public DataPage readPage()

in parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ColumnChunkPageReadStore.java [122:284]
149 lines of code
26 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();
            BytesInput decompressed;

            if (options.getAllocator().isDirect() && options.useOffHeapDecryptBuffer()) {
              ByteBuffer byteBuffer = bytes.toByteBuffer();
              if (!byteBuffer.isDirect()) {
                throw new ParquetDecodingException("Expected a direct buffer");
              }
              if (blockDecryptor != null) {
                byteBuffer = blockDecryptor.decrypt(byteBuffer, dataPageAAD);
              }
              long compressedSize = byteBuffer.limit();

              ByteBuffer decompressedBuffer =
                  options.getAllocator().allocate(dataPageV1.getUncompressedSize());
              decompressor.decompress(byteBuffer, (int) compressedSize, decompressedBuffer,
                  dataPageV1.getUncompressedSize());

              // HACKY: sometimes we need to do `flip` because the position of output bytebuffer is
              // not reset.
              if (decompressedBuffer.position() != 0) {
                decompressedBuffer.flip();
              }
              decompressed = BytesInput.from(decompressedBuffer);
            } else { // use on-heap buffer
              if (null != blockDecryptor) {
                bytes = BytesInput.from(blockDecryptor.decrypt(bytes.toByteArray(), dataPageAAD));
              }
              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();
          try {
            BytesInput decompressed;
            long compressedSize;

            if (options.getAllocator().isDirect() && options.useOffHeapDecryptBuffer()) {
              ByteBuffer byteBuffer = pageBytes.toByteBuffer();
              if (!byteBuffer.isDirect()) {
                throw new ParquetDecodingException("Expected a direct buffer");
              }
              if (blockDecryptor != null) {
                byteBuffer = blockDecryptor.decrypt(byteBuffer, dataPageAAD);
              }
              compressedSize = byteBuffer.limit();
              if (dataPageV2.isCompressed()) {
                int uncompressedSize = Math.toIntExact(
                    dataPageV2.getUncompressedSize()
                        - dataPageV2.getDefinitionLevels().size()
                        - dataPageV2.getRepetitionLevels().size());
                ByteBuffer decompressedBuffer =
                    options.getAllocator().allocate(uncompressedSize);
                decompressor.decompress(byteBuffer, (int) compressedSize, decompressedBuffer,
                    uncompressedSize);

                // HACKY: sometimes we need to do `flip` because the position of output bytebuffer is
                // not reset.
                if (decompressedBuffer.position() != 0) {
                  decompressedBuffer.flip();
                }
                pageBytes = BytesInput.from(decompressedBuffer);
              } else {
                pageBytes = BytesInput.from(byteBuffer);
              }
            } else {
              if (null != blockDecryptor) {
                pageBytes = BytesInput.from(
                    blockDecryptor.decrypt(pageBytes.toByteArray(), dataPageAAD));
              }
              if (dataPageV2.isCompressed()) {
                int uncompressedSize = Math.toIntExact(
                    dataPageV2.getUncompressedSize()
                        - dataPageV2.getDefinitionLevels().size()
                        - dataPageV2.getRepetitionLevels().size());
                pageBytes = decompressor.decompress(pageBytes, uncompressedSize);
              }
            }
          } catch (IOException e) {
            throw new ParquetDecodingException("could not decompress page", e);
          }

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