How do you set, clear and toggle a single bit in Rust?

Question

How do I set, clear and toggle a bit in Rust?

Answer 1

Like many other languages, the bitwise operators & (bitwise AND), | (bitwise OR), ^ (bitwise XOR) exist:

fn main() {
    let mut byte: u8 = 0b0000_0000;

    byte |= 0b0000_1000; // Set a bit
    println!("0b{:08b}", byte);

    byte &= 0b1111_0111; // Unset a bit
    println!("0b{:08b}", byte);

    byte ^= 0b0000_1000; // Toggle a bit
    println!("0b{:08b}", byte);
}

The main difference from other languages is in bitwise NOT, which uses ! instead of ~:

fn main() {
    let mut byte: u8 = 0b0000_0000;

    byte = !byte; // Flip all bits
    println!("0b{:08b}", byte);
}

You can also shift bits left or right:

fn main() {
    let mut byte: u8 = 0b0000_1000;

    byte <<= 1; // shift left one bit
    println!("0b{:08b}", byte);

    byte >>= 1; // shift right one bit
    println!("0b{:08b}", byte);
}

There are many other conceptual things that ultimately do bit-level manipulation that are not expressed with operators. Check out the documentation for an integer for examples. One interesting example is leading_zeros. Here is how to rotate by a certain number of bits:

fn main() {
    let mut byte: u8 = 0b1000_0000;

    byte = byte.rotate_left(1); // rotate left one bit
    println!("0b{:08b}", byte);

    byte = byte.rotate_right(1); // rotate right one bit
    println!("0b{:08b}", byte);
}

The book has some more information

Answer 2

Rust has both bit-twiddling operators and binary format printing (very helpful for debugging):

fn bit_twiddling(original: u8, bit: u8) {
    let mask = 1 << bit;

    println!(
        "Original: {:b}, Set: {:b}, Cleared: {:b}, Toggled: {:b}",
        original,
        original |  mask,
        original & !mask,
        original ^  mask
    );
}

fn main() {
    bit_twiddling(0, 3);
    bit_twiddling(8, 3);
}

It also has the compound assignment variants (|=, &= and ^=).

The book has some more information

Answer 3

Additionally, I'd like to add the following use case: If you have a bitfield like 0b10001000 and you want to update bit 3 in any case to true or false, you can do it like this:

    const SHIFT: u8 = 3;
    let set_bit_3 = false;
    let bits = 0b10001000;
    let bits = bits & !(1 << SHIFT) | (u16::from(set_bit_3) << SHIFT);