Help with some clever bit operations

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Hi,

I have a problem I can solve with some loops and if-thens, but I'm sure it
can be done with bit operations -- that would be prettier. I've tried to
work it out on paper, but I keep missing the final solution. Maybe I'm
missing something obvious...

The problem: A function tries to update an existing value, but is only
allowed to write certain bits.

There are 3 variables:
A: the existing value, eg. 10110101
B: what the function wants to write, eg. 01011100
C: which bits the function is allowed to write, eg. 00001111

With these examples, 10111100 should be written.

How do I combine A, B and C to get that result?


Thanks,
Niels

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