matter_btp.c
BTP handshake codec, fragmenter and reassembler.
Overview
BTP handshake codec, fragmenter and reassembler.
depends on matter_btp.h
API
Fstatic uint16_t rd16(const uint8_t *p)
Read a little-endian 16-bit unsigned integer from the buffer.
matter_btp_req_decode, matter_btp_resp_decode, matter_btp_rx_fragmentFstatic void wr16(uint8_t *p, uint16_t v)
Write a little-endian 16-bit unsigned integer to the buffer.
matter_btp_req_encode, matter_btp_resp_encode, matter_btp_tx_nextFint matter_btp_req_decode(const uint8_t *buf, size_t len, struct matter_btp_handshake_req *out)
Decode a Matter BTP handshake request from a buffer: extract protocol versions (8 4-bit slots across 4 bytes), MTU, and window size. Returns MATTER_OK on success, MATTER_E_INVAL if header check fails, MATTER_E_TRUNC if buffer is too short.
rd16Fint matter_btp_req_encode(const struct matter_btp_handshake_req *r, uint8_t *buf, size_t cap, size_t *written)
Encode a Matter BTP handshake request into a buffer: write header check bytes, 8 protocol versions (4-bit slots, even indices in low nibble), MTU, and window size. Returns MATTER_OK on success, MATTER_E_NOSPACE if buffer capacity is insufficient.
wr16Fint matter_btp_resp_decode(const uint8_t *buf, size_t len, struct matter_btp_handshake_resp *out)
Decode a Matter BTP handshake response from a buffer: extract selected version, fragment size, and window size. Returns MATTER_OK on success, MATTER_E_INVAL if header check fails, MATTER_E_TRUNC if buffer is too short.
rd16Fint matter_btp_resp_encode(const struct matter_btp_handshake_resp *r, uint8_t *buf, size_t cap, size_t *written)
Encode a Matter BTP handshake response into a buffer: write header check bytes, selected version, fragment size, and window size. Returns MATTER_OK on success, MATTER_E_NOSPACE if buffer capacity is insufficient.
wr16Fint matter_btp_accept(const struct matter_btp_handshake_req *req, uint16_t local_att_mtu, uint8_t local_window, struct matter_btp_handshake_resp *out)
Accept a BLE transport handshake request and produce a response. Negotiate the highest mutually supported BTP version (V4), derive the fragment size from both MTU values (clamped to min/max bounds), and use the minimum window size from both sides. Return MATTER_E_INVAL if pointers are null, MATTER_E_TYPE if no common version exists, MATTER_OK on success.
Fvoid matter_btp_rx_init(struct matter_btp_rx *rx, uint8_t *buf, size_t cap, uint8_t first_seq)
Initialize a BTP RX reassembler: clear state, set buffer and capacity, mark idle, and set the expected first sequence number.
Fvoid matter_btp_rx_reset(struct matter_btp_rx *rx)
Reset a BTP RX reassembler for the next message: clear buffered data and state flags, but preserve sequence numbers (they belong to the connection, not the message).
Fint matter_btp_rx_fragment(struct matter_btp_rx *rx, const uint8_t *frag, size_t len)
Process an incoming BTP fragment: validate sequence number, extract flags and optional ACK, accumulate payload across fragments, and detect message completion. Enforces strict ordering (no reordering or gaps), prevents receiver restart mid-message, and caps total payload against declared length. Returns MATTER_OK on continuation, MATTER_END on completion, MATTER_E_STATE on sequence error or mid-message restart, MATTER_E_TRUNC on truncation, MATTER_E_NOSPACE on buffer overflow.
rd16Fint matter_btp_tx_init(struct matter_btp_tx *tx, const uint8_t *msg, size_t len, uint16_t fragment_size, uint8_t first_seq)
Initialize a BTP TX fragmenter with a message of length <= 0xFFFF, a fragment size within min/max bounds. Return MATTER_E_INVAL if pointers/sizes are invalid, MATTER_OK on success.
Fint matter_btp_tx_next(struct matter_btp_tx *tx, const uint8_t *ack, uint8_t *out, size_t cap, size_t *written)
Encode the next BTP transmission fragment from buffered message: emit flags, optional ACK, sequence number, and payload chunk. Splits message across fragments respecting fragment_size; Start fragment includes declared length, End fragment marks completion. Returns MATTER_OK on success, MATTER_END when all bytes sent, MATTER_E_NOSPACE if fragment or output buffer capacity exceeded.
wr16Fint matter_btp_standalone_ack(uint8_t ack, uint8_t seq, uint8_t *out, size_t cap, size_t *written)
Encode a standalone BTP acknowledgement: set the ACK flag, write the ack and seq fields. Return MATTER_E_INVAL if out is null, MATTER_E_NOSPACE if cap < 3, MATTER_OK on success; write the 3-byte frame size if written is not null.