Help: C char bits operations to python converting

[gangli at msn.com]

In article <hmoA5.965$jk1.66868 at newsc.telia.net>,
  "Fredrik Lundh" <effbot at telia.com> wrote:
>
> are you trying to solve a real problem, or an is this just
> some kind of homework?
It is for real ?:). It is part of scurity function for the company I am
working for.

I used a list to skip using the shift operator:

   shift4 = [0, 16, 32, 48, 64, 80, 96, 112, -128, -112,
              -96, -80, -64, -48, -32, -16, 0, 16, 32, 48,
              64, 80, 96, 112, -128, -112
            ]

>
> (if it's a real problem, note that your C code isn't portable)
>
> anyway, to "cast" a python integer to an 8-bit signed
> integer, mask with 255 and subtract 256 from it if it's
> larger than 127:
>
>     def char(value):
>         value = value & 255
>         if value > 127:
>             return value - 256
>         return value
>
Thanks for your help. Here my version based on your's:

def char_rshift(n, s=4):
    c = (n << s) & 255
    if c > 127:
        c = c - 256
    return c




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