MbedCRC.h

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2018 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #ifndef MBED_CRC_API_H
00017 #define MBED_CRC_API_H
00018 
00019 #include "drivers/TableCRC.h"
00020 #include "hal/crc_api.h"
00021 #include "platform/mbed_assert.h"
00022 #include "platform/SingletonPtr.h"
00023 #include "platform/PlatformMutex.h"
00024 
00025 /* This is invalid warning from the compiler for below section of code
00026 if ((width < 8) && (NULL == _crc_table)) {
00027     p_crc = (uint32_t)(p_crc << (8 - width));
00028 }
00029 Compiler warns of the shift operation with width as it is width=(std::uint8_t),
00030 but we check for ( width < 8) before performing shift, so it should not be an issue.
00031 */
00032 #if defined ( __CC_ARM )
00033 #pragma diag_suppress 62  // Shift count is negative
00034 #elif defined ( __GNUC__ )
00035 #pragma GCC diagnostic push
00036 #pragma GCC diagnostic ignored "-Wshift-count-negative"
00037 #elif defined (__ICCARM__)
00038 #pragma diag_suppress=Pe062  // Shift count is negative
00039 #endif
00040 
00041 namespace mbed {
00042 /** \addtogroup drivers */
00043 /** @{*/
00044 
00045 /** CRC object provides CRC generation through hardware/software
00046  *
00047  *  ROM polynomial tables for supported polynomials (:: crc_polynomial_t) will be used for
00048  *  software CRC computation, if ROM tables are not available then CRC is computed runtime
00049  *  bit by bit for all data input.
00050  *  @note Synchronization level: Thread safe
00051  *
00052  *  @tparam  polynomial CRC polynomial value in hex
00053  *  @tparam  width CRC polynomial width
00054  *
00055  * Example: Compute CRC data
00056  * @code
00057  *
00058  *  #include "mbed.h"
00059  *
00060  *  int main() {
00061  *      MbedCRC<POLY_32BIT_ANSI, 32> ct;
00062  *
00063  *      char  test[] = "123456789";
00064  *      uint32_t crc = 0;
00065  *
00066  *      printf("\nPolynomial = 0x%lx  Width = %d \n", ct.get_polynomial(), ct.get_width());
00067  *
00068  *      ct.compute((void *)test, strlen((const char*)test), &crc);
00069  *
00070  *      printf("The CRC of data \"123456789\" is : 0x%lx\n", crc);
00071  *      return 0;
00072  *  }
00073  * @endcode
00074  * Example: Compute CRC with data available in parts
00075  * @code
00076  *
00077  *  #include "mbed.h"
00078  *  int main() {
00079  *      MbedCRC<POLY_32BIT_ANSI, 32> ct;
00080  *
00081  *      char  test[] = "123456789";
00082  *      uint32_t crc = 0;
00083  *
00084  *      printf("\nPolynomial = 0x%lx  Width = %d \n", ct.get_polynomial(), ct.get_width());
00085  *      ct.compute_partial_start(&crc);
00086  *      ct.compute_partial((void *)&test, 4, &crc);
00087  *      ct.compute_partial((void *)&test[4], 5, &crc);
00088  *      ct.compute_partial_stop(&crc);
00089  *      printf("The CRC of data \"123456789\" is : 0x%lx\n", crc);
00090  *      return 0;
00091  *  }
00092  * @endcode
00093  * @ingroup drivers
00094  */
00095 
00096 extern SingletonPtr<PlatformMutex>  mbed_crc_mutex;
00097 
00098 template <uint32_t polynomial = POLY_32BIT_ANSI, uint8_t width = 32>
00099 class MbedCRC {
00100 
00101 public:
00102     enum CrcMode
00103     {
00104 #ifdef DEVICE_CRC
00105         HARDWARE = 0,
00106 #endif
00107         TABLE = 1,
00108         BITWISE
00109     };
00110 
00111     typedef uint64_t crc_data_size_t;
00112 
00113     /** Lifetime of CRC object
00114      *
00115      *  @param  initial_xor  Inital value/seed to Xor
00116      *  @param  final_xor  Final Xor value
00117      *  @param  reflect_data
00118      *  @param  reflect_remainder
00119      *  @note   Default constructor without any arguments is valid only for supported CRC polynomials. :: crc_polynomial_t
00120      *          MbedCRC <POLY_7BIT_SD, 7> ct; --- Valid POLY_7BIT_SD
00121      *          MbedCRC <0x1021, 16> ct; --- Valid POLY_16BIT_CCITT
00122      *          MbedCRC <POLY_16BIT_CCITT, 32> ct; --- Invalid, compilation error
