241 lines
5.8 KiB
Python
241 lines
5.8 KiB
Python
"""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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