[Tutor] stumped again adding bytes
alan.gauld at btinternet.com
Sat Feb 24 02:54:11 CET 2007
"shawn bright" <nephish at gmail.com> wrote
> so i believe i do shifting here. as in i do a
> (a << 4) * 32 + b
Don't use shifting to extract the bits, use a bitmask
and & its much easier.
If you want to extract the left-most 4 bits use 0xf0
If you want to extract the righ-most bits use 0x0f
1 & 1 = 1
1 & 0 = 0
Or more generically:
1 & A = A
right = data & 0xf0
left = data & 0x0f
As easy as that.
Now if you need to stich the bits together you need to move
one element up by 4 bits which is where shifting comes in.
result = (data << 4) & right
> but i am not getting what i think that i should be, and i think it's
> because i am not getting rid of the bytes that i am not using.
Its easier to extract the bits into a new variable using a mask
> i have looked at the struct module, but can't figgure out how to do
> this type of thing with it.
This is not what struct is for, don't try uising it for this. even if
you make it work its not the best tool.
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