Mbed OS Reference | MbedCRC.h Source File

 /* mbed Microcontroller Library
  * Copyright (c) 2018 ARM Limited
  * SPDX-License-Identifier: Apache-2.0
  *
  * 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 an invalid warning from the compiler for the 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 */
 /** @{*/
 
 extern SingletonPtr<PlatformMutex> mbed_crc_mutex;
 
 /** CRC object provides CRC generation through hardware or software
  *
  *  CRC sums can be generated using three different methods: hardware, software ROM tables
  *  and bitwise computation. The mode used is selected automatically based on required
  *  polynomial and hardware capabilities. Any polynomial in standard form (`x^3 + x + 1`)
  *  can be used for computation, but custom ones can affect the performance.
  *
  *  First choice is the hardware mode. The supported polynomials are hardware specific, and
  *  you need to consult your MCU manual to discover them. Next, ROM polynomial tables
  *  are tried (you can find list of supported polynomials here ::crc_polynomial). If the selected
  *  configuration is supported, it will accelerate the software computations. If ROM tables
  *  are not available for the selected polynomial, then CRC is computed at run time 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
  */
 template <uint32_t polynomial = POLY_32BIT_ANSI, uint8_t width = 32>
 class MbedCRC {
 
 public:
     enum CrcMode {
 #if 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(const 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(const void *buffer, crc_data_size_t size, uint32_t *crc)
     {
         int32_t status = 0;
 
         switch (_mode) {
 #if DEVICE_CRC
             case HARDWARE:
                 hal_crc_compute_partial(static_cast<const 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);
 
 #if 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);
 
 #if 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;
     }
 
 #if !defined(DOXYGEN_ONLY)
 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()
     {
 #if DEVICE_CRC
         if (_mode == HARDWARE) {
             mbed_crc_mutex->lock();
         }
 #endif
     }
 
     /** Release exclusive access to CRC hardware/software.
      */
     virtual void unlock()
     {
 #if 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 constructor common code should be in this function.
      */
     void mbed_crc_ctor(void)
     {
         MBED_STATIC_ASSERT(width <= 32, "Max 32-bit CRC supported");
 
 #if 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;
     }
 #endif
 };
 
 #if   defined ( __CC_ARM )
 #elif defined ( __GNUC__ )
 #pragma GCC diagnostic pop
 #elif defined (__ICCARM__)
 #endif
 
 /** @}*/
 } // namespace mbed
 
 #endif
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