crc16.c

00001 /*
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00006  * are permitted provided that the following conditions are met:
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00010  *
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00012  *   list of conditions and the following disclaimer in the documentation and/or
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00014  *
00015  *   3. Neither the name of Nordic Semiconductor ASA nor the names of other
00016  *   contributors to this software may be used to endorse or promote products
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00019  *
00020  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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00022  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
00023  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
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00032 
00033 #include "crc16.h "
00034 #include <stdio.h>
00035 
00036 uint16_t crc16_compute(const uint8_t * p_data, uint32_t size, const uint16_t * p_crc)
00037 {
00038     uint32_t i;
00039     uint16_t crc = (p_crc == NULL) ? 0xffff : *p_crc;
00040 
00041     for (i = 0; i < size; i++)
00042     {
00043         crc  = (unsigned char)(crc >> 8) | (crc << 8);
00044         crc ^= p_data[i];
00045         crc ^= (unsigned char)(crc & 0xff) >> 4;
00046         crc ^= (crc << 8) << 4;
00047         crc ^= ((crc & 0xff) << 4) << 1;
00048     }
00049 
00050     return crc;
00051 }