I want to change 1 bit and keep the same values as other neighboring bits.
The bit operator shifts left or right by changing the 1-bit 0 bit, but it changes the entire 8-bit sequence. I did not want that to happen.
Alternatively, I change the integer itself, so the bit I want changes.
Please, can anyone help?
Thank you!
If you use XOR with 1 you can change a bit:
0 ^ 1 = 1
1 ^ 1 = 0
for example to change a 0 to a 4 we changed the 3rd bit.
char a = 0x00;
int bit = 2;
a ^= (1 << bit)
The C language even allows us to use struct and union to be able to directly determine the value of one or more bits with the = operator.
This functionality is little used - and anyway, it requires you to define a Union by naming bits (or fields with different sizes of bits).
To change a "generic" bit by one byte, the most common is:
This is if you want to pass the bit always from 0 to 1. The use of "xor" will always reverse the bit. And if you want to delete a bit, then the process involves creating a mask where the desired bit has the value "0", and apply the "&" operation.
We can do a function to set or reset a bit that does this: receive a pointer for the byte to be changed, the bit position, and the desired value. We create the byte with the bit in "1" in the correct position - (using the << operator), from it we create a mask with that bit at zero, and apply the bit with the value sent. In C:
void altera_bit(char *alvo, char posicao, char valor) {
char mascara = ~(1 << posicao);
*alvo = (*alvo & mascara) | (valor << posicao);
}