From: jzakiya@... (Jabari Zakiya)
Date: 2002-04-10T10:31:47+09:00
Subject: Rotate, et al

I have a newbie question about rotate operators.

I want to do 32-bit left/right rotates.

I can do something like the following:

List 1.

def rol(n, s)
  n &= 0xffffffff
  n = (n<<s|n>>32-s)&0xffffffff
end

which does what I want, even for values > 32-bits.

Thus, given some 32-bit hex value: a = 0x12345678

I can do:  rol(a, s) or rol a, s  where s = 0..32

But what I really want to do is:  a.rol(s).

1) Is this the best way to want to do this?

2) What is the fastest way to do 32-bit rotates in Ruby?

I also want to do this with the arithmetic operations
'+', '-', '*', and '/', where everything is for 32 bits.

I know this must seem trivial, but hey, help me out here. :-)

Also,  a = 0x40000000 --  a.type  -> BIGNUM
       b = 0x20000000 --  b.type  -> FIXNUM 

A number up to 30-bits long is type FIXNUM, while
any number > 30-bits is type BIGNUM. Why dat?

On a 32-bit machine  a = 0x80000000 will fit in a single
register and memory location. 

3) What's was the philosphy for removing the machine
architecture from the consideration of number types?

4) What is the easiest way to check for 'endianess' of
a machine in Ruby?

Also, coming from Forth, where I have virtually complete
access and control over the machine, I was wondering if there
are any libraries or extensions in Ruby (not C, etc) that
allow you to write essentially assmebly code to make things
faster. Since Pentium (PC) class CPUs have single cycle rotate,
et al, instructions, it would be nice to somehow access them,
or at least have classes/methods compile directly to them.

Jabari Zakiya