Crate tympan_aspl 

tympan-aspl — a Rust framework for writing macOS AudioServerPlugins.

AudioServerPlugins are the user-space audio drivers that run inside coreaudiod and appear to the system as audio devices. tympan-aspl provides safe Rust abstractions over the Core Audio HAL AudioServerPlugin C interface so a Rust crate can implement a virtual audio device — a loopback, a virtual microphone, a routing or processing driver — without writing C++ or Objective-C.

See docs/overview.md for the project’s scope and docs/architecture.md for the design that drives this crate.

Layering

The crate is built bottom-up in conceptual layers, isolated by module boundary:

• raw — the low-level FFI to the AudioServerPlugin C ABI. Its ABI type definitions (raw::abi) and marshalling (raw::marshal) are plain data, compiled and tested on every host; only the live extern "C" entry points and CoreFoundation calls (a later PR) are macOS-gated.
• realtime — allocation-free, lock-free primitives for the IOProc realtime callback. Cross-platform, so the realtime invariants are unit-testable on any host.
• The object model — error, fourcc, object, property, format, io — cross-platform plain-data mirrors of the Core Audio C types.
• The property protocol — objects (the object tree) and dispatch (the cross-platform answer to the HAL’s property reads).
• The public API — driver, device, stream — the traits and declarative types a consumer implements against.
• bundle — .driver bundle Info.plist generation.

Realtime safety

Any code reachable from the IOProc realtime callback must be allocation-free, lock-free, and free of blocking syscalls. The realtime module exposes a RealtimeContext marker that acts as a compile-time witness for the realtime context; Driver::process_io takes one. Mechanical enforcement lives in tests/realtime_safety.rs via an assert_no_alloc global-allocator guard.

Implementing a driver

A consumer implements Driver for a type carrying its per-plug-in state, describes the device it exposes with a DeviceSpec, and — on macOS — exposes the type as a CFPlugIn with the plugin_entry! macro.

Re-exports

pub use bundle::BundleConfig;

pub use device::Device;

pub use device::DeviceId;

pub use device::DeviceSpec;

pub use dispatch::DeviceState;

pub use driver::AnyDriver;

pub use driver::Driver;

pub use driver::DriverInfo;

pub use error::OsStatus;

pub use format::FormatNegotiation;

pub use format::SampleFormat;

pub use format::StreamFormat;

pub use fourcc::FourCharCode;

pub use io::IoBuffer;

pub use io::IoOperation;

pub use io::Sample;

pub use io::Timestamp;

pub use object::AudioObjectId;

pub use object::ObjectKind;

pub use objects::Object;

pub use objects::ObjectMap;

pub use property::PropertyAddress;

pub use property::PropertyElement;

pub use property::PropertyScope;

pub use property::PropertySelector;

pub use property::PropertyValue;

pub use property::ValueRange;

pub use realtime::RealtimeContext;

pub use stream::StreamDirection;

pub use stream::StreamSpec;

Modules

bundle

.driver bundle packaging helpers.

device

Device abstraction.

dispatch

Core Audio property dispatch.

driver

The top-level Driver trait and its framework-side wrapper.

error

OSStatus wrapper and Core Audio error constants.

format

Audio stream formats.

fourcc

Four-character codes.

io

The IO cycle: timestamps, operations, and the realtime buffer wrapper.

object

Audio object identifiers and the AudioServerPlugin object model.

objects

The AudioServerPlugin object tree.

property

The Core Audio property protocol.

raw

Low-level FFI to the Core Audio AudioServerPlugin C ABI.

realtime

Realtime-safe primitives.

stream

Stream abstraction.

Macros

plugin_entry

Expose a T: Driver implementation as the AudioServerPlugin this .driver bundle provides.