NetChecksum.cpp

//------------------------------------------------------------------------------
//This file is part of embKernel. 
//See license.txt for the full license governing this code.
//------------------------------------------------------------------------------

#include "NetChecksum.hpp"

uint32_t NetChecksum::calcPartialChecksum(uint8_t* buffer, uint16_t len) {
    uint32_t sum = 0;
    uint16_t i = 0;

    if (len <= 0) {
        return 0;
    }

    for (; i < len - 1; i += 2) {
        sum += *((uint16_t*) (&buffer[i]));
    }

    if (i < len) {
        sum += buffer[i];
    }

    return sum;
}

uint16_t NetChecksum::finalizeCheckSum(uint32_t tempCheckSum) {
    while (tempCheckSum >> 16) {
        tempCheckSum = (tempCheckSum & 0xFFFF) + (tempCheckSum >> 16);
    }
    return ~((uint16_t) tempCheckSum);
}