packet_utils.c File Reference

Plant-B application layer protocol - packet encoding and decoding. More...

#include "packet_utils.h"

Data Structures
struct	packet
struct	tx_strip_pkt
struct	pkt_enc_pool
struct	rx_strip_pkt
struct	pkt_dec_pool

Macros
#define	U16_BYTES   (2)
#define	XOR_BYTES   (53)
#define	POOL_DEPTH   (32)
#define	SYNC8   (0xAA)
#define	ALL_KNOWN_MASK   (0xFFFFFFFF)
#define	XOR_LOCATIONS   { 0, 3, 7, 15, 31 }
#define	XOR_GROUP_MASK   (0x80008088)
#define	ONLY_N03_UNKNOWN_MASK   (XOR_GROUP_MASK & ~(1U << (3)))
#define	ONLY_N07_UNKNOWN_MASK   (XOR_GROUP_MASK & ~(1U << (7)))
#define	ONLY_N15_UNKNOWN_MASK   (XOR_GROUP_MASK & ~(1U << (15)))
#define	ONLY_N31_UNKNOWN_MASK   (XOR_GROUP_MASK & ~(1U << (31)))
#define	RAND_THRESHOLD   (5)
#define	BYTES_STR_SIZE(n)
#define	PKT_CHECK(cond, tag, msg)

Functions
static const char *	domain_to_str (domain_t domain)
static const char *	category_to_str (domain_t domain, category_t category)
static const char *	type_to_str (domain_t domain, category_t category, type_t type)
static void	bytes_to_str (const uint8_t *restrict buffer, size_t sz, char *restrict out, size_t out_sz)
static void	enc_pool_update_slot (pkt_enc_pool_t *restrict pool, const packet_t *restrict pkt)
static const struct tx_strip_pkt *	enc_pool_get_slot_n (const pkt_enc_pool_t *restrict pool, uint8_t n)
static void	dec_pool_update_slot (pkt_dec_pool_t *restrict pool, const packet_t *restrict pkt)
static void	dec_pool_mark_known (pkt_dec_pool_t *restrict pool, const packet_t *restrict pkt)
static bool	dec_pool_has_unknown_pkt (const pkt_dec_pool_t *restrict pool)
static const struct rx_strip_pkt *	dec_pool_get_slot_n (const pkt_dec_pool_t *restrict pool, uint16_t n)
static int8_t	dec_pool_try_recovery (pkt_dec_pool_t *restrict pool)
static void	pkt_set_xor_part (const pkt_enc_pool_t *restrict pool, packet_t *restrict pkt)
static void	pkt_set_sync8 (packet_t *restrict pkt)
static uint8_t	pkt_get_sync8 (const packet_t *restrict pkt)
static bool	pkt_sync8_is_valid (const packet_t *restrict pkt)
static uint16_t	pkt_compute_crc16_ccitt_false (const packet_t *restrict pkt)
static void	pkt_set_crc16 (packet_t *restrict pkt)
static uint16_t	pkt_get_crc16 (const packet_t *restrict pkt)
static bool	pkt_crc16_is_valid (const packet_t *restrict pkt)
packet_t *	pkt_create (void)
	Allocate and initialize a packet, with each byte set to 0.
void	pkt_destroy (packet_t *restrict pkt)
	Free a packet allocated by pkt_create().
pkt_enc_pool_t *	enc_pool_create (void)
	Allocate and initialize an encoder pool.
void	enc_pool_destroy (pkt_enc_pool_t *restrict pool)
	Free an encoder pool allocated by enc_pool_create().
pkt_dec_pool_t *	dec_pool_create (void)
	Allocate and initialize a decoder pool.
void	dec_pool_destroy (pkt_dec_pool_t *restrict pool)
	Free a decoder pool allocated by dec_pool_create().
pkt_err_t	pkt_encode (packet_t *restrict pkt, pkt_enc_pool_t *restrict pool)
	Finalize and encode a packet for transmission.
pkt_err_t	pkt_decode (const packet_t *restrict pkt, pkt_dec_pool_t *restrict pool, int8_t *restrict relative_loc)
	Validate and decode a received packet.
pkt_err_t	dec_pool_get_pkt_from_relative_loc (const pkt_dec_pool_t *restrict pool, int8_t relative_loc, packet_t *restrict pkt)
	Reconstruct a recovered packet from the decoder pool.
pkt_err_t	pkt_get_id (const packet_t *restrict pkt, uint16_t *id)
	Read the packet identifier.
pkt_err_t	header_sensor_config (header_t *restrict header)
	Configure a header for a current sensor measurement packet.
pkt_err_t	header_old_sensor_config (header_t *restrict header, uint16_t old_id)
	Configure a header for a retransmitted (old) sensor measurement packet.
pkt_err_t	pkt_get_header (const packet_t *restrict pkt, header_t *header)
	Unpack the header fields from a raw packet.
pkt_err_t	pkt_set_header (packet_t *restrict pkt, const header_t *restrict header)
	Pack header fields into a raw packet.
pkt_err_t	pkt_get_payload (const packet_t *restrict pkt, uint8_t *payload, size_t len)
	Copy the payload field out of a packet.
pkt_err_t	pkt_set_payload (packet_t *restrict pkt, const uint8_t *restrict payload, size_t len)
	Copy data into the payload field of a packet.
bool	pkt_is_chunked (const packet_t *restrict pkt)
	Check whether a packet carries chunked data.
pkt_err_t	pkt_log (const packet_t *restrict pkt)
	Log a human-readable dump of a packet to the PAL logger.
pkt_err_t	pkt_test_random_set_sync8 (packet_t *restrict pkt, bool *failed)
	Randomly corrupt the SYNC8 field for testing purposes.
pkt_err_t	pkt_test_random_set_crc16 (packet_t *restrict pkt)
	Randomly corrupt the CRC16 field for testing purposes.

