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) Constructor 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. 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      *  @return  0  on success or a negative in case of failure.
00262      */
00263     int32_t compute_partial_stop(uint32_t *crc)
00264     {
00265         MBED_ASSERT(crc != NULL);
00266 
00267 #ifdef DEVICE_CRC
00268         if (_mode == HARDWARE) {
00269             *crc = hal_crc_get_result();
00270             unlock();
00271             return 0;
00272         }
00273 #endif
00274         uint32_t p_crc = *crc;
00275         if ((width < 8) && (NULL == _crc_table)) {
00276             p_crc = (uint32_t)(p_crc << (8 - width));
00277         }
00278         // Optimized algorithm for 32BitANSI does not need additional reflect_remainder
00279         if ((TABLE == _mode) && (POLY_32BIT_REV_ANSI == polynomial)) {
00280             *crc = (p_crc ^ _final_xor) & get_crc_mask();
00281         } else {
00282             *crc = (reflect_remainder(p_crc) ^ _final_xor) & get_crc_mask();
00283         }
00284         unlock();
00285         return 0;
00286     }
00287 
00288     /** Get the current CRC polynomial.
00289      *
00290      * @return  Polynomial value
00291      */
00292     uint32_t get_polynomial(void) const
00293     {
00294         return polynomial;
00295     }
00296 
00297     /** Get the current CRC width
00298      *
00299      * @return  CRC width
00300      */
00301     uint8_t get_width(void) const
00302     {
00303         return width;
00304     }
00305 
00306 private:
00307     uint32_t _initial_value;
00308     uint32_t _final_xor;
00309     bool _reflect_data;
00310     bool _reflect_remainder;
00311     uint32_t *_crc_table;
00312     CrcMode _mode;
00313 
00314     /** Acquire exclusive access to CRC hardware/software.
00315      */
00316      void lock()
00317     {
00318 #ifdef DEVICE_CRC
00319         if (_mode == HARDWARE) {
00320             mbed_crc_mutex->lock();
00321         }
00322 #endif
00323     }
00324 
00325     /** Release exclusive access to CRC hardware/software.
00326      */
00327     virtual void unlock()
00328     {
00329 #ifdef DEVICE_CRC
00330         if (_mode == HARDWARE) {
00331             mbed_crc_mutex->unlock();
00332         }
00333 #endif
00334     }
00335 
00336     /** Get the current CRC data size.
00337      *
00338      * @return  CRC data size in bytes
00339      */
00340     uint8_t get_data_size(void) const
00341     {
00342         return (width <= 8 ? 1 : (width <= 16 ? 2 : 4));
00343     }
00344 
00345     /** Get the top bit of current CRC.
00346      *
00347      * @return  Top bit is set high for respective data width of current CRC
00348      *          Top bit for CRC width less then 8 bits will be set as 8th bit.
00349      */
00350     uint32_t get_top_bit(void) const
00351     {
00352         return (width < 8 ? (1u << 7) : (uint32_t)(1ul << (width - 1)));
00353     }
00354 
00355     /** Get the CRC data mask.
00356      *
00357      * @return  CRC data mask is generated based on current CRC width
00358      */
00359     uint32_t get_crc_mask(void) const
00360     {
00361         return (width < 8 ? ((1u << 8) - 1) : (uint32_t)((uint64_t)(1ull << width) - 1));
00362     }
00363 
00364     /** Final value of CRC is reflected.
00365      *
00366      * @param  data final crc value, which should be reflected
00367      * @return  Reflected CRC value
00368      */
00369     uint32_t reflect_remainder(uint32_t data) const
00370     {
00371         if (_reflect_remainder) {
00372             uint32_t reflection = 0x0;
00373             uint8_t const nBits = (width < 8 ? 8 : width);
00374 
00375             for (uint8_t bit = 0; bit < nBits; ++bit) {
00376                 if (data & 0x01) {
00377                     reflection |= (1 << ((nBits - 1) - bit));
00378                 }
00379                 data = (data >> 1);
00380             }
00381             return (reflection);
00382         } else {
00383             return data;
00384         }
00385     }
00386 
00387     /** Data bytes are reflected.
00388      *
00389      * @param  data value to be reflected
00390      * @return  Reflected data value
00391      */
00392     uint32_t reflect_bytes(uint32_t data) const
00393     {
00394         if (_reflect_data) {
00395             uint32_t reflection = 0x0;
00396 
00397             for (uint8_t bit = 0; bit < 8; ++bit) {
00398                 if (data & 0x01) {
00399                     reflection |= (1 << (7 - bit));
00400                 }
00401                 data = (data >> 1);
00402             }
00403             return (reflection);
00404         } else {
00405             return data;
00406         }
00407     }
00408 
00409     /** Bitwise CRC computation.