00123      *          MbedCRC <POLY_16BIT_CCITT, 32> ct (i,f,rd,rr) Consturctor can be used for not supported polynomials
00124      *          MbedCRC<POLY_16BIT_CCITT, 16> sd(0, 0, false, false); Constructor can also be used for supported
00125      *             polynomials with different intial/final/reflect values
00126      *
00127      */
00128     MbedCRC(uint32_t initial_xor, uint32_t final_xor, bool reflect_data, bool reflect_remainder) :
00129         _initial_value(initial_xor), _final_xor(final_xor), _reflect_data(reflect_data),
00130         _reflect_remainder(reflect_remainder)
00131     {
00132         mbed_crc_ctor();
00133     }
00134     MbedCRC();
00135     virtual ~MbedCRC()
00136     {
00137         // Do nothing
00138     }
00139 
00140     /** Compute CRC for the data input
00141      *  Compute CRC performs the initialization, computation and collection of
00142      *  final CRC.
00143      *
00144      *  @param  buffer  Data bytes
00145      *  @param  size  Size of data
00146      *  @param  crc  CRC is the output value
00147      *  @return  0 on success, negative error code on failure
00148      */
00149     int32_t compute(void *buffer, crc_data_size_t size, uint32_t *crc)
00150     {
00151         MBED_ASSERT(crc != NULL);
00152         int32_t status = 0;
00153 
00154         status = compute_partial_start(crc);
00155         if (0 != status) {
00156             unlock();
00157             return status;
00158         }
00159 
00160         status = compute_partial(buffer, size, crc);
00161         if (0 != status) {
00162             unlock();
00163             return status;
00164         }
00165 
00166         status = compute_partial_stop(crc);
00167         if (0 != status) {
00168            *crc = 0;
00169         }
00170 
00171         return status;
00172 
00173     }
00174 
00175     /** Compute partial CRC for the data input.
00176      *
00177      *  CRC data if not available fully, CRC can be computed in parts with available data.
00178      *
00179      *  In case of hardware, intermediate values and states are saved by hardware and mutex
00180      *  locking is used to serialize access to hardware CRC.
00181      *
00182      *  In case of software CRC, previous CRC output should be passed as argument to the
00183      *  current compute_partial call. Please note the intermediate CRC value is maintained by
00184      *  application and not the driver.
00185      *
00186      *  @pre: Call `compute_partial_start` to start the partial CRC calculation.
00187      *  @post: Call `compute_partial_stop` to get the final CRC value.
00188      *
00189      *  @param  buffer  Data bytes
00190      *  @param  size  Size of data
00191      *  @param  crc  CRC value is intermediate CRC value filled by API.
00192      *  @return  0  on success or a negative error code on failure
00193      *  @note: CRC as output in compute_partial is not final CRC value, call `compute_partial_stop`
00194      *         to get final correct CRC value.
00195      */
00196     int32_t compute_partial(void *buffer, crc_data_size_t size, uint32_t *crc)
00197     {
00198         int32_t status = 0;
00199 
00200         switch (_mode) {
00201 #ifdef DEVICE_CRC
00202             case HARDWARE:
00203                 hal_crc_compute_partial((uint8_t *)buffer, size);
00204                 *crc = 0;
00205                 break;
00206 #endif
00207             case TABLE:
00208                 status = table_compute_partial(buffer, size, crc);
00209                 break;
00210             case BITWISE:
00211                 status = bitwise_compute_partial(buffer, size, crc);
00212                 break;
00213             default:
00214                 status = -1;
00215                 break;
00216         }
00217 
00218         return status;
00219     }
00220 
00221     /** Compute partial start, indicate start of partial computation
00222      *
00223      *  This API should be called before performing any partial computation
00224      *  with compute_partial API.
