mirror of
https://github.com/RIOT-OS/RIOT.git
synced 2024-12-29 04:50:03 +01:00
37 lines
842 B
C
37 lines
842 B
C
|
/*
|
||
|
|
* Copyright (C) 2015 Martine Lenders <mlenders@inf.fu-berlin.de>
|
||
|
|
*
|
||
|
|
* This file is subject to the terms and conditions of the GNU Lesser
|
||
|
|
* General Public License v2.1. See the file LICENSE in the top level
|
||
|
|
* directory for more details.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/**
|
||
|
|
* @{
|
||
|
|
*
|
||
|
|
* @file
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <stdio.h>
|
||
|
|
#include "net/ng_inet_csum.h"
|
||
|
|
|
||
|
|
uint16_t ng_inet_csum(uint16_t sum, const uint8_t *buf, uint16_t len)
|
||
|
|
{
|
||
|
|
uint32_t csum = sum;
|
||
|
|
|
||
|
|
for (int i = 0; i < (len >> 1); buf += 2, i++) {
|
||
|
|
csum += (*buf << 8) + *(buf + 1); /* group bytes by 16-byte words
|
||
|
|
* and add them*/
|
||
|
|
}
|
||
|
|
|
||
|
|
if (len & 1) { /* if len is odd */
|
||
|
|
csum += (*buf << 8); /* add last byte as top half of 16-byte word */
|
||
|
|
}
|
||
|
|
|
||
|
|
csum += csum >> 16;
|
||
|
|
|
||
|
|
return (csum & 0xffff);
|
||
|
|
}
|
||
|
|
|
||
|
|
/** @} */
|