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mbed-os/drivers/MbedCRC.h

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/* mbed Microcontroller Library
* Copyright (c) 2018 ARM Limited
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef MBED_CRC_API_H
#define MBED_CRC_API_H
#include "drivers/TableCRC.h"
#include "hal/crc_api.h"
#include "platform/mbed_assert.h"
#include "platform/SingletonPtr.h"
#include "platform/PlatformMutex.h"
/* This is invalid warning from the compiler for below section of code
if ((width < 8) && (NULL == _crc_table)) {
p_crc = (uint32_t)(p_crc << (8 - width));
}
Compiler warns of the shift operation with width as it is width=(std::uint8_t),
but we check for ( width < 8) before performing shift, so it should not be an issue.
*/
#if defined ( __CC_ARM )
#pragma diag_suppress 62 // Shift count is negative
#elif defined ( __GNUC__ )
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wshift-count-negative"
#elif defined (__ICCARM__)
#pragma diag_suppress=Pe062 // Shift count is negative
#endif
namespace mbed {
/** \addtogroup drivers */
/** @{*/
/** CRC object provides CRC generation through hardware/software
*
* ROM polynomial tables for supported polynomials (:: crc_polynomial_t) will be used for
* software CRC computation, if ROM tables are not available then CRC is computed runtime
* bit by bit for all data input.
* @note Synchronization level: Thread safe
*
* @tparam polynomial CRC polynomial value in hex
* @tparam width CRC polynomial width
*
* Example: Compute CRC data
* @code
*
* #include "mbed.h"
*
* int main() {
* MbedCRC<POLY_32BIT_ANSI, 32> ct;
*
* char test[] = "123456789";
* uint32_t crc = 0;
*
* printf("\nPolynomial = 0x%lx Width = %d \n", ct.get_polynomial(), ct.get_width());
*
* ct.compute((void *)test, strlen((const char*)test), &crc);
*
* printf("The CRC of data \"123456789\" is : 0x%lx\n", crc);
* return 0;
* }
* @endcode
* Example: Compute CRC with data available in parts
* @code
*
* #include "mbed.h"
* int main() {
* MbedCRC<POLY_32BIT_ANSI, 32> ct;
*
* char test[] = "123456789";
* uint32_t crc = 0;
*
* printf("\nPolynomial = 0x%lx Width = %d \n", ct.get_polynomial(), ct.get_width());
* ct.compute_partial_start(&crc);
* ct.compute_partial((void *)&test, 4, &crc);
* ct.compute_partial((void *)&test[4], 5, &crc);
* ct.compute_partial_stop(&crc);
* printf("The CRC of data \"123456789\" is : 0x%lx\n", crc);
* return 0;
* }
* @endcode
* @ingroup drivers
*/
extern SingletonPtr<PlatformMutex> mbed_crc_mutex;
template <uint32_t polynomial = POLY_32BIT_ANSI, uint8_t width = 32>
class MbedCRC {
public:
enum CrcMode {
#ifdef DEVICE_CRC
HARDWARE = 0,
#endif
TABLE = 1,
BITWISE
};
typedef uint64_t crc_data_size_t;
/** Lifetime of CRC object
*
* @param initial_xor Inital value/seed to Xor
* @param final_xor Final Xor value
* @param reflect_data
* @param reflect_remainder
* @note Default constructor without any arguments is valid only for supported CRC polynomials. :: crc_polynomial_t
* MbedCRC <POLY_7BIT_SD, 7> ct; --- Valid POLY_7BIT_SD
* MbedCRC <0x1021, 16> ct; --- Valid POLY_16BIT_CCITT
* MbedCRC <POLY_16BIT_CCITT, 32> ct; --- Invalid, compilation error
* MbedCRC <POLY_16BIT_CCITT, 32> ct (i,f,rd,rr) Constructor can be used for not supported polynomials
* MbedCRC<POLY_16BIT_CCITT, 16> sd(0, 0, false, false); Constructor can also be used for supported
* polynomials with different intial/final/reflect values
*
*/
MbedCRC(uint32_t initial_xor, uint32_t final_xor, bool reflect_data, bool reflect_remainder) :
_initial_value(initial_xor), _final_xor(final_xor), _reflect_data(reflect_data),
_reflect_remainder(reflect_remainder)
{
mbed_crc_ctor();
}
MbedCRC();
virtual ~MbedCRC()
{
// Do nothing
}
/** Compute CRC for the data input
* Compute CRC performs the initialization, computation and collection of
* final CRC.
