index.js

const crypto = require('crypto')
const fs = require('fs')

const BUFFER_SIZE = 8192

function md5FileSync (path) {
  const fd = fs.openSync(path, 'r')
  const hash = crypto.createHash('md5')
  const buffer = Buffer.alloc(BUFFER_SIZE)

  try {
    let bytesRead

    do {
      bytesRead = fs.readSync(fd, buffer, 0, BUFFER_SIZE)
      hash.update(buffer.slice(0, bytesRead))
    } while (bytesRead === BUFFER_SIZE)
  } finally {
    fs.closeSync(fd)
  }

  return hash.digest('hex')
}

function md5File (path) {
  return new Promise((resolve, reject) => {
    const output = crypto.createHash('md5')
    const input = fs.createReadStream(path)

    input.on('error', (err) => {
      reject(err)
    })

    output.once('readable', () => {
      resolve(output.read().toString('hex'))
    })

    input.pipe(output)
  })
}

module.exports = md5File
module.exports.sync = md5FileSync