Python struct.error() Examples

def close(self,

              remove=os.unlink,error=os.error):

        if self.pipe:
            rc = self.pipe.close()
        else:
            rc = 255
        if self.tmpfile:
            try:
                remove(self.tmpfile)
            except error:
                pass
        return rc

    # Alias 

def _syscmd_uname(option,default=''):

    """ Interface to the system's uname command.
    """
    if sys.platform in ('dos','win32','win16','os2'):
        # XXX Others too ?
        return default
    try:
        f = os.popen('uname %s 2> %s' % (option, DEV_NULL))
    except (AttributeError,os.error):
        return default
    output = string.strip(f.read())
    rc = f.close()
    if not output or rc:
        return default
    else:
        return output 

def __init__(self, file, align=True, bigendian=True, inclheader=False):
        import struct
        self.closed = False
        self.align = align      # whether to align to word (2-byte) boundaries
        if bigendian:
            strflag = '>'
        else:
            strflag = '<'
        self.file = file
        self.chunkname = file.read(4)
        if len(self.chunkname) < 4:
            raise EOFError
        try:
            self.chunksize = struct.unpack(strflag+'L', file.read(4))[0]
        except struct.error:
            raise EOFError
        if inclheader:
            self.chunksize = self.chunksize - 8 # subtract header
        self.size_read = 0
        try:
            self.offset = self.file.tell()
        except (AttributeError, IOError):
            self.seekable = False
        else:
            self.seekable = True 

def seek(self, pos, whence=0):
        """Seek to specified position into the chunk.
        Default position is 0 (start of chunk).
        If the file is not seekable, this will result in an error.
        """

        if self.closed:
            raise ValueError, "I/O operation on closed file"
        if not self.seekable:
            raise IOError, "cannot seek"
        if whence == 1:
            pos = pos + self.size_read
        elif whence == 2:
            pos = pos + self.chunksize
        if pos < 0 or pos > self.chunksize:
            raise RuntimeError
        self.file.seek(self.offset + pos, 0)
        self.size_read = pos 

def test_consistence(self):
        self.assertRaises(struct.error, struct.calcsize, 'Z')

        sz = struct.calcsize('i')
        self.assertEqual(sz * 3, struct.calcsize('iii'))

        fmt = 'cbxxxxxxhhhhiillffd?'
        fmt3 = '3c3b18x12h6i6l6f3d3?'
        sz = struct.calcsize(fmt)
        sz3 = struct.calcsize(fmt3)
        self.assertEqual(sz * 3, sz3)

        self.assertRaises(struct.error, struct.pack, 'iii', 3)
        self.assertRaises(struct.error, struct.pack, 'i', 3, 3, 3)
        self.assertRaises((TypeError, struct.error), struct.pack, 'i', 'foo')
        self.assertRaises((TypeError, struct.error), struct.pack, 'P', 'foo')
        self.assertRaises(struct.error, struct.unpack, 'd', 'flap')
        s = struct.pack('ii', 1, 2)
        self.assertRaises(struct.error, struct.unpack, 'iii', s)
        self.assertRaises(struct.error, struct.unpack, 'i', s) 

def test_pack_into_fn(self):
        test_string = 'Reykjavik rocks, eow!'
        writable_buf = array.array('c', ' '*100)
        fmt = '21s'
        pack_into = lambda *args: struct.pack_into(fmt, *args)

        # Test without offset.
        pack_into(writable_buf, 0, test_string)
        from_buf = writable_buf.tostring()[:len(test_string)]
        self.assertEqual(from_buf, test_string)

        # Test with offset.
        pack_into(writable_buf, 10, test_string)
        from_buf = writable_buf.tostring()[:len(test_string)+10]
        self.assertEqual(from_buf, test_string[:10] + test_string)

        # Go beyond boundaries.
        small_buf = array.array('c', ' '*10)
        self.assertRaises((ValueError, struct.error), pack_into, small_buf, 0,
                          test_string)
        self.assertRaises((ValueError, struct.error), pack_into, small_buf, 2,
                          test_string) 

def _parse_image_info_bytes(data: bytes) -> Optional[_ImageInfo]:
    try:
        parsed = list(struct.unpack(_IMAGE_INFO_FORMAT, data))
    except struct.error:
        pass
    else:
        magic_begin = parsed[:_IMAGE_INFO_MAGIC_SIZE]
        magic_end = parsed[-_IMAGE_INFO_MAGIC_SIZE:]
        if magic_begin == magic_end == _IMAGE_INFO_MAGIC:
            image_name_bytes = b"".join(parsed[
                _IMAGE_INFO_MAGIC_SIZE  # noqa: E203
                :
                _IMAGE_INFO_MAGIC_SIZE + _IMAGE_INFO_NAME_SIZE
            ])
            return _ImageInfo(
                name=image_name_bytes.decode("utf-8", errors="ignore").strip("\x00").strip(),
                size=parsed[_IMAGE_INFO_MAGIC_SIZE + _IMAGE_INFO_NAME_SIZE + 1],
                complete=parsed[_IMAGE_INFO_MAGIC_SIZE + _IMAGE_INFO_NAME_SIZE],
            )
    return None 

def v4_int_to_packed(address):
    """Represent an address as 4 packed bytes in network (big-endian) order.

    Args:
        address: An integer representation of an IPv4 IP address.

    Returns:
        The integer address packed as 4 bytes in network (big-endian) order.

    Raises:
        ValueError: If the integer is negative or too large to be an
          IPv4 IP address.

    """
    try:
        return _compat_to_bytes(address, 4, 'big')
    except (struct.error, OverflowError):
        raise ValueError("Address negative or too large for IPv4") 

def _parse_hextet(cls, hextet_str):
        """Convert an IPv6 hextet string into an integer.

        Args:
            hextet_str: A string, the number to parse.

        Returns:
            The hextet as an integer.

        Raises:
            ValueError: if the input isn't strictly a hex number from
              [0..FFFF].

        """
        # Whitelist the characters, since int() allows a lot of bizarre stuff.
        if not cls._HEX_DIGITS.issuperset(hextet_str):
            raise ValueError("Only hex digits permitted in %r" % hextet_str)
        # We do the length check second, since the invalid character error
        # is likely to be more informative for the user
        if len(hextet_str) > 4:
            msg = "At most 4 characters permitted in %r"
            raise ValueError(msg % hextet_str)
        # Length check means we can skip checking the integer value
        return int(hextet_str, 16) 

def v4_int_to_packed(address):
    """Represent an address as 4 packed bytes in network (big-endian) order.

    Args:
        address: An integer representation of an IPv4 IP address.

    Returns:
        The integer address packed as 4 bytes in network (big-endian) order.

    Raises:
        ValueError: If the integer is negative or too large to be an
          IPv4 IP address.

    """
    try:
        return _compat_to_bytes(address, 4, 'big')
    except (struct.error, OverflowError):
        raise ValueError("Address negative or too large for IPv4") 

def _parse_hextet(cls, hextet_str):
        """Convert an IPv6 hextet string into an integer.

