bitflags

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

Usage

Add this to your Cargo.toml:

[dependencies]
bitflags = "2.13.1"

and this to your source code:

use bitflags::bitflags;

Example

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)]structFlags:u32{/// The value `A`, at bit position `0`.constA = 0b00000001;/// The value `B`, at bit position `1`.constB = 0b00000010;/// The value `C`, at bit position `2`.constC = 0b00000100;/// The combination of `A`, `B`, and `C`.constABC = Self::A.bits() | Self::B.bits() | Self::C.bits();}}fnmain(){let e1 = Flags::A | Flags::C;let e2 = Flags::B | Flags::C;assert_eq!((e1 | e2),Flags::ABC);// unionassert_eq!((e1 & e2),Flags::C);// intersectionassert_eq!((e1 - e2),Flags::A);// set differenceassert_eq!(!e2,Flags::A);// set complement}

Cargo features

The bitflags library defines a few Cargo features that you can opt-in to:

• std: Implement the Error trait on error types used by bitflags.
• serde: Support deriving serde traits on generated flags types.
• arbitrary: Support deriving arbitrary traits on generated flags types.
• bytemuck: Support deriving bytemuck traits on generated flags types.

Also see bitflags_derive for other flags-aware traits.

Rust Version Support

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