# gbp-core
Core type vocabulary for the **Group Protocol Stack** — `StreamType`, frame
flags, FSM states, control opcodes, signal opcodes and the canonical error
code registry.
This crate is dependency-light (only `core` / `alloc`) and is the foundation
every other crate in the stack builds on.
Key types:
* `StreamType` — `Audio=1`, `Text=2`, `Signaling=3`
* `PayloadCodec` — `Cbor=0`, `Protobuf=1`, `FlatBuffers=2`; controls which
wire format is used for sub-protocol payloads (signalled via GBP frame `pf`)
* `ControlOpcode`, `SignalOpcode` — numeric registries
* `GbpError` / error code constants
## Stack overview
```
┌── application ──────────────────────────────────────────────────────┐
│ gtp-protocol · gap-protocol · gsp-protocol (TCP/UDP/SCTP-like) │
├──────────────────────────────────────────────────────────────────────┤
│ gbp-protocol (the IP-like base) │
├──────────────────────────────────────────────────────────────────────┤
│ gbp-core ← you are here │
└──────────────────────────────────────────────────────────────────────┘
```
## License
Licensed under [Apache License, Version 2.0](../../../LICENSE).