code: void readCheckpointDelta(TableKelp table,
                             PageServiceImpl pageActor,
                             ReadStream is,
                             int length)
      throws IOException
    {
      Row row = table.row();
      
      // int keyLength = row.getKeyLength();
      int removeLength = row.removeLength();
      int rowLength = row.length();
      
      BlockLeaf block = _blocks[0];
  
      long endPosition = is.position() + length;
      int rowHead = block.rowHead();
      int blobTail = block.getBlobTail();
      long pos;
  
      while ((pos = is.position()) < endPosition) {
        int code = is.read();
        is.unread();
        
        code = code & CODE_MASK;
        
        if (code == REMOVE) {
          rowHead -= removeLength;
          
          if (rowHead < blobTail) {
            block = extendBlocks();
  
            rowHead = BLOCK_SIZE - removeLength;
            blobTail = 0;
          }
          
          is.readAll(block.getBuffer(), rowHead, removeLength);
        }
        else if (code == INSERT) {
          rowHead -= rowLength;
        
          while ((blobTail = row.readCheckpoint(is, block.getBuffer(), 
                                                rowHead, blobTail)) < 0) {
            //is.setPosition(pos + 1);
            is.position(pos);
  
            block = extendBlocks();
  
            rowHead = BLOCK_SIZE - rowLength;
            blobTail = 0;
          }
        
          // byte []buffer = block.getBuffer();
          // buffer[rowHead] = (byte) ((buffer[rowHead] & ~CODE_MASK) | INSERT);
        }
        else {
          throw new IllegalStateException(L.l("{0} Corrupted checkpoint at pos={1} with code {2}",
                                              this, pos, code));
        }
        
        block.rowHead(rowHead);
        block.setBlobTail(blobTail);
      }
  
      clearDirty();
      
      validate(table);
    }
docs: Reads a delta entry from the checkpoint.