"""Implements (a subset of) Sun XDR -- eXternal Data Representation.
See: RFC 1014
"""
import struct
from io import BytesIO
from functools import wraps
__all__ = ["Error", "Packer", "Unpacker", "ConversionError"]
# exceptions
[docs]class Error(Exception):
"""Exception class for this module. Use:
except xdrlib.Error as var:
# var has the Error instance for the exception
Public ivars:
msg -- contains the message
"""
def __init__(self, msg):
self.msg = msg
def __repr__(self):
return repr(self.msg)
def __str__(self):
return str(self.msg)
[docs]class ConversionError(Error):
pass
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]) from None
return result
[docs]class Packer:
"""Pack various data representations into a buffer."""
def __init__(self):
self.reset()
[docs] def reset(self):
self.__buf = BytesIO()
[docs] def get_buffer(self):
return self.__buf.getvalue()
# backwards compatibility
get_buf = get_buffer
@raise_conversion_error
def pack_uint(self, x):
self.__buf.write(struct.pack('>L', x))
@raise_conversion_error
def pack_int(self, x):
self.__buf.write(struct.pack('>l', x))
pack_enum = pack_int
def pack_bool(self, x):
if x: self.__buf.write(b'\0\0\0\1')
else: self.__buf.write(b'\0\0\0\0')
def pack_uhyper(self, x):
try:
self.pack_uint(x>>32 & 0xffffffff)
except (TypeError, struct.error) as e:
raise ConversionError(e.args[0]) from None
try:
self.pack_uint(x & 0xffffffff)
except (TypeError, struct.error) as e:
raise ConversionError(e.args[0]) from None
pack_hyper = pack_uhyper
[docs] @raise_conversion_error
def pack_float(self, x):
self.__buf.write(struct.pack('>f', x))
[docs] @raise_conversion_error
def pack_double(self, x):
self.__buf.write(struct.pack('>d', x))
[docs] def pack_fstring(self, n, s):
if n < 0:
raise ValueError('fstring size must be nonnegative')
data = s[:n]
n = ((n+3)//4)*4
data = data + (n - len(data)) * b'\0'
self.__buf.write(data)
pack_fopaque = pack_fstring
[docs] def pack_string(self, s):
n = len(s)
self.pack_uint(n)
self.pack_fstring(n, s)
pack_opaque = pack_string
pack_bytes = pack_string
[docs] def pack_list(self, list, pack_item):
for item in list:
self.pack_uint(1)
pack_item(item)
self.pack_uint(0)
[docs] def pack_farray(self, n, list, pack_item):
if len(list) != n:
raise ValueError('wrong array size')
for item in list:
pack_item(item)
[docs] def pack_array(self, list, pack_item):
n = len(list)
self.pack_uint(n)
self.pack_farray(n, list, pack_item)
[docs]class Unpacker:
"""Unpacks various data representations from the given buffer."""
def __init__(self, data):
self.reset(data)
[docs] def reset(self, data):
self.__buf = data
self.__pos = 0
[docs] def get_position(self):
return self.__pos
[docs] def set_position(self, position):
self.__pos = position
[docs] def get_buffer(self):
return self.__buf
[docs] def done(self):
if self.__pos < len(self.__buf):
raise Error('unextracted data remains')
def unpack_uint(self):
i = self.__pos
self.__pos = j = i+4
data = self.__buf[i:j]
if len(data) < 4:
raise EOFError
return struct.unpack('>L', data)[0]
def unpack_int(self):
i = self.__pos
self.__pos = j = i+4
data = self.__buf[i:j]
if len(data) < 4:
raise EOFError
return struct.unpack('>l', data)[0]
unpack_enum = unpack_int
def unpack_bool(self):
return bool(self.unpack_int())
def unpack_uhyper(self):
hi = self.unpack_uint()
lo = self.unpack_uint()
return int(hi)<<32 | lo
def unpack_hyper(self):
x = self.unpack_uhyper()
if x >= 0x8000000000000000:
x = x - 0x10000000000000000
return x
[docs] def unpack_float(self):
i = self.__pos
self.__pos = j = i+4
data = self.__buf[i:j]
if len(data) < 4:
raise EOFError
return struct.unpack('>f', data)[0]
[docs] def unpack_double(self):
i = self.__pos
self.__pos = j = i+8
data = self.__buf[i:j]
if len(data) < 8:
raise EOFError
return struct.unpack('>d', data)[0]
[docs] def unpack_fstring(self, n):
if n < 0:
raise ValueError('fstring size must be nonnegative')
i = self.__pos
j = i + (n+3)//4*4
if j > len(self.__buf):
raise EOFError
self.__pos = j
return self.__buf[i:i+n]
unpack_fopaque = unpack_fstring
[docs] def unpack_string(self):
n = self.unpack_uint()
return self.unpack_fstring(n)
unpack_opaque = unpack_string
unpack_bytes = unpack_string
[docs] def unpack_list(self, unpack_item):
list = []
while 1:
x = self.unpack_uint()
if x == 0: break
if x != 1:
raise ConversionError('0 or 1 expected, got %r' % (x,))
item = unpack_item()
list.append(item)
return list
[docs] def unpack_farray(self, n, unpack_item):
list = []
for i in range(n):
list.append(unpack_item())
return list
[docs] def unpack_array(self, unpack_item):
n = self.unpack_uint()
return self.unpack_farray(n, unpack_item)