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Add 256 byte block hamming code implementation

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This commit is contained in:
Lucas Jenss 2015-11-04 16:54:33 +01:00
parent 4d27214a8d
commit ddaa9863f2
9 changed files with 525 additions and 0 deletions
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21
dist/tools/licenses/patterns/3c-BSD-atmel4 vendored Normal file
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All rights reserved\.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice,
this list of conditions and the disclaimer below\.
Atmel's name may not be used to endorse or promote products derived from
this software without specific prior written permission\.
DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
DISCLAIMED\. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES \(INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
OR PROFITS; OR BUSINESS INTERRUPTION\) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT \(INCLUDING
NEGLIGENCE OR OTHERWISE\) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE\.

4
sys/Makefile
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@ -68,6 +68,10 @@ ifneq (,$(filter udp,$(USEMODULE)))
DIRS += net/transport_layer/udp
endif
ifneq (,$(filter hamming256,$(USEMODULE)))
DIRS += ecc/hamming256
endif
ifneq (,$(filter netopt,$(USEMODULE)))
DIRS += net/crosslayer/netopt
endif

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sys/ecc/doc.txt Normal file
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/*
* Copyright (C) 2015 Lucas Jenß
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @defgroup sys_ecc ECC
* @ingroup sys
*
* @brief A collection of error correction code (ECC) algorithms.
*/

1
sys/ecc/hamming256/Makefile Normal file
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include $(RIOTBASE)/Makefile.base

