Trait Flags

pub trait Flags: Sized + 'static

A set of defined flags using a bits type as storage.

Implementing Flags

This trait is implemented by the bitflags macro:

use bitflags::bitflags;

bitflags! {
    struct MyFlags: u8 {
        const A = 1;
        const B = 1 << 1;
    }
}

It can also be implemented manually:

use bitflags::{Flag, Flags};

struct MyFlags(u8);

impl Flags for MyFlags {
    const FLAGS: &'static [Flag<Self>] = &[
        Flag::new("A", MyFlags(1)),
        Flag::new("B", MyFlags(1 << 1)),
    ];

    type Bits = u8;

    fn from_bits_retain(bits: Self::Bits) -> Self {
        MyFlags(bits)
    }

    fn bits(&self) -> Self::Bits {
        self.0
    }
}

Using Flags

The Flags trait can be used generically to work with any flags types. In this example, we can count the number of defined named flags:

# use bitflags::{bitflags, Flags};
fn defined_flags<F: Flags>() -> usize {
    F::FLAGS.iter().filter(|f| f.is_named()).count()
}

bitflags! {
    struct MyFlags: u8 {
        const A = 1;
        const B = 1 << 1;
        const C = 1 << 2;

        const _ = !0;
    }
}

assert_eq!(3, defined_flags::<MyFlags>());

Associated Types

type Bits: Bits;

The underlying bits type.

Associated Constants

const FLAGS: &'static [Flag<Self>];

The set of defined flags.

Required Methods

fn bits(&self) -> Self::Bits

Get the underlying bits value.

The returned value is exactly the bits set in this flags value.

fn from_bits_retain(bits: Self::Bits) -> Self

Convert from a bits value exactly.

Provided Methods

fn empty() -> Self

Get a flags value with all bits unset.

fn all() -> Self

Get a flags value with all known bits set.

fn all_named() -> Self

Get a flags value with all bits from named flags set.

This method is equivalent to Flags::all unless Flags::FLAGS contains unnamed flags.

fn known_bits(&self) -> Self::Bits

Get the known bits from a flags value.

fn unknown_bits(&self) -> Self::Bits

Get the unknown bits from a flags value.

fn contains_unknown_bits(&self) -> bool

This method will return true if any unknown bits are set.

fn from_bits(bits: Self::Bits) -> Option<Self>

Convert from a bits value.

This method will return None if any unknown bits are set.

fn from_bits_truncate(bits: Self::Bits) -> Self

Convert from a bits value, unsetting any unknown bits.

fn from_name(name: &str) -> Option<Self>

Get a flags value with the bits of a flag with the given name set.

This method will return None if name is empty or doesn't correspond to any named flag.

fn iter(&self) -> Iter<Self>

Yield a set of contained flags values.

Each yielded flags value will correspond to a defined named flag. Any unknown bits will be yielded together as a final flags value.

fn iter_names(&self) -> IterNames<Self>

Yield a set of contained named flags values.

This method is like Flags::iter, except only yields bits in contained named flags. Any unknown bits, or bits not corresponding to a contained flag will not be yielded.

fn iter_defined_names() -> IterDefinedNames<Self>

Yield a set of all named flags defined by Self::FLAGS.

fn iter_equal_names(&self) -> IterEqualNames<Self>

Get an iterator over all defined names for this flags value.

This iterator will yield all defined names for the flags value, including any convenience flags.

fn is_empty(&self) -> bool

Whether all bits in this flags value are unset.

fn is_all(&self) -> bool

Whether all known bits in this flags value are set.

fn intersects(&self, other: Self) -> bool
where
    Self: Sized,

Whether any set bits in other are also set in self.

fn contains(&self, other: Self) -> bool
where
    Self: Sized,

Whether all set bits in other are also set in self.

fn truncate(&mut self)
where
    Self: Sized,

Remove any unknown bits from the flags.

fn insert(&mut self, other: Self)
where
    Self: Sized,

The bitwise or (|) of the bits in self and other.

fn remove(&mut self, other: Self)
where
    Self: Sized,

The intersection of self with the complement of other (&!).

This method is not equivalent to self & !other when other has unknown bits set. remove won't truncate other, but the ! operator will.

fn toggle(&mut self, other: Self)
where
    Self: Sized,

The bitwise exclusive-or (^) of the bits in self and other.

fn set(&mut self, other: Self, value: bool)
where
    Self: Sized,

Call Flags::insert when value is true or Flags::remove when value is false.

fn clear(&mut self)
where
    Self: Sized,

Unsets all bits in the flags.

fn intersection(self, other: Self) -> Self

The bitwise and (&) of the bits in self and other.

fn union(self, other: Self) -> Self

The bitwise or (|) of the bits in self and other.

fn difference(self, other: Self) -> Self

The intersection of self with the complement of other (&!).

This method is not equivalent to self & !other when other has unknown bits set. difference won't truncate other, but the ! operator will.

fn symmetric_difference(self, other: Self) -> Self

The bitwise exclusive-or (^) of the bits in self and other.

fn complement(self) -> Self

The bitwise negation (!) of the bits in self, truncating the result.