cxorparity

How to XOR all of the bits of a single number in C?

Is there a simple way to XOR all of the bits of a single number together, i.e. a unary XOR in C?

Something that has the effect of:

result = ^(0x45); // ( 0 ^ 1 ^ 0 ^ 0 ^ 0 ^ 1 ^ 0 ^ 1 = 1)
result = ^(0x33); // ( 0 ^ 0 ^ 1 ^ 1 ^ 0 ^ 0 ^ 1 ^ 1 = 0)
Solution

  • There's no special operator for that. You would need to do that manually as follows:

    unsigned int value = 0x45;
unsigned int result = 0;
while (value) {
    result ^= value & 1;
    value >>= 1;
}

    You can also create a lookup table containing the parity for all 1 byte values:

    char parity[256] = { 0, 1, 1, 0, 1, 0, 0, 1,
                    ...
                     1, 0, 0, 1, 0, 1, 1, 0 };