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/*
* Copyright 2002-2017 Drew Noakes
*
* 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
*
* http://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.jpeg;
import com.drew.imaging.jpeg.JpegSegmentMetadataReader;
import com.drew.imaging.jpeg.JpegSegmentType;
import com.drew.lang.SequentialByteArrayReader;
import com.drew.lang.SequentialReader;
import com.drew.lang.annotations.NotNull;
import com.drew.metadata.Metadata;
import com.drew.metadata.jpeg.HuffmanTablesDirectory.HuffmanTable;
import com.drew.metadata.jpeg.HuffmanTablesDirectory.HuffmanTable.HuffmanTableClass;
import java.io.IOException;
import java.util.Collections;
/**
* Reader for JPEG Huffman tables, found in the DHT JPEG segment.
*
* @author Nadahar
*/
public class JpegDhtReader implements JpegSegmentMetadataReader
{
@NotNull
public Iterable<JpegSegmentType> getSegmentTypes()
{
return Collections.singletonList(JpegSegmentType.DHT);
}
public void readJpegSegments(@NotNull Iterable<byte[]> segments, @NotNull Metadata metadata, @NotNull JpegSegmentType segmentType)
{
for (byte[] segmentBytes : segments) {
extract(new SequentialByteArrayReader(segmentBytes), metadata);
}
}
/**
* Performs the DHT tables extraction, adding found tables to the specified
* instance of {@link Metadata}.
*/
public void extract(@NotNull final SequentialReader reader, @NotNull final Metadata metadata)
{
HuffmanTablesDirectory directory = metadata.getFirstDirectoryOfType(HuffmanTablesDirectory.class);
if (directory == null) {
directory = new HuffmanTablesDirectory();
metadata.addDirectory(directory);
}
try {
while (reader.available() > 0) {
byte header = reader.getByte();
HuffmanTableClass tableClass = HuffmanTableClass.typeOf((header & 0xF0) >> 4);
int tableDestinationId = header & 0xF;
byte[] lBytes = getBytes(reader, 16);
int vCount = 0;
for (byte b : lBytes) {
vCount += (b & 0xFF);
}
byte[] vBytes = getBytes(reader, vCount);
directory.getTables().add(new HuffmanTable(tableClass, tableDestinationId, lBytes, vBytes));
}
} catch (IOException me) {
directory.addError(me.getMessage());
}
directory.setInt(HuffmanTablesDirectory.TAG_NUMBER_OF_TABLES, directory.getTables().size());
}
private byte[] getBytes(@NotNull final SequentialReader reader, int count) throws IOException {
byte[] bytes = new byte[count];
for (int i = 0; i < count; i++) {
byte b = reader.getByte();
if ((b & 0xFF) == 0xFF) {
byte stuffing = reader.getByte();
if (stuffing != 0x00) {
throw new IOException("Marker " + JpegSegmentType.fromByte(stuffing) + " found inside DHT segment");
}
}
bytes[i] = b;
}
return bytes;
}
}
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