4. Registry

4.1 Endpoints

To register, under the registry lock:

1. Reclaim dead endpoints (4.3).
2. If the requested UID is 0, or already owned by an active endpoint, generate random non-zero UIDs until one is free. A plugin whose saved UID was taken (the user duplicated the device) MUST save the new UID.
3. Take the first free endpoint record, fill it, store state = 1.
4. Increment registry_generation.

UIDs are chosen by plugins and saved in their state, so cables survive closing and reopening a set. A plugin SHOULD register immediately (with a random UID) and switch to its saved UID when the host restores its state (bb_set_instance_uid); the switch fails with BB_ERR_UID_IN_USE if that UID is live elsewhere.

4.2 Ports

Outputs and inputs are records in their own tables with the owner's endpoint index. Names:

• 1..31 bytes of UTF-8, no control characters, no /.
• Unique per endpoint and direction (an input and an output MAY share a name).
• Stable: cables refer to outputs by name. Renaming an output breaks existing cables to it.
• Convention: the bus input for modulating a parameter carries the parameter's display name, e.g. Cutoff.

To allocate an output: set blocks_written = 0, increment incarnation, fill the remaining fields, store state = 1, increment registry_generation. An input is reset with its seqlock held odd and its connections zeroed.

Limits per bus: 64 endpoints, 256 outputs, 512 inputs; per endpoint the reference SDK allows 64 outputs and 64 inputs.

4.3 Reclamation

An active endpoint whose pid is not a live process (POSIX: kill(pid, 0) fails with ESRCH; Windows: the process cannot be opened or has exited) is dead. On registration (and MAY on other occasions) implementations free it: its outputs and inputs (with their connections) are freed, the endpoint record is freed, and both generations are incremented.

Unregistering frees an endpoint the same way. Cables from a removed endpoint stay stored at their receivers and read silence ("ghost source") until an endpoint with that UID and output name appears again.

4.4 Addressing

Bridges (OSC, network) address ports as /<track>/<instance>/<port>, where each segment is the corresponding name lower-cased, with runs of characters outside [a-z0-9] replaced by -. Example: track "Bass", instance "Function 1", output "A" → /bass/function-1/a. Inside the bus, ports are addressed by (endpoint UID, port name).