crc.cpp

Go to the documentation of this file.

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

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

#include <mrpt/core/exceptions.h>
#include <mrpt/system/crc.h>

uint16_t mrpt::system::compute_CRC16(
    const std::vector<uint8_t>& data, const uint16_t gen_pol)
{
    ASSERT_(!data.empty());
    return compute_CRC16(&data[0], data.size(), gen_pol);
}

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

uint16_t mrpt::system::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::system::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;
}