private void writeIFDs(List<TiffIFDEntry> ifds) throws IOException {
long offset = this.theChannel.position();
// This is supposed to start on a word boundary, via decree of the spec.
long adjust = offset % 4L;
offset += (adjust == 0) ? 0 : (4L - adjust);
this.theChannel.position(offset);
Collections.sort(ifds);
ByteBuffer dataBuff = ByteBuffer.allocateDirect(ifds.size() * 12);
// The IFD directory is preceeded by a SHORT count of the number of entries...
putUnsignedShort(dataBuff, ifds.size());
dataBuff.flip();
this.theChannel.write(dataBuff);
dataBuff.clear();
for (TiffIFDEntry ifd : ifds) {
putUnsignedShort(dataBuff, ifd.tag);
putUnsignedShort(dataBuff, ifd.type);
putUnsignedInt(dataBuff, ifd.count);
if (ifd.type == Tiff.Type.SHORT && ifd.count == 1) {
// these get packed in the first few bytes...
putUnsignedShort(dataBuff, (int) ifd.valOffset);
dataBuff.putShort((short) 0);
} else putUnsignedInt(dataBuff, ifd.valOffset);
}
dataBuff.flip();
this.theChannel.write(dataBuff);
// The spec requires 4 bytes of zeros at the end...
dataBuff.clear();
dataBuff.putInt(0);
dataBuff.flip();
this.theChannel.write(dataBuff);
// go back and patch up the ifd offset in header...
this.theChannel.position(4);
dataBuff.clear();
putUnsignedInt(dataBuff, offset);
dataBuff.flip();
this.theChannel.write(dataBuff);
}