        Args:
            hextet_str: A string, the number to parse.

        Returns:
            The hextet as an integer.

        Raises:
            ValueError: if the input isn't strictly a hex number from
              [0..FFFF].

        """
        # Whitelist the characters, since int() allows a lot of bizarre stuff.
        if not cls._HEX_DIGITS.issuperset(hextet_str):
            raise ValueError("Only hex digits permitted in %r" % hextet_str)
        # We do the length check second, since the invalid character error
        # is likely to be more informative for the user
        if len(hextet_str) > 4:
            msg = "At most 4 characters permitted in %r"
            raise ValueError(msg % hextet_str)
        # Length check means we can skip checking the integer value
        return int(hextet_str, 16) 

def main():
    """Small main program"""
    import sys, getopt
    try:
        opts, args = getopt.getopt(sys.argv[1:], 'deut')
    except getopt.error as msg:
        sys.stdout = sys.stderr
        print(msg)
        print("""usage: %s [-d|-e|-u|-t] [file|-]
        -d, -u: decode
        -e: encode (default)
        -t: encode and decode string 'Aladdin:open sesame'"""%sys.argv[0])
        sys.exit(2)
    func = encode
    for o, a in opts:
        if o == '-e': func = encode
        if o == '-d': func = decode
        if o == '-u': func = decode
        if o == '-t': test(); return
    if args and args[0] != '-':
        with open(args[0], 'rb') as f:
            func(f, sys.stdout.buffer)
    else:
        func(sys.stdin.buffer, sys.stdout.buffer) 

def _StructPackDecoder(wire_type, format):
  """Return a constructor for a decoder for a fixed-width field.

  Args:
      wire_type:  The field's wire type.
      format:  The format string to pass to struct.unpack().
  """

  value_size = struct.calcsize(format)
  local_unpack = struct.unpack

  # Reusing _SimpleDecoder is slightly slower than copying a bunch of code, but
  # not enough to make a significant difference.

  # Note that we expect someone up-stack to catch struct.error and convert
  # it to _DecodeError -- this way we don't have to set up exception-
  # handling blocks every time we parse one value.

  def InnerDecode(buffer, pos):
    new_pos = pos + value_size
    result = local_unpack(format, buffer[pos:new_pos])[0]
    return (result, new_pos)
  return _SimpleDecoder(wire_type, InnerDecode) 

def close(self):
        """
        Closes the file pointer, if possible.

        This operation will destroy the image core and release its memory.
        The image data will be unusable afterward.

        This function is only required to close images that have not
        had their file read and closed by the
        :py:meth:`~PIL.Image.Image.load` method.
        """
        try:
            self.fp.close()
            self.fp = None
        except Exception as msg:
            logger.debug("Error closing: %s", msg)

        if getattr(self, 'map', None):
            self.map = None
    
        # Instead of simply setting to None, we're setting up a
        # deferred error that will better explain that the core image
        # object is gone.
        self.im = deferred_error(ValueError("Operation on closed image")) 

def crc(self, cid, data):
        "Read and verify checksum"

        # Skip CRC checks for ancillary chunks if allowed to load truncated images
        # 5th byte of first char is 1 [specs, section 5.4]
        if ImageFile.LOAD_TRUNCATED_IMAGES and (i8(cid[0]) >> 5 & 1):
            self.crc_skip(cid, data)
            return

        try:
            crc1 = Image.core.crc32(data, Image.core.crc32(cid))
            crc2 = i16(self.fp.read(2)), i16(self.fp.read(2))
            if crc1 != crc2:
                raise SyntaxError("broken PNG file (bad header checksum in %r)"
                                  % cid)
        except struct.error:
            raise SyntaxError("broken PNG file (incomplete checksum in %r)"
                              % cid) 

def verify(self, endchunk=b"IEND"):

        # Simple approach; just calculate checksum for all remaining
        # blocks.  Must be called directly after open.

        cids = []

        while True:
            try:
                cid, pos, length = self.read()
            except struct.error:
                raise IOError("truncated PNG file")

            if cid == endchunk:
                break
            self.crc(cid, ImageFile._safe_read(self.fp, length))
            cids.append(cid)

        return cids 

def v4_int_to_packed(address):
    """Represent an address as 4 packed bytes in network (big-endian) order.

    Args:
        address: An integer representation of an IPv4 IP address.

    Returns:
        The integer address packed as 4 bytes in network (big-endian) order.

    Raises:
        ValueError: If the integer is negative or too large to be an
          IPv4 IP address.

    """
    try:
        return _compat_to_bytes(address, 4, 'big')
    except (struct.error, OverflowError):
        raise ValueError("Address negative or too large for IPv4") 

def _parse_hextet(cls, hextet_str):
        """Convert an IPv6 hextet string into an integer.

        Args:
            hextet_str: A string, the number to parse.

        Returns:
            The hextet as an integer.

        Raises:
            ValueError: if the input isn't strictly a hex number from
              [0..FFFF].

        """
        # Whitelist the characters, since int() allows a lot of bizarre stuff.
        if not cls._HEX_DIGITS.issuperset(hextet_str):
            raise ValueError("Only hex digits permitted in %r" % hextet_str)
        # We do the length check second, since the invalid character error
        # is likely to be more informative for the user
        if len(hextet_str) > 4:
            msg = "At most 4 characters permitted in %r"
            raise ValueError(msg % hextet_str)
        # Length check means we can skip checking the integer value
        return int(hextet_str, 16) 

def gunzip(data):
    """Gunzip the given data and return as much data as possible.

    This is resilient to CRC checksum errors.
    """
    f = GzipFile(fileobj=StringIO(data))
    output = ''
    chunk = '.'
    while chunk:
        try:
            chunk = f.read(8196)
            output += chunk
        except (IOError, struct.error):
            # complete only if there is some data, otherwise re-raise
            # see issue 87 about catching struct.error
            if output:
                output += f.extrabuf
                break
            else:
                raise
    return output 

def readline(self):
        if self.eof:
            raise EOFError()

        if not self.first_byte and self.plusbytes != 0:
            self.first_byte = self.sb.read(self.plusbytes)
            if self.first_byte != b'\n':
                logger.debug('Discarding first partial row')
                self.sb._raw_stream.readline()
        try:
            retval = self.sb._raw_stream.readline()
        except struct.error:
            raise EOFError()
        self.pos += len(retval)

        if self.pos >= self.size:
            self.eof = True

        return retval 

def mutagen_call(action, path, func, *args, **kwargs):
    """Call a Mutagen function with appropriate error handling.

    `action` is a string describing what the function is trying to do,
    and `path` is the relevant filename. The rest of the arguments
    describe the callable to invoke.