*
* @param buffer Data bytes
* @param size Size of data
* @param crc CRC is the output value
* @return 0 on success, negative error code on failure
*/
int32_t compute(void *buffer, crc_data_size_t size, uint32_t *crc)
{
MBED_ASSERT(crc != NULL);
int32_t status = 0;
status = compute_partial_start(crc);
if (0 != status) {
unlock();
return status;
}
status = compute_partial(buffer, size, crc);
if (0 != status) {
unlock();
return status;
}
status = compute_partial_stop(crc);
if (0 != status) {
*crc = 0;
}
return status;
}
/** Compute partial CRC for the data input.
*
* CRC data if not available fully, CRC can be computed in parts with available data.
*
* In case of hardware, intermediate values and states are saved by hardware. Mutex
* locking is used to serialize access to hardware CRC.
*
* In case of software CRC, previous CRC output should be passed as argument to the
* current compute_partial call. Please note the intermediate CRC value is maintained by
* application and not the driver.
*
* @pre: Call `compute_partial_start` to start the partial CRC calculation.
* @post: Call `compute_partial_stop` to get the final CRC value.
*
* @param buffer Data bytes
* @param size Size of data
* @param crc CRC value is intermediate CRC value filled by API.
* @return 0 on success or a negative error code on failure
* @note: CRC as output in compute_partial is not final CRC value, call `compute_partial_stop`
* to get final correct CRC value.
*/
int32_t compute_partial(void *buffer, crc_data_size_t size, uint32_t *crc)
{
int32_t status = 0;
switch (_mode) {
#ifdef DEVICE_CRC
case HARDWARE:
hal_crc_compute_partial((uint8_t *)buffer, size);
*crc = 0;
break;
#endif
case TABLE:
status = table_compute_partial(buffer, size, crc);
break;
case BITWISE:
status = bitwise_compute_partial(buffer, size, crc);
break;
default:
status = -1;
break;
}
return status;
}
/** Compute partial start, indicate start of partial computation.
*
* This API should be called before performing any partial computation
* with compute_partial API.
*
* @param crc Initial CRC value set by the API
* @return 0 on success or a negative in case of failure
* @note: CRC is an out parameter and must be reused with compute_partial
* and `compute_partial_stop` without any modifications in application.
*/
int32_t compute_partial_start(uint32_t *crc)
{
MBED_ASSERT(crc != NULL);
#ifdef DEVICE_CRC
if (_mode == HARDWARE) {
lock();
crc_mbed_config_t config;
config.polynomial = polynomial;
config.width = width;
config.initial_xor = _initial_value;
config.final_xor = _final_xor;
config.reflect_in = _reflect_data;
config.reflect_out = _reflect_remainder;
hal_crc_compute_partial_start(&config);
}
#endif
*crc = _initial_value;
return 0;
}
/** Get the final CRC value of partial computation.
*
* CRC value available in partial computation is not correct CRC, as some
* algorithms require remainder to be reflected and final value to be XORed
* This API is used to perform final computation to get correct CRC value.
*
* @param crc CRC result
* @return 0 on success or a negative in case of failure.
*/
int32_t compute_partial_stop(uint32_t *crc)
{
MBED_ASSERT(crc != NULL);
#ifdef DEVICE_CRC
if (_mode == HARDWARE) {
*crc = hal_crc_get_result();
unlock();
return 0;
}
#endif
uint32_t p_crc = *crc;
if ((width < 8) && (NULL == _crc_table)) {
p_crc = (uint32_t)(p_crc << (8 - width));
}
// Optimized algorithm for 32BitANSI does not need additional reflect_remainder
if ((TABLE == _mode) && (POLY_32BIT_REV_ANSI == polynomial)) {
*crc = (p_crc ^ _final_xor) & get_crc_mask();
} else {
*crc = (reflect_remainder(p_crc) ^ _final_xor) & get_crc_mask();
}
unlock();
return 0;
}
/** Get the current CRC polynomial.
