code: private boolean matchesFingerprint(byte[] buffer, Pattern fingerprint)
     {
        return fingerprint.matcher(m_charset == null ? new String(buffer) : new String(buffer, m_charset)).matches();
     }
docs: Determine if the buffer, when expressed as text, matches a fingerprint regular expression.
  
  @param buffer bytes from file
  @param fingerprint fingerprint regular expression
  @return true if the file matches the fingerprint