Enum IdentityKind 

pub enum IdentityKind {
    DmaBuf,
    Shm,
    IoSurface,
    AHardwareBufferId,
    AHardwareBufferPtr,
    HostPtr,
    Pbo,
}

What kind of system key an identity was derived from. Participates in the id so that, say, inode 7 and IOSurfaceID 7 cannot collide.

Invariant every variant must uphold: the key passed to BufferIdentity::derived is unique among live buffers of that kind that own an allocation. There is no “no identity” case — where no system-wide key exists a process-local one does (a pointer, a GL name), and a process-local key is exactly as sound as a system-wide one: pointer/name reuse after free is the same ABA hazard as inode reuse, and is mitigated the same way, by the retaining cache (see the design spec’s Task 6).

The allocation qualifier is load-bearing, not a hedge. A zero-element tensor ([0, num_protos], the tracker’s “no detections this frame” sentinel — see [crate::mem]) owns no allocation, so its Vec yields the dangling well-aligned pointer align_of::<T>(). Every zero-element Tensor<f32> in a process therefore shares one identity, and can even collide across kinds with a small integer key from another variant.

That is safe rather than tolerated: an identity exists to answer “are these the same bytes?”, and buffers with no bytes have nothing to alias. Nor can they reach an import cache — both GPU import paths require a dma-buf fd or an IOSurface ref and reject anything else, so a HostPtr identity is never a cache key. Do not “fix” this by minting a distinct id per empty tensor: that reintroduces a counter, which is the state this whole design exists to remove.

Variants

DmaBuf

(st_dev, st_ino) of a dma-buf or memfd. Survives dup, and is the same value in every process that holds the buffer.

Shm

IoSurface

IOSurfaceGetID.

AHardwareBufferId

AHardwareBuffer_getId, API 31+.

AHardwareBufferPtr

The AHardwareBuffer* pointer, pre-API-31 where no id exists. Process-local: unique among live buffers here, meaningless elsewhere.

HostPtr

A host mapping address. Process-local.

Pbo

A GL buffer name. Valid only in the context that created it.

Trait Implementations

impl Clone for IdentityKind

fn clone(&self) -> IdentityKind

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for IdentityKind

impl Debug for IdentityKind

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

Formats the value using the given formatter.

impl Eq for IdentityKind

impl PartialEq for IdentityKind

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for IdentityKind