gf256.h File Reference

#include <stddef.h>
#include <stdint.h>

Go to the source code of this file.

Functions
uint8_t	gf256_mul (uint8_t a, uint8_t b)
	Multiply two elements in GF(2^8) with polynomial 0x11D.
uint8_t	gf256_div (uint8_t a, uint8_t b)
	Divide two elements in GF(2^8).
uint8_t	gf256_inv (uint8_t a)
	Compute multiplicative inverse in GF(2^8).
void	gf256_mul_region (uint8_t *dst, const uint8_t *src, uint8_t coeff, size_t len)
	Multiply-accumulate a region: dst[i] ^= GF_mul(src[i], coeff) for all i.
void	gf256_xor_region (uint8_t *dst, const uint8_t *src, size_t len)
	XOR a region: dst[i] ^= src[i] for all i.

Function Documentation

gf256_div()

uint8_t gf256_div	(	uint8_t	a,
		uint8_t	b )

Divide two elements in GF(2^8).

Parameters

a	Dividend.
b	Divisor (must be non-zero).

Returns

Quotient a/b in GF(2^8).

Definition at line 84 of file gf256.c.

References gf256_div(), gf256_exp_table, gf256_init_tables(), and gf256_log_table.

Referenced by gf256_div().

gf256_inv()

uint8_t gf256_inv

(

uint8_t

a

)

Compute multiplicative inverse in GF(2^8).

Parameters

a	Element (must be non-zero).

Returns

Inverse a^(-1) in GF(2^8).

Definition at line 92 of file gf256.c.

References gf256_exp_table, gf256_init_tables(), gf256_inv(), and gf256_log_table.

Referenced by gf256_inv(), and invert_matrix().

gf256_mul()

uint8_t gf256_mul	(	uint8_t	a,
		uint8_t	b )

Multiply two elements in GF(2^8) with polynomial 0x11D.

Parameters

a	First operand.
b	Second operand.

Returns

Product a*b in GF(2^8).

Definition at line 77 of file gf256.c.

References gf256_exp_table, gf256_init_tables(), gf256_log_table, and gf256_mul().

Referenced by build_vandermonde(), gf256_build_mul_tables(), gf256_mul(), invert_matrix(), rs_create(), and rs_decode().

gf256_mul_region()

void gf256_mul_region	(	uint8_t *	dst,
		const uint8_t *	src,
		uint8_t	coeff,
		size_t	len )

Multiply-accumulate a region: dst[i] ^= GF_mul(src[i], coeff) for all i.

Uses SIMD acceleration when available (AVX2 > SSSE3 > NEON > scalar). If coeff is 0, this is a no-op. If coeff is 1, this is XOR.

Parameters

dst	Destination buffer (read-modify-write).
src	Source buffer (read-only).
coeff	GF(2^8) coefficient.
len	Number of bytes to process.

Definition at line 350 of file gf256.c.

References gf256_init_tables(), gf256_mul_region(), gf256_mul_region_scalar(), and gf256_xor_region().

Referenced by gf256_mul_region(), rs_decode(), and rs_encode_incremental().

gf256_xor_region()

void gf256_xor_region	(	uint8_t *	dst,
		const uint8_t *	src,
		size_t	len )

XOR a region: dst[i] ^= src[i] for all i.

Uses SIMD acceleration when available.

Parameters

dst	Destination buffer (read-modify-write).
src	Source buffer (read-only).
len	Number of bytes to process.

Definition at line 370 of file gf256.c.

References gf256_xor_region(), and gf256_xor_region_scalar().

Referenced by gf256_mul_region(), and gf256_xor_region().