CRC

Checksums stored or exchanged by the firmware. More...

Data Structures
struct	pbl_crc32_legacy
	Running state of the legacy checksum. More...

Macros
#define	PBL_CRC32_RESIDUE   0x2144DF1CU
	CRC-32 of a message with its little-endian CRC-32 appended, when the message is intact.

Functions
uint8_t	pbl_crc8 (uint8_t crc, const void *data, size_t len)
	CRC-8/OPENSAFETY.
uint8_t	pbl_crc8_reversed (uint8_t crc, const void *data, size_t len)
	pbl_crc8() consuming data from its last byte to its first.
uint32_t	pbl_crc32 (uint32_t crc, const void *data, size_t len)
	CRC-32/ISO-HDLC, as used by zlib and PNG.
void	pbl_crc32_legacy_init (struct pbl_crc32_legacy *ctx)
	Start a legacy checksum.
void	pbl_crc32_legacy_update (struct pbl_crc32_legacy *ctx, const void *data, size_t len)
	Feed data to a legacy checksum.
uint32_t	pbl_crc32_legacy_finish (struct pbl_crc32_legacy *ctx)
	Finish a legacy checksum.
uint32_t	pbl_crc32_legacy (const void *data, size_t len)
	Legacy checksum of a single buffer.

Detailed Description

Checksums stored or exchanged by the firmware.

The software implementations are always built. Buffers of at least CONFIG_CRC_HW_MIN_LEN bytes are offloaded to a hardware CRC unit when a driver provides one (see CRC).

Every function takes the running value and returns the updated one, so data can be fed in chunks:

uint32_t crc = pbl_crc32(0, &hdr, sizeof(hdr));
crc = pbl_crc32(crc, payload, payload_len);

---

Data Structure Documentation

pbl_crc32_legacy

struct pbl_crc32_legacy

Running state of the legacy checksum.

The legacy checksum is the CRC-32/MPEG-2 computed by the STM32F2/F4 CRC unit over little-endian 32-bit words, MSB first: the checksum of bytes A B C D E F G H is the CRC of D C B A H G F E. A trailing partial word is zero-padded at the front, so bytes 1 2 3 4 5 6 are checksummed as 4 3 2 1 0 0 5 6. It persists in on-flash and on-wire formats.

struct pbl_crc32_legacy ctx;
 
pbl_crc32_legacy_init(&ctx);
pbl_crc32_legacy_update(&ctx, hdr, hdr_len);
pbl_crc32_legacy_update(&ctx, body, body_len);
uint32_t crc = pbl_crc32_legacy_finish(&ctx);

Data Fields
uint8_t	accumulated_length	Number of valid bytes in accumulator.
uint8_t	accumulator[3]	Bytes of an incomplete word, pending until the next update or finish.
uint32_t	reg	CRC register.

Macro Definition Documentation

PBL_CRC32_RESIDUE

#define PBL_CRC32_RESIDUE   0x2144DF1CU

CRC-32 of a message with its little-endian CRC-32 appended, when the message is intact.

Function Documentation

pbl_crc32()

uint32_t pbl_crc32	(	uint32_t	crc,
		const void *	data,
		size_t	len
	)

CRC-32/ISO-HDLC, as used by zlib and PNG.

Compatible with zlib's crc32().

Parameters

crc	Running value, 0 to start.
data	Data to checksum.
len	Length of data in bytes.

Returns

Updated CRC.

pbl_crc32_legacy()

uint32_t pbl_crc32_legacy	(	const void *	data,
		size_t	len
	)

Legacy checksum of a single buffer.

Parameters

data	Data to checksum.
len	Length of data in bytes.

Returns

Checksum.

pbl_crc32_legacy_finish()

uint32_t pbl_crc32_legacy_finish

(

struct pbl_crc32_legacy *

ctx

)

Finish a legacy checksum.

Pads and consumes any trailing partial word.

Parameters

ctx	Checksum state.

Returns

Checksum of all data fed since pbl_crc32_legacy_init().

pbl_crc32_legacy_init()

void pbl_crc32_legacy_init

(

struct pbl_crc32_legacy *

ctx

)

Start a legacy checksum.

Parameters

ctx	Checksum state.

pbl_crc32_legacy_update()

void pbl_crc32_legacy_update	(	struct pbl_crc32_legacy *	ctx,
		const void *	data,
		size_t	len
	)

Feed data to a legacy checksum.

Parameters

ctx	Checksum state.
data	Data to checksum.
len	Length of data in bytes.

pbl_crc8()

uint8_t pbl_crc8	(	uint8_t	crc,
		const void *	data,
		size_t	len
	)

CRC-8/OPENSAFETY.

Polynomial 0x2F, zero initial value, no reflection and no final XOR.

Parameters

crc	Running value, 0 to start.
data	Data to checksum.
len	Length of data in bytes.

Returns

Updated CRC.

pbl_crc8_reversed()

uint8_t pbl_crc8_reversed	(	uint8_t	crc,
		const void *	data,
		size_t	len
	)

pbl_crc8() consuming data from its last byte to its first.

Parameters

crc	Running value, 0 to start.
data	Data to checksum.
len	Length of data in bytes.

Returns

Updated CRC.