"""Implements (a subset of) Sun XDR -- eXternal Data Representation.

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See: RFC 1014

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"""

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import struct

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from io import BytesIO

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from functools import wraps

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__all__ = ["Error", "Packer", "Unpacker", "ConversionError"]

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# exceptions

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class Error(Exception):

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"""Exception class for this module. Use:

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except xdrlib.Error as var:

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# var has the Error instance for the exception

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Public ivars:

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msg -- contains the message

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"""

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def __init__(self, msg):

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self.msg = msg

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def __repr__(self):

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return repr(self.msg)

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def __str__(self):

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return str(self.msg)

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class ConversionError(Error):

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pass

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def raise_conversion_error(function):

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""" Wrap any raised struct.errors in a ConversionError. """

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@wraps(function)

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def result(self, value):

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try:

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return function(self, value)

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except struct.error as e:

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raise ConversionError(e.args[0]) from None

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return result

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class Packer:

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"""Pack various data representations into a buffer."""

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def __init__(self):

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self.reset()

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def reset(self):

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self.__buf = BytesIO()

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def get_buffer(self):

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return self.__buf.getvalue()

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# backwards compatibility

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get_buf = get_buffer

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@raise_conversion_error

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def pack_uint(self, x):

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self.__buf.write(struct.pack('>L', x))

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@raise_conversion_error

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def pack_int(self, x):

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self.__buf.write(struct.pack('>l', x))

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pack_enum = pack_int

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def pack_bool(self, x):

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if x: self.__buf.write(b'\0\0\0\1')

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else: self.__buf.write(b'\0\0\0\0')

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def pack_uhyper(self, x):

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try:

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self.pack_uint(x>>32 & 0xffffffff)

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except (TypeError, struct.error) as e:

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raise ConversionError(e.args[0]) from None

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try:

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self.pack_uint(x & 0xffffffff)

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except (TypeError, struct.error) as e:

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raise ConversionError(e.args[0]) from None

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pack_hyper = pack_uhyper

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@raise_conversion_error

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def pack_float(self, x):

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self.__buf.write(struct.pack('>f', x))

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@raise_conversion_error

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def pack_double(self, x):

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self.__buf.write(struct.pack('>d', x))

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def pack_fstring(self, n, s):

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if n < 0:

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raise ValueError('fstring size must be nonnegative')

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data = s[:n]

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n = ((n+3)//4)*4

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data = data + (n - len(data)) * b'\0'

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self.__buf.write(data)

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pack_fopaque = pack_fstring

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def pack_string(self, s):

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n = len(s)

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self.pack_uint(n)

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self.pack_fstring(n, s)

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pack_opaque = pack_string

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pack_bytes = pack_string

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def pack_list(self, list, pack_item):

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for item in list:

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self.pack_uint(1)

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pack_item(item)

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self.pack_uint(0)

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def pack_farray(self, n, list, pack_item):

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if len(list) != n:

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raise ValueError('wrong array size')

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for item in list:

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pack_item(item)

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def pack_array(self, list, pack_item):

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n = len(list)

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self.pack_uint(n)

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self.pack_farray(n, list, pack_item)

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class Unpacker:

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"""Unpacks various data representations from the given buffer."""

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def __init__(self, data):

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self.reset(data)

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def reset(self, data):

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self.__buf = data

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self.__pos = 0

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def get_position(self):

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return self.__pos

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def set_position(self, position):

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self.__pos = position

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def get_buffer(self):

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return self.__buf

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def done(self):

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if self.__pos < len(self.__buf):

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raise Error('unextracted data remains')

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def unpack_uint(self):

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i = self.__pos

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self.__pos = j = i+4

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data = self.__buf[i:j]

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if len(data) < 4:

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raise EOFError

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return struct.unpack('>L', data)[0]

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def unpack_int(self):

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i = self.__pos

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self.__pos = j = i+4

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data = self.__buf[i:j]

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if len(data) < 4:

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raise EOFError

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return struct.unpack('>l', data)[0]

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unpack_enum = unpack_int

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def unpack_bool(self):

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return bool(self.unpack_int())

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def unpack_uhyper(self):

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hi = self.unpack_uint()

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lo = self.unpack_uint()

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return int(hi)<<32 | lo

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def unpack_hyper(self):

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x = self.unpack_uhyper()

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if x >= 0x8000000000000000:

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x = x - 0x10000000000000000

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return x

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def unpack_float(self):

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i = self.__pos

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self.__pos = j = i+4

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data = self.__buf[i:j]

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if len(data) < 4:

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raise EOFError

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return struct.unpack('>f', data)[0]

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def unpack_double(self):

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i = self.__pos

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self.__pos = j = i+8

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data = self.__buf[i:j]

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if len(data) < 8:

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raise EOFError

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return struct.unpack('>d', data)[0]

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def unpack_fstring(self, n):

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if n < 0:

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raise ValueError('fstring size must be nonnegative')

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i = self.__pos

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j = i + (n+3)//4*4

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if j > len(self.__buf):

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raise EOFError

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self.__pos = j

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return self.__buf[i:i+n]

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unpack_fopaque = unpack_fstring

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def unpack_string(self):

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n = self.unpack_uint()

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return self.unpack_fstring(n)

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unpack_opaque = unpack_string

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unpack_bytes = unpack_string

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def unpack_list(self, unpack_item):

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list = []

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while 1:

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x = self.unpack_uint()

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if x == 0: break

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if x != 1:

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raise ConversionError('0 or 1 expected, got %r' % (x,))

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item = unpack_item()

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list.append(item)

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return list

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def unpack_farray(self, n, unpack_item):

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list = []

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for i in range(n):

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list.append(unpack_item())

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return list

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def unpack_array(self, unpack_item):

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n = self.unpack_uint()

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return self.unpack_farray(n, unpack_item)

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