a -= (block[k%block.length]&0xff) + char_offset; b -= l * ((block[k%block.length]&0xff) + char_offset);
a -= block[k % block.length] + char_offset; b -= l * (block[k % block.length] + char_offset);
   public void trim() {      a -= (block[k%block.length]&0xff) + char_offset;      b -= l * ((block[k%block.length]&0xff) + char_offset);      k++;      l--;   }