code: function copy_block(buf, // the input data
  		len, // its length
  		header // true if block header must be written
  		) {
  			bi_windup(); // align on byte boundary
  			last_eob_len = 8; // enough lookahead for inflate
  
  			if (header) {
  				put_short(len);
  				put_short(~len);
  			}
  
  			that.pending_buf.set(window.subarray(buf, buf + len), that.pending);
  			that.pending += len;
  		}
docs: Copy a stored block, storing first the length and its one's complement if requested.