1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21/*
22 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
23 * Use is subject to license terms.
24 */
25
26#include <sys/types.h>
27
28/*
29 * Fast CRC32 calculation algorithm suggested by Ferenc Rakoczi
30 * (ferenc.rakoczi@sun.com).  The basic idea is to look at it
31 * four bytes (one word) at a time, using four tables.  The
32 * standard algorithm in RFC 3309 uses one table.
33 */
34
35/*
36 * SCTP uses reflected/reverse polynomial CRC32 with generating
37 * polynomial 0x1EDC6F41L
38 */
39#define	SCTP_POLY 0x1EDC6F41L
40
41/* The four CRC tables. */
42static uint32_t crctab[4][256];
43
44static uint32_t
45reflect_32(uint32_t b)
46{
47	int i;
48	uint32_t rw = 0;
49
50	for (i = 0; i < 32; i++) {
51		if (b & 1) {
52			rw |= 1 << (31 - i);
53		}
54		b >>= 1;
55	}
56	return (rw);
57}
58
59#ifdef _BIG_ENDIAN
60
61/*
62 * This function is only used for big endian processor.
63 */
64static uint32_t
65flip32(uint32_t w)
66{
67	return (((w >> 24) | ((w >> 8) & 0xff00) | ((w << 8) & 0xff0000) |
68	    (w << 24)));
69}
70
71#endif
72
73void
74sctp_crc32_init(void)
75{
76	uint32_t i, j, k, crc;
77
78	for (i = 0; i < 256; i++) {
79		crc = reflect_32(i);
80		for (k = 0; k < 4; k++) {
81			for (j = 0; j < 8; j++) {
82				crc = (crc & 0x80000000) ?
83				    (crc << 1) ^ SCTP_POLY : crc << 1;
84			}
85#ifdef _BIG_ENDIAN
86			crctab[3 - k][i] = flip32(reflect_32(crc));
87#else
88			crctab[k][i] = reflect_32(crc);
89#endif
90		}
91	}
92}
93
94static void
95sctp_crc_byte(uint32_t *crcptr, const uint8_t *buf, int len)
96{
97	uint32_t crc;
98	int i;
99
100	crc = *crcptr;
101	for (i = 0; i < len; i++) {
102#ifdef _BIG_ENDIAN
103		crc = (crc << 8) ^ crctab[3][buf[i] ^ (crc >> 24)];
104#else
105		crc = (crc >> 8) ^ crctab[0][buf[i] ^ (crc & 0xff)];
106#endif
107	}
108	*crcptr = crc;
109}
110
111static void
112sctp_crc_word(uint32_t *crcptr, const uint32_t *buf, int len)
113{
114	uint32_t w, crc;
115	int i;
116
117	crc = *crcptr;
118	for (i = 0; i < len; i++) {
119		w = crc ^ buf[i];
120		crc = crctab[0][w >> 24] ^ crctab[1][(w >> 16) & 0xff] ^
121		    crctab[2][(w >> 8) & 0xff] ^ crctab[3][w & 0xff];
122	}
123	*crcptr = crc;
124}
125
126uint32_t
127sctp_crc32(uint32_t crc32, const uint8_t *buf, int len)
128{
129	int rem;
130
131	rem = 4 - ((uintptr_t)buf) & 3;
132	if (rem != 0) {
133		if (len < rem) {
134			rem = len;
135		}
136		sctp_crc_byte(&crc32, buf, rem);
137		buf = buf + rem;
138		len = len - rem;
139	}
140
141	if (len > 3) {
142		sctp_crc_word(&crc32, (const uint32_t *)buf, len / 4);
143	}
144
145	rem = len & 3;
146	if (rem != 0) {
147		sctp_crc_byte(&crc32, buf + len - rem, rem);
148	}
149	return (crc32);
150}
151