Struct ShutdownCallbackHandle 

#[repr(transparent)]
pub struct ShutdownCallbackHandle(pub u32);

Handle to a registered shutdown hook, returned by Executor::add_pre_shutdown_callback / Executor::add_on_shutdown_callback and consumed by the matching remove_*. rclcpp’s PreShutdownCallbackHandle / OnShutdownCallbackHandle.

Why an index and not a pointer

rclcpp’s handle owns a std::shared_ptr to the callback. There is no allocator here and the hooks live in a fixed-capacity static table, so the handle is the SLOT INDEX — the smallest thing that identifies a row of a static array, and trivially passable through the C ABI as one uint32_t.

The phase is packed into the high half rather than left implicit, so a handle from one list cannot silently remove a callback from the other. A slot index is only meaningful next to the table it indexes, and there are two tables.

Tuple Fields

0: u32

Implementations

impl ShutdownCallbackHandle

pub const INVALID: ShutdownCallbackHandle

The value no registration ever returns. C callers compare against NROS_SHUTDOWN_CALLBACK_HANDLE_INVALID, which is this number.

pub const fn new( phase: ShutdownPhase, index: usize, ) -> Option<ShutdownCallbackHandle>

Pack a (phase, slot) pair. None when index does not fit the 16-bit index field — unreachable for any table this crate builds, and an honest None rather than a silent truncation if one ever grows.

pub const fn phase(self) -> Option<ShutdownPhase>

The phase this handle was issued for, or None if the value is not a handle this crate ever issued (including Self::INVALID).

pub const fn index(self) -> usize

The slot index within this handle’s phase table.

pub const fn is_valid(self) -> bool

True for anything Self::new could have produced.

Trait Implementations

impl Clone for ShutdownCallbackHandle

fn clone(&self) -> ShutdownCallbackHandle

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ShutdownCallbackHandle

impl Debug for ShutdownCallbackHandle

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

Formats the value using the given formatter.

impl Eq for ShutdownCallbackHandle

impl PartialEq for ShutdownCallbackHandle

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for ShutdownCallbackHandle