bcp-js

BlockChain Payloads (BCP)

Immutable pointers to digital data, saved on the BCH blockchain

Objectives

There are already a lot of projects, working with NFT on BCH blockchain (SLP tokens), but they all choose their own way to connect these tokens to the related content.

it is difficult for the wallets and exchanges developers to support these projects, because it requires individual changes for every additional project.

With the increased usage of NFT tokens on the BCH blockchain, there is a need to unify the way these tokens connect to the tokenized data - audio, video, images etc.

Current repository contains bcp-js JavaScript Library for building transactions for the BlockChain Payloads (BCP) Protocol.

BCP Protocol Reference

This library is a reference code for the BlockChain Payloads (BCP) Protocol. The examples in this repository contain the full code necessary for the BCP message types and sources described in the protocol specification. Please reference these examples when building or testing your own applications.

Used libraries and services

• bignumber.js - A JavaScript library for arbitrary-precision arithmetic

Installation

• for node.js

npm install bcp-js

• for browser

<script src="https://unpkg.com/bcp-js"></script>

for a specific version:

<script src="https://unpkg.com/bcp-js@1.0.1/dist/bcp.min.js"></script>

Development

The easiest way is to download the library sources from the GitHub repository and rebuild them for your project:

git clone https://github.com/zh/bcp-js.git
cd bcp-js
npm install
npm run build

Testing

There are some basic tests implemented. More will be added.

npm test

Usage

Library instantiation

const { BCP } = require('bcp-js')
const bcp = new BCP()

BCP types and sources

The library provides definitions for all BCP types and sources, mentiobed in the protocol specification:

• 1.) BCP Types

• BCP_TYPE_GENERIC - Generic type. Can be any content

• BCP_TYPE_TEXT - Simple string (UTF-8 encoded)

• BCP_TYPE_IMAGE - .png, .gif etc. images

• BCP_TYPE_AUDIO - .mp3, .ogg etc. audio files

• BCP_TYPE_VIDEO - .mpv, .mp4 etc. video files

• BCP_TYPE_JSON - JSON formated data - still not implemented

• 2.) BCP Sources

• BCP_SRC_NONE - data is inside the OP_RETURN itself

• BCP_SRC_TXID - on-chain data, represented by transaction ID

• BCP_SRC_URL - URL, standart HTTP (web) location

• BCP_SRC_IPFS - IPFS, represented by IPFS hash of the data (depricated, use BCP_SRC_URL instead)

• BCP_SRC_ADDR - BCH (bitcoincash:) or SLP (simpleledger:) address

To use these definitions you need to import them in your sources:

const { BCP, BCP_TYPE_IMAGE, BCP_SRC_IPFS } = require('bcp-js')

Methods for BCP creation

• create(type, source, data) - Need to explicitly specify BCP type and source. All methods below using this method.
• createChainText(data) - on-chain string data, inside the OP_RETURN itself
• createText(source, data) - off-chain UFT-8 encoded string (is this needed?)
• createAudio(source, data) - points to audio file (.mp3, .ogg etc.)
• createImage(source, data) - points to an image file (.png, .gif etc.)
• createState(address, type = BCP_TYPE_GENERIC) - points to BCH or SLP address (bitcoincash:, simpleledger:)
• createFromString(str) - automatically detects source from the string - TxID, IPFS etc.

Create BCP for a simple blockchain saved text

Simple text message, similar to the memo.cash ones (text is in the OP_RETURN itself):

const opReturn = bcp.createChainText('Hello BCP')
console.log(opReturn.toString('hex')) // 6a0442435000010201010948656c6c6f20424350

Create BCP for an audio file on IPFS

Short .mp3 file with rain drops, hosted on IPFS - BCP points to the IPFS hash

Use a general method, which allow BCP type argument:

const { BCP_TYPE_AUDIO, BCP_SRC_IPFS } = require('bcp-js')
const ipfsHash = 'QmZmqLskJmghru919cvU4qSy3L5vc1S2JdzsUXrM17ZqT9'
const opReturn = bcp.create(BCP_TYPE_AUDIO, BCP_SRC_IPFS, ipfsHash)
console.log(opReturn.toString('hex'))
// 6a0442435000010401042e516d5a6d714c736b4a6d6768727539313963765534715379334c3576633153324a647a735558724d31375a715439

or use specific method for the given BCP type

const ipfsHash = 'QmZmqLskJmghru919cvU4qSy3L5vc1S2JdzsUXrM17ZqT9'
const opReturn = bcp.createAudio(BCP_SRC_IPFS, ipfsHash)

Create BCP to SLP address

Creating a pointer to BCH or SLP address allow simulatiion of mutable (changable) objects, for example tracking the state of some game player etc. The BCP itself is immutable, saved on the blockchaain, but changes in the object can be tracked by sending transaction to the address, encoded in the BCP. Like items a game player owns, payments for given contract etc.

const { BCP_SRC_ADDR } = require('bcp-js')
const slpAddress = 'simpleledger:qq2fg599ysqvfefr2ur0z34n2dk6f0aszg5pskpe06'
const opReturn = bcp.createState(slpAddress)
console.log(opReturn.toString('hex'))
// 6a0442435000010101053773696d706c656c65646765723a71713266673539397973717666656672327572307a33346e32646b36663061737a673570736b70653036

If you know the type of transactions, that will be send to the address above, you can also add it to the parameters. For example changable image gallery on IPFS: on adding/changing images, just send a transaction to the provided address with the new image IPFS hash (Qm...)

const opReturn = bcp.createState(slpAddress, BCP_TYPE_IMAGE)

Methods for parsing BCP

• parse(payload) - parse OP_RETURN with BCP and return JS object

Parse IPFS save audio file

Using the audio-file on IPFS OP_RETURN from the creation example above.

const op = '6a0442435000010401042e516d5a6d714c736b4a6d6768727539313963765534715379334c3576633153324a647a735558724d31375a715439'
parsed = bcp.parse(op)
console.log(JSON.stringify(parsed, null,2))

{
  "type": 4,   // BCP_TYPE_AUDIO
  "source": 4, // BCP_SOURCE_IPFS
  "data": {
    "hash": {  // QmZmqLskJmghru919cvU4qSy3L5vc1S2JdzsUXrM17ZqT9
      "type": "Buffer",
      "data": [
      ...

You can see more usage examples in the examples directory.

Future plans

SLP on BCH blockchain providing pretty mature infrastrucure for working with NFT tokens - grouping (parent+children), indexing etc. There is no need to invite the same for the BCPs. Just create NFT with documentUri pointing to BCP and all these services can be used for working with the data, pointed by BCP. This will also provide ownership prove of the digital content.

There is already a proposal for adding several OP_RETURN data to one transaction. This will make connecting NFT to the BCP pointed data even easier - one OP_RETURN for the SLP and one for the BCP!

Some real code for create/view NFTs with BCP pointed data will be added.

Hope more wallets and exchanges developers agree on the current proposal, so more implementations will be done - other languages etc.

Donations

Every amount of BCH will help the future development

• BCH: bitcoincash:qq3t709lskk7tpg5nl8xdfvu8rx4v66ys5cwlxw3ac