*
* @return Polynomial value
*/
uint32_t get_polynomial(void) const
{
return polynomial;
}
/** Get the current CRC width
*
* @return CRC width
*/
uint8_t get_width(void) const
{
return width;
}
private:
uint32_t _initial_value;
uint32_t _final_xor;
bool _reflect_data;
bool _reflect_remainder;
uint32_t *_crc_table;
CrcMode _mode;
/** Acquire exclusive access to CRC hardware/software.
*/
void lock()
{
#ifdef DEVICE_CRC
if (_mode == HARDWARE) {
mbed_crc_mutex->lock();
}
#endif
}
/** Release exclusive access to CRC hardware/software.
*/
virtual void unlock()
{
#ifdef DEVICE_CRC
if (_mode == HARDWARE) {
mbed_crc_mutex->unlock();
}
#endif
}
/** Get the current CRC data size.
*
* @return CRC data size in bytes
*/
uint8_t get_data_size(void) const
{
return (width <= 8 ? 1 : (width <= 16 ? 2 : 4));
}
/** Get the top bit of current CRC.
*
* @return Top bit is set high for respective data width of current CRC
* Top bit for CRC width less then 8 bits will be set as 8th bit.
*/
uint32_t get_top_bit(void) const
{
return (width < 8 ? (1u << 7) : (uint32_t)(1ul << (width - 1)));
}
/** Get the CRC data mask.
*
* @return CRC data mask is generated based on current CRC width
*/
uint32_t get_crc_mask(void) const
{
return (width < 8 ? ((1u << 8) - 1) : (uint32_t)((uint64_t)(1ull << width) - 1));
}
/** Final value of CRC is reflected.
*
* @param data final crc value, which should be reflected
* @return Reflected CRC value
*/
uint32_t reflect_remainder(uint32_t data) const
{
if (_reflect_remainder) {
uint32_t reflection = 0x0;
uint8_t const nBits = (width < 8 ? 8 : width);
for (uint8_t bit = 0; bit < nBits; ++bit) {
if (data & 0x01) {
reflection |= (1 << ((nBits - 1) - bit));
}
data = (data >> 1);
}
return (reflection);
} else {
return data;
}
}
/** Data bytes are reflected.
*
* @param data value to be reflected
* @return Reflected data value
*/
uint32_t reflect_bytes(uint32_t data) const
{
if (_reflect_data) {
uint32_t reflection = 0x0;
for (uint8_t bit = 0; bit < 8; ++bit) {
if (data & 0x01) {
reflection |= (1 << (7 - bit));
}
data = (data >> 1);
}
return (reflection);
} else {
return data;
}
}
/** Bitwise CRC computation.
*
* @param buffer data buffer
* @param size size of the data
* @param crc CRC value is filled in, but the value is not the final
* @return 0 on success or a negative error code on failure
*/
int32_t bitwise_compute_partial(const void *buffer, crc_data_size_t size, uint32_t *crc) const
{
MBED_ASSERT(crc != NULL);
const uint8_t *data = static_cast<const uint8_t *>(buffer);
uint32_t p_crc = *crc;
if (width < 8) {
uint8_t data_byte;
for (crc_data_size_t byte = 0; byte < size; byte++) {
data_byte = reflect_bytes(data[byte]);
for (uint8_t bit = 8; bit > 0; --bit) {
p_crc <<= 1;
if ((data_byte ^ p_crc) & get_top_bit()) {
p_crc ^= polynomial;
}
data_byte <<= 1;
}
}
} else {
for (crc_data_size_t byte = 0; byte < size; byte++) {
p_crc ^= (reflect_bytes(data[byte]) << (width - 8));
// Perform modulo-2 division, a bit at a time
for (uint8_t bit = 8; bit > 0; --bit) {
if (p_crc & get_top_bit()) {
p_crc = (p_crc << 1) ^ polynomial;
} else {
p_crc = (p_crc << 1);
}
}
}
}
*crc = p_crc & get_crc_mask();
return 0;
}
/** CRC computation using ROM tables.