00225      *
00226      *  @param  crc  Initial CRC value set by the API
00227      *  @return  0  on success or a negative in case of failure
00228      *  @note: CRC is an out parameter and must be reused with compute_partial
00229      *         and `compute_partial_stop` without any modifications in application.
00230      */
00231     int32_t compute_partial_start(uint32_t *crc)
00232     {
00233         MBED_ASSERT(crc != NULL);
00234 
00235 #ifdef DEVICE_CRC
00236         if (_mode == HARDWARE) {
00237             lock();
00238             crc_mbed_config_t config;
00239             config.polynomial  = polynomial;
00240             config.width       = width;
00241             config.initial_xor = _initial_value;
00242             config.final_xor   = _final_xor;
00243             config.reflect_in  = _reflect_data;
00244             config.reflect_out = _reflect_remainder;
00245 
00246             hal_crc_compute_partial_start(&config);
00247         }
00248 #endif
00249 
00250         *crc = _initial_value;
00251         return 0;
00252     }
00253 
00254     /** Get the final CRC value of partial computation.
00255      *
00256      *  CRC value available in partial computation is not correct CRC, as some
00257      *  algorithms require remainder to be reflected and final value to be XORed
00258      *  This API is used to perform final computation to get correct CRC value.
00259      *
00260      *  @param crc  CRC result
00261      */
00262     int32_t compute_partial_stop(uint32_t *crc)
00263     {
00264         MBED_ASSERT(crc != NULL);
00265 
00266 #ifdef DEVICE_CRC
00267         if (_mode == HARDWARE) {
00268             *crc = hal_crc_get_result();
00269             unlock();
00270             return 0;
00271         }
00272 #endif
00273         uint32_t p_crc = *crc;
00274         if ((width < 8) && (NULL == _crc_table)) {
00275             p_crc = (uint32_t)(p_crc << (8 - width));
00276         }
00277         // Optimized algorithm for 32BitANSI does not need additional reflect_remainder
00278         if ((TABLE == _mode) && (POLY_32BIT_REV_ANSI == polynomial)) {
00279             *crc = (p_crc ^ _final_xor) & get_crc_mask();
00280         } else {
00281             *crc = (reflect_remainder(p_crc) ^ _final_xor) & get_crc_mask();
00282         }
00283         unlock();
00284         return 0;
00285     }
00286 
00287     /** Get the current CRC polynomial
00288      *
00289      * @return  Polynomial value
00290      */
00291     uint32_t get_polynomial(void) const
00292     {
00293         return polynomial;
00294     }
00295 
00296     /** Get the current CRC width
00297      *
00298      * @return  CRC width
00299      */
00300     uint8_t get_width(void) const
00301     {
00302         return width;
00303     }
00304 
00305 private:
00306     uint32_t _initial_value;
00307     uint32_t _final_xor;
00308     bool _reflect_data;
00309     bool _reflect_remainder;
00310     uint32_t *_crc_table;
00311     CrcMode _mode;
00312 
00313     /** Acquire exclusive access to CRC hardware/software
00314      */
00315      void lock()
00316     {
00317 #ifdef DEVICE_CRC
00318         if (_mode == HARDWARE) {
00319             mbed_crc_mutex->lock();
00320         }
00321 #endif
00322     }
00323 
00324     /** Release exclusive access to CRC hardware/software
00325      */
00326     virtual void unlock()
00327     {
00328 #ifdef DEVICE_CRC
00329         if (_mode == HARDWARE) {
00330             mbed_crc_mutex->unlock();
00331         }
00332 #endif
00333     }
00334 
00335     /** Get the current CRC data size
00336      *
00337      * @return  CRC data size in bytes
00338      */
00339     uint8_t get_data_size(void) const
00340     {
00341         return (width <= 8 ? 1 : (width <= 16 ? 2 : 4));
00342     }
00343 
00344     /** Get the top bit of current CRC
00345      *
00346      * @return  Top bit is set high for respective data width of current CRC
00347      *          Top bit for CRC width less then 8 bits will be set as 8th bit.