    We require at least Mutagen 1.33, where `IOError` is *never* used,
    neither for internal parsing errors *nor* for ordinary IO error
    conditions such as a bad filename. Mutagen-specific parsing errors and IO
    errors are reraised as `UnreadableFileError`. Other exceptions
    raised inside Mutagen---i.e., bugs---are reraised as `MutagenError`.
    """
    try:
        return func(*args, **kwargs)
    except mutagen.MutagenError as exc:
        log.debug(u'%s failed: %s', action, six.text_type(exc))
        raise UnreadableFileError(path, six.text_type(exc))
    except Exception as exc:
        # Isolate bugs in Mutagen.
        log.debug(u'%s', traceback.format_exc())
        log.error(u'uncaught Mutagen exception in %s: %s', action, exc)
        raise MutagenError(path, exc)


# Utility. 

def _sc_decode(soundcheck):
    """Convert a Sound Check bytestring value to a (gain, peak) tuple as
    used by ReplayGain.
    """
    # We decode binary data. If one of the formats gives us a text
    # string, interpret it as UTF-8.
    if isinstance(soundcheck, six.text_type):
        soundcheck = soundcheck.encode('utf-8')

    # SoundCheck tags consist of 10 numbers, each represented by 8
    # characters of ASCII hex preceded by a space.
    try:
        soundcheck = codecs.decode(soundcheck.replace(b' ', b''), 'hex')
        soundcheck = struct.unpack('!iiiiiiiiii', soundcheck)
    except (struct.error, TypeError, binascii.Error):
        # SoundCheck isn't in the format we expect, so return default
        # values.
        return 0.0, 0.0

    # SoundCheck stores absolute calculated/measured RMS value in an
    # unknown unit. We need to find the ratio of this measurement
    # compared to a reference value of 1000 to get our gain in dB. We
    # play it safe by using the larger of the two values (i.e., the most
    # attenuation).
    maxgain = max(soundcheck[:2])
    if maxgain > 0:
        gain = math.log10(maxgain / 1000.0) * -10
    else:
        # Invalid gain value found.
        gain = 0.0

    # SoundCheck stores peak values as the actual value of the sample,
    # and again separately for the left and right channels. We need to
    # convert this to a percentage of full scale, which is 32768 for a
    # 16 bit sample. Once again, we play it safe by using the larger of
    # the two values.
    peak = max(soundcheck[6:8]) / 32768.0

    return round(gain, 2), round(peak, 6) 

def test_sizes(self):
        for t in signed_types + unsigned_types + float_types + bool_types:
            try:
                size = struct.calcsize(t._type_)
            except struct.error:
                continue
            # sizeof of the type...
            self.assertEqual(sizeof(t), size)
            # and sizeof of an instance
            self.assertEqual(sizeof(t()), size) 

def popen(cmd, mode='r', bufsize=None):

    """ Portable popen() interface.
    """
    # Find a working popen implementation preferring win32pipe.popen
    # over os.popen over _popen
    popen = None
    if os.environ.get('OS','') == 'Windows_NT':
        # On NT win32pipe should work; on Win9x it hangs due to bugs
        # in the MS C lib (see MS KnowledgeBase article Q150956)
        try:
            import win32pipe
        except ImportError:
            pass
        else:
            popen = win32pipe.popen
    if popen is None:
        if hasattr(os,'popen'):
            popen = os.popen
            # Check whether it works... it doesn't in GUI programs
            # on Windows platforms
            if sys.platform == 'win32': # XXX Others too ?
                try:
                    popen('')
                except os.error:
                    popen = _popen
        else:
            popen = _popen
    if bufsize is None:
        return popen(cmd,mode)
    else:
        return popen(cmd,mode,bufsize) 

def _syscmd_ver(system='', release='', version='',

               supported_platforms=('win32','win16','dos','os2')):

    """ Tries to figure out the OS version used and returns
        a tuple (system,release,version).

        It uses the "ver" shell command for this which is known
        to exists on Windows, DOS and OS/2. XXX Others too ?

        In case this fails, the given parameters are used as
        defaults.

    """
    if sys.platform not in supported_platforms:
        return system,release,version

    # Try some common cmd strings
    for cmd in ('ver','command /c ver','cmd /c ver'):
        try:
            pipe = popen(cmd)
            info = pipe.read()
            if pipe.close():
                raise os.error,'command failed'
            # XXX How can I suppress shell errors from being written
            #     to stderr ?
        except os.error,why:
            #print 'Command %s failed: %s' % (cmd,why)
            continue
        except IOError,why:
            #print 'Command %s failed: %s' % (cmd,why)
            continue 

def _read_long(file):
    try:
        return struct.unpack('>l', file.read(4))[0]
    except struct.error:
        raise EOFError 

def _read_short(file):
    try:
        return struct.unpack('>h', file.read(2))[0]
    except struct.error:
        raise EOFError 

def _read_ushort(file):
    try:
        return struct.unpack('>H', file.read(2))[0]
    except struct.error:
        raise EOFError 

def raise_conversion_error(function):
    """ Wrap any raised struct.errors in a ConversionError. """

    @wraps(function)
    def result(self, value):
        try:
            return function(self, value)
        except struct.error as e:
            raise ConversionError(e.args[0])
    return result 

def pack_uhyper(self, x):
        try:
            self.pack_uint(x>>32 & 0xffffffffL)
        except (TypeError, struct.error) as e:
            raise ConversionError(e.args[0])
        try:
            self.pack_uint(x & 0xffffffffL)
        except (TypeError, struct.error) as e:
            raise ConversionError(e.args[0]) 

def test_pack_into(self):
        test_string = 'Reykjavik rocks, eow!'
        writable_buf = array.array('c', ' '*100)
        fmt = '21s'
        s = struct.Struct(fmt)

        # Test without offset
        s.pack_into(writable_buf, 0, test_string)
        from_buf = writable_buf.tostring()[:len(test_string)]
        self.assertEqual(from_buf, test_string)

        # Test with offset.
        s.pack_into(writable_buf, 10, test_string)
        from_buf = writable_buf.tostring()[:len(test_string)+10]
        self.assertEqual(from_buf, test_string[:10] + test_string)

        # Go beyond boundaries.
        small_buf = array.array('c', ' '*10)
        self.assertRaises((ValueError, struct.error), s.pack_into, small_buf, 0,
                          test_string)
        self.assertRaises((ValueError, struct.error), s.pack_into, small_buf, 2,
                          test_string)