*
* @param buffer data buffer
* @param size size of the data
* @param crc CRC value is filled in, but the value is not the final
* @return 0 on success or a negative error code on failure
*/
int32_t table_compute_partial(const void *buffer, crc_data_size_t size, uint32_t *crc) const
{
MBED_ASSERT(crc != NULL);
const uint8_t *data = static_cast<const uint8_t *>(buffer);
uint32_t p_crc = *crc;
uint8_t data_byte = 0;
if (width <= 8) {
uint8_t *crc_table = (uint8_t *)_crc_table;
for (crc_data_size_t byte = 0; byte < size; byte++) {
data_byte = reflect_bytes(data[byte]) ^ p_crc;
p_crc = crc_table[data_byte];
}
} else if (width <= 16) {
uint16_t *crc_table = (uint16_t *)_crc_table;
for (crc_data_size_t byte = 0; byte < size; byte++) {
data_byte = reflect_bytes(data[byte]) ^ (p_crc >> (width - 8));
p_crc = crc_table[data_byte] ^ (p_crc << 8);
}
} else {
uint32_t *crc_table = (uint32_t *)_crc_table;
if (POLY_32BIT_REV_ANSI == polynomial) {
for (crc_data_size_t i = 0; i < size; i++) {
p_crc = (p_crc >> 4) ^ crc_table[(p_crc ^ (data[i] >> 0)) & 0xf];
p_crc = (p_crc >> 4) ^ crc_table[(p_crc ^ (data[i] >> 4)) & 0xf];
}
} else {
for (crc_data_size_t byte = 0; byte < size; byte++) {
data_byte = reflect_bytes(data[byte]) ^ (p_crc >> (width - 8));
p_crc = crc_table[data_byte] ^ (p_crc << 8);
}
}
}
*crc = p_crc & get_crc_mask();
return 0;
}
/** Constructor init called from all specialized cases of constructor.
* Note: All construtor common code should be in this function.
*/
void mbed_crc_ctor(void)
{
MBED_STATIC_ASSERT(width <= 32, "Max 32-bit CRC supported");
#ifdef DEVICE_CRC
if (POLY_32BIT_REV_ANSI == polynomial) {
_crc_table = (uint32_t *)Table_CRC_32bit_Rev_ANSI;
_mode = TABLE;
return;
}
crc_mbed_config_t config;
config.polynomial = polynomial;
config.width = width;
config.initial_xor = _initial_value;
config.final_xor = _final_xor;
config.reflect_in = _reflect_data;
config.reflect_out = _reflect_remainder;
if (hal_crc_is_supported(&config)) {
_mode = HARDWARE;
return;
}
#endif
switch (polynomial) {
case POLY_32BIT_ANSI:
_crc_table = (uint32_t *)Table_CRC_32bit_ANSI;
break;
case POLY_32BIT_REV_ANSI:
_crc_table = (uint32_t *)Table_CRC_32bit_Rev_ANSI;
break;
case POLY_8BIT_CCITT:
_crc_table = (uint32_t *)Table_CRC_8bit_CCITT;
break;
case POLY_7BIT_SD:
_crc_table = (uint32_t *)Table_CRC_7Bit_SD;
break;
case POLY_16BIT_CCITT:
_crc_table = (uint32_t *)Table_CRC_16bit_CCITT;
break;
case POLY_16BIT_IBM:
_crc_table = (uint32_t *)Table_CRC_16bit_IBM;
break;
default:
_crc_table = NULL;
break;
}
_mode = (_crc_table != NULL) ? TABLE : BITWISE;
}
};
#if defined ( __CC_ARM )
#elif defined ( __GNUC__ )
#pragma GCC diagnostic pop
#elif defined (__ICCARM__)
#endif
/** @}*/
} // namespace mbed
#endif
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