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// SPDX-License-Identifier: GPL-2.0
/*
* Network Checksum & Copy routine
*
* Copyright (C) 1999, 2003-2004 Hewlett-Packard Co
* Stephane Eranian <eranian@hpl.hp.com>
*
* Most of the code has been imported from Linux/Alpha
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <net/checksum.h>
/*
* XXX Fixme: those 2 inlines are meant for debugging and will go away
*/
static inline unsigned
short from64to16(unsigned long x)
{
/* add up 32-bit words for 33 bits */
x = (x & 0xffffffff) + (x >> 32);
/* add up 16-bit and 17-bit words for 17+c bits */
x = (x & 0xffff) + (x >> 16);
/* add up 16-bit and 2-bit for 16+c bit */
x = (x & 0xffff) + (x >> 16);
/* add up carry.. */
x = (x & 0xffff) + (x >> 16);
return x;
}
static inline
unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
{
int odd, count;
unsigned long result = (unsigned long)psum;
if (len <= 0)
goto out;
odd = 1 & (unsigned long) buff;
if (odd) {
result = *buff << 8;
len--;
buff++;
}
count = len >> 1; /* nr of 16-bit words.. */
if (count) {
if (2 & (unsigned long) buff) {
result += *(unsigned short *) buff;
count--;
len -= 2;
buff += 2;
}
count >>= 1; /* nr of 32-bit words.. */
if (count) {
if (4 & (unsigned long) buff) {
result += *(unsigned int *) buff;
count--;
len -= 4;
buff += 4;
}
count >>= 1; /* nr of 64-bit words.. */
if (count) {
unsigned long carry = 0;
do {
unsigned long w = *(unsigned long *) buff;
count--;
buff += 8;
result += carry;
result += w;
carry = (w > result);
} while (count);
result += carry;
result = (result & 0xffffffff) + (result >> 32);
}
if (len & 4) {
result += *(unsigned int *) buff;
buff += 4;
}
}
if (len & 2) {
result += *(unsigned short *) buff;
buff += 2;
}
}
if (len & 1)
result += *buff;
result = from64to16(result);
if (odd)
result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
out:
return result;
}
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