public long getLength( FSEntry entry ) {
		if ( entry != null & entry.isFile() ) {
			FSFork mainFork = entry.asFile().getMainFork();
			if ( mainFork.getLength() > 0 ) {
				return mainFork.getLength();
			}
			try {
				if (parser != null) {
					DecmpfsHeader header = parser.getDecmpfsHeader(entry.asFile());
					if (header != null) {
						return header.getUncompressedSize();
					}
				}
			}
			catch (IOException e) {
				return 1;//TODO lookup valid length in DECMPFS
			}
		}
		return -1;
	}
Returns the length of the given file system entry.
If the entry is actually a directory, then -1 is returned.
GPL/DMG/src/dmg/java/mobiledevices/dmg/reader/DmgFileReader.java