321
sys/ecc/hamming256/hamming256.c Normal file
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/* ----------------------------------------------------------------------------
* ATMEL Microcontroller Software Support
* ----------------------------------------------------------------------------
* Copyright (c) 2008, Atmel Corporation
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the disclaimer below.
*
* Atmel's name may not be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
* DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
* ----------------------------------------------------------------------------
*/
/**
* @file
*
* Implementation of the hamming code functions.
*
*/
/*----------------------------------------------------------------------------
* Headers
*----------------------------------------------------------------------------*/
#include <stdint.h>
#define ENABLE_DEBUG (0)
#include "debug.h"
#include "ecc/hamming256.h"
#include "bitarithm.h"
/*----------------------------------------------------------------------------
* Internal function
*----------------------------------------------------------------------------*/
/**
* @brief Counts and return the number of bits set to '1' in the given hamming code.
* @param code Hamming code.
*/
static uint8_t count_bits_in_code256(uint8_t *code)
{
return bitarithm_bits_set(code[0]) + bitarithm_bits_set(code[1]) + bitarithm_bits_set(code[2]);
}
/**
* @brief Calculates the 22-bit hamming code for a 256-bytes block of data.
* @param data Data buffer to calculate code for.
* @param code Pointer to a buffer where the code should be stored.
* @param padding Amount of zeroes to be appended to the data such that it sizes
* equals 256 bytes
*/
static void compute256(const uint8_t *data, uint8_t *code, uint8_t padding)
{
uint32_t i;
uint8_t columnSum = 0;
uint8_t evenLineCode = 0;
uint8_t oddLineCode = 0;
uint8_t evenColumnCode = 0;
uint8_t oddColumnCode = 0;
/*
* Xor all bytes together to get the column sum;
* At the same time, calculate the even and odd line codes
*/
for (i = 0; i < 256; i++) {
/* Allow non-multiples of 256 to be calculated by padding the data with zeroes */
uint8_t current = 0;
if (i < ((uint16_t)(256 - padding))) {
current = data[i];
}
columnSum ^= current;
/*
* If the xor sum of the byte is 0, then this byte has no incidence on
* the computed code; so check if the sum is 1.
*/
if ((bitarithm_bits_set(current) & 1) == 1) {
/*
* Parity groups are formed by forcing a particular index bit to 0
* (even) or 1 (odd).
* Example on one byte:
*
* bits (dec) 7 6 5 4 3 2 1 0
* (bin) 111 110 101 100 011 010 001 000
* '---'---'---'----------.
* |
* groups P4' ooooooooooooooo eeeeeeeeeeeeeee P4 |
* P2' ooooooo eeeeeee ooooooo eeeeeee P2 |
* P1' ooo eee ooo eee ooo eee ooo eee P1 |
* |
* We can see that: |
* - P4 -> bit 2 of index is 0 --------------------'
* - P4' -> bit 2 of index is 1.
* - P2 -> bit 1 of index if 0.
* - etc...
* We deduce that a bit position has an impact on all even Px if
* the log2(x)nth bit of its index is 0
* ex: log2(4) = 2, bit2 of the index must be 0 (-> 0 1 2 3)
* and on all odd Px' if the log2(x)nth bit of its index is 1
* ex: log2(2) = 1, bit1 of the index must be 1 (-> 0 1 4 5)
*
* As such, we calculate all the possible Px and Px' values at the
* same time in two variables, evenLineCode and oddLineCode, such as
* evenLineCode bits: P128 P64 P32 P16 P8 P4 P2 P1
* oddLineCode bits: P128' P64' P32' P16' P8' P4' P2' P1'
*/
evenLineCode ^= (255 - i);
oddLineCode ^= i;
}
}
/*
* At this point, we have the line parities, and the column sum. First, We
* must caculate the parity group values on the column sum.
*/
for (i = 0; i < 8; i++) {
if (columnSum & 1) {
evenColumnCode ^= (7 - i);
oddColumnCode ^= i;
}
columnSum >>= 1;
}
/*
* Now, we must interleave the parity values, to obtain the following layout:
* Code[0] = Line1
* Code[1] = Line2
* Code[2] = Column
* Line = Px' Px P(x-1)- P(x-1) ...
* Column = P4' P4 P2' P2 P1' P1 PadBit PadBit
*/
code[0] = 0;
code[1] = 0;
code[2] = 0;
for (i = 0; i < 4; i++) {
code[0] <<= 2;
code[1] <<= 2;
code[2] <<= 2;
/* Line 1 */
if ((oddLineCode & 0x80) != 0) {
code[0] |= 2;
}
if ((evenLineCode & 0x80) != 0) {
code[0] |= 1;
}
/* Line 2 */
if ((oddLineCode & 0x08) != 0) {
code[1] |= 2;
}
if ((evenLineCode & 0x08) != 0) {
code[1] |= 1;
}
/* Column */
if ((oddColumnCode & 0x04) != 0) {
code[2] |= 2;
}
if ((evenColumnCode & 0x04) != 0) {
code[2] |= 1;
}
oddLineCode <<= 1;
evenLineCode <<= 1;
oddColumnCode <<= 1;
evenColumnCode <<= 1;
}
/* Invert codes (linux compatibility) */
code[0] = (~(uint32_t)code[0]);
code[1] = (~(uint32_t)code[1]);
code[2] = (~(uint32_t)code[2]);
DEBUG("Computed code = %02X %02X %02X\n\r",
code[0], code[1], code[2]);
}
/**
* @brief Verifies and corrects a 256-bytes block of data using the given 22-bits
* hamming code.
*
* @param data Data buffer to check.
* @param originalCode Hamming code to use for verifying the data.
* @param padding Amount of zeroes to be appended to the data such that it sizes
* equals 256 bytes
*
* @return 0 if there is no error, otherwise returns a HAMMING_ERROR code.
*/
uint8_t verify256( uint8_t *pucData, const uint8_t *pucOriginalCode, uint8_t padding )
{
/* Calculate new code */
uint8_t computedCode[3];
uint8_t correctionCode[3];
compute256( pucData, computedCode, padding);
/* Xor both codes together */
correctionCode[0] = computedCode[0] ^ pucOriginalCode[0];
correctionCode[1] = computedCode[1] ^ pucOriginalCode[1];
correctionCode[2] = computedCode[2] ^ pucOriginalCode[2];
DEBUG( "Correction code = %02X %02X %02X\n\r", correctionCode[0], correctionCode[1], correctionCode[2] );
/* If all bytes are 0, there is no error */
if ((correctionCode[0] == 0) && (correctionCode[1] == 0) && (correctionCode[2] == 0)) {
return 0;
}
/* If there is a single bit error, there are 11 bits set to 1 */
if (count_bits_in_code256( correctionCode ) == 11) {
/* Get byte and bit indexes */
uint8_t byte;
uint8_t bit;
byte = correctionCode[0] & 0x80;
byte |= (correctionCode[0] << 1) & 0x40;
byte |= (correctionCode[0] << 2) & 0x20;
byte |= (correctionCode[0] << 3) & 0x10;
byte |= (correctionCode[1] >> 4) & 0x08;
byte |= (correctionCode[1] >> 3) & 0x04;
byte |= (correctionCode[1] >> 2) & 0x02;
byte |= (correctionCode[1] >> 1) & 0x01;
bit = (correctionCode[2] >> 5) & 0x04;
bit |= (correctionCode[2] >> 4) & 0x02;
bit |= (correctionCode[2] >> 3) & 0x01;
/* Correct bit */
DEBUG("Correcting byte #%d at bit %d\n\r", byte, bit );
pucData[byte] ^= (1 << bit);
return Hamming_ERROR_SINGLEBIT;
}
/* Check if ECC has been corrupted */
if (count_bits_in_code256( correctionCode ) == 1) {
return Hamming_ERROR_ECC;
}
/* Otherwise, this is a multi-bit error */
else {
return Hamming_ERROR_MULTIPLEBITS;
}
}
/*----------------------------------------------------------------------------
* Exported functions
*----------------------------------------------------------------------------*/
void hamming_compute256x( const uint8_t *pucData, uint32_t dwSize, uint8_t *puCode )
{
DEBUG("hamming_compute256x()\n\r");
uint8_t padding;
while (dwSize > 0) {
padding = 0;
if (dwSize < 256) {
padding = 256 - dwSize;
}
compute256( pucData, puCode, padding );
pucData += 256;
puCode += 3;
dwSize -= (256 - padding);
}
}
uint8_t hamming_verify256x( uint8_t *pucData, uint32_t dwSize, const uint8_t *pucCode )
{
uint8_t error;
uint8_t result = 0;
DEBUG( "hamming_verify256x()\n\r" );
uint8_t padding;
while (dwSize > 0) {
padding = 0;
if (dwSize < 256) {
padding = 256 - dwSize;
}
error = verify256( pucData, pucCode, padding );
if (error == Hamming_ERROR_SINGLEBIT) {
result = Hamming_ERROR_SINGLEBIT;
}
else {
if (error) {
return error;
}
}
pucData += 256;
pucCode += 3;
dwSize -= (256 - padding);
}
return result;
}

