Testing Integers - Individual Limb values

Jim White mathimagics at yahoo.co.uk
Tue Jun 6 02:33:07 CEST 2006

> For examle, one of the functions is testing the
> 1024th bit of an integer number. I could use the
> standard gmp bit functions, but why not simply 
> read the 32nd limb (bits per limb are equal
> to 32 on my system) and then get its 
> msb.

Accessing individual limbs is simple, but the GMP
functions use that simple method anyway, so why

If you want to do it yourself, assuming BYTE
addressing, if P is the pointer to the limbs, and S is
the current size, in limbs, then the address of the
most-significant limb is P + 4(S-1), then subtract 4
for the next limb, and so on....

Jim White
ANU, Canberra

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