I have a 32 bit value which represents 32 individual states. I also have another 32 bit value which controls which bits are either locked or can be altered by an application.
For instance ( using a 4 bit mask for succinctness )
Example 1
Value 1010
Lock Mask 1000 - i.e. the 4th bit is locked, i.e. can't be altered
Incoming value 0100
New Result 1100 - 4th bit unchanged
Example 2
Value 0011
Lock Mask 1000 - i.e. the 4th bit is locked, i.e. can't be altered
Incoming value 1100
New Result 0100 - 4th bit unchanged
Can someone kindly explain how I could achieve this. Maybe I need to change the mask so that it show bits that can be changed, i.e. 0111 in the above example... I don't know.
Regards Mark.
Assuming a C-like language where & is bitwise-and; | is bitwise-or; and ~ is bitwise-complement:
new_value = (value & locked) | (incoming & ~locked);
You could use + instead of |, if you felt it was more readable.