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Bitflag attribute macro for Rust enums

License: Apache License 2.0

Rust 100.00%

bitflag-attr's Introduction

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.

Besides the Debug, Clone and Copy traits, all other derivable traits can be used together with the type

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
}