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 from io import BytesIO
   9
  10 __all__ = ["Error", "Packer", "Unpacker", "ConversionError"]
  11
  12 # exceptions
  13 class Error(Exception):
  14     """Exception class for this module. Use:
  15
  16     except xdrlib.Error, var:
  17         # var has the Error instance for the exception
  18
  19     Public ivars:
  20         msg -- contains the message
  21
  22     """
  23     def __init__(self, msg):
  24         self.msg = msg
  25     def __repr__(self):
  26         return repr(self.msg)
  27     def __str__(self):
  28         return str(self.msg)
  29
  30
  31 class ConversionError(Error):
  32     pass
  33
  34
  35
  36 class Packer:
  37     """Pack various data representations into a buffer."""
  38
  39     def __init__(self):
  40         self.reset()
  41
  42     def reset(self):
  43         self.__buf = BytesIO()
  44
  45     def get_buffer(self):
  46         return self.__buf.getvalue()
  47     # backwards compatibility
  48     get_buf = get_buffer
  49
  50     def pack_uint(self, x):
  51         self.__buf.write(struct.pack('>L', x))
  52
  53     pack_int = pack_uint
  54     pack_enum = pack_int
  55
  56     def pack_bool(self, x):
  57         if x: self.__buf.write(b'\0\0\0\1')
  58         else: self.__buf.write(b'\0\0\0\0')
  59
  60     def pack_uhyper(self, x):
  61         self.pack_uint(x>>32 & 0xffffffff)
  62         self.pack_uint(x & 0xffffffff)
  63
  64     pack_hyper = pack_uhyper
  65
  66     def pack_float(self, x):
  67         try: self.__buf.write(struct.pack('>f', x))
  68         except struct.error as msg:
  69             raise ConversionError(msg)
  70
  71     def pack_double(self, x):
  72         try: self.__buf.write(struct.pack('>d', x))
  73         except struct.error as msg:
  74             raise ConversionError(msg)
  75
  76     def pack_fstring(self, n, s):
  77         if n < 0:
  78             raise ValueError('fstring size must be nonnegative')
  79         data = s[:n]
  80         n = ((n+3)//4)*4
  81         data = data + (n - len(data)) * b'\0'
  82         self.__buf.write(data)
  83
  84     pack_fopaque = pack_fstring
  85
  86     def pack_string(self, s):
  87         n = len(s)
  88         self.pack_uint(n)
  89         self.pack_fstring(n, s)
  90
  91     pack_opaque = pack_string
  92     pack_bytes = pack_string
  93
  94     def pack_list(self, list, pack_item):
  95         for item in list:
  96             self.pack_uint(1)
  97             pack_item(item)
  98         self.pack_uint(0)
  99
 100     def pack_farray(self, n, list, pack_item):
 101         if len(list) != n:
 102             raise ValueError('wrong array size')
 103         for item in list:
 104             pack_item(item)
 105
 106     def pack_array(self, list, pack_item):
 107         n = len(list)
 108         self.pack_uint(n)
 109         self.pack_farray(n, list, pack_item)
 110
 111
 112
 113 class Unpacker:
 114     """Unpacks various data representations from the given buffer."""
 115
 116     def __init__(self, data):
 117         self.reset(data)
 118
 119     def reset(self, data):
 120         self.__buf = data
 121         self.__pos = 0
 122
 123     def get_position(self):
 124         return self.__pos
 125
 126     def set_position(self, position):
 127         self.__pos = position
 128
 129     def get_buffer(self):
 130         return self.__buf
 131
 132     def done(self):
 133         if self.__pos < len(self.__buf):
 134             raise Error('unextracted data remains')
 135
 136     def unpack_uint(self):
 137         i = self.__pos
 138         self.__pos = j = i+4
 139         data = self.__buf[i:j]
 140         if len(data) < 4:
 141             raise EOFError
 142         x = struct.unpack('>L', data)[0]
 143         try:
 144             return int(x)
 145         except OverflowError:
 146             return x
 147
 148     def unpack_int(self):
 149         i = self.__pos
 150         self.__pos = j = i+4
 151         data = self.__buf[i:j]
 152         if len(data) < 4:
 153             raise EOFError
 154         return struct.unpack('>l', data)[0]
 155
 156     unpack_enum = unpack_int
 157
 158     def unpack_bool(self):
 159         return bool(self.unpack_int())
 160
 161     def unpack_uhyper(self):
 162         hi = self.unpack_uint()
 163         lo = self.unpack_uint()
 164         return int(hi)<<32 | lo
 165
 166     def unpack_hyper(self):
 167         x = self.unpack_uhyper()
 168         if x >= 0x8000000000000000:
 169             x = x - 0x10000000000000000
 170         return x
 171
 172     def unpack_float(self):
 173         i = self.__pos
 174         self.__pos = j = i+4
 175         data = self.__buf[i:j]
 176         if len(data) < 4:
 177             raise EOFError
 178         return struct.unpack('>f', data)[0]
 179
 180     def unpack_double(self):
 181         i = self.__pos
 182         self.__pos = j = i+8
 183         data = self.__buf[i:j]
 184         if len(data) < 8:
 185             raise EOFError
 186         return struct.unpack('>d', data)[0]
 187
 188     def unpack_fstring(self, n):
 189         if n < 0:
 190             raise ValueError('fstring size must be nonnegative')
 191         i = self.__pos
 192         j = i + (n+3)//4*4
 193         if j > len(self.__buf):
 194             raise EOFError
 195         self.__pos = j
 196         return self.__buf[i:i+n]
 197
 198     unpack_fopaque = unpack_fstring
 199
 200     def unpack_string(self):
 201         n = self.unpack_uint()
 202         return self.unpack_fstring(n)
 203
 204     unpack_opaque = unpack_string
 205     unpack_bytes = unpack_string
 206
 207     def unpack_list(self, unpack_item):
 208         list = []
 209         while 1:
 210             x = self.unpack_uint()
 211             if x == 0: break
 212             if x != 1:
 213                 raise ConversionError('0 or 1 expected, got %r' % (x,))
 214             item = unpack_item()
 215             list.append(item)
 216         return list
 217
 218     def unpack_farray(self, n, unpack_item):
 219         list = []
 220         for i in range(n):
 221             list.append(unpack_item())
 222         return list
 223
 224     def unpack_array(self, unpack_item):
 225         n = self.unpack_uint()
 226         return self.unpack_farray(n, unpack_item)