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/*
* Copyright (C) 2015 Lucas Jenß
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup sys_ecc
* @brief
* @{
*
* @brief Hamming Code implementation for 256byte data segments
* @author Lucas Jenß <lucas@x3ro.de>
*/
#ifndef _HAMMING256_H
#define _HAMMING256_H
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif
/** No bit errors were detected in the message */
#define Hamming_ERROR_NONE 0
/** A single bit was incorrect but has been recovered. */
#define Hamming_ERROR_SINGLEBIT 1
/** The original code has been corrupted. */
#define Hamming_ERROR_ECC 2
/** Multiple bits are incorrect in the data and they cannot be corrected. */
#define Hamming_ERROR_MULTIPLEBITS 3
/**
* @brief Computes 3-bytes hamming codes for a data block whose size is multiple of
* 256 bytes. Each 256 bytes block gets its own code.
*
* @param[in] data Data to compute code for.
* @param[in] size Data size in bytes.
* @param[out] code Codes buffer.
*/
void hamming_compute256x( const uint8_t *data, uint32_t size, uint8_t *code );
/**
* @brief Verifies 3-bytes hamming codes for a data block whose size is multiple of
* 256 bytes. Each 256-bytes block is verified with its own code.
*
* @return Hamming_ERROR_NONE if the data is correct, Hamming_ERROR_SINGLEBIT if one or more
* block(s) have had a single bit corrected, or either Hamming_ERROR_ECC
* or Hamming_ERROR_MULTIPLEBITS.
*
* @param[in] data Data buffer to verify.
* @param[in] size Size of the data in bytes.
* @param[in] code Original codes.
*/
uint8_t hamming_verify256x( uint8_t *data, uint32_t size, const uint8_t *code );
#ifdef __cplusplus
}
#endif
#endif
/** @} */

