docs: private long split_block(long block_addr, int request_size, int rem)
      throws IOException
      {
          allocated_words += request_size;
          allocated_blocks++;
          free_words -= request_size;
          ml_hits++;
          ml_splits++;
          seek_and_count(block_addr + request_size);
          writeInt(rem);
          seek_and_count(block_addr);
          writeInt(- request_size);
          return(block_addr + HDR_SIZE);
      }