        # Test bogus offset (issue 3694)
        sb = small_buf
        self.assertRaises((TypeError, struct.error), struct.pack_into, b'', sb,
                          None) 

def test_count_overflow(self):
        hugecount = '{}b'.format(sys.maxsize+1)
        self.assertRaises(struct.error, struct.calcsize, hugecount)

        hugecount2 = '{}b{}H'.format(sys.maxsize//2, sys.maxsize//2)
        self.assertRaises(struct.error, struct.calcsize, hugecount2) 

def __init__(  # pylint: disable=super-init-not-called
        self,
        target_pin: int,
        reset_pin: int,

        device_path: str,
        init_delay: float,
        init_retries: int,
        reset_delay: float,
    ) -> None:

        self.__target_pin = gpio.set_output(target_pin)
        self.__reset_pin = gpio.set_output(reset_pin)

        self.__device_path = device_path
        self.__init_delay = init_delay
        self.__init_retries = init_retries
        self.__reset_delay = reset_delay

        self.__region = aioregion.AioExclusiveRegion(MsdIsBusyError)

        self.__device_info: Optional[_DeviceInfo] = None
        self.__connected = False

        self.__device_file: Optional[aiofiles.base.AiofilesContextManager] = None
        self.__written = 0

        self.__state_queue: asyncio.queues.Queue = asyncio.Queue()

        logger = get_logger(0)
        logger.info("Using %r as MSD", self.__device_path)
        try:
            aiotools.run_sync(self.__load_device_info())
        except Exception as err:
            log = (logger.error if isinstance(err, MsdError) else logger.exception)
            log("MSD is offline: %s", err) 

def __write_image_info(self, name: str, complete: bool) -> None:
        assert self.__device_file
        assert self.__device_info
        if self.__device_info.size - self.__written > _IMAGE_INFO_SIZE:
            await self.__device_file.seek(self.__device_info.size - _IMAGE_INFO_SIZE)
            await aiotools.afile_write_now(self.__device_file, _make_image_info_bytes(name, self.__written, complete))
            await self.__device_file.seek(0)
        else:
            get_logger().error("Can't write image info because device is full") 

def _compat_to_bytes(intval, length, endianess):
    assert isinstance(intval, _compat_int_types)
    assert endianess == 'big'
    if length == 4:
        if intval < 0 or intval >= 2 ** 32:
            raise struct.error("integer out of range for 'I' format code")
        return struct.pack(b'!I', intval)
    elif length == 16:
        if intval < 0 or intval >= 2 ** 128:
            raise struct.error("integer out of range for 'QQ' format code")
        return struct.pack(b'!QQ', intval >> 64, intval & 0xffffffffffffffff)
    else:
        raise NotImplementedError() 

def v6_int_to_packed(address):
    """Represent an address as 16 packed bytes in network (big-endian) order.

    Args:
        address: An integer representation of an IPv6 IP address.

    Returns:
        The integer address packed as 16 bytes in network (big-endian) order.

    """
    try:
        return _compat_to_bytes(address, 16, 'big')
    except (struct.error, OverflowError):
        raise ValueError("Address negative or too large for IPv6") 

def _parse_octet(cls, octet_str):
        """Convert a decimal octet into an integer.

        Args:
            octet_str: A string, the number to parse.

        Returns:
            The octet as an integer.

        Raises:
            ValueError: if the octet isn't strictly a decimal from [0..255].

        """
        if not octet_str:
            raise ValueError("Empty octet not permitted")
        # Whitelist the characters, since int() allows a lot of bizarre stuff.
        if not cls._DECIMAL_DIGITS.issuperset(octet_str):
            msg = "Only decimal digits permitted in %r"
            raise ValueError(msg % octet_str)
        # We do the length check second, since the invalid character error
        # is likely to be more informative for the user
        if len(octet_str) > 3:
            msg = "At most 3 characters permitted in %r"
            raise ValueError(msg % octet_str)
        # Convert to integer (we know digits are legal)
        octet_int = int(octet_str, 10)
        # Any octets that look like they *might* be written in octal,
        # and which don't look exactly the same in both octal and
        # decimal are rejected as ambiguous
        if octet_int > 7 and octet_str[0] == '0':
            msg = "Ambiguous (octal/decimal) value in %r not permitted"
            raise ValueError(msg % octet_str)
        if octet_int > 255:
            raise ValueError("Octet %d (> 255) not permitted" % octet_int)
        return octet_int 

def DecodePacket(self, packet):
        """Initialize the object from raw packet data.  Decode a packet as
        received from the network and decode it.

        :param packet: raw packet
        :type packet:  string"""

        try:
            (self.code, self.id, length, self.authenticator)=struct.unpack("!BBH16s", packet[0:20])
        except struct.error:
            raise PacketError, "Packet header is corrupt"
        if len(packet)!=length:
            raise PacketError, "Packet has invalid length"
        if length>8192:
            raise PacketError, "Packet length is too long (%d)" % length

        self.clear()

        packet=packet[20:]
        while packet:
            try:
                (key, attrlen)=struct.unpack("!BB", packet[0:2])
            except struct.error:
                raise PacketError, "Attribute header is corrupt"

            if attrlen<2:
                raise PacketError, "Attribute length is too small (%d)" % attrlen

            value=packet[2:attrlen]
            if key==26:
                (key,value)=self._PktDecodeVendorAttribute(value)

            if self.data.has_key(key):
                self.data[key].append(value)
            else:
                self.data[key]=[value]

            packet=packet[attrlen:] 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def _compat_to_bytes(intval, length, endianess):
    assert isinstance(intval, _compat_int_types)
    assert endianess == 'big'
    if length == 4:
        if intval < 0 or intval >= 2 ** 32:
            raise struct.error("integer out of range for 'I' format code")
        return struct.pack(b'!I', intval)
    elif length == 16:
        if intval < 0 or intval >= 2 ** 128:
            raise struct.error("integer out of range for 'QQ' format code")
        return struct.pack(b'!QQ', intval >> 64, intval & 0xffffffffffffffff)
    else:
        raise NotImplementedError() 

def v6_int_to_packed(address):
    """Represent an address as 16 packed bytes in network (big-endian) order.

    Args:
        address: An integer representation of an IPv6 IP address.

    Returns:
        The integer address packed as 16 bytes in network (big-endian) order.

    """
    try:
        return _compat_to_bytes(address, 16, 'big')
    except (struct.error, OverflowError):
        raise ValueError("Address negative or too large for IPv6") 

def _parse_octet(cls, octet_str):
        """Convert a decimal octet into an integer.

        Args:
            octet_str: A string, the number to parse.

        Returns:
            The octet as an integer.

        Raises:
            ValueError: if the octet isn't strictly a decimal from [0..255].

        """
        if not octet_str:
            raise ValueError("Empty octet not permitted")
        # Whitelist the characters, since int() allows a lot of bizarre stuff.
        if not cls._DECIMAL_DIGITS.issuperset(octet_str):
            msg = "Only decimal digits permitted in %r"
            raise ValueError(msg % octet_str)
        # We do the length check second, since the invalid character error
        # is likely to be more informative for the user
        if len(octet_str) > 3:
            msg = "At most 3 characters permitted in %r"
            raise ValueError(msg % octet_str)
        # Convert to integer (we know digits are legal)
        octet_int = int(octet_str, 10)
        # Any octets that look like they *might* be written in octal,
        # and which don't look exactly the same in both octal and
        # decimal are rejected as ambiguous
        if octet_int > 7 and octet_str[0] == '0':
            msg = "Ambiguous (octal/decimal) value in %r not permitted"
            raise ValueError(msg % octet_str)
        if octet_int > 255:
            raise ValueError("Octet %d (> 255) not permitted" % octet_int)
        return octet_int 

def _DoubleDecoder():
  """Returns a decoder for a double field.

