content: /*
   * Copyright 2002-2019 Drew Noakes and contributors
   *
   *    Licensed under the Apache License, Version 2.0 (the "License");
   *    you may not use this file except in compliance with the License.
   *    You may obtain a copy of the License at
   *
   *        https://www.apache.org/licenses/LICENSE-2.0
   *
   *    Unless required by applicable law or agreed to in writing, software
   *    distributed under the License is distributed on an "AS IS" BASIS,
   *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *    See the License for the specific language governing permissions and
   *    limitations under the License.
   *
   * More information about this project is available at:
   *
   *    https://drewnoakes.com/code/exif/
   *    https://github.com/drewnoakes/metadata-extractor
   */
  package com.drew.metadata.exif;
  
  import com.drew.imaging.jpeg.JpegSegmentMetadataReader;
  import com.drew.imaging.jpeg.JpegSegmentType;
  import com.drew.imaging.tiff.TiffProcessingException;
  import com.drew.imaging.tiff.TiffReader;
  import com.drew.lang.ByteArrayReader;
  import com.drew.lang.RandomAccessReader;
  import com.drew.lang.annotations.NotNull;
  import com.drew.lang.annotations.Nullable;
  import com.drew.metadata.Directory;
  import com.drew.metadata.Metadata;
  
  import java.io.IOException;
  import java.util.Collections;
  
  /**
   * Decodes Exif binary data, populating a {@link Metadata} object with tag values in {@link ExifSubIFDDirectory},
   * {@link ExifThumbnailDirectory}, {@link ExifInteropDirectory}, {@link GpsDirectory} and one of the many camera
   * makernote directories.
   *
   * @author Drew Noakes https://drewnoakes.com
   */
  @SuppressWarnings("WeakerAccess")
  public class ExifReader implements JpegSegmentMetadataReader
  {
      /** Exif data stored in JPEG files' APP1 segment are preceded by this six character preamble "Exif\0\0". */
      public static final String JPEG_SEGMENT_PREAMBLE = "Exif\0\0";
  
      @NotNull
      public Iterable<JpegSegmentType> getSegmentTypes()
      {
          return Collections.singletonList(JpegSegmentType.APP1);
      }
  
      public void readJpegSegments(@NotNull final Iterable<byte[]> segments, @NotNull final Metadata metadata, @NotNull final JpegSegmentType segmentType)
      {
          assert(segmentType == JpegSegmentType.APP1);
  
          for (byte[] segmentBytes : segments) {
              // Segment must have the expected preamble
              if (startsWithJpegExifPreamble(segmentBytes)) {
                  extract(new ByteArrayReader(segmentBytes), metadata, JPEG_SEGMENT_PREAMBLE.length());
              }
          }
      }
  
      /** Indicates whether 'bytes' starts with 'JpegSegmentPreamble'. */
      public static boolean startsWithJpegExifPreamble(byte[] bytes)
      {
          return bytes.length >= JPEG_SEGMENT_PREAMBLE.length() &&
              new String(bytes, 0, JPEG_SEGMENT_PREAMBLE.length()).equals(JPEG_SEGMENT_PREAMBLE);
      }
  
      /** Reads TIFF formatted Exif data from start of the specified {@link RandomAccessReader}. */
      public void extract(@NotNull final RandomAccessReader reader, @NotNull final Metadata metadata)
      {
          extract(reader, metadata, 0);
      }
  
      /** Reads TIFF formatted Exif data a specified offset within a {@link RandomAccessReader}. */
      public void extract(@NotNull final RandomAccessReader reader, @NotNull final Metadata metadata, int readerOffset)
      {
          extract(reader, metadata, readerOffset, null);
      }
  
      /** Reads TIFF formatted Exif data at a specified offset within a {@link RandomAccessReader}. */
      public void extract(@NotNull final RandomAccessReader reader, @NotNull final Metadata metadata, int readerOffset, @Nullable Directory parentDirectory)
      {
          ExifTiffHandler exifTiffHandler = new ExifTiffHandler(metadata, parentDirectory, readerOffset);
  
          try {
              // Read the TIFF-formatted Exif data
              new TiffReader().processTiff(
                  reader,
                  exifTiffHandler,
                  readerOffset
              );
          } catch (TiffProcessingException e) {
              exifTiffHandler.error("Exception processing TIFF data: " + e.getMessage());
          } catch (IOException e) {
              exifTiffHandler.error("Exception processing TIFF data: " + e.getMessage());
          }
      }
  }
  