How to use the idna.decode function in idna

"Cached file is not readable for current user."
            )

        set_of_tlds = set()
        with open(self._tld_list_path, 'r') as f_cache_tld:
            for line in f_cache_tld:
                tld = line.strip().lower()
                # skip empty lines
                if not tld:
                    continue
                # skip comments
                if tld[0] == '#':
                    continue

                set_of_tlds.add("." + tld)
                set_of_tlds.add("." + idna.decode(tld))

        return set_of_tlds

:param length: The amount of data we are allowed to read from the buffer
    :param allow_relative: Allow domain names that do not end with a zero-length label
    :return: The number of bytes used from the buffer and the extracted domain name
    """
    my_offset = 0
    max_offset = length or (len(buffer) - offset)

    current_labels = []
    while max_offset > my_offset:
        label_length = buffer[offset + my_offset]
        my_offset += 1

        # End of a sequence of labels
        if label_length == 0:
            domain_name_bytes = b'.'.join(current_labels) + b'.'
            domain_name = idna.decode(domain_name_bytes)
            if len(domain_name) > 254:
                raise ValueError("Domain too long")
            return my_offset, domain_name

        if label_length > 63:
            raise ValueError('Label too long')

        # Check if we stay below the max offset
        if my_offset + label_length > max_offset:
            raise ValueError('Invalid encoded domain name, exceeds available buffer')

        # New label
        current_label_bytes = buffer[offset + my_offset:offset + my_offset + label_length]
        my_offset += label_length

        current_labels.append(current_label_bytes)

def _decode_general_name(backend, gn):
    if gn.type == backend._lib.GEN_DNS:
        data = _asn1_string_to_bytes(backend, gn.d.dNSName)
        if not data:
            decoded = u""
        elif data.startswith(b"*."):
            # This is a wildcard name. We need to remove the leading wildcard,
            # IDNA decode, then re-add the wildcard. Wildcard characters should
            # always be left-most (RFC 2595 section 2.4).
            decoded = u"*." + idna.decode(data[2:])
        else:
            # Not a wildcard, decode away. If the string has a * in it anywhere
            # invalid this will raise an InvalidCodePoint
            decoded = idna.decode(data)
            if data.startswith(b"."):
                # idna strips leading periods. Name constraints can have that
                # so we need to re-add it. Sigh.
                decoded = u"." + decoded

        return x509.DNSName(decoded)
    elif gn.type == backend._lib.GEN_URI:
        data = _asn1_string_to_ascii(backend, gn.d.uniformResourceIdentifier)
        parsed = urllib_parse.urlparse(data)
        if parsed.hostname:
            hostname = idna.decode(parsed.hostname)
        else:
            hostname = ""
        if parsed.port:
            netloc = hostname + u":" + six.text_type(parsed.port)
        else:

decoded = u"*." + idna.decode(data[2:])
        else:
            # Not a wildcard, decode away. If the string has a * in it anywhere
            # invalid this will raise an InvalidCodePoint
            decoded = idna.decode(data)
            if data.startswith(b"."):
                # idna strips leading periods. Name constraints can have that
                # so we need to re-add it. Sigh.
                decoded = u"." + decoded

        return x509.DNSName(decoded)
    elif gn.type == backend._lib.GEN_URI:
        data = _asn1_string_to_ascii(backend, gn.d.uniformResourceIdentifier)
        parsed = urllib_parse.urlparse(data)
        if parsed.hostname:
            hostname = idna.decode(parsed.hostname)
        else:
            hostname = ""
        if parsed.port:
            netloc = hostname + u":" + six.text_type(parsed.port)
        else:
            netloc = hostname

        # Note that building a URL in this fashion means it should be
        # semantically indistinguishable from the original but is not
        # guaranteed to be exactly the same.
        uri = urllib_parse.urlunparse((
            parsed.scheme,
            netloc,
            parsed.path,
            parsed.params,
            parsed.query,

Convert some IDNA-encoded octets into some human-readable text.

    Currently only used by the tests.

