/*
 * eth_checksum.c
 *
 *  Created on: 13 мар. 2023 г.
 *      Author: sychev
 */
#include "ethernet_ip/eth_checksum.h"

uint16_t eth_calcChksum(uint32_t sum, uint8_t * const data, uint16_t len)
{
    uint16_t i;
    uint16_t size = len - 1;

    if ( !len )
      return 0;

    for ( i = 0; i < size; i+=2 )
      sum += ((uint16_t)data[i] << 8) + data[i+1];

    if (len & 0x01)
      sum += (uint16_t)data[i] << 8;

    while ( sum >> 16 )
      sum = (sum & 0xFFFF) + (sum >> 16);

    return ~sum;
}