Esempio n. 1
0
    def __init__(self, database, mode=MODE_AUTO):
        """Reader for the MaxMind DB file format

        Arguments:
        database -- A path to a valid MaxMind DB file such as a GeoIP2 database
                    file, or a file descriptor in the case of MODE_FD.
        mode -- mode to open the database with. Valid mode are:
            * MODE_MMAP - read from memory map.
            * MODE_FILE - read database as standard file.
            * MODE_MEMORY - load database into memory.
            * MODE_AUTO - tries MODE_MMAP and then MODE_FILE. Default.
            * MODE_FD - the param passed via database is a file descriptor, not
                        a path. This mode implies MODE_MEMORY.
        """
        if (mode == MODE_AUTO and mmap) or mode == MODE_MMAP:
            with open(database, 'rb') as db_file:
                self._buffer = mmap.mmap(db_file.fileno(),
                                         0,
                                         access=mmap.ACCESS_READ)
                self._buffer_size = self._buffer.size()
            filename = database
        elif mode in (MODE_AUTO, MODE_FILE):
            self._buffer = FileBuffer(database)
            self._buffer_size = self._buffer.size()
            filename = database
        elif mode == MODE_MEMORY:
            with open(database, 'rb') as db_file:
                self._buffer = db_file.read()
                self._buffer_size = len(self._buffer)
            filename = database
        elif mode == MODE_FD:
            self._buffer = database.read()
            self._buffer_size = len(self._buffer)
            filename = database.name
        else:
            raise ValueError(
                'Unsupported open mode ({0}). Only MODE_AUTO, MODE_FILE, '
                'MODE_MEMORY and MODE_FD are supported by the pure Python '
                'Reader'.format(mode))

        metadata_start = self._buffer.rfind(
            self._METADATA_START_MARKER, max(0,
                                             self._buffer_size - 128 * 1024))

        if metadata_start == -1:
            self.close()
            raise InvalidDatabaseError('Error opening database file ({0}). '
                                       'Is this a valid MaxMind DB file?'
                                       ''.format(filename))

        metadata_start += len(self._METADATA_START_MARKER)
        metadata_decoder = Decoder(self._buffer, metadata_start)
        (metadata, _) = metadata_decoder.decode(metadata_start)
        self._metadata = Metadata(**metadata)  # pylint: disable=bad-option-value

        self._decoder = Decoder(
            self._buffer, self._metadata.search_tree_size +
            self._DATA_SECTION_SEPARATOR_SIZE)
        self.closed = False
Esempio n. 2
0
    def __init__(self, database, mode=MODE_AUTO):
        """Reader for the MaxMind DB file format

        Arguments:
        database -- A path to a valid MaxMind DB file such as a GeoIP2 database
                    file, or a file descriptor in the case of MODE_FD.
        mode -- mode to open the database with. Valid mode are:
            * MODE_MMAP - read from memory map.
            * MODE_FILE - read database as standard file.
            * MODE_MEMORY - load database into memory.
            * MODE_AUTO - tries MODE_MMAP and then MODE_FILE. Default.
            * MODE_FD - the param passed via database is a file descriptor, not
                        a path. This mode implies MODE_MEMORY.
        """
        if (mode == MODE_AUTO and mmap) or mode == MODE_MMAP:
            with open(database, 'rb') as db_file:
                self._buffer = mmap.mmap(db_file.fileno(),
                                         0,
                                         access=mmap.ACCESS_READ)
                self._buffer_size = self._buffer.size()
            filename = database
        elif mode in (MODE_AUTO, MODE_FILE):
            self._buffer = FileBuffer(database)
            self._buffer_size = self._buffer.size()
            filename = database
        elif mode == MODE_MEMORY:
            with open(database, 'rb') as db_file:
                self._buffer = db_file.read()
                self._buffer_size = len(self._buffer)
            filename = database
        elif mode == MODE_FD:
            self._buffer = database.read()
            self._buffer_size = len(self._buffer)
            filename = database.name
        else:
            raise ValueError(
                'Unsupported open mode ({0}). Only MODE_AUTO, MODE_FILE, '
                'MODE_MEMORY and MODE_FD are supported by the pure Python '
                'Reader'.format(mode))

