Struct CapabilitySet 

pub struct CapabilitySet { /* private fields */ }

A set of capabilities.

The set is a fixed 32 bytes, so it holds 256 capabilities and needs no allocation. On the wire it is a variable-length byte string, so a future version can make it wider without breaking anything, and CapabilitySet::has_bits_beyond_this_build is how this version notices that happened instead of silently ignoring the extra bits.

Implementations

impl CapabilitySet

pub const BYTES: usize = 32

How many bytes of bitset this build carries.

pub const MAX_BIT: u16 = 255

The highest capability bit this build can represent.

pub const fn new() -> Self

An empty set.

pub const fn with(self, cap: Capability) -> Self

Adds a capability and returns the set, so sets can be built in one expression.

A capability above CapabilitySet::MAX_BIT cannot be represented by this build and is ignored. That cannot happen by accident, because every capability this build knows about is a constant in this file.

pub const fn contains(self, cap: Capability) -> bool

Whether the set contains a capability.

pub fn is_empty(self) -> bool

Whether the set is empty as far as this build can tell.

pub const fn has_bits_beyond_this_build(self) -> bool

Whether the bytes this set was decoded from had bits set past what this build can hold.

This matters on the required side. A decoder built against a later version of the ABI may require a capability that did not exist when this host was compiled, and a host that just truncated the bitset would conclude the decoder required nothing and run it anyway. That is the failure this flag exists to prevent.

pub fn from_bytes(bytes: &[u8]) -> Self

Reads a set from its wire form.

Bytes past what this build can hold are not stored, but if any of them are non-zero the set remembers that.

pub fn as_bytes(&self) -> &[u8]

The wire form, with trailing zero bytes trimmed off so an empty set costs nothing.

Trimming is safe because a reader treats a missing byte as zero, which is what CapabilitySet::from_bytes does.

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

The capabilities in this set that are not in other.

The beyond flag rides along, because a bit this build cannot name is by definition a bit other does not offer.

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

The capabilities in both sets.

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

The capabilities in either set.

pub fn iter(&self) -> impl Iterator<Item = Capability> + '_

Every capability in the set, lowest bit first.

Bits past CapabilitySet::MAX_BIT cannot be listed, which is what CapabilitySet::has_bits_beyond_this_build is for.

Trait Implementations

impl Clone for CapabilitySet

fn clone(&self) -> CapabilitySet

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for CapabilitySet

impl Debug for CapabilitySet

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for CapabilitySet

fn default() -> CapabilitySet

Returns the “default value” for a type.

impl Eq for CapabilitySet

impl PartialEq for CapabilitySet

fn eq(&self, other: &CapabilitySet) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for CapabilitySet