Lib/xdrlib.py

   1 """Implements (a subset of) Sun XDR -- eXternal Data Representation.
   2
   3 See: RFC 1014
   4
   5 """
   6
   7 import struct
   8
   9 __all__ = ["Error", "Packer", "Unpacker", "ConversionError"]
  10
  11 # exceptions
  12 class Error:
  13     """Exception class for this module. Use:
  14
  15     except xdrlib.Error, var:
  16         # var has the Error instance for the exception
  17
  18     Public ivars:
  19         msg -- contains the message
  20
  21     """
  22     def __init__(self, msg):
  23         self.msg = msg
  24     def __repr__(self):
  25         return repr(self.msg)
  26     def __str__(self):
  27         return str(self.msg)
  28
  29
  30 class ConversionError(Error):
  31     pass
  32
  33
  34
  35 class Packer:
  36     """Pack various data representations into a buffer."""
  37
  38     def __init__(self):
  39         self.reset()
  40
  41     def reset(self):
  42         self.__buf = ''
  43
  44     def get_buffer(self):
  45         return self.__buf
  46     # backwards compatibility
  47     get_buf = get_buffer
  48
  49     def pack_uint(self, x):
  50         self.__buf = self.__buf + struct.pack('>L', x)
  51
  52     pack_int = pack_uint
  53     pack_enum = pack_int
  54
  55     def pack_bool(self, x):
  56         if x: self.__buf = self.__buf + '\0\0\0\1'
  57         else: self.__buf = self.__buf + '\0\0\0\0'
  58
  59     def pack_uhyper(self, x):
  60         self.pack_uint(x>>32 & 0xffffffffL)
  61         self.pack_uint(x & 0xffffffffL)
  62
  63     pack_hyper = pack_uhyper
  64
  65     def pack_float(self, x):
  66         try: self.__buf = self.__buf + struct.pack('>f', x)
  67         except struct.error, msg:
  68             raise ConversionError, msg
  69
  70     def pack_double(self, x):
  71         try: self.__buf = self.__buf + struct.pack('>d', x)
  72         except struct.error, msg:
  73             raise ConversionError, msg
  74
  75     def pack_fstring(self, n, s):
  76         if n < 0:
  77             raise ValueError, 'fstring size must be nonnegative'
  78         n = ((n+3)/4)*4
  79         data = s[:n]
  80         data = data + (n - len(data)) * '\0'
  81         self.__buf = self.__buf + data
  82
  83     pack_fopaque = pack_fstring
  84
  85     def pack_string(self, s):
  86         n = len(s)
  87         self.pack_uint(n)
  88         self.pack_fstring(n, s)
  89
  90     pack_opaque = pack_string
  91     pack_bytes = pack_string
  92
  93     def pack_list(self, list, pack_item):
  94         for item in list:
  95             self.pack_uint(1)
  96             pack_item(item)
  97         self.pack_uint(0)
  98
  99     def pack_farray(self, n, list, pack_item):
 100         if len(list) != n:
 101             raise ValueError, 'wrong array size'
 102         for item in list:
 103             pack_item(item)
 104
 105     def pack_array(self, list, pack_item):
 106         n = len(list)
 107         self.pack_uint(n)
 108         self.pack_farray(n, list, pack_item)
 109
 110
 111
 112 class Unpacker:
 113     """Unpacks various data representations from the given buffer."""
