Crate zerodds_transport_shm

Expand description

Crate zerodds-transport-shm. Safety classification: STANDARD.

Cross-process shared-memory transport for ZeroDDS — POSIX shm_open/mmap with a lock-free single-producer-single-consumer ring buffer.

§Spec

DDSI-RTPS 2.5 §9.4 — locator kind LOCATOR_KIND_SHM (vendor- reserved range; the ZeroDDS value in crates/rtps/src/wire_types.rs).
ZeroDDS SHM Transport 1.0 — vendor-specific transport spec (segment layout, SpSc ring buffer, cleanup semantics), docs/spec-coverage/zerodds-shm-transport-1.0.md.

§Note on OMG normativity

OMG standardizes no SHM transport for DDS. Vendors each have their own implementations: Cyclone DDS integrates iceoryx (third-party), FastDDS has its own SHM transport, RTI has RTI Connext DDS SHM. ZeroDDS defines its own variant explicitly as the ZeroDDS SHM Transport 1.0 spec.

§Implemented (RC1)

POSIX shm_open + mmap via the shared_memory crate.
SpSc ring buffer per (writer, reader) pair — lock-free head/tail AcqRel atomics on shared memory.
Owner crash recovery via a predictable os_id + shm_unlink before every owner create(). Idempotent.
Advisory flock race protection on owner-create (Linux/macOS).
Length-prefix frame format with a wraparound padding marker.
Shutdown flag in the segment header for owner→consumer termination signaling.

§Platform support

Platform	Status
Linux	✅ primary
macOS	✅ supported
Windows	untested (the `shared_memory` crate provides the mapping primitives, but our `flock` race protection and `shm_unlink` cleanup are unix-only)

§Public API

PosixShmTransport — Transport trait impl.
ShmConfig — segment configuration.
ShmRole — owner / consumer.
PosixShmError — typed errors.

§Unsafe scope

Limited to the posix module: two ptr::read/ptr::write on mapped memory plus the libc::flock FFI. Everything else is AtomicU{32,64} over shared memory; Rust guarantees well-defined behavior of atomic operations across process boundaries when both processes map the same address.

Re-exports§

pub use posix::PosixShmError;
pub use posix::PosixShmTransport;
pub use posix::ShmConfig;
pub use posix::ShmRole;

Modules§

posix: POSIX SHM transport.