void ClearNoncleanCardWrapper::do_MemRegion(MemRegion mr) {

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

      assert(mr.word_size() > 0, "Error");
      assert(_ct->is_aligned(mr.start()), "mr.start() should be card aligned");

  {- -------------------------------------------
  (1) (変数宣言など)
      ---------------------------------------- -}

      // mr.end() may not necessarily be card aligned.
      jbyte* cur_entry = _ct->byte_for(mr.last());
      const jbyte* limit = _ct->byte_for(mr.start());
      HeapWord* end_of_non_clean = mr.end();
      HeapWord* start_of_non_clean = end_of_non_clean;

  {- -------------------------------------------
  (1) 以下のループで引数で指定されたメモリ範囲を調べ, 
      dirty が連続する箇所を全て見つけだす.

      見つかった範囲については, (その範囲を表す MemRegion オブジェクトを引数として) 
      DirtyCardToOopClosure::do_MemRegion() を呼び出して処理を行う.
      ---------------------------------------- -}

      while (cur_entry >= limit) {
        HeapWord* cur_hw = _ct->addr_for(cur_entry);
        if ((*cur_entry != CardTableRS::clean_card_val()) && clear_card(cur_entry)) {
          // Continue the dirty range by opening the
          // dirty window one card to the left.
          start_of_non_clean = cur_hw;
        } else {
          // We hit a "clean" card; process any non-empty
          // "dirty" range accumulated so far.
          if (start_of_non_clean < end_of_non_clean) {
            const MemRegion mrd(start_of_non_clean, end_of_non_clean);
            _dirty_card_closure->do_MemRegion(mrd);
          }
          // Reset the dirty window, while continuing to look
          // for the next dirty card that will start a
          // new dirty window.
          end_of_non_clean = cur_hw;
          start_of_non_clean = cur_hw;
        }
        // Note that "cur_entry" leads "start_of_non_clean" in
        // its leftward excursion after this point
        // in the loop and, when we hit the left end of "mr",
        // will point off of the left end of the card-table
        // for "mr".
        cur_entry--;
      }

  {- -------------------------------------------
  (1) もし未処理な dirty range が残っていれば, その範囲も処理しておく.
      ---------------------------------------- -}

      // If the first card of "mr" was dirty, we will have
      // been left with a dirty window, co-initial with "mr",
      // which we now process.
      if (start_of_non_clean < end_of_non_clean) {
        const MemRegion mrd(start_of_non_clean, end_of_non_clean);
        _dirty_card_closure->do_MemRegion(mrd);
      }
    }