Bitbite  

Bitbite is a simple trait that would help you interact bytes with flags easily

• How to use
• Bigger flags
• Mutability
• Derive

How to use

All you need to do is declare the flags and implement the trait.

use bitbite::{Flag, Bitbite};
use std::ops::{Deref, DerefMut};

struct NesCartridgeF6(pub u8);
impl NesCartridgeF6 {
  pub const LOWER_MAPPER: Flag<u8> = Flag::<u8>::new(0b1111_0000);
}

impl Deref for NesCartridgeF6 {
    type Target = u8;

    fn deref(&self) -> &Self::Target {
      &self.0    
    }       
}

impl DerefMut for NesCartridgeF6 {
    fn deref_mut(&mut self) -> &mut Self::Target {
      &mut self.0    
    }       
}

impl Bitbite for NesCartridgeF6 {
    type Unit = u8;
}
 
let mut t = NesCartridgeF6(0b0110_0000);
let lower_mapper = t.get_flag(&NesCartridgeF6::LOWER_MAPPER);
assert_eq!(lower_mapper, 0b0110);

Getting the flag value will always be shifted so you won't need to shift the data yourself

Bigger flags

The trait BitBite and the struct Flag are generics and can hold any primitive integer, so you could have a struct that hold 1,2,4 bytes of data and still use the flags seamlessly.

Mutability

You can now edit your bytes with flags with ease, you can use set_flag to override the entire flag's mask and change it as you please.
And in case you don't want to override the previous values you can set_on different bits to hold their state as it is.

Derive  

For easier use you can add the bitbite_derive crate
I also recommend using defer-derive for maximum ease

use bitbite::*;
use bitbite_derive::Bitbite;
use deref_derive::*;

#[derive(Bitbite, Deref, DerefMut)]
struct Header(pub u8);