/**
 * @file crc32.c
 *
 * Copyright (c) 2021 Semidrive Semiconductor.
 * All rights reserved.
 *
 * Description:compute the CRC-32 of a data stream
 */

#include <stddef.h>

#include "crc32_data.h"

#define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
#define DO8                                                                    \
    DO1;                                                                       \
    DO1;                                                                       \
    DO1;                                                                       \
    DO1;                                                                       \
    DO1;                                                                       \
    DO1;                                                                       \
    DO1;                                                                       \
    DO1

/**
 * @brief Calculate the CRC-32 checksum for a given data buffer.This function
 * uses a predefined CRC-32 table to compute the CRC-32 checksum of the input
 * data buffer.
 *
 * @param crc Initial CRC value, typically 0.
 * @param buf Pointer to the unsigned character data buffer for which the CRC-32
 * is to be calculated.
 * @param len Length of the data buffer in bytes.
 * @return The computed CRC-32 checksum.
 */
unsigned long crc32(unsigned long crc, const unsigned char *buf,
                    unsigned int len)
{
    if (buf == NULL)
        return 0UL;

    crc = crc ^ 0xffffffffUL;
    while (len >= 8) {
        DO8;
        len -= 8;
    }
    if (len)
        do {
            DO1;
        } while (--len);
    return crc ^ 0xffffffffUL;
}