Use the new struct module's ability to pack and unpack standardized
data formats. The _xdr module is no longer used, since struct supports the required IEEE floats and doubles. (I have one doubt about not using _xdr. The struct module doesn't handle Inf, NaN and gradual underflow correctly. If the _xdr module does these things better, it may still have a (small) competitive advantage. On the other hand, since not all platforms support IEEE floating point, it's not clear that it would be a good idea to ever transfer Inf or NaNs. Gradual underflow can be fixed in the struct module.
This commit is contained in:
Guido van Rossum
parent
07ef655222
commit
6083f0e9ce
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@ -2,24 +2,9 @@
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See: RFC 1014
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This module will conditionally use the _xdrmodule.so module to get
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support for those representations we can't do much with from Python.
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"""
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import struct
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from types import LongType
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# use C layer XDR libraries for some data types if available
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try:
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import _xdr
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except ImportError:
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_xdr = None
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# this test is done to see if machine representation is the same as
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# network representation. if so, we can use module struct for packing
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# some data types
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_USE_MACHINE_REP = (struct.pack('l', 1) == '\0\0\0\1')
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# exceptions
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class Error:
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@ -60,14 +45,7 @@ class Packer:
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get_buf = get_buffer
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def pack_uint(self, x):
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self.__buf = self.__buf + \
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(chr(int(x>>24 & 0xff)) + chr(int(x>>16 & 0xff)) + \
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chr(int(x>>8 & 0xff)) + chr(int(x & 0xff)))
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if _USE_MACHINE_REP:
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def pack_uint(self, x):
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if type(x) == LongType:
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x = int((x + 0x80000000L) % 0x100000000L - 0x80000000L)
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self.__buf = self.__buf + struct.pack('l', x)
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self.__buf = self.__buf + struct.pack('>L', x)
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pack_int = pack_uint
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pack_enum = pack_int
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@ -83,18 +61,13 @@ class Packer:
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pack_hyper = pack_uhyper
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def pack_float(self, x):
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raise ConversionError('Not supported')
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def pack_double(self, x):
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raise ConversionError('Not supported')
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# get these from the C layer if available
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if _xdr:
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def pack_float(self, x):
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try: self.__buf = self.__buf + _xdr.pack_float(x)
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except _xdr.error, msg:
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try: self.__buf = self.__buf + struct.pack('>f', x)
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except struct.error, msg:
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raise ConversionError(msg)
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def pack_double(self, x):
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try: self.__buf = self.__buf + _xdr.pack_double(x)
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except _xdr.error, msg:
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try: self.__buf = self.__buf + struct.pack('>d', x)
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except struct.error, msg:
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raise ConversionError(msg)
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def pack_fstring(self, n, s):
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@ -163,27 +136,19 @@ class Unpacker:
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data = self.__buf[i:j]
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if len(data) < 4:
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raise EOFError
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x = long(ord(data[0]))<<24 | ord(data[1])<<16 | \
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ord(data[2])<<8 | ord(data[3])
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# Return a Python long only if the value is not representable
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# as a nonnegative Python int
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if x < 0x80000000L:
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x = int(x)
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x = struct.unpack('>L', data)[0]
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try:
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return int(x)
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except OverflowError:
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return x
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if _USE_MACHINE_REP:
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def unpack_uint(self):
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def unpack_int(self):
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i = self.__pos
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self.__pos = j = i+4
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data = self.__buf[i:j]
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if len(data) < 4:
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raise EOFError
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return struct.unpack('l', data)[0]
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def unpack_int(self):
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x = self.unpack_uint()
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if x >= 0x80000000L:
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x = x - 0x100000000L
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return int(x)
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return struct.unpack('>l', data)[0]
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unpack_enum = unpack_int
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unpack_bool = unpack_int
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@ -199,21 +164,13 @@ class Unpacker:
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x = x - 0x10000000000000000L
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return x
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def unpack_float(self):
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raise ConversionError('Not supported')
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def unpack_double(self):
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raise ConversionError('Not supported')
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# get these from the C layer if available
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if _xdr:
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def unpack_float(self):
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i = self.__pos
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self.__pos = j = i+4
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data = self.__buf[i:j]
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if len(data) < 4:
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raise EOFError
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try: return _xdr.unpack_float(data)
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except _xdr.error, msg:
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raise ConversionError(msg)
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return struct.unpack('>f', data)[0]
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def unpack_double(self):
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i = self.__pos
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@ -221,9 +178,7 @@ class Unpacker:
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data = self.__buf[i:j]
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if len(data) < 8:
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raise EOFError
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try: return _xdr.unpack_double(data)
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except _xdr.error, msg:
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raise ConversionError(msg)
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return struct.unpack('>d', data)[0]
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def unpack_fstring(self, n):
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if n < 0:
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