OpenEuphoria

32-bit operations

• Posted by "Derek Parnell" <ddparnell at bigpond.com> Feb 27, 2004
• 417 views

Hi all,
it turns out that I can't use Juergen's routines after all. I need to do
arithetic that can have temporary values that extend beyond Euphoria's
30-bit integer limit. Thanks to being reminded about the bits_to_int() and
int_to_bits() routines, I've come up with this little function that gives me
the correct values now. It seems to run fast enough for my uses too!

  global function ClipBits(atom pValue)
    if pValue > #FFFFFFFF  or pValue < 0 then
      pValue = bits_to_int(int_to_bits(pValue,32))
    end if
    return pValue
  end function


I use it in this context ...

  global function TEA_encypher(atom y, atom z, atom k1, atom k2, atom sum)
    -- The input parameters are all 32-bit unsigned integers.
    -- I return a 32-bit unsigned integer

    -- The seperate assignments are there to ensure that I
    -- don't lose any precision by simulating 32-bit UINTs
    -- with atoms.

    y = ClipBits(y + ClipBits(z * 16))  -- z<<4
    y = ClipBits(y + xor_bits(k1, z))
    y = ClipBits(y + xor_bits(sum, (z / 32))) -- z>>5
    y = ClipBits(y + k2)
    return y
  end function

--
Derek