KeyBoard_QT/docs/host_com_rebuild.md

Host COM Rebuild

Goal

Keep the protocol layer small and explicit.

The COM layer should:

• define packet-facing helpers
• own frame parsing and packet building
• avoid transport concerns
• avoid UI and session concerns

Completed Nodes

Node 1: legacy protocol baseline

Files already present before this step:

• KeyBorad/KeyBorad/COM/Com_Cdc.h
• KeyBorad/KeyBorad/COM/Com_CdcEncode.h
• KeyBorad/KeyBorad/COM/Com_CdcEncode.cpp
• KeyBorad/KeyBorad/COM/Com_CdcDecode.h
• KeyBorad/KeyBorad/COM/Com_CdcDecode.cpp

Design notes:

• these files preserve the old packet format
• they already encode and decode complete CDC frames
• they also contain per-packet payload helpers

Node 2: unified protocol entry

Files added in this step:

• KeyBorad/KeyBorad/COM/Com_ProtoCodec.h
• KeyBorad/KeyBorad/COM/Com_ProtoCodec.cpp

Design notes:

• provides a thin and readable entry point for higher layers
• keeps DRI from depending on packet parsing
• keeps LGC from depending on low-level byte layout details
• starts from the smallest useful handshake path

Implemented behavior:

• build HelloReq frame
• validate whether a parsed packet is HelloRsp
• decode HelloRsp
• forward frame parsing and stream extraction to the existing low-level codec

Next COM nodes

• bitmap encode/decode helper
• ack/error helper
• time sync and theme helper
• replace direct Com_Cdc* calls in higher layers with Com_ProtoCodec*