        metadata_start = self._buffer.rfind(
            self._METADATA_START_MARKER, max(0,
                                             self._buffer_size - 128 * 1024))

        if metadata_start == -1:
            self.close()
            raise InvalidDatabaseError('Error opening database file ({0}). '
                                       'Is this a valid MaxMind DB file?'
                                       ''.format(filename))

        metadata_start += len(self._METADATA_START_MARKER)
        metadata_decoder = Decoder(self._buffer, metadata_start)
        (metadata, _) = metadata_decoder.decode(metadata_start)
        self._metadata = Metadata(**metadata)  # pylint: disable=bad-option-value

        self._decoder = Decoder(
            self._buffer, self._metadata.search_tree_size +
            self._DATA_SECTION_SEPARATOR_SIZE)
        self.closed = False
Esempio n. 3
0
class Reader(object):

    """
    Instances of this class provide a reader for the MaxMind DB format. IP
    addresses can be looked up using the ``get`` method.
    """

    _DATA_SECTION_SEPARATOR_SIZE = 16
    _METADATA_START_MARKER = b"\xAB\xCD\xEFMaxMind.com"

    _ipv4_start = None

    def __init__(self, database, mode=MODE_AUTO):
        """Reader for the MaxMind DB file format

        Arguments:
        database -- A path to a valid MaxMind DB file such as a GeoIP2
                    database file.
        mode -- mode to open the database with. Valid mode are:
            * MODE_MMAP - read from memory map.
            * MODE_FILE - read database as standard file.
            * MODE_MEMORY - load database into memory.
            * MODE_AUTO - tries MODE_MMAP and then MODE_FILE. Default.
        """
        if (mode == MODE_AUTO and mmap) or mode == MODE_MMAP:
            with open(database, 'rb') as db_file:
                self._buffer = mmap.mmap(
                    db_file.fileno(), 0, access=mmap.ACCESS_READ)
                self._buffer_size = self._buffer.size()
        elif mode in (MODE_AUTO, MODE_FILE):
            self._buffer = FileBuffer(database)
            self._buffer_size = self._buffer.size()
        elif mode == MODE_MEMORY:
            with open(database, 'rb') as db_file:
                self._buffer = db_file.read()
                self._buffer_size = len(self._buffer)
        else:
            raise ValueError('Unsupported open mode ({0}). Only MODE_AUTO, '
                             ' MODE_FILE, and MODE_MEMORY are support by the pure Python '
                             'Reader'.format(mode))

        metadata_start = self._buffer.rfind(self._METADATA_START_MARKER,
                                            max(0, self._buffer_size
                                                - 128 * 1024))

        if metadata_start == -1:
            self.close()
            raise InvalidDatabaseError('Error opening database file ({0}). '
                                       'Is this a valid MaxMind DB file?'
                                       ''.format(database))

        metadata_start += len(self._METADATA_START_MARKER)
        metadata_decoder = Decoder(self._buffer, metadata_start)
        (metadata, _) = metadata_decoder.decode(metadata_start)
        self._metadata = Metadata(
            **metadata)  # pylint: disable=bad-option-value

        self._decoder = Decoder(self._buffer, self._metadata.search_tree_size
                                + self._DATA_SECTION_SEPARATOR_SIZE)

    def metadata(self):
        """Return the metadata associated with the MaxMind DB file"""
        return self._metadata

    def get(self, ip_address):
        """Return the record for the ip_address in the MaxMind DB


