aatifsyed / bitbag

Use bitflags defined in an enum

bitbag

This crate provides [BitBag], a type intended for tracking bitflags defined in a field-less enum. Get started like this:

use bitbag::{BitBag, BitBaggable};
use strum::EnumIter;

#[derive(BitBaggable, EnumIter, Clone, Copy)]
#[repr(u8)]
enum Flags {
    A = 0b0001,
    B = 0b0010,
    C = 0b0100,
}

Basic functionality is provided by [BitBag]

let mut bag = BitBag::<Flags>::new_unchecked(0b0011);
assert!(bag.is_set(Flags::A));
assert!(bag.is_set(Flags::B));
assert!(!bag.is_set(Flags::C));

bag.set(Flags::C);
assert_eq!(*bag, 0b0111);

Deriving [BitBaggable] will also give you very ergonomic constructors

use Flags::*;
let bag = A | B | C;
assert!(bag.is_set(Flags::A));
assert!(bag.is_set(Flags::B));
assert!(bag.is_set(Flags::C));

Additionally deriving [EnumIter], and [Copy] will allow fallible creation, and iteration over the set flags

//                                  ⬇ this bit is not defined in Flags
let result = BitBag::<Flags>::new(0b1000);
assert!(matches!(
    result,
    Err(e) if e.given() == 0b1000
));

let bag = BitBag::<Flags>::new_unchecked(0b0110);
for flag in &bag {
    match flag {
        Flags::A => println!("Flag A was set"),
        Flags::B => println!("Flag B was set"),
        Flags::C => println!("Flag C was set"),
    }
};

bitbag's Issues

Compilation error on 1.50.0

Interesting crate! When attempting to run the example from the reddit post, I get the error:

jon@r4 ~/src/oss/bitbag_test $ cargo run
   Compiling bitbag v0.1.4
error[E0391]: cycle detected when computing the supertraits of `BitBaggable`
   --> /home/jon/.cargo/registry/src/github.com-1ecc6299db9ec823/bitbag-0.1.4/src/lib.rs:103:1
    |
103 | pub trait BitBaggable: Into<Self::Repr> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: ...which again requires computing the supertraits of `BitBaggable`, completing the cycle
note: cycle used when computing trait implemented by `<impl at /home/jon/.cargo/registry/src/github.com-1ecc6299db9ec823/bitbag-0.1.4/src/lib.rs:109:45: 109:50>`
   --> /home/jon/.cargo/registry/src/github.com-1ecc6299db9ec823/bitbag-0.1.4/src/lib.rs:109:45
    |
109 | #[derive(Clone, Copy, Debug, Deref, Binary, AsRef)]
    |                                             ^^^^^
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error

For more information about this error, try `rustc --explain E0391`.
error: could not compile `bitbag`

But running with nightly (1.55.0), it compiles and runs as expected:

    Finished dev [unoptimized + debuginfo] target(s) in 14.03s
     Running `target/debug/bitbag_test`
A was set
B was set

Perhaps there is a MSRV, or nightly-only limitation that could be called out in the docs?