XDR interface, evolved from Demo/rpc/xdr.py by Barry.

Lib/xdrlib.py

+"""Implements (a subset of) Sun XDR -- eXternal Data Representation.
+
+See: RFC 1014
+
+This module will conditionally use the _xdrmodule.so module to get
+support for those representations we can't do much with from Python.
+
+"""
+
+import struct
+from types import LongType
+
+# workaround Python 1.4b2 bug
+import sys
+sys.path[0] = '.'
+
+# use C layer XDR libraries for some data types if available
+try:
+    import _xdr
+except ImportError:
+    _xdr = None
+
+# this test is done to see if machine representation is the same as
+# network representation.  if so, we can use module struct for packing
+# some data types
+__USE_MACHINE_REP = (struct.pack('l', 1) == '\0\0\0\1')
+
+# exceptions
+class Error:
+    """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
+
+
+
+class Packer:
+    """Pack various data representations into a buffer."""
+
+    def __init__(self):
+	self.reset()
+
+    def reset(self):
+	self.__buf = ''
+
+    def get_buffer(self):
+	return self.__buf
+    # backwards compatibility
+    get_buf = get_buffer
+
+    def pack_uint(self, x):
+	self.__buf = self.__buf + \
+		     (chr(int(x>>24 & 0xff)) + chr(int(x>>16 & 0xff)) + \
+		      chr(int(x>>8 & 0xff)) + chr(int(x & 0xff)))
+    if __USE_MACHINE_REP:
+	def pack_uint(self, x):
+	    if type(x) == LongType:
+		x = int((x + 0x80000000L) % 0x100000000L - 0x80000000L)
+	    self.__buf = self.__buf + struct.pack('l', x)
+
+    pack_int = pack_uint
+    pack_enum = pack_int
+
+    def pack_bool(self, x):
+	if x: self.__buf = self.__buf + '\0\0\0\1'
+	else: self.__buf = self.__buf + '\0\0\0\0'
+
+    def pack_uhyper(self, x):
+	self.pack_uint(int(x>>32 & 0xffffffff))
+	self.pack_uint(int(x & 0xffffffff))
+
+    pack_hyper = pack_uhyper
+
+    def pack_float(self, x):
+	raise ConversionError('Not supported')
+    def pack_double(self, x):
+	raise ConversionError('Not supported')
+    # get these from the C layer if available
+    if _xdr:
+	def pack_float(self, x):
+	    try: self.__buf = self.__buf + _xdr.pack_float(x)
+	    except _xdr.error, msg:
+		raise ConversionError(msg)
+	def pack_double(self, x):
+	    try: self.__buf = self.__buf + _xdr.pack_double(x)
+	    except _xdr.error, msg:
+		raise ConversionError(msg)
+
+    def pack_fstring(self, n, s):
+	if n < 0:
+	    raise ValueError, 'fstring size must be nonnegative'
+	n = ((n+3)/4)*4
+	data = s[:n]
+	data = data + (n - len(data)) * '\0'
+	self.__buf = self.__buf + 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 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 = long(ord(data[0]))<<24 | ord(data[1])<<16 | \
+	    ord(data[2])<<8 | ord(data[3])
+	# Return a Python long only if the value is not representable
+	# as a nonnegative Python int
+	if x < 0x80000000L:
+	    x = int(x)
+	return x
+    if __USE_MACHINE_REP:
+	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):
+	x = self.unpack_uint()
+	if x >= 0x80000000L:
+	    x = x - 0x100000000L
+	return int(x)
+
+    unpack_enum = unpack_int
+    unpack_bool = 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):
+	raise ConversionError('Not supported')
+    def unpack_double(self):
+	raise ConversionError('Not supported')
+    # get these from the C layer if available
+    if _xdr:
+	def unpack_float(self):
+	    i = self.__pos
+	    self.__pos = j = i+4
+	    data = self.__buf[i:j]
+	    if len(data) < 4:
+		raise EOFError
+	    try: return _xdr.unpack_float(data)
+	    except _xdr.error, msg:
+		raise ConversionError(msg)
+
+	def unpack_double(self):
+	    i = self.__pos
+	    self.__pos = j = i+8
+	    data = self.__buf[i:j]
+	    if len(data) < 8:
+		raise EOFError
+	    try: return _xdr.unpack_double(data)
+	    except _xdr.error, msg:
+		raise ConversionError(msg)
+
+    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 ' + `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)
+
+
+# test suite
+def __test():
+    p = Packer()
+    packtest = [
+	(p.pack_uint,    (9,)),
+	(p.pack_bool,    (None,)),
+	(p.pack_bool,    ('hello',)),
+	(p.pack_uhyper,  (45L,)),
+	(p.pack_float,   (1.9,)),
+	(p.pack_double,  (1.9,)),
+	(p.pack_string,  ('hello world',)),
+	(p.pack_list,    (range(5), p.pack_uint)),
+	(p.pack_array,   (['what', 'is', 'hapnin', 'doctor'], p.pack_string)),
+	]
+    succeedlist = [1] * len(packtest)
+    count = 0
+    for method, args in packtest:
+	print 'pack test', count,
+	try:
+	    apply(method, args)
+	    print 'succeeded'
+	except ConversionError, var:
+	    print 'ConversionError:', var.msg
+	    succeedlist[count] = 0
+	count = count + 1
+    data = p.get_buffer()
+    # now verify
+    up = Unpacker(data)
+    unpacktest = [
+	(up.unpack_uint,   (), lambda x: x == 9),
+	(up.unpack_bool,   (), lambda x: not x),
+	(up.unpack_bool,   (), lambda x: x),
+	(up.unpack_uhyper, (), lambda x: x == 45L),
+	(up.unpack_float,  (), lambda x: 1.89 < x < 1.91),
+	(up.unpack_double, (), lambda x: 1.89 < x < 1.91),
+	(up.unpack_string, (), lambda x: x == 'hello world'),
+	(up.unpack_list,   (up.unpack_uint,), lambda x: x == range(5)),
+	(up.unpack_array,  (up.unpack_string,),
+	 lambda x: x == ['what', 'is', 'hapnin', 'doctor']),
+	]
+    count = 0
+    for method, args, pred in unpacktest:
+	print 'unpack test', count,
+	try:
+	    if succeedlist[count]:
+		x = apply(method, args)
+		print pred(x) and 'succeeded' or 'failed', ':', x
+	    else:
+		print 'skipping'
+	except ConversionError, var:
+	    print 'ConversionError:', var.msg
+	count = count + 1
+
+if __name__ == '__main__':
+    __test()