public static Uri companionFileExists(final List<ContentStorage.FileInformation> files, final String filename) {
        final String lookFor = filename + INFOFILE_SUFFIX;
        for (ContentStorage.FileInformation fi : files) {
            if (fi.name.equals(lookFor)) {
                return fi.uri;
            }
        }
        return null;
    }
returns a list of downloaded offline files from requested source which are still available in the local filesystem
main/src/main/java/cgeo/geocaching/downloader/CompanionFileUtils.java