int l = (int) Math.min(1000, HttpUtils.getInstance().getContentLength(url));
if (l > 100) {
byte[] firstBytes = new byte[l];
str = new IGVSeekableHTTPStream(url);
str.readFully(firstBytes);
int end = firstBytes.length;
int start = end - 100;
str.seek(start);
int len = end - start;