private boolean tagExists(FileChannel fc) throws IOException {
ByteBuffer b = ByteBuffer.allocate(3);
fc.position(0);
fc.read(b);
String tagString = new String(b.array());
return tagString.equals("ID3");
}
public RandomAccessFile delete(RandomAccessFile raf, RandomAccessFile tempRaf)
throws IOException {
FileChannel fc = raf.getChannel();
fc.position(0);
if (!tagExists(fc)) return raf;
fc.position(6);
ByteBuffer b = ByteBuffer.allocate(4);
fc.read(b);
b.rewind();
int tagSize = (b.get() & 0xFF) << 21;
tagSize += (b.get() & 0xFF) << 14;
tagSize += (b.get() & 0xFF) << 7;
tagSize += b.get() & 0xFF;
FileChannel tempFC = tempRaf.getChannel();
tempFC.position(0);
fc.position(tagSize + 10);
// Here we will try to skip eventual trash afer the tag and before the
// audio data
b = ByteBuffer.allocate(4);
int skip = 0;
while (fc.read(b) != -1) {
if ((b.get(0) & 0xFF) == 0xFF
&& (b.get(1) & 0xE0) == 0xE0
&& (b.get(1) & 0x06) != 0
&& (b.get(2) & 0xF0) != 0xF0
&& (b.get(2) & 0x08) != 0x08) {
fc.position(fc.position() - 4);
break;
}
fc.position(fc.position() - 3);
b.rewind();
skip++;
}
tempFC.transferFrom(fc, 0, fc.size() - tagSize - 10 - skip);
return tempRaf;
}
public void write(Tag tag, RandomAccessFile raf, RandomAccessFile tempRaf)
throws CannotWriteException, IOException {
FileChannel fc = raf.getChannel();
int oldTagSize = 0;
if (tagExists(fc)) {
// read the length
if (!canOverwrite(raf))
throw new CannotWriteException("Overwritting of this kind of ID3v2 tag not supported yet");
fc.position(6);
ByteBuffer buf = ByteBuffer.allocate(4);
fc.read(buf);
oldTagSize = (buf.get(0) & 0xFF) << 21;
oldTagSize += (buf.get(1) & 0xFF) << 14;
oldTagSize += (buf.get(2) & 0xFF) << 7;
oldTagSize += buf.get(3) & 0xFF;
oldTagSize += 10;
// System.err.println("Old tag size: "+oldTagSize);
int newTagSize = tc.getTagLength(tag);
if (oldTagSize >= newTagSize) {
// replace
// System.err.println("Old ID32v Tag found, replacing the old
// tag");
fc.position(0);
fc.write(tc.convert(tag, oldTagSize - newTagSize));
// ID3v2 Tag Written
return;
}
}
// create new tag with padding
// System.err.println("Creating a new ID3v2 Tag");
fc.position(oldTagSize);
if (fc.size() > 15 * 1024 * 1024) {
FileChannel tempFC = tempRaf.getChannel();
tempFC.position(0);
tempFC.write(tc.convert(tag, Id3v2TagCreator.DEFAULT_PADDING));
tempFC.transferFrom(fc, tempFC.position(), fc.size() - oldTagSize);
fc.close();
} else {
ByteBuffer[] content = new ByteBuffer[2];
content[1] = ByteBuffer.allocate((int) fc.size());
fc.read(content[1]);
content[1].rewind();
content[0] = tc.convert(tag, Id3v2TagCreator.DEFAULT_PADDING);
fc.position(0);
fc.write(content);
}
}