsn: 3n,
  source_hash: 'e50758c624dcacd485db1f9e76208c5858dd968f6218637d055fd4a3b2850baa',
  aevmTypeInfo: [],
  compilerVersion: '6.1.0',
  payable: false,
  bytecode: {
    functions: [
      {
        id: '077a0e02',
        name: 'test_nested_list',
        attributes: [],
        args: {
          name: 'tuple',
          valueTypes: [
            {
              name: 'list',
              valuesType: { name: 'list', valuesType: { name: 'int' } }
            }
          ]
        },
        returnType: {
          name: 'list',
          valuesType: { name: 'list', valuesType: { name: 'int' } }
        },
        instructions: [
          [
            { mnemonic: 'RETURNR', args: [ { mod: 'arg', arg: 0n } ] }
          ]
        ]
      },
      .....
    ],
    symbols: {
      '67419061': 'test_unit',
      ....
    },
    annotations: Map(0) {}
  }
}

Please note that the bytecode is for debugging/print purposes and it's structure WON'T be kept backward compatible

Data types

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

• 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.

Versioning

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 below classes:

• AciContractCallEncoder
• BytecodeContractCallEncoder
• ContractByteArrayEncoder
• FateApiEncoder
• ContractEncoder
• TypeResolver

The public API is also defined in TypeScript declation file.

Errors

Error names are also part of the public API and it is guaranteed to get the same error name between compatible versions. Since error classes are not exported as public API, the library users should rely only on Error.name property to handle exceptions. Please also note that error messages are NOT part of the public API and they may change any time between versions without notice.

Development

Please make sure you get familiar with Contributing Guidelines first.

Install

npm install

Tests

Unit tests can be run with:

make tests

Integration tests:

make integration-tests

One can use the benchmarks to do relative comparison on performance for a given change:

make benchmark-tests

Verify browser compatibility with:

make browser-tests

To see the test coverage run:

make coverage