function calculateSHA512()

in src/core/calculate_sha_other.js [241:394]
142 lines of code
11 McCabe index (conditional complexity)

function calculateSHA512(data, offset, length, mode384 = false) {
  // initial hash values
  let h0, h1, h2, h3, h4, h5, h6, h7;
  if (!mode384) {
    h0 = new Word64(0x6a09e667, 0xf3bcc908);
    h1 = new Word64(0xbb67ae85, 0x84caa73b);
    h2 = new Word64(0x3c6ef372, 0xfe94f82b);
    h3 = new Word64(0xa54ff53a, 0x5f1d36f1);
    h4 = new Word64(0x510e527f, 0xade682d1);
    h5 = new Word64(0x9b05688c, 0x2b3e6c1f);
    h6 = new Word64(0x1f83d9ab, 0xfb41bd6b);
    h7 = new Word64(0x5be0cd19, 0x137e2179);
  } else {
    // SHA384 is exactly the same
    // except with different starting values and a trimmed result
    h0 = new Word64(0xcbbb9d5d, 0xc1059ed8);
    h1 = new Word64(0x629a292a, 0x367cd507);
    h2 = new Word64(0x9159015a, 0x3070dd17);
    h3 = new Word64(0x152fecd8, 0xf70e5939);
    h4 = new Word64(0x67332667, 0xffc00b31);
    h5 = new Word64(0x8eb44a87, 0x68581511);
    h6 = new Word64(0xdb0c2e0d, 0x64f98fa7);
    h7 = new Word64(0x47b5481d, 0xbefa4fa4);
  }

  // pre-processing
  const paddedLength = Math.ceil((length + 17) / 128) * 128;
  const padded = new Uint8Array(paddedLength);
  let i, j;
  for (i = 0; i < length; ++i) {
    padded[i] = data[offset++];
  }
  padded[i++] = 0x80;
  const n = paddedLength - 16;
  if (i < n) {
    i = n;
  }
  i += 11;
  padded[i++] = (length >>> 29) & 0xff;
  padded[i++] = (length >> 21) & 0xff;
  padded[i++] = (length >> 13) & 0xff;
  padded[i++] = (length >> 5) & 0xff;
  padded[i++] = (length << 3) & 0xff;

  const w = new Array(80);
  for (i = 0; i < 80; i++) {
    w[i] = new Word64(0, 0);
  }
  const { k } = PARAMS;

  let a = new Word64(0, 0),
    b = new Word64(0, 0),
    c = new Word64(0, 0);
  let d = new Word64(0, 0),
    e = new Word64(0, 0),
    f = new Word64(0, 0);
  let g = new Word64(0, 0),
    h = new Word64(0, 0);
  const t1 = new Word64(0, 0),
    t2 = new Word64(0, 0);
  const tmp1 = new Word64(0, 0),
    tmp2 = new Word64(0, 0);
  let tmp3;

  // for each 1024 bit block
  for (i = 0; i < paddedLength; ) {
    for (j = 0; j < 16; ++j) {
      w[j].high =
        (padded[i] << 24) |
        (padded[i + 1] << 16) |
        (padded[i + 2] << 8) |
        padded[i + 3];
      w[j].low =
        (padded[i + 4] << 24) |
        (padded[i + 5] << 16) |
        (padded[i + 6] << 8) |
        padded[i + 7];
      i += 8;
    }
    for (j = 16; j < 80; ++j) {
      tmp3 = w[j];
      littleSigmaPrime(tmp3, w[j - 2], tmp2);
      tmp3.add(w[j - 7]);
      littleSigma(tmp1, w[j - 15], tmp2);
      tmp3.add(tmp1);
      tmp3.add(w[j - 16]);
    }

    a.assign(h0);
    b.assign(h1);
    c.assign(h2);
    d.assign(h3);
    e.assign(h4);
    f.assign(h5);
    g.assign(h6);
    h.assign(h7);
    for (j = 0; j < 80; ++j) {
      t1.assign(h);
      sigmaPrime(tmp1, e, tmp2);
      t1.add(tmp1);
      ch(tmp1, e, f, g, tmp2);
      t1.add(tmp1);
      t1.add(k[j]);
      t1.add(w[j]);

      sigma(t2, a, tmp2);
      maj(tmp1, a, b, c, tmp2);
      t2.add(tmp1);

      tmp3 = h;
      h = g;
      g = f;
      f = e;
      d.add(t1);
      e = d;
      d = c;
      c = b;
      b = a;
      tmp3.assign(t1);
      tmp3.add(t2);
      a = tmp3;
    }
    h0.add(a);
    h1.add(b);
    h2.add(c);
    h3.add(d);
    h4.add(e);
    h5.add(f);
    h6.add(g);
    h7.add(h);
  }

  let result;
  if (!mode384) {
    result = new Uint8Array(64);
    h0.copyTo(result, 0);
    h1.copyTo(result, 8);
    h2.copyTo(result, 16);
    h3.copyTo(result, 24);
    h4.copyTo(result, 32);
    h5.copyTo(result, 40);
    h6.copyTo(result, 48);
    h7.copyTo(result, 56);
  } else {
    result = new Uint8Array(48);
    h0.copyTo(result, 0);
    h1.copyTo(result, 8);
    h2.copyTo(result, 16);
    h3.copyTo(result, 24);
    h4.copyTo(result, 32);
    h5.copyTo(result, 40);
  }
  return result;
}