Function md5

src/Encoder/Hash/md5.js:32–104

(bytes)

 * @return {Uint8Array} Md5 message digest
 */
export default function md5 (bytes) {
  // make array mutable
  bytes = Array.from(bytes)

  // track number of bytes before preprocessing
  const b = bytes.length

  // RFC 1321 3.1: Step 1. Append Padding Bits

  // append a single "1" bit to the message
  // it's okay to add a whole byte, because it gets padded anyway
  bytes.push(0b10000000)

  // "0" bits are appended so that the length in bits of the padded message
  // becomes congruent to 448 (56 bytes), modulo 512 (64 bytes)
  while (bytes.length % 64 !== 56) {
    bytes.push(0x00)
  }

  // RFC 1321 3.2 Step 2. Append Length

  // append the low-order 64 bits of b modulo 2^64 to bytes
  // these bits are appended as two 32-bit words, appended low-order word first
  let shift
  for (let i = 0; i < 8; i++) {
    if (i === 0) {
      // multiply bytes by 8 (left shift by 3 bits)
      bytes.push((b & 0b11111) << 3)
    } else {
      // limit right shift to 31 bits
      shift = i * 8 - 3
      bytes.push(shift < 32 ? (b >> shift) & 0xff : 0)
    }
  }

  // let m denote the words of the resulting message
  const n = bytes.length / 4
  const m = new Array(n)

  for (let i = 0; i < n; i++) {
    // each consecutive group of four bytes is interpreted as a word with the
    // low-order (least significant) byte given first
    m[i] =
      (bytes[i * 4 + 3] << 24) +
      (bytes[i * 4 + 2] << 16) +
      (bytes[i * 4 + 1] << 8) +
      bytes[i * 4]
  }

  // RFC 1321 3.3: Step 3. Initialize MD Buffer

  // load magic initialization constants A, B, C & D
  const context = [IA, IB, IC, ID]

  // RFC 1321 3.4 Step 4. Process Message in 16-Word Blocks
  for (let i = 0; i < n; i += 16) {
    md5Transform(context, m.slice(i, i + 16))
  }