1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Network Checksum & Copy routine
 4 *
 5 * Copyright (C) 1999, 2003-2004 Hewlett-Packard Co
 6 *	Stephane Eranian <eranian@hpl.hp.com>
 7 *
 8 * Most of the code has been imported from Linux/Alpha
 9 */
10
11#include <linux/module.h>
12#include <linux/types.h>
13#include <linux/string.h>
14
15#include <net/checksum.h>
16
17/*
18 * XXX Fixme: those 2 inlines are meant for debugging and will go away
19 */
20static inline unsigned
21short from64to16(unsigned long x)
22{
23	/* add up 32-bit words for 33 bits */
24	x = (x & 0xffffffff) + (x >> 32);
25	/* add up 16-bit and 17-bit words for 17+c bits */
26	x = (x & 0xffff) + (x >> 16);
27	/* add up 16-bit and 2-bit for 16+c bit */
28	x = (x & 0xffff) + (x >> 16);
29	/* add up carry.. */
30	x = (x & 0xffff) + (x >> 16);
31	return x;
32}
33
34static inline
35unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
36{
37	int odd, count;
38	unsigned long result = (unsigned long)psum;
39
40	if (len <= 0)
41		goto out;
42	odd = 1 & (unsigned long) buff;
43	if (odd) {
44		result = *buff << 8;
45		len--;
46		buff++;
47	}
48	count = len >> 1;		/* nr of 16-bit words.. */
49	if (count) {
50		if (2 & (unsigned long) buff) {
51			result += *(unsigned short *) buff;
52			count--;
53			len -= 2;
54			buff += 2;
55		}
56		count >>= 1;		/* nr of 32-bit words.. */
57		if (count) {
58			if (4 & (unsigned long) buff) {
59				result += *(unsigned int *) buff;
60				count--;
61				len -= 4;
62				buff += 4;
63			}
64			count >>= 1;	/* nr of 64-bit words.. */
65			if (count) {
66				unsigned long carry = 0;
67				do {
68					unsigned long w = *(unsigned long *) buff;
69					count--;
70					buff += 8;
71					result += carry;
72					result += w;
73					carry = (w > result);
74				} while (count);
75				result += carry;
76				result = (result & 0xffffffff) + (result >> 32);
77			}
78			if (len & 4) {
79				result += *(unsigned int *) buff;
80				buff += 4;
81			}
82		}
83		if (len & 2) {
84			result += *(unsigned short *) buff;
85			buff += 2;
86		}
87	}
88	if (len & 1)
89		result += *buff;
90
91	result = from64to16(result);
92
93	if (odd)
94		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
95
96out:
97	return result;
98}