Pedro Correia
mbed library sources. Supersedes mbed-src.
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mbed official
Diff: drivers/MbedCRC.h
- Revision:
- 184:08ed48f1de7f
- Child:
- 186:707f6e361f3e
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/drivers/MbedCRC.h Thu Apr 19 17:12:19 2018 +0100
@@ -0,0 +1,425 @@
+/* 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 <stdint.h>
+#include "drivers/TableCRC.h"
+#include "platform/mbed_assert.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"
+#endif
+
+namespace mbed {
+/** \addtogroup drivers */
+/** @{*/
+
+/** CRC Polynomial value
+ *
+ * Different polynomial values supported
+ */
+typedef enum crc_polynomial {
+ POLY_OTHER = 0,
+ POLY_8BIT_CCITT = 0x07, // x8+x2+x+1
+ POLY_7BIT_SD = 0x9, // x7+x3+1;
+ POLY_16BIT_CCITT = 0x1021, // x16+x12+x5+1
+ POLY_16BIT_IBM = 0x8005, // x16+x15+x2+1
+ POLY_32BIT_ANSI = 0x04C11DB7, // x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x+1
+} crc_polynomial_t;
+
+/** 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.
+ *
+ * @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:
+ 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) Consturctor 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), _crc_table(NULL)
+ {
+ mbed_crc_ctor();
+ }
+ MbedCRC();
+ virtual ~MbedCRC()
+ {
+ // Do nothing
+ }
+
+ /** Compute CRC for the data input
+ *
+ * @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;
+ if (0 != (status = compute_partial_start(crc))) {
+ *crc = 0;
+ return status;
+ }
+ if (0 != (status = compute_partial(buffer, size, crc))) {
+ *crc = 0;
+ return status;
+ }
+ if (0 != (status = compute_partial_stop(crc))) {
+ *crc = 0;
+ return status;
+ }
+ return 0;
+ }
+
+ /** Compute partial CRC for the data input.
+ *
+ * CRC data if not available fully, CRC can be computed in parts with available data.
+ * Previous CRC output should be passed as argument to the current compute_partial call.
+ * @pre: Call \ref compute_partial_start to start the partial CRC calculation.
+ * @post: Call \ref 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 @ref compute_partial_stop
+ * to get final correct CRC value.
+ */
+ int32_t compute_partial(void *buffer, crc_data_size_t size, uint32_t *crc)
+ {
+ if (NULL == _crc_table) {
+ // Compute bitwise CRC
+ return bitwise_compute_partial(buffer, size, crc);
+ } else {
+ // Table CRC
+ return table_compute_partial(buffer, size, crc);
+ }
+ }
+
+ /** 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);
+ *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
+ */
+ int32_t compute_partial_stop(uint32_t *crc)
+ {
+ MBED_ASSERT(crc != NULL);
+ uint32_t p_crc = *crc;
+ if ((width < 8) && (NULL == _crc_table)) {
+ p_crc = (uint32_t)(p_crc << (8 - width));
+ }
+ *crc = (reflect_remainder(p_crc) ^ _final_xor) & get_crc_mask();
+ 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;
+
+ /** 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);
+ MBED_ASSERT(buffer != 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);
+ MBED_ASSERT(buffer != 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;
+ 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) const
+ {
+ MBED_STATIC_ASSERT(width <= 32, "Max 32-bit CRC supported");
+ }
+};
+
+#if defined ( __CC_ARM )
+#elif defined ( __GNUC__ )
+#pragma GCC diagnostic pop
+#endif
+
+/** @}*/
+} // namespace mbed
+
+#endif