now-cli/lib/hash.js

// Native
const { createHash } = require('crypto')

// Packages
const { readFile } = require('fs-extra')

/**
  * Computes hashes for the contents of each file given.
  *
  * @param {Array} of {String} full paths
  * @return {Map}
  */

async function hashes(files) {
  const map = new Map()

  await Promise.all(
    files.map(async name => {
      const data = await readFile(name)

      const h = hash(data)
      const entry = map.get(h)
      if (entry) {
        entry.names.push(name)
      } else {
        map.set(hash(data), { names: [name], data })
      }
    })
  )
  return map
}

/**
 * Computes a hash for the given buf.
 *
 * @param {Buffer} file data
 * @return {String} hex digest
 */

function hash(buf) {
  return createHash('sha1').update(buf).digest('hex')
}

module.exports = hashes