XOR code

Simple XOR based coding algorithms. More...

Detailed Description

Simple XOR based coding algorithms.

Warning

This feature is experimental!
This is a very basic implementation, it can only recover 1 lost block in 3 and only has a 33% chance of recovering two consecutive lost blocks. API / Algorithm might change if that means we can do better.

Files
file	xor.h
	XOR coding definitions.

Macros
#define	CONFIG_CODING_XOR_CHECK_BYTES   3U
	Number of payload bytes per parity byte.
#define	CODING_XOR_PARITY_LEN(in)
	Get the size of the needed parity buffer for a given payload size.

Functions
void	coding_xor_generate (void *data, size_t len, uint8_t *parity)
	Generate parity and mix data buffer.
bool	coding_xor_recover (void *data, size_t len, uint8_t *parity, uint8_t *blocks, size_t block_size, bool recover_parity)
	Restore and unmix buffer.

Macro Definition Documentation

CODING_XOR_PARITY_LEN

#define CODING_XOR_PARITY_LEN

(

in

)

Value:

                                          (((in) + CONFIG_CODING_XOR_CHECK_BYTES - 1) \
                                          / CONFIG_CODING_XOR_CHECK_BYTES)

Get the size of the needed parity buffer for a given payload size.

Parameters

in	Payload length

Definition at line 49 of file xor.h.

CONFIG_CODING_XOR_CHECK_BYTES

#define CONFIG_CODING_XOR_CHECK_BYTES   3U

Number of payload bytes per parity byte.

Definition at line 41 of file xor.h.

Function Documentation

coding_xor_generate()

void coding_xor_generate	(	void *	data,
		size_t	len,
		uint8_t *	parity
	)

Generate parity and mix data buffer.

This generates parity data to recover one in CONFIG_CODING_XOR_CHECK_BYTES bytes. The data buffer is then mixed to distribute bytes amongst transfer blocks, so that the chance for consecutive bytes to be in the same block is lowered.

Parameters

[in,out]	data	The data buffer to be processed
[in]	len	Size of the data buffer
[out]	parity	Buffer to hold parity data. Must be at least CODING_XOR_PARITY_LEN(len) bytes

coding_xor_recover()

bool coding_xor_recover	(	void *	data,
		size_t	len,
		uint8_t *	parity,
		uint8_t *	blocks,
		size_t	block_size,
		bool	recover_parity
	)

Restore and unmix buffer.

Parameters

[in,out]	data	The data buffer to be restored
[in]	len	Size of the data buffer
[in,out]	parity	Buffer with parity data. Must be at least CODING_XOR_PARITY_LEN(len) bytes
[in,out]	blocks	Bitfieled to indicate which blocks were received. This indicates the presence of both data and parity blocks. Parity blocks are appended after the last data block. If a block was restored it's bit will be set.
[in]	block_size	Size of a data/payload block
[in]	recover_parity	If true, missing parity blocks will be re-generated from data blocks.

Returns

True if all data blocks were recovered