00410      *
00411      * @param  buffer  data buffer
00412      * @param  size  size of the data
00413      * @param  crc  CRC value is filled in, but the value is not the final
00414      * @return  0  on success or a negative error code on failure
00415      */
00416     int32_t bitwise_compute_partial(const void *buffer, crc_data_size_t size, uint32_t *crc) const
00417     {
00418         MBED_ASSERT(crc != NULL);
00419 
00420         const uint8_t *data = static_cast<const uint8_t *>(buffer);
00421         uint32_t p_crc = *crc;
00422 
00423         if (width < 8) {
00424             uint8_t data_byte;
00425             for (crc_data_size_t byte = 0; byte < size; byte++) {
00426                 data_byte = reflect_bytes(data[byte]);
00427                 for (uint8_t bit = 8; bit > 0; --bit) {
00428                     p_crc <<= 1;
00429                     if ((data_byte ^ p_crc) & get_top_bit()) {
00430                         p_crc ^= polynomial;
00431                     }
00432                     data_byte <<= 1;
00433                 }
00434             }
00435         } else {
00436             for (crc_data_size_t byte = 0; byte < size; byte++) {
00437                 p_crc ^= (reflect_bytes(data[byte]) << (width - 8));
00438 
00439                 // Perform modulo-2 division, a bit at a time
00440                 for (uint8_t bit = 8; bit > 0; --bit) {
00441                     if (p_crc & get_top_bit()) {
00442                         p_crc = (p_crc << 1) ^ polynomial;
00443                     } else {
00444                         p_crc = (p_crc << 1);
00445                     }
00446                 }
00447             }
00448         }
00449         *crc = p_crc & get_crc_mask();
00450         return 0;
00451     }
00452 
00453     /** CRC computation using ROM tables.
00454     *
00455     * @param  buffer  data buffer
00456     * @param  size  size of the data
00457     * @param  crc  CRC value is filled in, but the value is not the final
00458     * @return  0  on success or a negative error code on failure
00459     */
00460     int32_t table_compute_partial(const void *buffer, crc_data_size_t size, uint32_t *crc) const
00461     {
00462         MBED_ASSERT(crc != NULL);
00463 
00464         const uint8_t *data = static_cast<const uint8_t *>(buffer);
00465         uint32_t p_crc = *crc;
00466         uint8_t data_byte = 0;
00467 
00468         if (width <= 8) {
00469             uint8_t *crc_table = (uint8_t *)_crc_table;
00470             for (crc_data_size_t byte = 0; byte < size; byte++) {
00471                 data_byte = reflect_bytes(data[byte]) ^ p_crc;
00472                 p_crc = crc_table[data_byte];
00473             }
00474         } else if (width <= 16) {
00475             uint16_t *crc_table = (uint16_t *)_crc_table;
00476             for (crc_data_size_t byte = 0; byte < size; byte++) {
00477                 data_byte = reflect_bytes(data[byte]) ^ (p_crc >> (width - 8));
00478                 p_crc = crc_table[data_byte] ^ (p_crc << 8);
00479             }
00480         } else {
00481             uint32_t *crc_table = (uint32_t *)_crc_table;
00482             if (POLY_32BIT_REV_ANSI == polynomial) {
00483                 for (crc_data_size_t i = 0; i < size; i++) {
00484                     p_crc = (p_crc >> 4) ^ crc_table[(p_crc ^ (data[i] >> 0)) & 0xf];
00485                     p_crc = (p_crc >> 4) ^ crc_table[(p_crc ^ (data[i] >> 4)) & 0xf];
00486                 }
00487             }
00488             else {
00489                 for (crc_data_size_t byte = 0; byte < size; byte++) {
00490                     data_byte = reflect_bytes(data[byte]) ^ (p_crc >> (width - 8));
00491                     p_crc = crc_table[data_byte] ^ (p_crc << 8);
00492                 }
00493             }
00494         }
00495         *crc = p_crc & get_crc_mask();
00496         return 0;
00497     }
00498 
00499     /** Constructor init called from all specialized cases of constructor.
00500      *  Note: All construtor common code should be in this function.
00501      */
00502     void mbed_crc_ctor(void)
00503     {
00504         MBED_STATIC_ASSERT(width <= 32, "Max 32-bit CRC supported");
00505 
00506 #ifdef DEVICE_CRC
00507         if (POLY_32BIT_REV_ANSI == polynomial) {
00508             _crc_table = (uint32_t *)Table_CRC_32bit_Rev_ANSI;
00509             _mode = TABLE;
00510             return;
00511         }
00512         crc_mbed_config_t config;
00513         config.polynomial  = polynomial;
00514         config.width       = width;
00515         config.initial_xor = _initial_value;
00516         config.final_xor   = _final_xor;
00517         config.reflect_in  = _reflect_data;
00518         config.reflect_out = _reflect_remainder;
00519 
00520         if (hal_crc_is_supported(&config)) {
00521             _mode = HARDWARE;
00522             return;
00523         }
00524 #endif
00525 
00526         switch (polynomial) {
00527             case POLY_32BIT_ANSI:
00528                 _crc_table = (uint32_t *)Table_CRC_32bit_ANSI;
00529                 break;
00530             case POLY_32BIT_REV_ANSI:
00531                 _crc_table = (uint32_t *)Table_CRC_32bit_Rev_ANSI;
00532                 break;
00533             case POLY_8BIT_CCITT:
00534                 _crc_table = (uint32_t *)Table_CRC_8bit_CCITT;
00535                 break;
00536             case POLY_7BIT_SD:
00537                 _crc_table = (uint32_t *)Table_CRC_7Bit_SD;
00538                 break;
00539             case POLY_16BIT_CCITT:
00540                 _crc_table = (uint32_t *)Table_CRC_16bit_CCITT;
00541                 break;
00542             case POLY_16BIT_IBM:
00543                 _crc_table = (uint32_t *)Table_CRC_16bit_IBM;
00544                 break;
00545             default:
00546                 _crc_table = NULL;
00547                 break;
00548         }
00549         _mode = (_crc_table != NULL) ? TABLE : BITWISE;
00550     }
00551 };
00552 
00553 #if   defined ( __CC_ARM )
00554 #elif defined ( __GNUC__ )
00555 #pragma GCC diagnostic pop
00556 #elif defined (__ICCARM__)
00557 #endif
00558 
00559 /** @}*/
00560 } // namespace mbed
00561 
00562 #endif