CoreMIDI UMP endpoints¶

ravet-core-midi is an explicit macOS-only backend outside the portable umbrella. It builds a narrow Objective-C++ CoreMIDI ownership shim with local Xcode tools; Rust owns names, packet framing, queue preparation, delivery and statistics. Other workspace targets compile the package with no backend API. Cross-compilation is not configured. The UMP APIs require an Apple SDK providing the protocol-selected CoreMIDI facilities; runtime evidence here is macOS 27.0.1 arm64 only.

sources() and destinations() return bounded control-thread snapshots of at most 4096 exact signed unique IDs and complete UTF-8 display names (1023 bytes maximum). Names need not be unique. Concurrent removal/metadata failure rejects the snapshot; there is no implicit reconnection or fallback to another device.

CoreUmpInput::connect selects a source ID, explicit MIDI 1/2 receive protocol and 1..4096 packet queue. virtual_destination instead owns an explicit endpoint and returns its unique ID. CoreUmpOutput::connect targets an exact destination ID with explicit send protocol. send submits one complete framed numeric packet; native success is submission, rather than an application acknowledgement. The native service can translate to a peer's protocol; this crate does not perform MIDI-CI negotiation or convert semantic messages itself.

CoreUmpSource::new owns a named protocol-selected virtual source. Its id permits exact source subscriptions; send distributes to every connected input port. Other applications can discover and subscribe to this visible endpoint. The backend opens no hardware connections automatically. IDs are assigned per lifetime; persistent IDs and reconnection remain consumer policy. Closing a source removes it from enumeration without destroying subscriber input owners. This follows Apple's virtual source API and event distribution API.

Timestamps are CoreMIDI host-clock ticks. Zero output means now. Queue records retain callback timestamps; no conversion to connection-local microseconds or audio sample offsets occurs. Framing accepts complete packets independently of semantic/protocol validity. Consumer policy must choose supported messages.

Native callbacks bound lists to 1024 event packets/4096 total words before Rust entry. Each native packet's word batch receives framing preflight and normal accepted-prefix/full-suffix handoff; earlier native packets can already have been published if a later packet is malformed. Metadata errors and concurrent native callback entry have separate diagnostics. A nonblocking atomic gate discards an overlapping whole callback; unique mutable Rust producer ownership is preserved.

Construction/close belong outside callbacks. Native handles have thread-local Rust ownership and cannot be moved/shared between threads; construct an output inside its selected worker. Receive endpoints transfer a separate Send consumer to audio/worker code. Closing gates new Rust callbacks, disposes native ports, waits for any entered callback, then frees the Rust context on the owner thread. No physical-device, sample-clock, hotplug or real-time deadline claim follows.

Run an explicit synthetic native test without sending to hardware:

CARGO_BUILD_JOBS=2 cargo run -p ravet-core-midi --example virtual-probe --locked
CARGO_BUILD_JOBS=2 cargo run -p ravet-core-midi --example source-probe --locked

The local macOS run preserves MIDI 1/2 numeric words across all 16 groups, including MIDI 2 16-bit velocity and attribute data, for 96 packets/six owned endpoint cycles. It checks exact-ID enumeration, diagnostics, queue producer teardown and endpoint removal. Ten additional cycles close owned destinations while worker outputs submit packets, then verify producer teardown, bounded retained packets and endpoint removal. Framework callback fixtures exercise 10,000 raw-entry handoffs and 30,000 rejected metadata cases with zero measured heap operations. The native service and SDK wrapper internals have no heap/deadline guarantee. The source probe also passes 198 exact deliveries to two subscribers across all groups and six MIDI 1/2 lifecycles, direction mismatch/name rejection, independent subscriber teardown and source removal/new-connection rejection. Physical MIDI 2 devices, protocol negotiation and other OS backends remain separately unvalidated. See decision 0061 and decision 0072.