  This code works around a bug in struct.unpack for not-a-number.
  """

  local_unpack = struct.unpack

  def InnerDecode(buffer, pos):
    """Decode serialized double to a double and new position.

    Args:
      buffer: memoryview of the serialized bytes.
      pos: int, position in the memory view to start at.

    Returns:
      Tuple[float, int] of the decoded double value and new position
      in the serialized data.
    """
    # We expect a 64-bit value in little-endian byte order.  Bit 1 is the sign
    # bit, bits 2-12 represent the exponent, and bits 13-64 are the significand.
    new_pos = pos + 8
    double_bytes = buffer[pos:new_pos].tobytes()

    # If this value has all its exponent bits set and at least one significand
    # bit set, it's not a number.  In Python 2.4, struct.unpack will treat it
    # as inf or -inf.  To avoid that, we treat it specially.
    if ((double_bytes[7:8] in b'\x7F\xFF')
        and (double_bytes[6:7] >= b'\xF0')
        and (double_bytes[0:7] != b'\x00\x00\x00\x00\x00\x00\xF0')):
      return (_NAN, new_pos)

    # Note that we expect someone up-stack to catch struct.error and convert
    # it to _DecodeError -- this way we don't have to set up exception-
    # handling blocks every time we parse one value.
    result = local_unpack('<d', double_bytes)[0]
    return (result, new_pos)
  return _SimpleDecoder(wire_format.WIRETYPE_FIXED64, InnerDecode) 

def _SkipVarint(buffer, pos, end):
  """Skip a varint value.  Returns the new position."""
  # Previously ord(buffer[pos]) raised IndexError when pos is out of range.
  # With this code, ord(b'') raises TypeError.  Both are handled in
  # python_message.py to generate a 'Truncated message' error.
  while ord(buffer[pos:pos+1].tobytes()) & 0x80:
    pos += 1
  pos += 1
  if pos > end:
    raise _DecodeError('Truncated message.')
  return pos 

def Modified(self):
    if self.dirty:
      return
    try:
      # Propagate the signal to our parents iff this is the first field set.
      self._parent_message_weakref._Modified()
    except ReferenceError:
      # We can get here if a client has kept a reference to a child object,
      # and is now setting a field on it, but the child's parent has been
      # garbage-collected.  This is not an error.
      pass 

def decode(self, buffer):
        
        img = io.BytesIO()
        blank_line = bytearray((0xff,)*((self.state.xsize+7)//8))
        try:
            self.fd.seek(32)
            rowmap = struct.unpack_from("<%dH" % (self.state.ysize),
                                        self.fd.read(self.state.ysize*2))
        except struct.error:
            raise IOError("Truncated MSP file in row map")

        for x, rowlen in enumerate(rowmap):
            try:
                if rowlen == 0:
                    img.write(blank_line)
                    continue
                row = self.fd.read(rowlen)
                if len(row) != rowlen:
                    raise IOError("Truncated MSP file, expected %d bytes on row %s",
                                  (rowlen, x))
                idx = 0
                while idx < rowlen:
                    runtype = i8(row[idx])
                    idx += 1
                    if runtype == 0:
                        (runcount, runval) = struct.unpack("Bc", row[idx:idx+2])
                        img.write(runval * runcount)
                        idx += 2
                    else:
                        runcount = runtype
                        img.write(row[idx:idx+runcount])
                        idx += runcount
                        
            except struct.error:
                raise IOError("Corrupted MSP file in row %d" %x)
            
        self.set_as_raw(img.getvalue(), ("1", 0, 1))
                
        return 0,0 

def point(self, lut, mode=None):
        """
        Maps this image through a lookup table or function.

        :param lut: A lookup table, containing 256 (or 65336 if
           self.mode=="I" and mode == "L") values per band in the
           image.  A function can be used instead, it should take a
           single argument. The function is called once for each
           possible pixel value, and the resulting table is applied to
           all bands of the image.
        :param mode: Output mode (default is same as input).  In the
           current version, this can only be used if the source image
           has mode "L" or "P", and the output has mode "1" or the
           source image mode is "I" and the output mode is "L".
        :returns: An :py:class:`~PIL.Image.Image` object.
        """

        self.load()

        if isinstance(lut, ImagePointHandler):
            return lut.point(self)

        if callable(lut):
            # if it isn't a list, it should be a function
            if self.mode in ("I", "I;16", "F"):
                # check if the function can be used with point_transform
                # UNDONE wiredfool -- I think this prevents us from ever doing
                # a gamma function point transform on > 8bit images.
                scale, offset = _getscaleoffset(lut)
                return self._new(self.im.point_transform(scale, offset))
            # for other modes, convert the function to a table
            lut = [lut(i) for i in range(256)] * self.im.bands

        if self.mode == "F":
            # FIXME: _imaging returns a confusing error message for this case
            raise ValueError("point operation not supported for this mode")

        return self._new(self.im.point(lut, mode)) 

def raise_ioerror(error):
    try:
        message = Image.core.getcodecstatus(error)
    except AttributeError:
        message = ERRORS.get(error)
    if not message:
        message = "decoder error %d" % error
    raise IOError(message + " when reading image file")


#
# --------------------------------------------------------------------
# Helpers 

def chunk_iCCP(self, pos, length):

        # ICC profile
        s = ImageFile._safe_read(self.fp, length)
        # according to PNG spec, the iCCP chunk contains:
        # Profile name  1-79 bytes (character string)
        # Null separator        1 byte (null character)
        # Compression method    1 byte (0)
        # Compressed profile    n bytes (zlib with deflate compression)
        i = s.find(b"\0")
        logger.debug("iCCP profile name %r", s[:i])
        logger.debug("Compression method %s", i8(s[i]))
        comp_method = i8(s[i])
        if comp_method != 0:
            raise SyntaxError("Unknown compression method %s in iCCP chunk" %
                              comp_method)
        try:
            icc_profile = _safe_zlib_decompress(s[i+2:])
        except ValueError:
            if ImageFile.LOAD_TRUNCATED_IMAGES:
                icc_profile = None
            else:
                raise
        except zlib.error:
            icc_profile = None  # FIXME
        self.im_info["icc_profile"] = icc_profile
        return s 

def _compat_to_bytes(intval, length, endianess):
    assert isinstance(intval, _compat_int_types)
    assert endianess == 'big'
    if length == 4:
        if intval < 0 or intval >= 2 ** 32:
            raise struct.error("integer out of range for 'I' format code")
        return struct.pack(b'!I', intval)
    elif length == 16:
        if intval < 0 or intval >= 2 ** 128:
            raise struct.error("integer out of range for 'QQ' format code")
        return struct.pack(b'!QQ', intval >> 64, intval & 0xffffffffffffffff)
    else:
        raise NotImplementedError() 

def v6_int_to_packed(address):
    """Represent an address as 16 packed bytes in network (big-endian) order.

    Args:
        address: An integer representation of an IPv6 IP address.

    Returns:
        The integer address packed as 16 bytes in network (big-endian) order.

