public DataPage readPage()

in common/src/main/java/org/apache/comet/parquet/ColumnPageReader.java [110:223]
108 lines of code
15 McCabe index (conditional complexity)

  public DataPage readPage() {
    final DataPage compressedPage = compressedPages.poll();
    if (compressedPage == null) {
      return null;
    }
    final int currentPageIndex = pageIndex++;

    if (null != blockDecryptor) {
      AesCipher.quickUpdatePageAAD(dataPageAAD, getPageOrdinal(currentPageIndex));
    }

    return compressedPage.accept(
        new DataPage.Visitor<DataPage>() {
          @Override
          public DataPage visit(DataPageV1 dataPageV1) {
            try {
              BytesInput bytes = dataPageV1.getBytes();
              if (null != blockDecryptor) {
                bytes = BytesInput.from(blockDecryptor.decrypt(bytes.toByteArray(), dataPageAAD));
              }
              BytesInput decompressed =
                  decompressor.decompress(bytes, dataPageV1.getUncompressedSize());

              final DataPageV1 decompressedPage;
              if (offsetIndex == null) {
                decompressedPage =
                    new DataPageV1(
                        decompressed,
                        dataPageV1.getValueCount(),
                        dataPageV1.getUncompressedSize(),
                        dataPageV1.getStatistics(),
                        dataPageV1.getRlEncoding(),
                        dataPageV1.getDlEncoding(),
                        dataPageV1.getValueEncoding());
              } else {
                long firstRowIndex = offsetIndex.getFirstRowIndex(currentPageIndex);
                decompressedPage =
                    new DataPageV1(
                        decompressed,
                        dataPageV1.getValueCount(),
                        dataPageV1.getUncompressedSize(),
                        firstRowIndex,
                        Math.toIntExact(
                            offsetIndex.getLastRowIndex(currentPageIndex, rowCount)
                                - firstRowIndex
                                + 1),
                        dataPageV1.getStatistics(),
                        dataPageV1.getRlEncoding(),
                        dataPageV1.getDlEncoding(),
                        dataPageV1.getValueEncoding());
              }
              if (dataPageV1.getCrc().isPresent()) {
                decompressedPage.setCrc(dataPageV1.getCrc().getAsInt());
              }
              return decompressedPage;
            } catch (IOException e) {
              throw new ParquetDecodingException("could not decompress page", e);
            }
          }

          @Override
          public DataPage visit(DataPageV2 dataPageV2) {
            if (!dataPageV2.isCompressed() && offsetIndex == null && null == blockDecryptor) {
              return dataPageV2;
            }
            BytesInput pageBytes = dataPageV2.getData();

            if (null != blockDecryptor) {
              try {
                pageBytes =
                    BytesInput.from(blockDecryptor.decrypt(pageBytes.toByteArray(), dataPageAAD));
              } catch (IOException e) {
                throw new ParquetDecodingException(
                    "could not convert page ByteInput to byte array", e);
              }
            }
            if (dataPageV2.isCompressed()) {
              int uncompressedSize =
                  Math.toIntExact(
                      dataPageV2.getUncompressedSize()
                          - dataPageV2.getDefinitionLevels().size()
                          - dataPageV2.getRepetitionLevels().size());
              try {
                pageBytes = decompressor.decompress(pageBytes, uncompressedSize);
              } catch (IOException e) {
                throw new ParquetDecodingException("could not decompress page", e);
              }
            }

            if (offsetIndex == null) {
              return DataPageV2.uncompressed(
                  dataPageV2.getRowCount(),
                  dataPageV2.getNullCount(),
                  dataPageV2.getValueCount(),
                  dataPageV2.getRepetitionLevels(),
                  dataPageV2.getDefinitionLevels(),
                  dataPageV2.getDataEncoding(),
                  pageBytes,
                  dataPageV2.getStatistics());
            } else {
              return DataPageV2.uncompressed(
                  dataPageV2.getRowCount(),
                  dataPageV2.getNullCount(),
                  dataPageV2.getValueCount(),
                  offsetIndex.getFirstRowIndex(currentPageIndex),
                  dataPageV2.getRepetitionLevels(),
                  dataPageV2.getDefinitionLevels(),
                  dataPageV2.getDataEncoding(),
                  pageBytes,
                  dataPageV2.getStatistics());
            }
          }
        });
  }