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.photoshop;
  
  import com.drew.imaging.jpeg.JpegSegmentMetadataReader;
  import com.drew.imaging.jpeg.JpegSegmentType;
  import com.drew.lang.Charsets;
  import com.drew.lang.SequentialByteArrayReader;
  import com.drew.lang.SequentialReader;
  import com.drew.lang.annotations.NotNull;
  import com.drew.metadata.Metadata;
  
  import java.io.IOException;
  import java.util.Collections;
  
  /**
   * Reads Photoshop "ducky" segments, created during Save-for-Web.
   *
   * @author Drew Noakes https://drewnoakes.com
   */
  @SuppressWarnings("WeakerAccess")
  public class DuckyReader implements JpegSegmentMetadataReader
  {
      @NotNull
      private static final String JPEG_SEGMENT_PREAMBLE = "Ducky";
  
      @NotNull
      public Iterable<JpegSegmentType> getSegmentTypes()
      {
          return Collections.singletonList(JpegSegmentType.APPC);
      }
  
      public void readJpegSegments(@NotNull Iterable<byte[]> segments, @NotNull Metadata metadata, @NotNull JpegSegmentType segmentType)
      {
          final int preambleLength = JPEG_SEGMENT_PREAMBLE.length();
  
          for (byte[] segmentBytes : segments) {
              // Ensure data starts with the necessary preamble
              if (segmentBytes.length < preambleLength || !JPEG_SEGMENT_PREAMBLE.equals(new String(segmentBytes, 0, preambleLength)))
                  continue;
  
              extract(
                  new SequentialByteArrayReader(segmentBytes, preambleLength),
                  metadata);
          }
      }
  
      public void extract(@NotNull final SequentialReader reader, @NotNull final Metadata metadata)
      {
          DuckyDirectory directory = new DuckyDirectory();
          metadata.addDirectory(directory);
  
          try
          {
              while (true)
              {
                  int tag = reader.getUInt16();
  
                  // End of Segment is marked with zero
                  if (tag == 0)
                      break;
  
                  int length = reader.getUInt16();
  
                  switch (tag)
                  {
                      case DuckyDirectory.TAG_QUALITY:
                      {
                          if (length != 4)
                          {
                              directory.addError("Unexpected length for the quality tag");
                              return;
                          }
                          directory.setInt(tag, reader.getInt32());
                          break;
                      }
                      case DuckyDirectory.TAG_COMMENT:
                      case DuckyDirectory.TAG_COPYRIGHT:
                      {
                          reader.skip(4);
                          directory.setStringValue(tag, reader.getStringValue(length - 4, Charsets.UTF_16BE));
                          break;
                      }
                      default:
                      {
                          // Unexpected tag
                          directory.setByteArray(tag, reader.getBytes(length));
                          break;
                      }
                  }
              }
          }
          catch (IOException e)
          {
              directory.addError(e.getMessage());
          }
      }
  }
  