[Python-ideas] Exact integral types in struct

[Serhiy Storchaka]

20.03.12 21:54, Andrew Svetlov написав(ла):
> Floating points from IEEE 754 doesn't depends from machine byte order
> and C double is always coded in 8 bytes as I know,

Full code:

def _floatconstants():
     _BYTES = binascii.unhexlify(b'7FF80000000000007FF0000000000000')
     if sys.byteorder != 'big':
         _BYTES = _BYTES[:8][::-1] + _BYTES[8:][::-1]
     nan, inf = struct.unpack('dd', _BYTES)
     return nan, inf, -inf

NaN, PosInf, NegInf = _floatconstants()


But in xdrlib.py:

         return struct.unpack('>d', data)[0]

And in pickle.py:

         self.append(unpack('>d', self.read(8))[0])

Test:

  >>> import struct
  >>> struct.pack('>d', 1)
  b'?\xf0\x00\x00\x00\x00\x00\x00'
  >>> struct.pack('<d', 1)
  b'\x00\x00\x00\x00\x00\x00\xf0?'