1
tests/unittests/tests-ecc/Makefile Normal file
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include $(RIOTBASE)/Makefile.base

1
tests/unittests/tests-ecc/Makefile.include Normal file
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USEMODULE += hamming256

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tests/unittests/tests-ecc/tests-ecc.c Normal file
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/*
* Copyright (C) 2015 Lucas Jenß
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup fs
* @brief
* @{
*
* @brief Tests for Hamming Code implementation
* @author Lucas Jenß <lucas@x3ro.de>
*/
#include <string.h>
#include "embUnit.h"
#include "ecc/hamming256.h"
static void test_single(void)
{
uint8_t data[256];
uint8_t ecc[3];
uint8_t result;
memset(data, 0xAB, 256);
hamming_compute256x(data, 256, ecc);
result = hamming_verify256x(data, 256, ecc);
TEST_ASSERT_EQUAL_INT(Hamming_ERROR_NONE, result);
data[10] |= (2 << 3);
result = hamming_verify256x(data, 256, ecc);
TEST_ASSERT_EQUAL_INT(Hamming_ERROR_SINGLEBIT, result);
data[10] |= (2 << 3);
data[20] |= (2 << 5);
result = hamming_verify256x(data, 256, ecc);
TEST_ASSERT_EQUAL_INT(Hamming_ERROR_MULTIPLEBITS, result);
memset(data, 0xAB, 256);
ecc[1] ^= 1; // Flip first bit, corrupting the ECC
result = hamming_verify256x(data, 256, ecc);
TEST_ASSERT_EQUAL_INT(Hamming_ERROR_ECC, result);
}
static void test_padding(void)
{
uint8_t data[203];
uint8_t ecc[3];
uint8_t result;
memset(data, 0xAB, 203);
hamming_compute256x(data, 203, ecc);
result = hamming_verify256x(data, 203, ecc);
TEST_ASSERT_EQUAL_INT(Hamming_ERROR_NONE, result);
data[10] |= (2 << 3);
result = hamming_verify256x(data, 203, ecc);
TEST_ASSERT_EQUAL_INT(Hamming_ERROR_SINGLEBIT, result);
data[10] |= (2 << 3);
data[20] |= (2 << 5);
result = hamming_verify256x(data, 203, ecc);
TEST_ASSERT_EQUAL_INT(Hamming_ERROR_MULTIPLEBITS, result);
memset(data, 0xAB, 203);
ecc[1] ^= 1; // Flip first bit, corrupting the ECC
result = hamming_verify256x(data, 203, ecc);
TEST_ASSERT_EQUAL_INT(Hamming_ERROR_ECC, result);
}
TestRef test_all(void)
{
EMB_UNIT_TESTFIXTURES(fixtures) {
new_TestFixture(test_single),
new_TestFixture(test_padding),
};
EMB_UNIT_TESTCALLER(EccTest, 0, 0, fixtures);
return (TestRef) & EccTest;
}
void tests_ecc(void)
{
TESTS_RUN(test_all());
}