crc.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

#include "base-precomp.h"  // Precompiled headers

#include <mrpt/utils/crc.h>

using namespace mrpt::utils;
using namespace std;

/*---------------------------------------------------------------
                                        CRC16
 ---------------------------------------------------------------*/
uint16_t mrpt::utils::compute_CRC16(
        const std::vector<uint8_t>& data, const uint16_t gen_pol)
{
        return compute_CRC16(&data[0], data.size(), gen_pol);
}

uint32_t mrpt::utils::compute_CRC32(
        const std::vector<uint8_t>& data, const uint32_t gen_pol)
{
        return compute_CRC32(&data[0], data.size(), gen_pol);
}

/*---------------------------------------------------------------
                                        CRC16
 ---------------------------------------------------------------*/
uint16_t mrpt::utils::compute_CRC16(
        const uint8_t* data, const size_t len_, const uint16_t gen_pol)
{
        uint16_t uCrc16;
        uint8_t abData[2];

        size_t len = len_;

        uCrc16 = 0;
        abData[0] = 0;

        while (len--)
        {
                abData[1] = abData[0];
                abData[0] = *data++;

                if (uCrc16 & 0x8000)
                {
                        uCrc16 = (uCrc16 & 0x7fff) << 1;
                        uCrc16 ^= gen_pol;
                }
                else
                {
                        uCrc16 <<= 1;
                }
                uCrc16 ^= (abData[0] | (abData[1] << 8));
        }
        return uCrc16;
}

unsigned long CRC32Value(int i, const uint32_t CRC32_POLYNOMIAL)
{
        unsigned long ulCRC = i;
        for (int j = 8; j > 0; j--)
        {
                if (ulCRC & 1)
                        ulCRC = (ulCRC >> 1) ^ CRC32_POLYNOMIAL;
                else
                        ulCRC >>= 1;
        }
        return ulCRC;
}

uint32_t mrpt::utils::compute_CRC32(
        const uint8_t* data, const size_t len_, const uint32_t gen_pol)
{
        size_t len = len_;
        unsigned long ulCRC = 0;
        while (len-- != 0)
        {
                unsigned long ulTemp1 = (ulCRC >> 8) & 0x00FFFFFFL;
                unsigned long ulTemp2 =
                        CRC32Value(((int)ulCRC ^ *data++) & 0xff, gen_pol);
                ulCRC = ulTemp1 ^ ulTemp2;
        }
        return ulCRC;
}