        Arguments:
        ip_address -- an IP address in the standard string notation
        """
        address = ipaddress.ip_address(ip_address)

        if address.version == 6 and self._metadata.ip_version == 4:
            raise ValueError('Error looking up {0}. You attempted to look up '
                             'an IPv6 address in an IPv4-only database.'.format(
                                 ip_address))
        pointer = self._find_address_in_tree(address)

        return self._resolve_data_pointer(pointer) if pointer else None

    def _find_address_in_tree(self, ip_address):
        packed = ip_address.packed

        bit_count = len(packed) * 8
        node = self._start_node(bit_count)

        for i in range(bit_count):
            if node >= self._metadata.node_count:
                break
            bit = 1 & (int_from_byte(packed[i >> 3]) >> 7 - (i % 8))
            node = self._read_node(node, bit)
        if node == self._metadata.node_count:
            # Record is empty
            return 0
        elif node > self._metadata.node_count:
            return node

        raise InvalidDatabaseError('Invalid node in search tree')

    def _start_node(self, length):
        if self._metadata.ip_version != 6 or length == 128:
            return 0

        # We are looking up an IPv4 address in an IPv6 tree. Skip over the
        # first 96 nodes.
        if self._ipv4_start:
            return self._ipv4_start

        node = 0
        for _ in range(96):
            if node >= self._metadata.node_count:
                break
            node = self._read_node(node, 0)
        self._ipv4_start = node
        return node

    def _read_node(self, node_number, index):
        base_offset = node_number * self._metadata.node_byte_size

        record_size = self._metadata.record_size
        if record_size == 24:
            offset = base_offset + index * 3
            node_bytes = b'\x00' + self._buffer[offset:offset + 3]
        elif record_size == 28:
            (middle,) = struct.unpack(
                b'!B', self._buffer[base_offset + 3:base_offset + 4])
            if index:
                middle &= 0x0F
            else:
                middle = (0xF0 & middle) >> 4
            offset = base_offset + index * 4
            node_bytes = byte_from_int(
                middle) + self._buffer[offset:offset + 3]
        elif record_size == 32:
            offset = base_offset + index * 4
            node_bytes = self._buffer[offset:offset + 4]
        else:
            raise InvalidDatabaseError(
                'Unknown record size: {0}'.format(record_size))
        return struct.unpack(b'!I', node_bytes)[0]

    def _resolve_data_pointer(self, pointer):
        resolved = pointer - self._metadata.node_count + \
            self._metadata.search_tree_size

        if resolved > self._buffer_size:
            raise InvalidDatabaseError(
                "The MaxMind DB file's search tree is corrupt")

        (data, _) = self._decoder.decode(resolved)
        return data

    def close(self):
        """Closes the MaxMind DB file and returns the resources to the system"""
        # pylint: disable=unidiomatic-typecheck
        if type(self._buffer) not in (str, bytes):
            self._buffer.close()
Esempio n. 4
0
class Reader:
    """
    Instances of this class provide a reader for the MaxMind DB format. IP
    addresses can be looked up using the ``get`` method.
    """

    _DATA_SECTION_SEPARATOR_SIZE = 16
    _METADATA_START_MARKER = b"\xAB\xCD\xEFMaxMind.com"

    _buffer: Union[bytes, FileBuffer, "mmap.mmap"]
    _ipv4_start: Optional[int] = None

    def __init__(self,
                 database: Union[AnyStr, int, PathLike, IO],
                 mode: int = MODE_AUTO) -> None:
        """Reader for the MaxMind DB file format