    @param octets: Some bytes representing a hostname.
    @type octets: L{bytes}

    @return: A human-readable domain name.
    @rtype: L{unicode}
    """
    try:
        import idna
    except ImportError:
        return octets.decode("idna")
    else:
        return idna.decode(octets)

raise ValueError('Label too long')

        # Check if we stay below the max offset
        if my_offset + label_length > max_offset:
            raise ValueError('Invalid encoded domain name, exceeds available buffer')

        # New label
        current_label_bytes = buffer[offset + my_offset:offset + my_offset + label_length]
        my_offset += label_length

        current_labels.append(current_label_bytes)

    if allow_relative:
        # We have reached the end of the data and we allow relative labels: we're done
        domain_name_bytes = b'.'.join(current_labels)
        domain_name = idna.decode(domain_name_bytes)
        if len(domain_name) > 253:
            raise ValueError("Domain too long")
        return my_offset, domain_name

    raise ValueError('Domain name must end with a 0-length label')

def _decode_general_name(backend, gn):
    if gn.type == backend._lib.GEN_DNS:
        data = backend._asn1_string_to_bytes(gn.d.dNSName)
        if not data:
            decoded = u""
        elif data.startswith(b"*."):
            # This is a wildcard name. We need to remove the leading wildcard,
            # IDNA decode, then re-add the wildcard. Wildcard characters should
            # always be left-most (RFC 2595 section 2.4).
            decoded = u"*." + idna.decode(data[2:])
        else:
            # Not a wildcard, decode away. If the string has a * in it anywhere
            # invalid this will raise an InvalidCodePoint
            decoded = idna.decode(data)
            if data.startswith(b"."):
                # idna strips leading periods. Name constraints can have that
                # so we need to re-add it. Sigh.
                decoded = u"." + decoded

        return x509.DNSName(decoded)
    elif gn.type == backend._lib.GEN_URI:
        data = backend._asn1_string_to_ascii(gn.d.uniformResourceIdentifier)
        parsed = urllib_parse.urlparse(data)
        if parsed.hostname:
            hostname = idna.decode(parsed.hostname)
        else:

def _decode_general_name(backend, gn):
    if gn.type == backend._lib.GEN_DNS:
        data = backend._asn1_string_to_bytes(gn.d.dNSName)
        if not data:
            decoded = u""
        elif data.startswith(b"*."):
            # This is a wildcard name. We need to remove the leading wildcard,
            # IDNA decode, then re-add the wildcard. Wildcard characters should
            # always be left-most (RFC 2595 section 2.4).
            decoded = u"*." + idna.decode(data[2:])
        else:
            # Not a wildcard, decode away. If the string has a * in it anywhere
            # invalid this will raise an InvalidCodePoint
            decoded = idna.decode(data)
            if data.startswith(b"."):
                # idna strips leading periods. Name constraints can have that
                # so we need to re-add it. Sigh.
                decoded = u"." + decoded

        return x509.DNSName(decoded)
    elif gn.type == backend._lib.GEN_URI:
        data = backend._asn1_string_to_ascii(gn.d.uniformResourceIdentifier)
        parsed = urllib_parse.urlparse(data)
        if parsed.hostname:
            hostname = idna.decode(parsed.hostname)
        else:
            hostname = ""
        if parsed.port:
            netloc = hostname + u":" + six.text_type(parsed.port)
        else:

self._display_name = mime_to_unicode(self._display_name)
        if (self._display_name.startswith('"') and
                self._display_name.endswith('"') and
                len(self._display_name) > 2):
            self._display_name = smart_unquote(self._display_name)
        if isinstance(self._display_name, str):
            self._display_name = self._display_name.decode('utf-8')

        # Convert localpart to unicode string.
        if isinstance(self._mailbox, str):
            self._mailbox = self._mailbox.decode('utf-8')

        # Convert hostname to lowercase unicode string.
        self._hostname = self._hostname.lower()
        if self._hostname.startswith('xn--') or '.xn--' in self._hostname:
            self._hostname = idna.decode(self._hostname)
        if isinstance(self._hostname, str):
            self._hostname = self._hostname.decode('utf-8')
        if not is_pure_ascii(self._hostname):
            idna.encode(self._hostname)