This is a JavaScript Library for uploading and downloading files per the Bitcoin Files Protocol specification to the Bitcoin Cash blockchain. It's important to understand that files uploaded to any blockchain are permanent and cannot be deleted. All uploaded content is associated with the public key(s) you use to pay for uploading the content.

Other tools using the Bitcoin Files Protocol include:

• Electron Cash SLP Edition

npm install bitcoinfiles

<script src='https://unpkg.com/bitcoinfiles'></script>

const Grpc = require('grpc-bchrpc-node'); // or window.bchrpc
const Bfp = require('bitcoinfiles').Bfp;  // or window.bitcoinfiles.Bfp
const grpc = new Grpc.GrpcClient;
const bfp = new Bfp(grpc);

// 1 - download file using URI
let result;
(async function() {
    result = await bfp.downloadFile('bitcoinfile:7e4600323c934926369c136562f5483e3df79baf087c8dd2b0ed1aea69d5ee49');

    // Wait for download to complete -- Mario.png TAKES ABOUT 6 SEC TO DOWNLOAD!
    console.log("download complete.");

    // 2 - result includes a boolean check telling you if the file's sha256 matches the file's metadata
    if (result.passesHashCheck) {
        console.log("Success: downloaded file sha256 matches file's metadata");
    }

    // 3 - do something with the file...
    let fileBuffer = result.fileBuf;
})();

Below is a simple example. For a more complete React.js file upload example visit SimpleToken.cash website

const Grpc = require('grpc-bchrpc-node'); // or window's property equivalents
const Bfp = require('bitcoinfiles').Bfp;
const Utils = require('bitcoinfiles').Utils;
const grpc = new Grpc.GrpcClient;
const bfp = new Bfp(grpc);


// 1 - get a file and file metadata somehow
const someFileBuffer = Buffer.from('aabbccddeeff', 'hex');
const fileName = 'a test file';
const fileExt = 'txt';
const fileSize = someFileBuffer.length
const fileSha256Hex = Utils.Sha256(someFileBuffer).toString('hex');

// 2 - estimate upload cost for funding the transaction
let uploadCost = Bfp.calculateFileUploadCost(fileSize);

// Alternatively, use the new protocol intended for larger files:
// let uploadCost = Bfp.calculateFileUploadCost(fileSize, null, 1, 2);

console.log('upload cost: ', uploadCost);

// 3 - create a funding transaction
let fundingAddress = 'bitcoincash:qqgvrkm0xpmwqgyhfm65qxv70tjtwma6lgk07ffv9u'
let fundingWif = 'KzcuA9xnDRrb9cPh29N7EQbBhQQLMWtcrDwKbEMoahmwBNACNRfa'

// 4 - Make sure address above is funded with at least uploadCost
let fundingUtxo = {
    "txid": "85c1b22c116b44539ead07353c509502b46106344bb5b4bd46a880ba8a530c27",
    "satoshis": 12000,
    "vout": 3
};

// wait for network to resolve...

// 5 - upload the file
let fileId;
(async function() {
    fileId = await bfp.uploadFile(fundingUtxo, fundingAddress, fundingWif, someFileBuffer, fileName, fileExt);
    console.log('fileId: ', fileId);
})();

// wait for upload to complete resolve... Done.

async uploadFile(
    fundingUtxo: utxo,
    fundingAddress: string,
    fundingWif: string,
    fileDataArrayBuffer: Buffer,
    fileName?: string,
    fileExt?: string,
    prevFileSha256Hex?: string,
    fileExternalUri?: string,
    fileReceiverAddress?: string,
    signProgressCallback?: Function,
    signFinishedCallback?: Function,
    uploadProgressCallback?: Function,
    uploadFinishedCallback?: Function,
    delay_ms = 500,
    uploadMethod = 1): Promise<string>;

uploadFile is the method used to a upload file

Mandatory parameters:

• fundingUtxo is the utxo to fund the uploading transaction(s). It must have a value no less than calculated by calculateFileUploadCost
• fundingAddress is the address to which belongs the utxo
• fundingWif is the private key which unlocks the funding address in Wallet Import Format
• fileDataArrayBuffer is the data to be uploaded, which may be a NodeJS Buffer or a browser ArrayBuffer; see bottom for notes about ArrayBuffer usage

Optional parameters:

• fileName is the file name
• fileExt is the file extension
• prevFileSha256Hex is a reference to the previous file
• fileExternalUri is a URI for the file
• fileReceiverAddress is a recipient address for the last uploading transaction, to be used instead of fundingAddress
• signProgressCallback, signFinishedCallback, uploadProgressCallback, uploadFinishedCallback are callback functions for upload progress updates
• delay_ms is the delay between uploading consecutive transactions
• uploadMethod refers to the upload protocol: 1 for small data pushes and backwards compatibility, 2 for 0.6.0+ compatible more efficient data pushes intended for larger files

Returns the fileId, which contains a prefix (bitcoinfile:) and the TXID

async downloadFile(
    bfpUri: string,
    progressCallback?: Function): Promise<{
        passesHashCheck: boolean;
        fileBuf: Buffer;
}>;

downloadFile is the method used to download a file

• bfpUri may be the TXID of the metadata-containing transaction, or the TXID prepended with bitcoinfile: or bitcoinfiles:
• progressCallback is an optional download progress callback function

Returns an object with passesHashCheck which determines if downloading was sucessful and fileBuf which has the file contents; see bottom for notes about ArrayBuffer usage

static calculateFileUploadCost(
    fileSizeBytes: number,
    configMetadataOpReturn?: FileMetadata,
    fee_rate?: number,
    uploadMethod?: number): number;

Mandatory parameter: fileSizeBytes is the length of file contents in terms of octets

Optional parameters: configMetadataOpReturn is the metadata that would be uploaded with the file, passing this instead of null may yield a better estimate with a lower calculated cost fee_rate is the fee rate in satoshis per byte uploadMethod is the upload protocol; see uploadFile documentation for details

export interface FileMetadata {
    msgType: number;
    chunkCount: number;
    fileName?: string;
    fileExt?: string;
    fileSize: number;
    fileSha256Hex?: string;
    prevFileSha256Hex?: string;
    fileUri?: string;
    chunkData?: Buffer;
}

• msgType is a synonym of uploadMethod, which is described in uploadFile documentation
• chunkCount is a placeholder that can be set as 1
• chunkData is a placeholder that can be set as null

The other values can be set as described earlier

export interface utxo {
    txid: string;
    vout: number;
    satoshis: number;
}

The fields that should be set are shown above for an unspent output

Buffer: This may be a NodeJS buffer or an ArrayBuffer. For use in a browser, it is suggested that an ArrayBuffer of Uint8Array should be used.

For a variable fileContents of type Uint8Array, the ArrayBuffer can be accessed as fileContents.buffer. However, this might not always work, for example if .subarray(...) was applied to fileContents before .buffer. In this case, the approach here can be taken.