mirror of
https://github.com/RIOT-OS/RIOT.git
synced 2024-12-29 04:50:03 +01:00
67 lines
1.6 KiB
C
67 lines
1.6 KiB
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 <inttypes.h>
|
|
#include <stdio.h>
|
|
#include "od.h"
|
|
#include "net/inet_csum.h"
|
|
|
|
#define ENABLE_DEBUG 0
|
|
#include "debug.h"
|
|
|
|
uint16_t inet_csum_slice(uint16_t sum, const uint8_t *buf, uint16_t len, size_t accum_len)
|
|
{
|
|
uint32_t csum = sum;
|
|
|
|
DEBUG("inet_sum: sum = 0x%04" PRIx16 ", len = %" PRIu16, sum, len);
|
|
|
|
if (IS_ACTIVE(ENABLE_DEBUG)) {
|
|
if (IS_USED(MODULE_OD)) {
|
|
DEBUG(", buf:\n");
|
|
od_hex_dump(buf, len, OD_WIDTH_DEFAULT);
|
|
} else {
|
|
DEBUG(", buf output only with od module\n");
|
|
}
|
|
}
|
|
|
|
if (len == 0)
|
|
return csum;
|
|
|
|
if (accum_len & 1) { /* if accumulated length is odd */
|
|
csum += *buf; /* add first byte as bottom half of 16-byte word */
|
|
buf++;
|
|
len--;
|
|
accum_len++;
|
|
}
|
|
|
|
for (unsigned i = 0; i < (len >> 1); buf += 2, i++) {
|
|
csum += (uint16_t)(*buf << 8) + *(buf + 1); /* group bytes by 16-byte words */
|
|
/* and add them */
|
|
}
|
|
|
|
if ((accum_len + len) & 1) /* if accumulated length is odd */
|
|
csum += (uint16_t)(*buf << 8); /* add last byte as top half of 16-byte word */
|
|
|
|
while (csum >> 16) {
|
|
uint16_t carry = csum >> 16;
|
|
csum = (csum & 0xffff) + carry;
|
|
}
|
|
|
|
DEBUG("inet_sum: new sum = 0x%04" PRIx32 "\n", csum);
|
|
|
|
return csum;
|
|
}
|
|
|
|
/** @} */
|