@Override
    public void open(long offset) throws ProxyCacheException {
        try {
            connection = openConnection(offset, -1);
            String mime = connection.getContentType();
            inputStream = new BufferedInputStream(connection.getInputStream(), DEFAULT_BUFFER_SIZE);
            long length = readSourceAvailableBytes(connection, offset, connection.getResponseCode());
            this.sourceInfo = new SourceInfo(sourceInfo.url, length, mime);
            this.sourceInfoStorage.put(sourceInfo.url, sourceInfo);
        } catch (IOException e) {
            throw new ProxyCacheException("Error opening connection for " + sourceInfo.url + " with offset " + offset, e);
        }
    }
{@link Source} that uses http resource as source for {@link ProxyCache}.
VideoCache/src/main/java/com/yc/videocache/HttpUrlSource.java