RIOT/sys/net/net_help/net_help.c

/*
 * common.c
 *
 *  Created on: 05.10.2011
 *      Author: Oliver
 */

#include <stdio.h>
#include <thread.h>
#include <string.h>

#include "net_help.h"

uint16_t csum(uint16_t sum, uint8_t *buf, uint16_t len)
	{
    int count;
    uint16_t carry;

    count = len >> 1;
    if(count)
		{
        if(count)
			{
            carry = 0;
            do
				{
                uint16_t t = (*buf << 8) + *(buf+1);
                count--;
                buf += 2;
                sum += carry;
                sum += t;
                carry = (t > sum);
				} while(count);
            sum += carry;
			}
		}
    if(len & 1)
		{
        uint16_t u = (*buf << 8);
        sum += (*buf << 8);
        if(sum < u)
			{
            sum++;
			}
		}

    return sum;
	}