# 2's complement conversion. Is this right?

Bob Greschke bob at passcal.nmt.edu
Tue Apr 22 01:06:39 CEST 2008

```On 2008-04-21 16:51:13 -0600, Bob Greschke <bob at passcal.nmt.edu> said:
JUST COMPLETELY IGNORE THAT LAST ONE.  What a dope.  Here:

#! /usr/bin/env python

from os import system
from struct import unpack

print "unpack 1"
system("date")
for x in xrange(0, 100000000):
Value = unpack(">B", "a")[0]
if Value > 0x800000:
Value -= 0x1000000
system("date")
print

print "ord 1"
system("date")
for x in xrange(0, 100000000):
Value = ord("a")
if Value > 0x800000:
Value -= 0x1000000
system("date")
print

print "unpack 3"
system("date")
for x in xrange(0, 100000000):
Value1, Value2, Value3 = unpack(">BBB", "abc")
Value = (Value1 << 16)+(Value2 << 8)+Value3
if Value > 0x800000:
Value -= 0x1000000
system("date")
print

print "ord 3"
system("date")
for x in xrange(0, 100000000):
Value = (ord("a") << 16)+(ord("b") << 8)+ord("c")
if Value > 0x800000:
Value -= 0x1000000
system("date")

Still, the differences between unpack and ord are significant (I just
threw in the if's for fun).

```