        Arguments:
        database -- A path to a valid MaxMind DB file such as a GeoIP2 database
                    file, or a file descriptor in the case of MODE_FD.
        mode -- mode to open the database with. Valid mode are:
            * MODE_MMAP - read from memory map.
            * MODE_FILE - read database as standard file.
            * MODE_MEMORY - load database into memory.
            * MODE_AUTO - tries MODE_MMAP and then MODE_FILE. Default.
            * MODE_FD - the param passed via database is a file descriptor, not
                        a path. This mode implies MODE_MEMORY.
        """
        filename: Any
        if (mode == MODE_AUTO and mmap) or mode == MODE_MMAP:
            with open(database, "rb") as db_file:  # type: ignore
                self._buffer = mmap.mmap(db_file.fileno(),
                                         0,
                                         access=mmap.ACCESS_READ)
                self._buffer_size = self._buffer.size()
            filename = database
        elif mode in (MODE_AUTO, MODE_FILE):
            self._buffer = FileBuffer(database)  # type: ignore
            self._buffer_size = self._buffer.size()
            filename = database
        elif mode == MODE_MEMORY:
            with open(database, "rb") as db_file:  # type: ignore
                self._buffer = db_file.read()
                self._buffer_size = len(self._buffer)
            filename = database
        elif mode == MODE_FD:
            self._buffer = database.read()  # type: ignore
            self._buffer_size = len(self._buffer)  # type: ignore
            filename = database.name  # type: ignore
        else:
            raise ValueError(
                "Unsupported open mode ({0}). Only MODE_AUTO, MODE_FILE, "
                "MODE_MEMORY and MODE_FD are supported by the pure Python "
                "Reader".format(mode))

        metadata_start = self._buffer.rfind(
            self._METADATA_START_MARKER, max(0,
                                             self._buffer_size - 128 * 1024))

        if metadata_start == -1:
            self.close()
            raise InvalidDatabaseError("Error opening database file ({0}). "
                                       "Is this a valid MaxMind DB file?"
                                       "".format(filename))

        metadata_start += len(self._METADATA_START_MARKER)
        metadata_decoder = Decoder(self._buffer, metadata_start)
        (metadata, _) = metadata_decoder.decode(metadata_start)

        if not isinstance(metadata, dict):
            raise InvalidDatabaseError(
                "Error reading metadata in database file ({0}).".format(
                    filename))

        self._metadata = Metadata(**metadata)  # pylint: disable=bad-option-value

        self._decoder = Decoder(
            self._buffer,
            self._metadata.search_tree_size +
            self._DATA_SECTION_SEPARATOR_SIZE,
        )
        self.closed = False

    def metadata(self) -> "Metadata":
        """Return the metadata associated with the MaxMind DB file"""
        return self._metadata

    def get(self, ip_address: Union[str, IPv6Address,
                                    IPv4Address]) -> Optional[Record]:
        """Return the record for the ip_address in the MaxMind DB


        Arguments:
        ip_address -- an IP address in the standard string notation
        """
        (record, _) = self.get_with_prefix_len(ip_address)
        return record

    def get_with_prefix_len(
        self, ip_address: Union[str, IPv6Address, IPv4Address]
    ) -> Tuple[Optional[Record], int]:
        """Return a tuple with the record and the associated prefix length


        Arguments:
        ip_address -- an IP address in the standard string notation
        """
        if isinstance(ip_address, str):
            address = ipaddress.ip_address(ip_address)
        else:
            address = ip_address

        try:
            packed_address = bytearray(address.packed)
        except AttributeError:
            raise TypeError("argument 1 must be a string or ipaddress object")

        if address.version == 6 and self._metadata.ip_version == 4:
            raise ValueError(
                "Error looking up {0}. You attempted to look up "
                "an IPv6 address in an IPv4-only database.".format(ip_address))

        (pointer, prefix_len) = self._find_address_in_tree(packed_address)

        if pointer:
            return self._resolve_data_pointer(pointer), prefix_len
        return None, prefix_len

    def _find_address_in_tree(self, packed: bytearray) -> Tuple[int, int]:
        bit_count = len(packed) * 8
        node = self._start_node(bit_count)
        node_count = self._metadata.node_count

        i = 0
        while i < bit_count and node < node_count:
            bit = 1 & (packed[i >> 3] >> 7 - (i % 8))
            node = self._read_node(node, bit)
            i = i + 1

        if node == node_count:
            # Record is empty
            return 0, i
        if node > node_count:
            return node, i

        raise InvalidDatabaseError("Invalid node in search tree")

    def _start_node(self, length: int) -> int:
        if self._metadata.ip_version != 6 or length == 128:
            return 0