00348      */
00349     uint32_t get_top_bit(void) const
00350     {
00351         return (width < 8 ? (1u << 7) : (uint32_t)(1ul << (width - 1)));
00352     }
00353 
00354     /** Get the CRC data mask
00355      *
00356      * @return  CRC data mask is generated based on current CRC width
00357      */
00358     uint32_t get_crc_mask(void) const
00359     {
00360         return (width < 8 ? ((1u << 8) - 1) : (uint32_t)((uint64_t)(1ull << width) - 1));
00361     }
00362 
00363     /** Final value of CRC is reflected
00364      *
00365      * @param  data final crc value, which should be reflected
00366      * @return  Reflected CRC value
00367      */
00368     uint32_t reflect_remainder(uint32_t data) const
00369     {
00370         if (_reflect_remainder) {
00371             uint32_t reflection = 0x0;
00372             uint8_t const nBits = (width < 8 ? 8 : width);
00373 
00374             for (uint8_t bit = 0; bit < nBits; ++bit) {
00375                 if (data & 0x01) {
00376                     reflection |= (1 << ((nBits - 1) - bit));
00377                 }
00378                 data = (data >> 1);
00379             }
00380             return (reflection);
00381         } else {
00382             return data;
00383         }
00384     }
00385 
00386     /** Data bytes are reflected
00387      *
00388      * @param  data value to be reflected
00389      * @return  Reflected data value
00390      */
00391     uint32_t reflect_bytes(uint32_t data) const
00392     {
00393         if (_reflect_data) {
00394             uint32_t reflection = 0x0;
00395 
00396             for (uint8_t bit = 0; bit < 8; ++bit) {
00397                 if (data & 0x01) {
00398                     reflection |= (1 << (7 - bit));
00399                 }
00400                 data = (data >> 1);
00401             }
00402             return (reflection);
00403         } else {
00404             return data;
00405         }
00406     }
00407 
00408     /** Bitwise CRC computation
00409      *
00410      * @param  buffer  data buffer
00411      * @param  size  size of the data
00412      * @param  crc  CRC value is filled in, but the value is not the final
00413      * @return  0  on success or a negative error code on failure
00414      */
00415     int32_t bitwise_compute_partial(const void *buffer, crc_data_size_t size, uint32_t *crc) const
00416     {
00417         MBED_ASSERT(crc != NULL);
00418 
00419         const uint8_t *data = static_cast<const uint8_t *>(buffer);
00420         uint32_t p_crc = *crc;
00421 
00422         if (width < 8) {
00423             uint8_t data_byte;
00424             for (crc_data_size_t byte = 0; byte < size; byte++) {
00425                 data_byte = reflect_bytes(data[byte]);
00426                 for (uint8_t bit = 8; bit > 0; --bit) {
00427                     p_crc <<= 1;
00428                     if ((data_byte ^ p_crc) & get_top_bit()) {
00429                         p_crc ^= polynomial;
00430                     }
00431                     data_byte <<= 1;
00432                 }
00433             }
00434         } else {
00435             for (crc_data_size_t byte = 0; byte < size; byte++) {
00436                 p_crc ^= (reflect_bytes(data[byte]) << (width - 8));
00437 
00438                 // Perform modulo-2 division, a bit at a time
00439                 for (uint8_t bit = 8; bit > 0; --bit) {
00440                     if (p_crc & get_top_bit()) {
00441                         p_crc = (p_crc << 1) ^ polynomial;
00442                     } else {
00443                         p_crc = (p_crc << 1);
00444                     }
00445                 }
00446             }
00447         }
00448         *crc = p_crc & get_crc_mask();
00449         return 0;
00450     }
00451 
00452     /** CRC computation using ROM tables
00453     *
00454     * @param  buffer  data buffer
00455     * @param  size  size of the data
00456     * @param  crc  CRC value is filled in, but the value is not the final
00457     * @return  0  on success or a negative error code on failure
00458     */