Variables
static const char *	TAG = "pkt_utils"
static _Atomic uint16_t	id = 0

Detailed Description

Plant-B application layer protocol - packet encoding and decoding.

Author

Adrien Chevrier

Copyright

Copyright (c) 2026 Adrien Chevrier. Under AGPL-3.0-or-later license.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/.

Version

0.1

Date

2026-02-05

---

Data Structure Documentation

packet

struct packet

Data Fields
uint8_t	crc16[U16_BYTES]
uint8_t	dct
uint8_t	id[U16_BYTES]
uint8_t	index[U16_BYTES]
uint8_t	payload[PAYLOAD_BYTES]
uint8_t	sync8
uint8_t	total[U16_BYTES]
uint8_t	xor_part[XOR_BYTES]

tx_strip_pkt

struct tx_strip_pkt

Data Fields
uint8_t	dct
uint8_t	index[U16_BYTES]
uint8_t	payload[PAYLOAD_BYTES]
uint8_t	total[U16_BYTES]

pkt_enc_pool

struct pkt_enc_pool

Data Fields
struct tx_strip_pkt *	pkt
struct tx_strip_pkt	pool[POOL_DEPTH]

rx_strip_pkt

struct rx_strip_pkt

Data Fields
uint8_t	dct
uint8_t	index[U16_BYTES]
uint8_t	payload[PAYLOAD_BYTES]
uint8_t	total[U16_BYTES]
uint8_t	xor_part[XOR_BYTES]

pkt_dec_pool

struct pkt_dec_pool

Data Fields
uint32_t	known
struct rx_strip_pkt *	pkt
struct rx_strip_pkt	pool[POOL_DEPTH]

Macro Definition Documentation

ALL_KNOWN_MASK

#define ALL_KNOWN_MASK   (0xFFFFFFFF)

BYTES_STR_SIZE

#define BYTES_STR_SIZE

(

n

)

Value:

((n) * 3 + 1)

ONLY_N03_UNKNOWN_MASK

#define ONLY_N03_UNKNOWN_MASK   (XOR_GROUP_MASK & ~(1U << (3)))

