@electron/asar/lib/integrity.js

Creating Electron app packages

import crypto from 'node:crypto';
import stream from 'node:stream';
import streamPromises from 'node:stream/promises';
const ALGORITHM = 'SHA256';
// 4MB default block size
const BLOCK_SIZE = 4 * 1024 * 1024;
function hashBlock(block) {
    return crypto.createHash(ALGORITHM).update(block).digest('hex');
}
export async function getFileIntegrity(inputFileStream) {
    const fileHash = crypto.createHash(ALGORITHM);
    const blockHashes = [];
    let currentBlockSize = 0;
    let currentBlock = [];
    await streamPromises.pipeline(inputFileStream, new stream.PassThrough({
        decodeStrings: false,
        transform(_chunk, encoding, callback) {
            fileHash.update(_chunk);
            function handleChunk(chunk) {
                const diffToSlice = Math.min(BLOCK_SIZE - currentBlockSize, chunk.byteLength);
                currentBlockSize += diffToSlice;
                currentBlock.push(chunk.slice(0, diffToSlice));
                if (currentBlockSize === BLOCK_SIZE) {
                    blockHashes.push(hashBlock(Buffer.concat(currentBlock)));
                    currentBlock = [];
                    currentBlockSize = 0;
                }
                if (diffToSlice < chunk.byteLength) {
                    handleChunk(chunk.slice(diffToSlice));
                }
            }
            handleChunk(_chunk);
            callback();
        },
        flush(callback) {
            blockHashes.push(hashBlock(Buffer.concat(currentBlock)));
            currentBlock = [];
            callback();
        },
    }));
    return {
        algorithm: ALGORITHM,
        hash: fileHash.digest('hex'),
        blockSize: BLOCK_SIZE,
        blocks: blockHashes,
    };
}
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