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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.imaging.riff;
import com.drew.lang.SequentialReader;
import com.drew.lang.annotations.NotNull;
import java.io.IOException;
/**
* Processes RIFF-formatted data, calling into client code via that {@link RiffHandler} interface.
* <p></p>
* For information on this file format, see:
* <ul>
* <li>http://en.wikipedia.org/wiki/Resource_Interchange_File_Format</li>
* <li>https://developers.google.com/speed/webp/docs/riff_container</li>
* <li>https://www.daubnet.com/en/file-format-riff</li>
* </ul>
* @author Drew Noakes https://drewnoakes.com
* @author Payton Garland
*/
public class RiffReader
{
/**
* Processes a RIFF data sequence.
*
* @param reader the {@link SequentialReader} from which the data should be read
* @param handler the {@link RiffHandler} that will coordinate processing and accept read values
* @throws RiffProcessingException if an error occurred during the processing of RIFF data that could not be
* ignored or recovered from
* @throws IOException an error occurred while accessing the required data
*/
public void processRiff(@NotNull final SequentialReader reader,
@NotNull final RiffHandler handler) throws RiffProcessingException, IOException
{
// RIFF files are always little-endian
reader.setMotorolaByteOrder(false);
// PROCESS FILE HEADER
final String fileFourCC = reader.getString(4);
if (!fileFourCC.equals("RIFF"))
throw new RiffProcessingException("Invalid RIFF header: " + fileFourCC);
// The total size of the chunks that follow plus 4 bytes for the FourCC
final int fileSize = reader.getInt32();
int sizeLeft = fileSize;
final String identifier = reader.getString(4);
sizeLeft -= 4;
if (!handler.shouldAcceptRiffIdentifier(identifier))
return;
// PROCESS CHUNKS
processChunks(reader, sizeLeft, handler);
}
public void processChunks(SequentialReader reader, int sectionSize, RiffHandler handler) throws IOException
{
while (reader.getPosition() < sectionSize) {
String fourCC = new String(reader.getBytes(4));
int size = reader.getInt32();
if (fourCC.equals("LIST") || fourCC.equals("RIFF")) {
String listName = new String(reader.getBytes(4));
if (handler.shouldAcceptList(listName)) {
processChunks(reader, size - 4, handler);
} else {
reader.skip(size - 4);
}
} else {
if (handler.shouldAcceptChunk(fourCC)) {
// TODO is it feasible to avoid copying the chunk here, and to pass the sequential reader to the handler?
handler.processChunk(fourCC, reader.getBytes(size));
} else {
reader.skip(size);
}
// Bytes read must be even - skip one if not
if (size % 2 == 1) {
reader.skip(1);
}
}
}
}
}
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