        # We are looking up an IPv4 address in an IPv6 tree. Skip over the
        # first 96 nodes.
        if self._ipv4_start:
            return self._ipv4_start

        node = 0
        for _ in range(96):
            if node >= self._metadata.node_count:
                break
            node = self._read_node(node, 0)
        self._ipv4_start = node
        return node

    def _read_node(self, node_number: int, index: int) -> int:
        base_offset = node_number * self._metadata.node_byte_size

        record_size = self._metadata.record_size
        if record_size == 24:
            offset = base_offset + index * 3
            node_bytes = b"\x00" + self._buffer[offset:offset + 3]
        elif record_size == 28:
            offset = base_offset + 3 * index
            node_bytes = bytearray(self._buffer[offset:offset + 4])
            if index:
                node_bytes[0] = 0x0F & node_bytes[0]
            else:
                middle = (0xF0 & node_bytes.pop()) >> 4
                node_bytes.insert(0, middle)
        elif record_size == 32:
            offset = base_offset + index * 4
            node_bytes = self._buffer[offset:offset + 4]
        else:
            raise InvalidDatabaseError(
                "Unknown record size: {0}".format(record_size))
        return struct.unpack(b"!I", node_bytes)[0]

    def _resolve_data_pointer(self, pointer: int) -> Record:
        resolved = pointer - self._metadata.node_count + self._metadata.search_tree_size

        if resolved >= self._buffer_size:
            raise InvalidDatabaseError(
                "The MaxMind DB file's search tree is corrupt")

        (data, _) = self._decoder.decode(resolved)
        return data

    def close(self) -> None:
        """Closes the MaxMind DB file and returns the resources to the system"""
        try:
            self._buffer.close()  # type: ignore
        except AttributeError:
            pass
        self.closed = True

    def __exit__(self, *args) -> None:
        self.close()

    def __enter__(self) -> "Reader":
        if self.closed:
            raise ValueError("Attempt to reopen a closed MaxMind DB")
        return self
Esempio n. 5
0
class Reader(object):
    """
    Instances of this class provide a reader for the MaxMind DB format. IP
    addresses can be looked up using the ``get`` method.
    """

    _DATA_SECTION_SEPARATOR_SIZE = 16
    _METADATA_START_MARKER = b"\xAB\xCD\xEFMaxMind.com"

    _ipv4_start = None

    def __init__(self, database, mode=MODE_AUTO):
        """Reader for the MaxMind DB file format

        Arguments:
        database -- A path to a valid MaxMind DB file such as a GeoIP2 database
                    file, or a file descriptor in the case of MODE_FD.
        mode -- mode to open the database with. Valid mode are:
            * MODE_MMAP - read from memory map.
            * MODE_FILE - read database as standard file.
            * MODE_MEMORY - load database into memory.
            * MODE_AUTO - tries MODE_MMAP and then MODE_FILE. Default.
            * MODE_FD - the param passed via database is a file descriptor, not
                        a path. This mode implies MODE_MEMORY.
        """
        if (mode == MODE_AUTO and mmap) or mode == MODE_MMAP:
            with open(database, 'rb') as db_file:
                self._buffer = mmap.mmap(db_file.fileno(),
                                         0,
                                         access=mmap.ACCESS_READ)
                self._buffer_size = self._buffer.size()
            filename = database
        elif mode in (MODE_AUTO, MODE_FILE):
            self._buffer = FileBuffer(database)
            self._buffer_size = self._buffer.size()
            filename = database
        elif mode == MODE_MEMORY:
            with open(database, 'rb') as db_file:
                self._buffer = db_file.read()
                self._buffer_size = len(self._buffer)
            filename = database
        elif mode == MODE_FD:
            self._buffer = database.read()
            self._buffer_size = len(self._buffer)
            filename = database.name
        else:
            raise ValueError(
                'Unsupported open mode ({0}). Only MODE_AUTO, MODE_FILE, '
                'MODE_MEMORY and MODE_FD are supported by the pure Python '
                'Reader'.format(mode))

