Bit set/clear in C?

Question

How do I write to a single bit? I have a variable that is either a 1 or 0 and I want to write its value to a single bit in a 8-bit reg variable.

I know this will set a bit:

reg |= mask; // mask is (1 << pin)

And this will clear a bit:

reg &= ~mask; // mask is (1 << pin)

Is there a way for me to do this in one line of code, without having to determine if the value is high or low as the input?

Answer 1

Assuming value is 0 or 1:

REG = (REG & ~(1 << pin)) | (value << pin);

I use REG instead of register because as @KerrekSB pointed out in OP comments, register is a C keyword.

The idea here is we compute a value of REG with the specified bit cleared and then depending on value we set the bit.