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Merge pull request #12926 from benpicco/sys-hashes-crc8

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sys/checksum: move crc8 implementation from sht3x to common code.
This commit is contained in:
Martine Lenders 2019-12-13 17:47:07 +01:00 committed by GitHub
commit 61a78cf817
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GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 189 additions and 26 deletions
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1
drivers/Makefile.dep
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@ -529,6 +529,7 @@ endif
ifneq (,$(filter sht3x,$(USEMODULE)))
USEMODULE += xtimer
USEMODULE += checksum
FEATURES_REQUIRED += periph_i2c
endif

31
drivers/sht3x/sht3x.c
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@ -20,6 +20,7 @@
#include <errno.h>
#include <string.h>
#include "checksum/crc8.h"
#include "sht3x.h"
#include "xtimer.h"
@ -99,8 +100,10 @@ static int _status (sht3x_dev_t* dev, uint16_t* status);
static int _send_command(sht3x_dev_t* dev, uint16_t cmd);
static int _read_data(sht3x_dev_t* dev, uint8_t *data, uint8_t len);
/* helper functions */
static uint8_t _crc8 (uint8_t data[], int len);
static inline uint8_t _crc8(const void* buf, size_t len)
{
return crc8(buf, len, 0x31, 0xff);
}
/* ------------------------------------------------ */
@ -416,27 +419,3 @@ static int _status (sht3x_dev_t* dev, uint16_t* status)
DEBUG_DEV("status=%02x", dev, *status);
return SHT3X_OK;
}
static const uint8_t g_polynom = 0x31;
static uint8_t _crc8 (uint8_t data[], int len)
{
/* initialization value */
uint8_t crc = 0xff;
/* iterate over all bytes */
for (int i=0; i < len; i++)
{
crc ^= data[i];
for (int i = 0; i < 8; i++)
{
bool xor = crc & 0x80;
crc = crc << 1;
crc = xor ? crc ^ g_polynom : crc;
}
}
return crc;
}

42
sys/checksum/crc8.c Normal file
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@ -0,0 +1,42 @@
/*
* Copyright (C) 2018 Gunar Schorcht
*
* 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_checksum_crc8
* @brief CRC-8 checksum algorithms
*
* @{
*
* @file
* @brief CRC-8 implementation
*
* @author Gunar Schorcht <gunar@schorcht.net>
*/
#include <stdbool.h>
#include "checksum/crc8.h"
uint8_t crc8(const uint8_t *data, size_t len, uint8_t g_polynom, uint8_t crc)
{
/* iterate over all bytes */
for (size_t i=0; i < len; i++)
{
crc ^= data[i];
for (int i = 0; i < 8; i++)
{
bool xor = crc & 0x80;
crc = crc << 1;
crc = xor ? crc ^ g_polynom : crc;
}
}
return crc;
}
/** @} */

51
sys/include/checksum/crc8.h Normal file
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@ -0,0 +1,51 @@
/*
* Copyright (C) 2018 Gunar Schorcht
*
* 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_checksum_crc8 CRC-8
* @ingroup sys_checksum
* @brief CRC-8 checksum algorithms
*
* @{
*
* @file
* @brief CRC-8 definitions
*
* @author Gunar Schorcht <gunar@schorcht.net>
*/
#ifndef CHECKSUM_CRC8_H
#define CHECKSUM_CRC8_H
#include <stddef.h>
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Calculate CRC-8
*
* @param[in] data Start of memory area to checksum
* @param[in] len Number of bytes in @p buf to calculate checksum for
* @param[in] poly The generator polynomial for the checksum
* @param[in] seed The seed (starting value) for the checksum
*
* @note Reflected inputs or outputs and final XOR must be realized
* by the caller if needed.
*
* @return Checksum of the specified memory area.
*/
uint8_t crc8(const uint8_t *data, size_t len, uint8_t poly, uint8_t seed);
#ifdef __cplusplus
}
#endif
#endif /* CHECKSUM_CRC8_H */
/** @} */

82
tests/unittests/tests-checksum/tests-checksum-crc8.c Normal file
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@ -0,0 +1,82 @@
/*
* Copyright 2019 Benjamin Valentin <benpicco@googlemail.com>
*
* 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.
*/
#include <stdint.h>
#include "embUnit/embUnit.h"
#include "checksum/crc8.h"
#include "tests-checksum.h"
#define CRC8_POLY 0x31
#define CRC8_INIT 0xff
static void test_checksum_crc8_sequence_empty(void)
{
unsigned char buf[] = "";
uint8_t expect = 0xFF;
TEST_ASSERT_EQUAL_INT(expect, crc8(buf, sizeof(buf) - 1, CRC8_POLY, CRC8_INIT));
}
static void test_checksum_crc8_sequence_1a(void)
{
unsigned char buf[] = "A";
uint8_t expect = 0xA0;
TEST_ASSERT_EQUAL_INT(expect, crc8(buf, sizeof(buf) - 1, CRC8_POLY, CRC8_INIT));
}
static void test_checksum_crc8_sequence_256a(void)
{
unsigned char buf[] = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
uint8_t expect = 0xF0;
TEST_ASSERT_EQUAL_INT(expect, crc8(buf, sizeof(buf) - 1, CRC8_POLY, CRC8_INIT));
}
static void test_checksum_crc8_sequence_1to9(void)
{
unsigned char buf[] = "123456789";
uint8_t expect = 0xF7;
TEST_ASSERT_EQUAL_INT(expect, crc8(buf, sizeof(buf) - 1, CRC8_POLY, CRC8_INIT));
}
static void test_checksum_crc8_sequence_4bytes(void)
{
unsigned char buf[] = { 0x12, 0x34, 0x56, 0x78 };
uint8_t expect = 0xE0;
TEST_ASSERT_EQUAL_INT(expect, crc8(buf, sizeof(buf), CRC8_POLY, CRC8_INIT));
}
Test *tests_checksum_crc8_tests(void)
{
EMB_UNIT_TESTFIXTURES(fixtures) {
/* Reference values according to
* http://srecord.sourceforge.net/crc16-ccitt.html */
new_TestFixture(test_checksum_crc8_sequence_empty),
new_TestFixture(test_checksum_crc8_sequence_1a),
new_TestFixture(test_checksum_crc8_sequence_256a),
new_TestFixture(test_checksum_crc8_sequence_1to9),
new_TestFixture(test_checksum_crc8_sequence_4bytes),
};
EMB_UNIT_TESTCALLER(checksum_crc8_tests, NULL, NULL, fixtures);
return (Test *)&checksum_crc8_tests;
}

1
tests/unittests/tests-checksum/tests-checksum.c
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@ -10,6 +10,7 @@
void tests_checksum(void)
{
TESTS_RUN(tests_checksum_crc8_tests());
TESTS_RUN(tests_checksum_crc16_ccitt_tests());
TESTS_RUN(tests_checksum_fletcher16_tests());
TESTS_RUN(tests_checksum_fletcher32_tests());

7
tests/unittests/tests-checksum/tests-checksum.h
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@ -29,6 +29,13 @@ extern "C" {
*/
void tests_checksum(void);
/**
* @brief Generates tests for checksum/crc8.h
*
* @return embUnit tests if successful, NULL if not.
*/
Test *tests_checksum_crc8_tests(void);
/**
* @brief Generates tests for checksum/crc16_ccitt.h
*