 114
 115     def __init__(self, data):
 116         self.reset(data)
 117
 118     def reset(self, data):
 119         self.__buf = data
 120         self.__pos = 0
 121
 122     def get_position(self):
 123         return self.__pos
 124
 125     def set_position(self, position):
 126         self.__pos = position
 127
 128     def get_buffer(self):
 129         return self.__buf
 130
 131     def done(self):
 132         if self.__pos < len(self.__buf):
 133             raise Error('unextracted data remains')
 134
 135     def unpack_uint(self):
 136         i = self.__pos
 137         self.__pos = j = i+4
 138         data = self.__buf[i:j]
 139         if len(data) < 4:
 140             raise EOFError
 141         x = struct.unpack('>L', data)[0]
 142         try:
 143             return int(x)
 144         except OverflowError:
 145             return x
 146
 147     def unpack_int(self):
 148         i = self.__pos
 149         self.__pos = j = i+4
 150         data = self.__buf[i:j]
 151         if len(data) < 4:
 152             raise EOFError
 153         return struct.unpack('>l', data)[0]
 154
 155     unpack_enum = unpack_int
 156     unpack_bool = unpack_int
 157
 158     def unpack_uhyper(self):
 159         hi = self.unpack_uint()
 160         lo = self.unpack_uint()
 161         return long(hi)<<32 | lo
 162
 163     def unpack_hyper(self):
 164         x = self.unpack_uhyper()
 165         if x >= 0x8000000000000000L:
 166             x = x - 0x10000000000000000L
 167         return x
 168
 169     def unpack_float(self):
 170         i = self.__pos
 171         self.__pos = j = i+4
 172         data = self.__buf[i:j]
 173         if len(data) < 4:
 174             raise EOFError
 175         return struct.unpack('>f', data)[0]
 176
 177     def unpack_double(self):
 178         i = self.__pos
 179         self.__pos = j = i+8
 180         data = self.__buf[i:j]
 181         if len(data) < 8:
 182             raise EOFError
 183         return struct.unpack('>d', data)[0]
 184
 185     def unpack_fstring(self, n):
 186         if n < 0:
 187             raise ValueError, 'fstring size must be nonnegative'
 188         i = self.__pos
 189         j = i + (n+3)/4*4
 190         if j > len(self.__buf):
 191             raise EOFError
 192         self.__pos = j
 193         return self.__buf[i:i+n]
 194
 195     unpack_fopaque = unpack_fstring
 196
 197     def unpack_string(self):
 198         n = self.unpack_uint()
 199         return self.unpack_fstring(n)
 200
 201     unpack_opaque = unpack_string
 202     unpack_bytes = unpack_string
 203
 204     def unpack_list(self, unpack_item):
 205         list = []
 206         while 1:
 207             x = self.unpack_uint()
 208             if x == 0: break
 209             if x != 1:
 210                 raise ConversionError, '0 or 1 expected, got ' + `x`
 211             item = unpack_item()
 212             list.append(item)
 213         return list
 214
 215     def unpack_farray(self, n, unpack_item):
 216         list = []
 217         for i in range(n):
 218             list.append(unpack_item())
 219         return list
 220
 221     def unpack_array(self, unpack_item):
 222         n = self.unpack_uint()
 223         return self.unpack_farray(n, unpack_item)
 224
 225
 226 # test suite
 227 def _test():
 228     p = Packer()
 229     packtest = [
 230         (p.pack_uint,    (9,)),
 231         (p.pack_bool,    (None,)),
 232         (p.pack_bool,    ('hello',)),
 233         (p.pack_uhyper,  (45L,)),
 234         (p.pack_float,   (1.9,)),
 235         (p.pack_double,  (1.9,)),
 236         (p.pack_string,  ('hello world',)),
 237         (p.pack_list,    (range(5), p.pack_uint)),
 238         (p.pack_array,   (['what', 'is', 'hapnin', 'doctor'], p.pack_string)),
 239         ]
 240     succeedlist = [1] * len(packtest)
 241     count = 0
 242     for method, args in packtest:
 243         print 'pack test', count,
 244         try:
 245             apply(method, args)
 246             print 'succeeded'
 247         except ConversionError, var:
 248             print 'ConversionError:', var.msg
 249             succeedlist[count] = 0
 250         count = count + 1
 251     data = p.get_buffer()
 252     # now verify
 253     up = Unpacker(data)
 254     unpacktest = [
 255         (up.unpack_uint,   (), lambda x: x == 9),
 256         (up.unpack_bool,   (), lambda x: not x),
 257         (up.unpack_bool,   (), lambda x: x),
 258         (up.unpack_uhyper, (), lambda x: x == 45L),
 259         (up.unpack_float,  (), lambda x: 1.89 < x < 1.91),
 260         (up.unpack_double, (), lambda x: 1.89 < x < 1.91),
 261         (up.unpack_string, (), lambda x: x == 'hello world'),
 262         (up.unpack_list,   (up.unpack_uint,), lambda x: x == range(5)),
 263         (up.unpack_array,  (up.unpack_string,),
 264          lambda x: x == ['what', 'is', 'hapnin', 'doctor']),
 265         ]
 266     count = 0
 267     for method, args, pred in unpacktest:
 268         print 'unpack test', count,
 269         try:
 270             if succeedlist[count]:
 271                 x = apply(method, args)
 272                 print pred(x) and 'succeeded' or 'failed', ':', x
 273             else:
 274                 print 'skipping'
 275         except ConversionError, var:
 276             print 'ConversionError:', var.msg
 277         count = count + 1
 278
 279
 280 if __name__ == '__main__':
 281     _test()