sha1.painless

byte[] digest(byte[] x) {
  int[] blks = new int[(((x.length + 8) >> 6) + 1) * 16];
  int i;

  for(i = 0; i < x.length; i++) {
    blks[i >> 2] |= x[i] << (24 - (i % 4) * 8);
  }

  blks[i >> 2] |= 0x80 << (24 - (i % 4) * 8);
  blks[blks.length - 1] = x.length * 8;

  int[] w = new int[80];

  int a =  1732584193;
  int b = -271733879;
  int c = -1732584194;
  int d =  271733878;
  int e = -1009589776;

  for(i = 0; i < blks.length; i += 16) {
    int olda = a;
    int oldb = b;
    int oldc = c;
    int oldd = d;
    int olde = e;

    for(int j = 0; j < 80; j++) {
      w[j] = (j < 16) ? blks[i + j] :
             ( rol(w[j-3] ^ w[j-8] ^ w[j-14] ^ w[j-16], 1) );

      int t = rol(a, 5) + e + w[j] +
         ( (j < 20) ?  1518500249 + ((b & c) | ((~b) & d))
         : (j < 40) ?  1859775393 + (b ^ c ^ d)
         : (j < 60) ? -1894007588 + ((b & c) | (b & d) | (c & d))
         : -899497514 + (b ^ c ^ d) );
      e = d;
      d = c;
      c = rol(b, 30);
      b = a;
      a = t;
    }

    a = a + olda;
    b = b + oldb;
    c = c + oldc;
    d = d + oldd;
    e = e + olde;
  }

  byte[] hash = new byte[20];
  System.arraycopy(intToBytes(a), 0, hash, 0, 4);
  System.arraycopy(intToBytes(b), 0, hash, 4, 4);
  System.arraycopy(intToBytes(c), 0, hash, 8, 4);
  System.arraycopy(intToBytes(d), 0, hash, 12, 4);
  System.arraycopy(intToBytes(e), 0, hash, 16, 4);
  return hash;
}

int rol(int num, int cnt) {
  return (num << cnt) | (num >>> (32 - cnt));
}

byte[] intToBytes(int i) {
  byte[] b = new byte[4];
  for (int c = 0; c < 4; c++) {
    b[c] = (byte) ((i >>> (56 - 8 * c)) & 255);
  }
  return b;
}

String bytesToHex(byte[] bytes) {
  char[] hexArray = "0123456789abcdef".toCharArray();
  char[] hexChars = new char[bytes.length * 2];
  for ( int j = 0; j < bytes.length; j++ ) {
    int v = bytes[j] & 255;
    hexChars[j * 2] = hexArray[v >>> 4];
    hexChars[j * 2 + 1] = hexArray[v & 15];
  }
  return String.copyValueOf(hexChars);
}

byte[] charArrayToByteArray(char[] charArray) {
  byte[] byteArray = new byte[charArray.length];
  for(int i= 0; i < charArray.length; i++) {
    byteArray[i] = (byte)(255 & (int)charArray[i]);
  }
  return byteArray;
}

// Main
byte[] data = charArrayToByteArray(doc['field.value.keyword'].value.toCharArray());
byte[] res = digest(data);
return bytesToHex(res);