a752c7ab
 elopes
add first test an...
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/*
* 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 ENABLE_DEBUG
#ifdef MODULE_OD
DEBUG(", buf:\n");
od_hex_dump(buf, len, OD_WIDTH_DEFAULT);
#else
DEBUG(", buf output only with od module\n");
#endif
#endif
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 (int 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;
}
/** @} */
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