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

See: RFC 1014

"""

import struct

try:

from cStringIO import StringIO as _StringIO

except ImportError:

from StringIO import StringIO as _StringIO

from functools import wraps

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

# exceptions

class Error(Exception):

"""Exception class for this module. Use:

except xdrlib.Error, 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)

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])

return result

class Packer:

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

def __init__(self):

self.reset()

def reset(self):

self.__buf = _StringIO()

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('\0\0\0\1')

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

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])

pack_hyper = pack_uhyper

@raise_conversion_error

def pack_float(self, x):

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

@raise_conversion_error

def pack_double(self, x):

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

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)) * '\0'

self.__buf.write(data)

pack_fopaque = pack_fstring

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

def pack_list(self, list, pack_item):

for item in list:

self.pack_uint(1)

pack_item(item)

self.pack_uint(0)

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

if len(list) != n:

raise ValueError, 'wrong array size'

for item in list:

pack_item(item)

def pack_array(self, list, pack_item):

n = len(list)

self.pack_uint(n)

self.pack_farray(n, list, pack_item)

class Unpacker:

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

def __init__(self, data):

self.reset(data)

def reset(self, data):

self.__buf = data

self.__pos = 0

def get_position(self):

return self.__pos

def set_position(self, position):

self.__pos = position

def get_buffer(self):

return self.__buf

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

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

try:

return int(x)

except OverflowError:

return x

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 long(hi)<<32 | lo

def unpack_hyper(self):

x = self.unpack_uhyper()

if x >= 0x8000000000000000L:

x = x - 0x10000000000000000L

return x

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]

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]

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

def unpack_string(self):

n = self.unpack_uint()

return self.unpack_fstring(n)

unpack_opaque = unpack_string

unpack_bytes = unpack_string

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

def unpack_farray(self, n, unpack_item):

list = []

for i in range(n):

list.append(unpack_item())

return list

def unpack_array(self, unpack_item):

n = self.unpack_uint()

return self.unpack_farray(n, unpack_item)