package org.jaudiotagger.tag.id3;
import org.jaudiotagger.logging.ErrorMessage;
import org.jaudiotagger.tag.InvalidFrameException;
import java.nio.ByteBuffer;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.zip.DataFormatException;
import java.util.zip.Inflater;
/**
* compresses frame data
* <p/>
* Is currently required for V23Frames and V24Frames
* <p/>
*/
//TODO also need to support compress framedata
public class ID3Compression {
//Logger
public static Logger logger = Logger.getLogger("org.jaudiotagger.tag.id3");
/**
* Decompress realFrameSize bytes to decompressedFrameSize bytes and return as ByteBuffer
*
* @param byteBuffer
* @param decompressedFrameSize
* @param realFrameSize
* @return
* @throws org.jaudiotagger.tag.InvalidFrameException
*
*/
protected static ByteBuffer uncompress(String identifier, String filename, ByteBuffer byteBuffer, int decompressedFrameSize, int realFrameSize) throws InvalidFrameException {
logger.config(filename + ":About to decompress " + realFrameSize + " bytes, expect result to be:" + decompressedFrameSize + " bytes");
// Decompress the bytes into this buffer, size initialized from header field
byte[] result = new byte[decompressedFrameSize];
byte[] input = new byte[realFrameSize];
//Store position ( just after frame header and any extra bits)
//Read frame data into array, and then put buffer back to where it was
int position = byteBuffer.position();
byteBuffer.get(input, 0, realFrameSize);
byteBuffer.position(position);
Inflater decompresser = new Inflater();
decompresser.setInput(input);
try {
int inflatedTo = decompresser.inflate(result);
logger.config(filename + ":Decompressed to " + inflatedTo + " bytes");
} catch (DataFormatException dfe) {
logger.log(Level.CONFIG, "Unable to decompress this frame:" + identifier, dfe);
//Update position of main buffer, so no attempt is made to reread these bytes
byteBuffer.position(byteBuffer.position() + realFrameSize);
throw new InvalidFrameException(ErrorMessage.ID3_UNABLE_TO_DECOMPRESS_FRAME.getMsg(identifier, filename, dfe.getMessage()));
}
decompresser.end();
return ByteBuffer.wrap(result);
}
}