/*
 * lfs util functions
 *
 * Copyright (c) 2017, Arm Limited. All rights reserved.
 * SPDX-License-Identifier: BSD-3-Clause
 */
#include "lfs_util.h"

// Only compile if user does not provide custom config
#ifndef LFS_CONFIG


// Software CRC implementation with small lookup table
uint32_t lfs_crc(uint32_t crc, const void *buffer, size_t size) {
    static uint32_t rtable[16] = {
        0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
        0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
        0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
        0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
    };

#if 0
    const uint8_t *data = buffer;

    for (size_t i = 0; i < size; i++) {
        crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 0)) & 0xf];
        crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 4)) & 0xf];
    }

#else

    uint32_t *data_32 = (uint32_t*)buffer;

    for(size_t i = 0; i < (size >> 2); i++, data_32++)
    {
        uint32_t aWord = *data_32;

        for(size_t j = 0; j < 4; j++)
        {
            crc = (crc >> 4) ^ rtable[(crc ^ ((aWord & 0xff) >> 0)) & 0xf];
            crc = (crc >> 4) ^ rtable[(crc ^ ((aWord & 0xff) >> 4)) & 0xf];
            aWord >>= 8;
        }

    }
    const uint8_t* data_8 = (uint8_t*)data_32;

    for (size_t i = 0; i < (size & 0x3); i++)
    {
        crc = (crc >> 4) ^ rtable[(crc ^ (data_8[i] >> 0)) & 0xf];
        crc = (crc >> 4) ^ rtable[(crc ^ (data_8[i] >> 4)) & 0xf];
    }

#endif
    return crc;
}


#endif