Crate gbp_stack 

C ABI surface for the Group Protocol Stack.

Designed for consumption from .NET (or any FFI-capable runtime) via P/Invoke. The C ABI is grouped into the following families:

• GBP (gbp_node_*) — the IP-like base layer: framing, AEAD, replay window, control plane.
• GTP (gtp_client_*) — text sub-protocol.
• GAP (gap_client_*) — audio sub-protocol.
• GSP (gsp_client_*) — signalling sub-protocol.
• MLS (gbp_mls_*) — RFC 9420 context.
• SFrame (gbp_sframe_*) — E2EE for GAP audio frames.

Conventions:

• Handle-based — every long-lived object lives in a Rust-side registry keyed by an i32 handle.
• GbpBuffer — binary blobs are returned as (ptr, len, cap) triples and MUST be released with gbp_buffer_free.
• Owned C-string — text values are returned as owned *mut c_char and MUST be released with gbp_string_free.
• Last error — every fallible call writes to a thread-local error slot that callers can read via gbp_last_error.

Structs

GbpBuffer

Binary buffer produced by Rust. The caller MUST release it via gbp_buffer_free.

Functions

gap_client_accept^⚠

Accepts a GAP audio payload.

gap_client_create

Creates a stateful GAP client.

gap_client_destroy

Destroys a GAP client.

gap_client_reset

Clears the client state. Intended for use after an epoch change.

gap_client_send^⚠

Sends an Opus audio frame via GAP.

gbp_buffer_free^⚠

Releases a GbpBuffer.

gbp_error_lookup

Returns a CBOR-encoded ErrorObject for the given code.

gbp_frame_encode_v^⚠

CBOR-encodes a [gbp::GbpFrame] with an arbitrary version byte.

gbp_last_error

Returns the text of the last error, or an empty string if none.

gbp_mls_accept_welcome^⚠

Replaces the local group with the one described by the given Welcome.

gbp_mls_clear_pending_commit

Discards any pending commit without applying it. Used on ABORT_TRANSITION to roll back to the pre-commit MLS state.

gbp_mls_create^⚠

Creates a new MLS context. Returns the new handle, or 0 on failure.

gbp_mls_destroy

Destroys an MLS context.

gbp_mls_epoch

Returns the current epoch of the MLS context, or 0 on failure.

gbp_mls_export_key_package

Exports the TLS-serialised KeyPackage that can be used to invite this member into someone else’s group.

gbp_mls_finalize_commit

Merges any pending commit produced by gbp_mls_invite_full or gbp_mls_remove. Returns true on success, false on failure.

gbp_mls_group_id^⚠

Writes the 16-byte group identifier into out16.

gbp_mls_invite^⚠

Invites the given KeyPackage into the local group. Returns the TLS-serialised Welcome bytes that the invitee must consume with gbp_mls_accept_welcome.

gbp_mls_invite_full^⚠

Invites the given KeyPackage and returns BOTH the MLS Commit (which the caller MUST broadcast to existing members so they can advance their MLS epoch) and the Welcome (which the caller MUST unicast to the new joiner).

gbp_mls_process_message^⚠

Applies a Commit (or staged Proposal) message to the local MLS group. Returns: 1 — Commit applied (epoch advanced) 2 — Application message (no-op for GBP) 3 — Proposal staged 4 — External message (no group state change) 0 — failure (see gbp_last_error).

gbp_mls_remove

Removes the member at the given MLS LeafIndex and returns the TLS-serialised Commit. Caller MUST broadcast the Commit to remaining members so they advance their MLS epoch.

gbp_node_apply_transition

Applies an epoch transition locally.

gbp_node_bootstrap_creator

Drives the node to ACTIVE as a creator.

gbp_node_bootstrap_joiner

Drives the node to ACTIVE as a joiner. expected_first_tid lets the joiner pre-arm pending transition state so that the first EXECUTE_TRANSITION after Welcome is accepted; pass 0 if the joiner recovered out-of-band and is already current.

gbp_node_create^⚠

Creates a new GBP node and returns its handle.

gbp_node_destroy

Destroys a GBP node.

gbp_node_drain_events

Drains the queued events (without consuming any wire bytes).

gbp_node_epoch

Returns the node’s current epoch.

gbp_node_last_transition_id

Returns the node’s last applied transition_id.

gbp_node_on_wire^⚠

Feeds wire bytes to the node. Returns a JSON-encoded array of events.

gbp_node_send_control^⚠

Sends a control plane message on Stream 0.

gbp_node_set_epoch

Forcibly sets the node’s current_epoch (intended for tests of late peers and EPOCH_MISMATCH recovery).

gbp_node_state

Returns the current NodeState encoded as u32.

gbp_sframe_decrypt^⚠

Decrypts one SFrame payload.

gbp_sframe_encrypt^⚠

Encrypts one audio frame.

gbp_sframe_encryptor_create^⚠

Creates an encryptor for the local sender (leaf_index) within an epoch.

gbp_sframe_encryptor_free

Frees an encryptor created by gbp_sframe_encryptor_create.

gbp_sframe_session_create^⚠

Creates an SFrame session from an existing MLS context.

gbp_sframe_session_free

Frees an SFrame session created by gbp_sframe_session_create.

gbp_string_free^⚠

Releases a string previously returned by an FFI function.

gbp_version

Returns the FFI library version with a short summary of the layers.

gsp_client_accept^⚠

Accepts a GSP signal payload.

gsp_client_create

Creates a stateful GSP client.

gsp_client_destroy

Destroys a GSP client.

gsp_client_reset

Clears the client state. Intended for use after an epoch change.

gsp_client_send

Sends a GSP signal.

gsp_client_send_with_args^⚠

Sends a GSP signal with opcode-specific CBOR args bytes. Use this for signals that require structured arguments (MUTE, UNMUTE, ROLE_CHANGE, STREAM_START, STREAM_STOP, CODEC_UPDATE).

gtp_client_accept^⚠

Accepts a plaintext payload that the GBP layer surfaced via a payload_received event. Returns a JSON object of the form {"status":"new|duplicate|error", ...}.

gtp_client_create

Creates a stateful GTP client (idempotency tracking).

gtp_client_destroy

Destroys a GTP client.

gtp_client_reset

Clears the client state. Intended for use after an epoch change.

gtp_client_send^⚠

Sends a text message via GTP.