    """
    try:
        return _compat_to_bytes(address, 16, 'big')
    except (struct.error, OverflowError):
        raise ValueError("Address negative or too large for IPv6") 

def _parse_octet(cls, octet_str):
        """Convert a decimal octet into an integer.

        Args:
            octet_str: A string, the number to parse.

        Returns:
            The octet as an integer.

        Raises:
            ValueError: if the octet isn't strictly a decimal from [0..255].

        """
        if not octet_str:
            raise ValueError("Empty octet not permitted")
        # Whitelist the characters, since int() allows a lot of bizarre stuff.
        if not cls._DECIMAL_DIGITS.issuperset(octet_str):
            msg = "Only decimal digits permitted in %r"
            raise ValueError(msg % octet_str)
        # We do the length check second, since the invalid character error
        # is likely to be more informative for the user
        if len(octet_str) > 3:
            msg = "At most 3 characters permitted in %r"
            raise ValueError(msg % octet_str)
        # Convert to integer (we know digits are legal)
        octet_int = int(octet_str, 10)
        # Any octets that look like they *might* be written in octal,
        # and which don't look exactly the same in both octal and
        # decimal are rejected as ambiguous
        if octet_int > 7 and octet_str[0] == '0':
            msg = "Ambiguous (octal/decimal) value in %r not permitted"
            raise ValueError(msg % octet_str)
        if octet_int > 255:
            raise ValueError("Octet %d (> 255) not permitted" % octet_int)
        return octet_int 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def b85decode(b):
        _b85dec = [None] * 256
        for i, c in enumerate(iterbytes(_b85alphabet)):
            _b85dec[c] = i

        padding = (-len(b)) % 5
        b = b + b'~' * padding
        out = []
        packI = struct.Struct('!I').pack
        for i in range(0, len(b), 5):
            chunk = b[i:i + 5]
            acc = 0
            try:
                for c in iterbytes(chunk):
                    acc = acc * 85 + _b85dec[c]
            except TypeError:
                for j, c in enumerate(iterbytes(chunk)):
                    if _b85dec[c] is None:
                        raise ValueError(
                            'bad base85 character at position %d' % (i + j)
                        )
                raise
            try:
                out.append(packI(acc))
            except struct.error:
                raise ValueError('base85 overflow in hunk starting at byte %d'
                                 % i)

        result = b''.join(out)
        if padding:
            result = result[:-padding]
        return result 

def __set__(self, obj, value):
        try:
            v = struct.pack("<I", value)
            self.data[obj] = v
        except struct.error as e:
            raise ValueError("Only DWORD values are allowed: %08x" % value) 

def __set__(self, obj, value):
        try:
            v = struct.pack("<H", value)
            self.data[obj] = v
        except struct.error as e:
            raise ValueError("Only WORD values are allowed: %04x" % value) 

def __set__(self, obj, value):
        try:
            v = struct.pack("<B", value)
            self.data[obj] = v
        except struct.error as e:
            raise ValueError("Only BYTE values are allowed: %02x" % value) 

def parse_header(filepath):
    header_size = 0
    try:
        with open(filepath, 'rb') as f:
            old_mode = struct.unpack('<I', f.read(4))[0]
            key_sz = struct.unpack('<I', f.read(4))[0]
            key = f.read(key_sz)
            iv_file = f.read(16)
            if not key or not iv_file:
                raise CorruptFile()
            header_size = f.tell()
    except struct.error:
        raise CorruptFile()

    return iv_file, header_size 

def readline(self):
        try:
            retval = self.sb.readline()
        except struct.error:
            raise EOFError()
        self.pos += len(retval)
        return retval 

def linux_distribution(distname='', version='', id='',

                       supported_dists=_supported_dists,
                       full_distribution_name=1):

    """ Tries to determine the name of the Linux OS distribution name.

        The function first looks for a distribution release file in
        /etc and then reverts to _dist_try_harder() in case no
        suitable files are found.

        supported_dists may be given to define the set of Linux
        distributions to look for. It defaults to a list of currently
        supported Linux distributions identified by their release file
        name.

        If full_distribution_name is true (default), the full
        distribution read from the OS is returned. Otherwise the short
        name taken from supported_dists is used.

        Returns a tuple (distname,version,id) which default to the
        args given as parameters.

    """
    try:
        etc = os.listdir('/etc')
    except os.error:
        # Probably not a Unix system
        return distname,version,id
    etc.sort()
    for file in etc:
        m = _release_filename.match(file)
        if m is not None:
            _distname,dummy = m.groups()
            if _distname in supported_dists:
                distname = _distname
                break
    else:
        return _dist_try_harder(distname,version,id)

    # Read the first line
    f = open('/etc/'+file, 'r')
    firstline = f.readline()
    f.close()
    _distname, _version, _id = _parse_release_file(firstline)

    if _distname and full_distribution_name:
        distname = _distname
    if _version:
        version = _version
    if _id:
        id = _id
    return distname, version, id

# To maintain backwards compatibility: 

def _syscmd_file(target,default=''):

    """ Interface to the system's file command.

        The function uses the -b option of the file command to have it
        ommit the filename in its output and if possible the -L option
        to have the command follow symlinks. It returns default in
        case the command should fail.

    """

    # We do the import here to avoid a bootstrap issue.
    # See c73b90b6dadd changeset.
    #
    # [..]
    # ranlib libpython2.7.a
    # gcc   -o python \
    #        Modules/python.o \
    #        libpython2.7.a -lsocket -lnsl -ldl    -lm
    # Traceback (most recent call last):
    #  File "./setup.py", line 8, in <module>
    #    from platform import machine as platform_machine
    #  File "[..]/build/Lib/platform.py", line 116, in <module>
    #    import sys,string,os,re,subprocess
    #  File "[..]/build/Lib/subprocess.py", line 429, in <module>
    #    import select
    # ImportError: No module named select

    import subprocess

    if sys.platform in ('dos','win32','win16','os2'):
        # XXX Others too ?
        return default
    target = _follow_symlinks(target)
    try:
        proc = subprocess.Popen(['file', target],
                stdout=subprocess.PIPE, stderr=subprocess.STDOUT)

    except (AttributeError,os.error):
        return default
    output = proc.communicate()[0]
    rc = proc.wait()
    if not output or rc:
        return default
    else:
        return output

### Information about the used architecture

# Default values for architecture; non-empty strings override the
# defaults given as parameters 

def _FloatDecoder():
  """Returns a decoder for a float field.

  This code works around a bug in struct.unpack for non-finite 32-bit
  floating-point values.
  """

  local_unpack = struct.unpack

  def InnerDecode(buffer, pos):
    """Decode serialized float to a float and new position.

    Args:
      buffer: memoryview of the serialized bytes
      pos: int, position in the memory view to start at.

