shellmatta/src/shellmatta_crc.c

/*
 * Copyright (c) 2019 - 2024 Stefan Strobel <stefan.strobel@shimatta.net>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

/**
 * @file    shellmatta_crc.c
 * @brief   cyclic redundancy check functions of shellmatta
 * @author  Simon Fischer <fischer.simon.1991@gmail.com>
 */

#include "shellmatta_crc.h"

#ifndef SHELLMATTA_TRANSPORT_CRC_NO_LOOKUP
/** \brief CRC Lookup table for 0x04c11db7 reflected */
uint32_t crc32Table[] = {
    0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
    0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
    0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
    0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
    0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
    0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
    0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
    0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924, 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
    0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
    0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
    0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
    0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
    0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
    0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
    0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
    0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
    0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
    0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
    0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
    0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
    0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
    0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
    0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236, 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
    0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
    0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
    0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
    0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
    0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
    0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
    0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
    0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
    0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
};
#endif

#ifdef SHELLMATTA_TRANSPORT_CRC_NO_LOOKUP
/**
 * @brief       Reverses bits of a value.
 * @param[in]   x       input value
 * @param[in]   size    amount of bits used in value
 * @return      reversed data
 */
static uint32_t reverse(uint32_t x, uint32_t bits)
{
    x = ((x & 0x55555555u) << 1u)  | ((x & 0xAAAAAAAAu) >> 1u);
    x = ((x & 0x33333333u) << 2u)  | ((x & 0xCCCCCCCCu) >> 2u);
    x = ((x & 0x0F0F0F0Fu) << 4u)  | ((x & 0xF0F0F0F0u) >> 4u);
    x = ((x & 0x00FF00FFu) << 8u)  | ((x & 0xFF00FF00u) >> 8u);
    x = ((x & 0x0000FFFFu) << 16u) | ((x & 0xFFFF0000u) >> 16u);
    return x >> (32u - bits);
}


/**
 * @brief       Computes the crc32-checksum of a buffer. O(4n)
 * @param[in]   data            pointer to data buffer
 * @param[in]   size            amount of bytes to be processed
 * @return      crc             calculated crc32 value
 */
static uint32_t crc32Slow(const char* data, uint32_t size)
{
    uint32_t i;
    uint8_t j;
    uint32_t polynom = reverse(CRC32_POLYNOM, 32u);
    uint8_t pivotByte;

    /* start with 0xffffffffu */
    uint32_t crcTemp = 0xffffffffu;

    for (i = 0u; i < size; i++)
    {
        pivotByte = data[i];
        for (j = 0u; j < BITS_PER_BYTE; j++)
        {
            if ((crcTemp & 1u) != (pivotByte & 1u))
            {
                crcTemp = (crcTemp >> 1u) ^ polynom;
            }
            else
            {
                crcTemp >>= 1u;
            }
            pivotByte >>= 1u;
        }
    }

    /* final xor */
    crcTemp ^= 0xffffffffu;

    return crcTemp;
}

#else
/**
 * @brief       Computes the crc32-checksum of a buffer. O(n)
 * @param[in]   data            pointer to data buffer
 * @param[in]   size            amount of bytes to be processed
 * @param[in]   lookupTable     pointer to uint32_t lookup table for crc computation
 * @return      crc             calculated crc32 value
 */
static uint32_t crc32Fast(const char* data, uint32_t size, const uint32_t* lookupTable)
{
    uint32_t i;
    uint32_t crcTemp = 0xffffffffu;

    for (i = 0u; i < size; i++)
    {
        uint8_t index = data[i] ^ (crcTemp & 0xffu);
        crcTemp = lookupTable[index] ^ (crcTemp >> 8u);
    }

    return ~crcTemp;
}
#endif


/**
 * @brief       Computes the crc32-checksum of a buffer.
 * @param[in]   data            pointer to data buffer
 * @param[in]   size            amount of bytes to be processed
 * @return      crc             calculated crc32 value
 */
uint32_t crc32Calc(const char* data, uint32_t size)
{
    #ifdef  SHELLMATTA_TRANSPORT_CRC_NO_LOOKUP
        return crc32Slow(data, size);
    #else
        return crc32Fast(data, size, crc32Table);
    #endif
}