Hjg.Pngcs.PngWriter.prepareEncodeRow C# (CSharp) Method

        private void prepareEncodeRow(int rown)
        {
            if (datStream == null)
                init();
            rowNum++;
            if (rown >= 0 && rowNum != rown)
                throw new PngjOutputException("rows must be written in order: expected:" + rowNum
                        + " passed:" + rown);
            // swap
            byte[] tmp = rowb;
            rowb = rowbprev;
            rowbprev = tmp;
        }