SHA256.scala

object SHA256 {
  val k: Seq[Int] = Seq(
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2)
  val h0: Seq[Int] = Seq(
    0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19)

  def rotr(x: Int, n: Int): Int = (x >>> n) | (x << (32 - n))
  def ch(x: Int, y: Int, z: Int): Int = (x & y) ^ (~x & z)
  def maj(x: Int, y: Int, z: Int): Int = (x & y) ^ (x & z) ^ (y & z)
  def Sigma0(x: Int): Int = rotr(x, 2) ^ rotr(x, 13) ^ rotr(x, 22)
  def Sigma1(x: Int): Int = rotr(x, 6) ^ rotr(x, 11) ^ rotr(x, 25)
  def sigma0(x: Int): Int = rotr(x, 7) ^ rotr(x, 18) ^ (x >>> 3)
  def sigma1(x: Int): Int = rotr(x, 17) ^ rotr(x, 19) ^ (x >>> 10)

  def main(args: Array[String]): Unit = {
    val bytes = "abc".getBytes("UTF-8")

    val l = (7 to 0 by -1).map(i => ((bytes.size.toLong * 8) >>> (i * 8)).toByte)
    val z = Seq.fill(64 - (bytes.length + 9) % 64)(0x00.toByte)
    val m = ((bytes :+ 0x80.toByte) ++ z ++ l)
      .grouped(4)
      .map(_.foldLeft(0)((a, b) => (a << 8) | (b & 0xff)))
      .grouped(16)

    val md = m.foldLeft(h0) { (hi, mi) =>
      val w = (16 to 63).foldLeft(mi) { (xs, t) =>
        xs :+ (sigma1(xs(t-2)) + xs(t-7) + sigma0(xs(t-15)) + xs(t-16))
      }

      val xs = (k, w).zipped.map(_ + _).foldLeft(hi) { (tmp, kw) =>
        val Seq(a, b, c, d, e, f, g, h) = tmp
        val t1 = h + Sigma1(e) + ch(e, f, g) + kw
        val t2 = Sigma0(a) + maj(a, b, c)
        Seq(t1 + t2, a, b, c, d + t1, e, f, g)
      }

      (hi, xs).zipped.map(_ + _)
    }

    println(md.map(x => f"$x%08x").mkString)
  }
}