CRC

CRC (Cyclic Redundancy Check) hash function implementation. More...

Files
file	crc.h
	Public header for CRC hash function implementation.

Typedefs
typedef uint32_t	AVCRC

Enumerations
enum	AVCRCId {   AV_CRC_8_ATM , AV_CRC_16_ANSI , AV_CRC_16_CCITT , AV_CRC_32_IEEE ,   AV_CRC_32_IEEE_LE , AV_CRC_16_ANSI_LE , AV_CRC_24_IEEE , AV_CRC_8_EBU ,   AV_CRC_MAX }

Functions
int	av_crc_init (AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
	Initialize a CRC table. More...
const AVCRC *	av_crc_get_table (AVCRCId crc_id)
	Get an initialized standard CRC table. More...
uint32_t	av_crc (const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length) av_pure
	Calculate the CRC of a block. More...

Detailed Description

CRC (Cyclic Redundancy Check) hash function implementation.

This module supports numerous CRC polynomials, in addition to the most widely used CRC-32-IEEE. See AVCRCId for a list of available polynomials.

Typedef Documentation

AVCRC

typedef uint32_t AVCRC

Definition at line 46 of file crc.h.

Enumeration Type Documentation

AVCRCId

enum AVCRCId

Enumerator
AV_CRC_8_ATM
AV_CRC_16_ANSI
AV_CRC_16_CCITT
AV_CRC_32_IEEE
AV_CRC_32_IEEE_LE
AV_CRC_16_ANSI_LE
AV_CRC_24_IEEE
AV_CRC_8_EBU
AV_CRC_MAX

Definition at line 48 of file crc.h.

Function Documentation

av_crc_init()

int av_crc_init	(	AVCRC *	ctx,
		int	le,
		int	bits,
		uint32_t	poly,
		int	ctx_size
	)

Initialize a CRC table.

Parameters

ctx	must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
le	If 1, the lowest bit represents the coefficient for the highest exponent of the corresponding polynomial (both for poly and actual CRC). If 0, you must swap the CRC parameter and the result of av_crc if you need the standard representation (can be simplified in most cases to e.g. bswap16): av_bswap32(crc << (32-bits))
bits	number of bits for the CRC
poly	generator polynomial without the x**bits coefficient, in the representation as specified by le
ctx_size	size of ctx in bytes

Returns

<0 on failure

av_crc_get_table()

const AVCRC * av_crc_get_table

(

AVCRCId

crc_id

)

Get an initialized standard CRC table.

Parameters

crc_id

ID of a standard CRC

Returns

a pointer to the CRC table or NULL on failure

av_crc()

uint32_t av_crc	(	const AVCRC *	ctx,
		uint32_t	crc,
		const uint8_t *	buffer,
		size_t	length
	)

Calculate the CRC of a block.

Parameters

crc	CRC of previous blocks if any or initial value for CRC

Returns

CRC updated with the data from the given block

See also

av_crc_init() "le" parameter