Commit f5d5a5cf authored by Tim Peters's avatar Tim Peters

Merge rev 29370 from 3.3 branch.

positive_id():  Use a trick from Armin Rigo to deduce the
native platorm address size.
parent e6f505df
......@@ -14,6 +14,7 @@
import sys
import time
import struct
from struct import pack, unpack
from binascii import hexlify
import cPickle as pickle
......@@ -140,22 +141,18 @@ def readable_tid_repr(tid):
# unsigned, but produces a FutureWarning, because Python 2.4 will display
# it as signed. So when you want to prodce an address, use positive_id() to
# obtain it.
# _ADDRESS_MASK is 2**(number_of_bits_in_a_native_pointer). Adding this to
# a negative address gives a positive int with the same hex representation as
# the significant bits in the original.
_ADDRESS_MASK = 256 ** struct.calcsize('P')
def positive_id(obj):
"""Return id(obj) as a non-negative integer."""
result = id(obj)
if result < 0:
# This is a puzzle: there's no way to know the natural width of
# addresses on this box (in particular, there's no necessary
# relation to sys.maxint). Try 32 bits first (and on a 32-bit
# box, adding 2**32 gives a positive number with the same hex
# representation as the original result).
result += 1L << 32
if result < 0:
# Undo that, and try 64 bits.
result -= 1L << 32
result += 1L << 64
assert result >= 0 # else addresses are fatter than 64 bits
result += _ADDRESS_MASK
assert result > 0
return result
# So full of undocumented magic it's hard to fathom.
......
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