00459     int32_t table_compute_partial(const void *buffer, crc_data_size_t size, uint32_t *crc) const
00460     {
00461         MBED_ASSERT(crc != NULL);
00462 
00463         const uint8_t *data = static_cast<const uint8_t *>(buffer);
00464         uint32_t p_crc = *crc;
00465         uint8_t data_byte = 0;
00466 
00467         if (width <= 8) {
00468             uint8_t *crc_table = (uint8_t *)_crc_table;
00469             for (crc_data_size_t byte = 0; byte < size; byte++) {
00470                 data_byte = reflect_bytes(data[byte]) ^ p_crc;
00471                 p_crc = crc_table[data_byte];
00472             }
00473         } else if (width <= 16) {
00474             uint16_t *crc_table = (uint16_t *)_crc_table;
00475             for (crc_data_size_t byte = 0; byte < size; byte++) {
00476                 data_byte = reflect_bytes(data[byte]) ^ (p_crc >> (width - 8));
00477                 p_crc = crc_table[data_byte] ^ (p_crc << 8);
00478             }
00479         } else {
00480             uint32_t *crc_table = (uint32_t *)_crc_table;
00481             if (POLY_32BIT_REV_ANSI == polynomial) {
00482                 for (crc_data_size_t i = 0; i < size; i++) {
00483                     p_crc = (p_crc >> 4) ^ crc_table[(p_crc ^ (data[i] >> 0)) & 0xf];
00484                     p_crc = (p_crc >> 4) ^ crc_table[(p_crc ^ (data[i] >> 4)) & 0xf];
00485                 }
00486             }
00487             else {
00488                 for (crc_data_size_t byte = 0; byte < size; byte++) {
00489                     data_byte = reflect_bytes(data[byte]) ^ (p_crc >> (width - 8));
00490                     p_crc = crc_table[data_byte] ^ (p_crc << 8);
00491                 }
00492             }
00493         }
00494         *crc = p_crc & get_crc_mask();
00495         return 0;
00496     }
00497 
00498     /** Constructor init called from all specialized cases of constructor
00499      *  Note: All construtor common code should be in this function.
00500      */
00501     void mbed_crc_ctor(void)
00502     {
00503         MBED_STATIC_ASSERT(width <= 32, "Max 32-bit CRC supported");
00504 
00505 #ifdef DEVICE_CRC
00506         if (POLY_32BIT_REV_ANSI == polynomial) {
00507             _crc_table = (uint32_t *)Table_CRC_32bit_Rev_ANSI;
00508             _mode = TABLE;
00509             return;
00510         }
00511         crc_mbed_config_t config;
00512         config.polynomial  = polynomial;
00513         config.width       = width;
00514         config.initial_xor = _initial_value;
00515         config.final_xor   = _final_xor;
00516         config.reflect_in  = _reflect_data;
00517         config.reflect_out = _reflect_remainder;
00518 
00519         if (hal_crc_is_supported(&config)) {
00520             _mode = HARDWARE;
00521             return;
00522         }
00523 #endif
00524 
00525         switch (polynomial) {
00526             case POLY_32BIT_ANSI:
00527                 _crc_table = (uint32_t *)Table_CRC_32bit_ANSI;
00528                 break;
00529             case POLY_32BIT_REV_ANSI:
00530                 _crc_table = (uint32_t *)Table_CRC_32bit_Rev_ANSI;
00531                 break;
00532             case POLY_8BIT_CCITT:
00533                 _crc_table = (uint32_t *)Table_CRC_8bit_CCITT;
00534                 break;
00535             case POLY_7BIT_SD:
00536                 _crc_table = (uint32_t *)Table_CRC_7Bit_SD;
00537                 break;
00538             case POLY_16BIT_CCITT:
00539                 _crc_table = (uint32_t *)Table_CRC_16bit_CCITT;
00540                 break;
00541             case POLY_16BIT_IBM:
00542                 _crc_table = (uint32_t *)Table_CRC_16bit_IBM;
00543                 break;
00544             default:
00545                 _crc_table = NULL;
00546                 break;
00547         }
00548         _mode = (_crc_table != NULL) ? TABLE : BITWISE;
00549     }
00550 };
00551 
00552 #if   defined ( __CC_ARM )
00553 #elif defined ( __GNUC__ )
00554 #pragma GCC diagnostic pop
00555 #elif defined (__ICCARM__)
00556 #endif
00557 
00558 /** @}*/
00559 } // namespace mbed
00560 
00561 #endif