Diff: src/crc16.c

Revision:

11:a2dcf0ebb5b5

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+++ b/src/crc16.c	Mon Aug 03 17:21:20 2020 +0530
@@ -0,0 +1,104 @@
+/***************************************************************************//**
+ *   @file   crc16.c
+ *   @brief  Source file of CRC-16 computation.
+ *   @author Darius Berghe (darius.berghe@analog.com)
+********************************************************************************
+ * Copyright 2020(c) Analog Devices, Inc.
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *  - Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  - Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *  - Neither the name of Analog Devices, Inc. nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *  - The use of this software may or may not infringe the patent rights
+ *    of one or more patent holders.  This license does not release you
+ *    from the requirement that you obtain separate licenses from these
+ *    patent holders to use this software.
+ *  - Use of the software either in source or binary form, must be run
+ *    on or directly connected to an Analog Devices Inc. component.
+ *
+ * THIS SOFTWARE IS PROVIDED BY ANALOG DEVICES "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, NON-INFRINGEMENT,
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL ANALOG DEVICES BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, INTELLECTUAL PROPERTY RIGHTS, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*******************************************************************************/
+#include "crc16.h"
+
+/***************************************************************************//**
+ * @brief Creates the CRC-16 lookup table for a given polynomial.
+ *
+ * @param table      - Pointer to a CRC-16 lookup table to write to.
+ * @param polynomial - msb-first representation of desired polynomial.
+ *
+ * Polynomials in CRC algorithms are typically represented as shown below.
+ *
+ *	poly = x^16 + x^14 + x^13 + x^12 + x^10 + x^8 + x^6 + x^4 + x^3 +
+ *             x^1 + 1
+ *
+ * Using msb-first direction, x^15 maps to the msb.
+ *
+ * 	msb first: poly = (1)0111010101011011 = 0xBAAD
+ *                           ^
+ *
+ * @return None.
+*******************************************************************************/
+void crc16_populate_msb(uint16_t * table, const uint16_t polynomial)
+{
+	if (!table)
+		return;
+
+	for (int16_t n = 0; n < CRC16_TABLE_SIZE; n++) {
+		uint16_t currByte = (uint16_t)(n << 8);
+		for (uint8_t bit = 0; bit < 8; bit++) {
+			if ((currByte & 0x8000) != 0) {
+				currByte <<= 1;
+				currByte ^= polynomial;
+			} else {
+				currByte <<= 1;
+			}
+		}
+		table[n] = currByte;
+	}
+}
+
+/***************************************************************************//**
+ * @brief Computes the CRC-16 over a buffer of data.
+ *
+ * @param table     - Pointer to a CRC-16 lookup table for the desired polynomial.
+ * @param pdata     - Pointer to data buffer.
+ * @param nbytes    - Number of bytes to compute the CRC-16 over.
+ * @param crc       - Initial value for the CRC-16 computation. Can be used to
+ *                    cascade calls to this function by providing a previous
+ *                    output of this function as the crc parameter.
+ *
+ * @return crc      - Computed CRC-16 value.
+*******************************************************************************/
+uint16_t crc16(const uint16_t * table,
+	       const uint8_t *pdata,
+	       size_t nbytes,
+	       uint16_t crc)
+{
+	unsigned int idx;
+
+	while (nbytes--) {
+		idx = ((crc >> 8) ^ *pdata) & 0xff;
+		crc = (table[idx] ^ (crc << 8)) & 0xffff;
+		pdata++;
+	}
+
+	return crc;
+}
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