bitflags 2.4.2

A macro to generate structures which behave like bitflags.


Rust Latest version Documentation License

bitflags generates flags enums with well-defined semantics and ergonomic end-user APIs.

You can use bitflags to:

  • provide more user-friendly bindings to C APIs where flags may or may not be fully known in advance.
  • generate efficient options types with string parsing and formatting support.

You can't use bitflags to:

  • guarantee only bits corresponding to defined flags will ever be set. bitflags allows access to the underlying bits type so arbitrary bits may be set.

  • define bitfields. bitflags only generates types where set bits denote the presence of some combination of flags.

  • Documentation

  • Specification

  • Release notes


Add this to your Cargo.toml:

bitflags = "2.4.2"

and this to your source code:

use bitflags::bitflags;


Generate a flags structure:

use bitflags::bitflags;

// The `bitflags!` macro generates `struct`s that manage a set of flags.
bitflags! {
    /// Represents a set of flags.
    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
    struct Flags: u32 {
        /// The value `A`, at bit position `0`.
        const A = 0b00000001;
        /// The value `B`, at bit position `1`.
        const B = 0b00000010;
        /// The value `C`, at bit position `2`.
        const C = 0b00000100;

        /// The combination of `A`, `B`, and `C`.
        const ABC = Self::A.bits() | Self::B.bits() | Self::C.bits();

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.