need the unsigned value from dl.call()

[Diez B. Roggisch]

Larry Bates wrote:

> eliss wrote:
>> I'm using dl.call() to call a C function in an external library. It's
>> working great so far except for one function, which returns an
>> unsigned int in the C version. However, in python it returns a signed
>> value to me. How can I get the unsigned value from this? I haven't
>> brushed up on my two's complement in a while, so I was hoping someone
>> could give me a hand.
>> 
>> Thanks
>> 
>> eliss
> It is returning 32 bits.  If the sign bit (bit 32) is on it appears as a
> negative number.  Test for negative and multiply the absolute value * 2.
> That should get you the unsigned value you want in a long.

Erm... Nope.

All bits set is -1 - so according to your recipe, that would be abs(-1) * 2
= 2

I'd suggest this formula:

if value < 0:
    value = 2^32 + value + 1

Diez