        metadata_start = self._buffer.rfind(
            self._METADATA_START_MARKER, max(0,
                                             self._buffer_size - 128 * 1024))

        if metadata_start == -1:
            self.close()
            raise InvalidDatabaseError('Error opening database file ({0}). '
                                       'Is this a valid MaxMind DB file?'
                                       ''.format(filename))

        metadata_start += len(self._METADATA_START_MARKER)
        metadata_decoder = Decoder(self._buffer, metadata_start)
        (metadata, _) = metadata_decoder.decode(metadata_start)
        self._metadata = Metadata(**metadata)  # pylint: disable=bad-option-value

        self._decoder = Decoder(
            self._buffer, self._metadata.search_tree_size +
            self._DATA_SECTION_SEPARATOR_SIZE)
        self.closed = False

    def metadata(self):
        """Return the metadata associated with the MaxMind DB file"""
        return self._metadata

    def get(self, ip_address):
        """Return the record for the ip_address in the MaxMind DB


        Arguments:
        ip_address -- an IP address in the standard string notation
        """
        (record, _) = self.get_with_prefix_len(ip_address)
        return record

    def get_with_prefix_len(self, ip_address):
        """Return a tuple with the record and the associated prefix length


        Arguments:
        ip_address -- an IP address in the standard string notation
        """
        if isinstance(ip_address, string_type):
            address = compat_ip_address(ip_address)
        else:
            address = ip_address

        try:
            packed_address = bytearray(address.packed)
        except AttributeError:
            raise TypeError('argument 1 must be a string or ipaddress object')

        if address.version == 6 and self._metadata.ip_version == 4:
            raise ValueError(
                'Error looking up {0}. You attempted to look up '
                'an IPv6 address in an IPv4-only database.'.format(ip_address))

        (pointer, prefix_len) = self._find_address_in_tree(packed_address)

        if pointer:
            return self._resolve_data_pointer(pointer), prefix_len
        return None, prefix_len

    def _find_address_in_tree(self, packed):
        bit_count = len(packed) * 8
        node = self._start_node(bit_count)
        node_count = self._metadata.node_count

        i = 0
        while i < bit_count and node < node_count:
            bit = 1 & (packed[i >> 3] >> 7 - (i % 8))
            node = self._read_node(node, bit)
            i = i + 1

        if node == node_count:
            # Record is empty
            return 0, i
        if node > node_count:
            return node, i

        raise InvalidDatabaseError('Invalid node in search tree')

    def _start_node(self, length):
        if self._metadata.ip_version != 6 or length == 128:
            return 0

        # We are looking up an IPv4 address in an IPv6 tree. Skip over the
        # first 96 nodes.
        if self._ipv4_start:
            return self._ipv4_start

        node = 0
        for _ in range(96):
            if node >= self._metadata.node_count:
                break
            node = self._read_node(node, 0)
        self._ipv4_start = node
        return node

    def _read_node(self, node_number, index):
        base_offset = node_number * self._metadata.node_byte_size

        record_size = self._metadata.record_size
        if record_size == 24:
            offset = base_offset + index * 3
            node_bytes = b'\x00' + self._buffer[offset:offset + 3]
        elif record_size == 28:
            (middle, ) = struct.unpack(
                b'!B', self._buffer[base_offset + 3:base_offset + 4])
            if index:
                middle &= 0x0F
            else:
                middle = (0xF0 & middle) >> 4
            offset = base_offset + index * 4
            node_bytes = byte_from_int(middle) + self._buffer[offset:offset +
                                                              3]
        elif record_size == 32:
            offset = base_offset + index * 4
            node_bytes = self._buffer[offset:offset + 4]
        else:
            raise InvalidDatabaseError(
                'Unknown record size: {0}'.format(record_size))
        return struct.unpack(b'!I', node_bytes)[0]