    Returns:
      Tuple[float, int] of the deserialized float value and new position
      in the serialized data.
    """
    # We expect a 32-bit value in little-endian byte order.  Bit 1 is the sign
    # bit, bits 2-9 represent the exponent, and bits 10-32 are the significand.
    new_pos = pos + 4
    float_bytes = buffer[pos:new_pos].tobytes()

    # If this value has all its exponent bits set, then it's non-finite.
    # In Python 2.4, struct.unpack will convert it to a finite 64-bit value.
    # To avoid that, we parse it specially.
    if (float_bytes[3:4] in b'\x7F\xFF' and float_bytes[2:3] >= b'\x80'):
      # If at least one significand bit is set...
      if float_bytes[0:3] != b'\x00\x00\x80':
        return (_NAN, new_pos)
      # If sign bit is set...
      if float_bytes[3:4] == b'\xFF':
        return (_NEG_INF, new_pos)
      return (_POS_INF, new_pos)

    # Note that we expect someone up-stack to catch struct.error and convert
    # it to _DecodeError -- this way we don't have to set up exception-
    # handling blocks every time we parse one value.
    result = local_unpack('<f', float_bytes)[0]
    return (result, new_pos)
  return _SimpleDecoder(wire_format.WIRETYPE_FIXED32, InnerDecode) 

def StringDecoder(field_number, is_repeated, is_packed, key, new_default,
                  is_strict_utf8=False):
  """Returns a decoder for a string field."""

  local_DecodeVarint = _DecodeVarint
  local_unicode = six.text_type

  def _ConvertToUnicode(memview):
    """Convert byte to unicode."""
    byte_str = memview.tobytes()
    try:
      value = local_unicode(byte_str, 'utf-8')
    except UnicodeDecodeError as e:
      # add more information to the error message and re-raise it.
      e.reason = '%s in field: %s' % (e, key.full_name)
      raise

    if is_strict_utf8 and six.PY2 and sys.maxunicode > _UCS2_MAXUNICODE:
      # Only do the check for python2 ucs4 when is_strict_utf8 enabled
      if _SURROGATE_PATTERN.search(value):
        reason = ('String field %s contains invalid UTF-8 data when parsing'
                  'a protocol buffer: surrogates not allowed. Use'
                  'the bytes type if you intend to send raw bytes.') % (
                      key.full_name)
        raise message.DecodeError(reason)

    return value

  assert not is_packed
  if is_repeated:
    tag_bytes = encoder.TagBytes(field_number,
                                 wire_format.WIRETYPE_LENGTH_DELIMITED)
    tag_len = len(tag_bytes)
    def DecodeRepeatedField(buffer, pos, end, message, field_dict):
      value = field_dict.get(key)
      if value is None:
        value = field_dict.setdefault(key, new_default(message))
      while 1:
        (size, pos) = local_DecodeVarint(buffer, pos)
        new_pos = pos + size
        if new_pos > end:
          raise _DecodeError('Truncated string.')
        value.append(_ConvertToUnicode(buffer[pos:new_pos]))
        # Predict that the next tag is another copy of the same repeated field.
        pos = new_pos + tag_len
        if buffer[new_pos:pos] != tag_bytes or new_pos == end:
          # Prediction failed.  Return.
          return new_pos
    return DecodeRepeatedField
  else:
    def DecodeField(buffer, pos, end, message, field_dict):
      (size, pos) = local_DecodeVarint(buffer, pos)
      new_pos = pos + size
      if new_pos > end:
        raise _DecodeError('Truncated string.')
      field_dict[key] = _ConvertToUnicode(buffer[pos:new_pos])
      return new_pos
    return DecodeField 

def _AddPropertiesForNonRepeatedCompositeField(field, cls):
  """Adds a public property for a nonrepeated, composite protocol message field.
  A composite field is a "group" or "message" field.

  Clients can use this property to get the value of the field, but cannot
  assign to the property directly.

  Args:
    field: A FieldDescriptor for this field.
    cls: The class we're constructing.
  """
  # TODO(robinson): Remove duplication with similar method
  # for non-repeated scalars.
  proto_field_name = field.name
  property_name = _PropertyName(proto_field_name)

  def getter(self):
    field_value = self._fields.get(field)
    if field_value is None:
      # Construct a new object to represent this field.
      field_value = field._default_constructor(self)

      # Atomically check if another thread has preempted us and, if not, swap
      # in the new object we just created.  If someone has preempted us, we
      # take that object and discard ours.
      # WARNING:  We are relying on setdefault() being atomic.  This is true
      #   in CPython but we haven't investigated others.  This warning appears
      #   in several other locations in this file.
      field_value = self._fields.setdefault(field, field_value)
    return field_value
  getter.__module__ = None
  getter.__doc__ = 'Getter for %s.' % proto_field_name

  # We define a setter just so we can throw an exception with a more
  # helpful error message.
  def setter(self, new_value):
    raise AttributeError('Assignment not allowed to composite field '
                         '"%s" in protocol message object.' % proto_field_name)

  # Add a property to encapsulate the getter.
  doc = 'Magic attribute generated for "%s" proto field.' % proto_field_name
  setattr(cls, property_name, _FieldProperty(field, getter, setter, doc=doc)) 

def tobytes(self, encoder_name="raw", *args):
        """
        Return image as a bytes object.

        .. warning::

            This method returns the raw image data from the internal
            storage.  For compressed image data (e.g. PNG, JPEG) use
            :meth:`~.save`, with a BytesIO parameter for in-memory
            data.

        :param encoder_name: What encoder to use.  The default is to
                             use the standard "raw" encoder.
        :param args: Extra arguments to the encoder.
        :rtype: A bytes object.
        """

        # may pass tuple instead of argument list
        if len(args) == 1 and isinstance(args[0], tuple):
            args = args[0]

        if encoder_name == "raw" and args == ():
            args = self.mode

        self.load()

        # unpack data
        e = _getencoder(self.mode, encoder_name, args)
        e.setimage(self.im)

        bufsize = max(65536, self.size[0] * 4)  # see RawEncode.c

        data = []
        while True:
            l, s, d = e.encode(bufsize)
            data.append(d)
            if s:
                break
        if s < 0:
            raise RuntimeError("encoder error %d in tobytes" % s)

        return b"".join(data) 

def _save(im, fp, tile, bufsize=0):
    """Helper to save image based on tile list

