private static boolean isValidContainer(String containerName) {
        if (containerName == null ||
                containerName.length() < 3 || containerName.length() > 255 ||
                containerName.startsWith(".") || containerName.endsWith(".") ||
                validateIpAddress(containerName) ||
                !VALID_BUCKET_FIRST_CHAR.matches(containerName.charAt(0)) ||
                !VALID_BUCKET.matchesAllOf(containerName)) {
            return false;
        }
        return true;
    }
S3 supports arbitrary keys for the marker while some blobstores only
support opaque markers.  Emulate the common case for these by mapping
the last key from a listing to the corresponding previously returned
marker.
src/main/java/org/gaul/s3proxy/S3ProxyHandler.java