Bug 84578 [Import/Export] Cannot import tar files with 8-bit filenames
On importing .tar.gz, the file is treated as a zip-file and produces a "Source file is not a valid Zip-file"-error message. This happens for all .tar.gz-files.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/wizards/datatransfer/TarInputStream.java
*/
	private long headerChecksum(byte[] header) {
		long sum = 0;
		for(int i = 0; i < 512; i++) {
			sum += header[i];
		}
		return sum;
	}
	/**
	 * Skips ahead to the position of the given entry in the file.
	 * 
	 * @param entry
	 * @returns false if the entry has already been passed
	 * @throws TarException
	 * @throws IOException
	 */
	boolean skipToEntry(TarEntry entry) throws TarException, IOException {
		int bytestoskip = entry.filepos - bytesread;
		if(bytestoskip < 0) return false;
		while(bytestoskip > 0) {
			long ret = in.skip(bytestoskip);
			if(ret < 0) {
				throw new IOException("early end of stream"); 
			}
			bytestoskip -= ret;
			bytesread += ret;
		}
		filepos = entry.filepos;
		nextEntry = 0;
		nextEOF = 0;