    def _resolve_data_pointer(self, pointer):
        resolved = pointer - self._metadata.node_count + \
            self._metadata.search_tree_size

        if resolved > self._buffer_size:
            raise InvalidDatabaseError(
                "The MaxMind DB file's search tree is corrupt")

        (data, _) = self._decoder.decode(resolved)
        return data

    def close(self):
        """Closes the MaxMind DB file and returns the resources to the system"""
        # pylint: disable=unidiomatic-typecheck
        if type(self._buffer) not in (str, bytes):
            self._buffer.close()
        self.closed = True

    def __exit__(self, *args):
        self.close()

    def __enter__(self):
        if self.closed:
            raise ValueError('Attempt to reopen a closed MaxMind DB')
        return self
Esempio n. 6
0
    def __init__(self,
                 database: Union[AnyStr, int, PathLike, IO],
                 mode: int = MODE_AUTO) -> None:
        """Reader for the MaxMind DB file format

        Arguments:
        database -- A path to a valid MaxMind DB file such as a GeoIP2 database
                    file, or a file descriptor in the case of MODE_FD.
        mode -- mode to open the database with. Valid mode are:
            * MODE_MMAP - read from memory map.
            * MODE_FILE - read database as standard file.
            * MODE_MEMORY - load database into memory.
            * MODE_AUTO - tries MODE_MMAP and then MODE_FILE. Default.
            * MODE_FD - the param passed via database is a file descriptor, not
                        a path. This mode implies MODE_MEMORY.
        """
        filename: Any
        if (mode == MODE_AUTO and mmap) or mode == MODE_MMAP:
            with open(database, "rb") as db_file:  # type: ignore
                self._buffer = mmap.mmap(db_file.fileno(),
                                         0,
                                         access=mmap.ACCESS_READ)
                self._buffer_size = self._buffer.size()
            filename = database
        elif mode in (MODE_AUTO, MODE_FILE):
            self._buffer = FileBuffer(database)  # type: ignore
            self._buffer_size = self._buffer.size()
            filename = database
        elif mode == MODE_MEMORY:
            with open(database, "rb") as db_file:  # type: ignore
                self._buffer = db_file.read()
                self._buffer_size = len(self._buffer)
            filename = database
        elif mode == MODE_FD:
            self._buffer = database.read()  # type: ignore
            self._buffer_size = len(self._buffer)  # type: ignore
            filename = database.name  # type: ignore
        else:
            raise ValueError(
                f"Unsupported open mode ({mode}). Only MODE_AUTO, MODE_FILE, "
                "MODE_MEMORY and MODE_FD are supported by the pure Python "
                "Reader")

        metadata_start = self._buffer.rfind(
            self._METADATA_START_MARKER, max(0,
                                             self._buffer_size - 128 * 1024))

        if metadata_start == -1:
            self.close()
            raise InvalidDatabaseError(
                f"Error opening database file ({filename}). "
                "Is this a valid MaxMind DB file?")

        metadata_start += len(self._METADATA_START_MARKER)
        metadata_decoder = Decoder(self._buffer, metadata_start)
        (metadata, _) = metadata_decoder.decode(metadata_start)

        if not isinstance(metadata, dict):
            raise InvalidDatabaseError(
                f"Error reading metadata in database file ({filename}).")

        self._metadata = Metadata(**metadata)  # pylint: disable=bad-option-value

        self._decoder = Decoder(
            self._buffer,
            self._metadata.search_tree_size +
            self._DATA_SECTION_SEPARATOR_SIZE,
        )
        self.closed = False