///|
// FIPS 180-4 sections 4.2.3, 5.1.2, 5.3.5 and 6.4.2.
fn Vm::sha512(self : Vm, s : String, loc : Location) -> String raise {
  let input = @utf8.encode(s)
  let blocks = input.length() / 128 +
    (if input.length() % 128 < 112 { 1 } else { 2 })
  let total = blocks.to_int64() * 128L
  let state : Array[UInt64] = [
    0x6a09e667f3bcc908, 0xbb67ae8584caa73b, 0x3c6ef372fe94f82b, 0xa54ff53a5f1d36f1,
    0x510e527fade682d1, 0x9b05688c2b3e6c1f, 0x1f83d9abfb41bd6b, 0x5be0cd19137e2179,
  ]
  let constants : Array[UInt64] = [
    0x428a2f98d728ae22, 0x7137449123ef65cd, 0xb5c0fbcfec4d3b2f, 0xe9b5dba58189dbbc,
    0x3956c25bf348b538, 0x59f111f1b605d019, 0x923f82a4af194f9b, 0xab1c5ed5da6d8118,
    0xd807aa98a3030242, 0x12835b0145706fbe, 0x243185be4ee4b28c, 0x550c7dc3d5ffb4e2,
    0x72be5d74f27b896f, 0x80deb1fe3b1696b1, 0x9bdc06a725c71235, 0xc19bf174cf692694,
    0xe49b69c19ef14ad2, 0xefbe4786384f25e3, 0x0fc19dc68b8cd5b5, 0x240ca1cc77ac9c65,
    0x2de92c6f592b0275, 0x4a7484aa6ea6e483, 0x5cb0a9dcbd41fbd4, 0x76f988da831153b5,
    0x983e5152ee66dfab, 0xa831c66d2db43210, 0xb00327c898fb213f, 0xbf597fc7beef0ee4,
    0xc6e00bf33da88fc2, 0xd5a79147930aa725, 0x06ca6351e003826f, 0x142929670a0e6e70,
    0x27b70a8546d22ffc, 0x2e1b21385c26c926, 0x4d2c6dfc5ac42aed, 0x53380d139d95b3df,
    0x650a73548baf63de, 0x766a0abb3c77b2a8, 0x81c2c92e47edaee6, 0x92722c851482353b,
    0xa2bfe8a14cf10364, 0xa81a664bbc423001, 0xc24b8b70d0f89791, 0xc76c51a30654be30,
    0xd192e819d6ef5218, 0xd69906245565a910, 0xf40e35855771202a, 0x106aa07032bbd1b8,
    0x19a4c116b8d2d0c8, 0x1e376c085141ab53, 0x2748774cdf8eeb99, 0x34b0bcb5e19b48a8,
    0x391c0cb3c5c95a63, 0x4ed8aa4ae3418acb, 0x5b9cca4f7763e373, 0x682e6ff3d6b2b8a3,
    0x748f82ee5defb2fc, 0x78a5636f43172f60, 0x84c87814a1f0ab72, 0x8cc702081a6439ec,
    0x90befffa23631e28, 0xa4506cebde82bde9, 0xbef9a3f7b2c67915, 0xc67178f2e372532b,
    0xca273eceea26619c, 0xd186b8c721c0c207, 0xeada7dd6cde0eb1e, 0xf57d4f7fee6ed178,
    0x06f067aa72176fba, 0x0a637dc5a2c898a6, 0x113f9804bef90dae, 0x1b710b35131c471b,
    0x28db77f523047d84, 0x32caab7b40c72493, 0x3c9ebe0a15c9bebc, 0x431d67c49c100d4c,
    0x4cc5d4becb3e42b6, 0x597f299cfc657e2a, 0x5fcb6fab3ad6faec, 0x6c44198c4a475817,
  ]
  let words = Array::make(80, 0UL)
  for block in 0..> 7)
      let b = digest_rotl64(y, 45) ^ digest_rotl64(y, 3) ^ (y >> 6)
      words[i] = words[i - 16] + a + words[i - 7] + b
    }
    let mut a = state[0]
    let mut b = state[1]
    let mut c = state[2]
    let mut d = state[3]
    let mut e = state[4]
    let mut f = state[5]
    let mut g = state[6]
    let mut h = state[7]
    for i in 0..<80 {
      self.tick(loc)
      let upper = digest_rotl64(e, 50) ^
        digest_rotl64(e, 46) ^
        digest_rotl64(e, 23)
      let t1 = h + upper + ((e & f) ^ (e.lnot() & g)) + constants[i] + words[i]
      let lower = digest_rotl64(a, 36) ^
        digest_rotl64(a, 30) ^
        digest_rotl64(a, 25)
      let t2 = lower + ((a & b) ^ (a & c) ^ (b & c))
      h = g
      g = f
      f = e
      e = d + t1
      d = c
      c = b
      b = a
      a = t1 + t2
    }
    for i, word in [a, b, c, d, e, f, g, h] {
      state[i] += word
    }
  }
  digest_hex(state, 8, false)
}