jcktrue.dk/content/post/bit-magic/index.md

title	subtitle	summary	authors	tags	categories	date	lastmod	featured	draft	image	projects
Bit magic in C (and C++)	Tips and trick for embedded C/C++	Tips and trick for embedded C/C++				2020-06-13T19:01:19+02:00	2020-06-13T19:01:19+02:00	false	false	caption focal_point preview_only false

Set a bit

// Set one bit high at position "bit" in input and store to output
output = input | (1 << bit);
// Shorthand
variable |= (1 << bit);
// Multiple bits
variable |= (0b101 << bit);

Clear a bit

// Clear one bit high at position "bit" in input and store to output
output = input & ~(1 << bit);
// Shorthand
variable &= ~(1 << bit);
// Multiple bits
variable &= ~(0b101 << bit);

Toggle a bit

// Clear one bit high at position "bit" in input and store to output
output = x ^ (1 << bit);
// Shorthand
variable ^= (1 << bit);
// Multiple bits
variable ^= (0b101 << bit);

Math

// Division using bitshift
output = input >> 1; // Divide by 2
output = input >> 2; // Divide by 4
output = input >> 3; // Divide by 8
// Multiply using bitshifting
output = input << 1; // Multiply by 2
output = input << 2; // Multiply by 4
output = input << 3; // Multiply by 8

Set X number of bits high.

output = (0b1 << X) -1;

Miscellaneous

// Check if number is ODD
if( (num & 1) == 1) {};
// Flip signed integer
num = ~num + 1;
// Power of two
num > 0 && (num & (num - 1)) == 0;