ONLY_N07_UNKNOWN_MASK

#define ONLY_N07_UNKNOWN_MASK   (XOR_GROUP_MASK & ~(1U << (7)))

ONLY_N15_UNKNOWN_MASK

#define ONLY_N15_UNKNOWN_MASK   (XOR_GROUP_MASK & ~(1U << (15)))

ONLY_N31_UNKNOWN_MASK

#define ONLY_N31_UNKNOWN_MASK   (XOR_GROUP_MASK & ~(1U << (31)))

PKT_CHECK

#define PKT_CHECK	(		cond,
			tag,
			msg )

Value:

    do { \
        if (!(cond)) { \
            PAL_LOGE(tag, msg); \
            return PKT_ERR_INVALID_ARG; \
        } \
    } while (0)

POOL_DEPTH

#define POOL_DEPTH   (32)

RAND_THRESHOLD

#define RAND_THRESHOLD   (5)

SYNC8

#define SYNC8   (0xAA)

U16_BYTES

#define U16_BYTES   (2)

XOR_BYTES

#define XOR_BYTES   (53)

XOR_GROUP_MASK

#define XOR_GROUP_MASK   (0x80008088)

XOR_LOCATIONS

#define XOR_LOCATIONS   { 0, 3, 7, 15, 31 }

Function Documentation

bytes_to_str()

static void bytes_to_str ( const uint8_t *restrict buffer, size_t sz, char *restrict out, size_t out_sz )

static

category_to_str()

static const char * category_to_str ( domain_t domain, category_t category )

static

dec_pool_get_slot_n()

static const struct rx_strip_pkt * dec_pool_get_slot_n ( const pkt_dec_pool_t *restrict pool, uint16_t n )

inlinestatic

dec_pool_has_unknown_pkt()

static bool dec_pool_has_unknown_pkt ( const pkt_dec_pool_t *restrict pool )

inlinestatic

dec_pool_mark_known()

static void dec_pool_mark_known ( pkt_dec_pool_t *restrict pool, const packet_t *restrict pkt )

inlinestatic

dec_pool_try_recovery()

static int8_t dec_pool_try_recovery ( pkt_dec_pool_t *restrict pool )

static

dec_pool_update_slot()

static void dec_pool_update_slot ( pkt_dec_pool_t *restrict pool, const packet_t *restrict pkt )

inlinestatic

domain_to_str()

static const char * domain_to_str ( domain_t domain )

static

enc_pool_get_slot_n()

static const struct tx_strip_pkt * enc_pool_get_slot_n ( const pkt_enc_pool_t *restrict pool, uint8_t n )

inlinestatic

enc_pool_update_slot()

static void enc_pool_update_slot ( pkt_enc_pool_t *restrict pool, const packet_t *restrict pkt )

inlinestatic

pkt_compute_crc16_ccitt_false()

static uint16_t pkt_compute_crc16_ccitt_false ( const packet_t *restrict pkt )

inlinestatic

pkt_crc16_is_valid()

static bool pkt_crc16_is_valid ( const packet_t *restrict pkt )

inlinestatic

pkt_get_crc16()

static uint16_t pkt_get_crc16 ( const packet_t *restrict pkt )

inlinestatic

pkt_get_sync8()

static uint8_t pkt_get_sync8 ( const packet_t *restrict pkt )

inlinestatic

pkt_set_crc16()

static void pkt_set_crc16 ( packet_t *restrict pkt )

inlinestatic

pkt_set_sync8()

static void pkt_set_sync8 ( packet_t *restrict pkt )

inlinestatic

pkt_set_xor_part()

static void pkt_set_xor_part ( const pkt_enc_pool_t *restrict pool, packet_t *restrict pkt )

static

pkt_sync8_is_valid()

static bool pkt_sync8_is_valid ( const packet_t *restrict pkt )

inlinestatic

type_to_str()

static const char * type_to_str ( domain_t domain, category_t category, type_t type )

static

Variable Documentation

id

_Atomic uint16_t id = 0

static

TAG

const char* TAG = "pkt_utils"

static