    :param im: Image object.
    :param fp: File object.
    :param tile: Tile list.
    :param bufsize: Optional buffer size
    """

    im.load()
    if not hasattr(im, "encoderconfig"):
        im.encoderconfig = ()
    tile.sort(key=_tilesort)
    # FIXME: make MAXBLOCK a configuration parameter
    # It would be great if we could have the encoder specify what it needs
    # But, it would need at least the image size in most cases. RawEncode is
    # a tricky case.
    bufsize = max(MAXBLOCK, bufsize, im.size[0] * 4)  # see RawEncode.c
    if fp == sys.stdout:
        fp.flush()
        return
    try:
        fh = fp.fileno()
        fp.flush()
    except (AttributeError, io.UnsupportedOperation):
        # compress to Python file-compatible object
        for e, b, o, a in tile:
            e = Image._getencoder(im.mode, e, a, im.encoderconfig)
            if o > 0:
                fp.seek(o, 0)
            e.setimage(im.im, b)
            if e.pushes_fd:
                e.setfd(fp)
                l, s = e.encode_to_pyfd()
            else:
                while True:
                    l, s, d = e.encode(bufsize)
                    fp.write(d)
                    if s:
                        break
            if s < 0:
                raise IOError("encoder error %d when writing image file" % s)
            e.cleanup()
    else:
        # slight speedup: compress to real file object
        for e, b, o, a in tile:
            e = Image._getencoder(im.mode, e, a, im.encoderconfig)
            if o > 0:
                fp.seek(o, 0)
            e.setimage(im.im, b)
            if e.pushes_fd:
                e.setfd(fp)
                l, s = e.encode_to_pyfd()
            else:
                s = e.encode_to_file(fh, bufsize)
            if s < 0:
                raise IOError("encoder error %d when writing image file" % s)
            e.cleanup()
    if hasattr(fp, "flush"):
        fp.flush() 

def _open(self):
        # check header
        n = 27 * 4  # read 27 float values
        f = self.fp.read(n)

        try:
            self.bigendian = 1
            t = struct.unpack('>27f', f)  # try big-endian first
            hdrlen = isSpiderHeader(t)
            if hdrlen == 0:
                self.bigendian = 0
                t = struct.unpack('<27f', f)  # little-endian
                hdrlen = isSpiderHeader(t)
            if hdrlen == 0:
                raise SyntaxError("not a valid Spider file")
        except struct.error:
            raise SyntaxError("not a valid Spider file")

        h = (99,) + t   # add 1 value : spider header index starts at 1
        iform = int(h[5])
        if iform != 1:
            raise SyntaxError("not a Spider 2D image")

        self.size = int(h[12]), int(h[2])  # size in pixels (width, height)
        self.istack = int(h[24])
        self.imgnumber = int(h[27])

        if self.istack == 0 and self.imgnumber == 0:
            # stk=0, img=0: a regular 2D image
            offset = hdrlen
            self._nimages = 1
        elif self.istack > 0 and self.imgnumber == 0:
            # stk>0, img=0: Opening the stack for the first time
            self.imgbytes = int(h[12]) * int(h[2]) * 4
            self.hdrlen = hdrlen
            self._nimages = int(h[26])
            # Point to the first image in the stack
            offset = hdrlen * 2
            self.imgnumber = 1
        elif self.istack == 0 and self.imgnumber > 0:
            # stk=0, img>0: an image within the stack
            offset = hdrlen + self.stkoffset
            self.istack = 2  # So Image knows it's still a stack
        else:
            raise SyntaxError("inconsistent stack header values")

        if self.bigendian:
            self.rawmode = "F;32BF"
        else:
            self.rawmode = "F;32F"
        self.mode = "F"

        self.tile = [
            ("raw", (0, 0) + self.size, offset,
                (self.rawmode, 0, 1))]
        self.__fp = self.fp  # FIXME: hack 

def chunk_iTXt(self, pos, length):

        # international text
        r = s = ImageFile._safe_read(self.fp, length)
        try:
            k, r = r.split(b"\0", 1)
        except ValueError:
            return s
        if len(r) < 2:
            return s
        cf, cm, r = i8(r[0]), i8(r[1]), r[2:]
        try:
            lang, tk, v = r.split(b"\0", 2)
        except ValueError:
            return s
        if cf != 0:
            if cm == 0:
                try:
                    v = _safe_zlib_decompress(v)
                except ValueError:
                    if ImageFile.LOAD_TRUNCATED_IMAGES:
                        return s
                    else:
                        raise
                except zlib.error:
                    return s
            else:
                return s
        if bytes is not str:
            try:
                k = k.decode("latin-1", "strict")
                lang = lang.decode("utf-8", "strict")
                tk = tk.decode("utf-8", "strict")
                v = v.decode("utf-8", "strict")
            except UnicodeError:
                return s

        self.im_info[k] = self.im_text[k] = iTXt(v, lang, tk)
        self.check_text_memory(len(v))

        return s


# --------------------------------------------------------------------
# PNG reader 

def process_complete(self):
        super(FRAData, self).process_complete()

        if self._stateid not in self.scales:
            # log.debug("Can't render FRAData frame, haven't saved calibration
            # data for state %d", self._stateid)
            self.complete = False
            return

        # Get scaling/correction factors based on current instrument
        # configuration
        scales = self.scales[self._stateid]

        try:
            self.frequency = scales['frequency_axis']

            smpls = int(len(self._raw1) / 4)
            dat = struct.unpack('<' + 'i' * smpls, self._raw1)
            dat = [x if x != -0x80000000 else None for x in dat]

            self.ch1_bits = [float(x) if x is not None else None for x in dat]
            self.ch1 = _FRAChannelData(self.ch1_bits,
                                       scales['gain_correction'],
                                       scales['g1'],
                                       scales['sweep_amplitude_ch1'])

            smpls = int(len(self._raw2) / 4)
            dat = struct.unpack('<' + 'i' * smpls, self._raw2)
            dat = [x if x != -0x80000000 else None for x in dat]

            self.ch2_bits = [float(x) if x is not None else None for x in dat]
            self.ch2 = _FRAChannelData(self.ch2_bits,
                                       scales['gain_correction'],
                                       scales['g2'],
                                       scales['sweep_amplitude_ch2'])

        except (IndexError, TypeError, struct.error):
            # If the data is bollocksed, force a reinitialisation on next
            # packet
            self.frameid = None
            self.complete = False

        # A valid frame is there's at least one valid sample in each channel
        return self.ch1 and self.ch2 

def _get_properties(self, properties):
        ret = []

        if len(properties) > 255:
            raise InvalidOperationException("Properties request too long (%d)"
                                            "" % len(properties))
        pkt = bytearray([0x46, self._get_seq(), len(properties)])

        for p in properties:
            pkt += bytearray([1, len(p)])  # Read action
            pkt += p.encode('ascii')
            pkt += bytearray([0])  # No data for reads

        with self._conn_lock:
            self._conn.send(pkt)
            reply = self._conn.recv()

        hdr, seq, stat, nr = struct.unpack("<BBBB", reply[:4])
        reply = reply[4:]

        if hdr != 0x46:
            raise NetworkError("Bad header %d" % hdr)

        p, d = '', ''
        for n in range(nr):
            plen, reply = ord(reply[:1]), reply[1:]
            p, reply = reply[:plen].decode('ascii'), reply[plen:]
            dlen, reply = ord(reply[:1]), reply[1:]
            d, reply = reply[:dlen].decode('ascii'), reply[dlen:]

            if stat == 0:
                ret.append((p, d))
            else:
                break

        # Reply should just contain the \r\n by this time.

        if stat:
            # An error will have exactly one property reply, the property that
            # caused the error with empty data
            raise InvalidOperationException(
                "Property Read Error, status %d on property %s" % (stat, p))

        return ret