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const crypto = require('crypto')
const fs = require('fs')
const stream = require('stream')
const { promisify } = require('util')
const ALGORITHM = 'SHA256'
// 4MB default block size
const BLOCK_SIZE = 4 * 1024 * 1024
const pipeline = promisify(stream.pipeline)
function hashBlock (block) {
return crypto.createHash(ALGORITHM).update(block).digest('hex')
}
async function getFileIntegrity (path) {
const fileHash = crypto.createHash(ALGORITHM)
const blocks = []
let currentBlockSize = 0
let currentBlock = []
await pipeline(
fs.createReadStream(path),
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) {
blocks.push(hashBlock(Buffer.concat(currentBlock)))
currentBlock = []
currentBlockSize = 0
}
if (diffToSlice < chunk.byteLength) {
handleChunk(chunk.slice(diffToSlice))
}
}
handleChunk(_chunk)
callback()
},
flush (callback) {
blocks.push(hashBlock(Buffer.concat(currentBlock)))
currentBlock = []
callback()
}
})
)
return {
algorithm: ALGORITHM,
hash: fileHash.digest('hex'),
blockSize: BLOCK_SIZE,
blocks: blocks
}
}
module.exports = getFileIntegrity
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