bitflag-attr

This is a proc-macro Rust crate that allows to turn a C-like enum into a bitflag structures with an API similar to bitfields crate.

You can use this crate to:

• provide more user-friendly bindings to C APIs where flags may or may not be fully known in advance.

You can't use this crate to:

• guarantee only bits corresponding to defined flags will ever be set. bitflag-attr allows access to the underlying bits type so arbitrary bits may be set.
• define bitfields. bitflag-attr only generates types where set bits denote the presence of some combination of flags.

Implemented traits

The macro will also implement some traits for bitwise operations and formatting.

• core::ops::Not
• core::ops::BitAnd
• core::ops::BitOr
• core::ops::BitXor
• core::ops::BitAndAssign
• core::ops::BitOrAssign
• core::ops::BitXorAssign
• core::ops::Sub
• core::ops::SubAssign
• core::fmt::Debug
• core::fmt::Binary
• core::fmt::UpperHex
• core::fmt::LowerHex
• core::fmt::Octal
• From

The macro doesn't implement Clone or Copy, but it is often a good idea to derive them.

Example

Generate a flags structure

use bitflag_attr::bitflag;

#[bitflag(u32)]
#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash)]
enum Flags {
    /// The value `A`, at bit position `0`.
    A = 0b00000001,
    /// The value `B`, at bit position `1`.
    B = 0b00000010,
    /// The value `C`, at bit position `2`.
    C = 0b00000100,

    /// The combination of `A`, `B`, and `C`.
    ABC = A | B | C,
}

fn main() {
    let e1 = Flags::A | Flags::C;
    let e2 = Flags::B | Flags::C;
    assert_eq!((e1 | e2), Flags::ABC);   // union
    assert_eq!((e1 & e2), Flags::C);     // intersection
    assert_eq!((e1 - e2), Flags::A);     // set difference
    assert_eq!(!e2, Flags::A);           // set complement
}

Rust Version Support

The minimum supported Rust version is documented in the Cargo.toml file. This may be bumped in minor releases as necessary.