FreeBSD/Linux Kernel Cross Reference
sys/net/mppcc.c
1 /*-
2 * Copyright (c) 2002-2004 Jan Dubiec <jdx@slackware.pl>
3 * Copyright (c) 2007 Alexander Motin <mav@freebsd.org>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice unmodified, this list of conditions, and the following
11 * disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * $FreeBSD: releng/12.0/sys/net/mppcc.c 302476 2016-07-09 02:33:45Z pfg $
29 */
30
31 /*
32 * MPPC decompression library.
33 * Version 1.0
34 *
35 * Note that Hi/Fn (later acquired by Exar Corporation) held US patents
36 * on some implementation-critical aspects of MPPC compression.
37 * These patents lapsed due to non-payment of fees in 2007 and by 2015
38 * expired altogether.
39 */
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43
44 #include <net/mppc.h>
45
46 #define MPPE_HIST_LEN 8192
47
48 #define HASH(x) (((40543*(((((x)[0]<<4)^(x)[1])<<4)^(x)[2]))>>4) & 0x1fff)
49
50 struct MPPC_comp_state {
51 uint8_t hist[2*MPPE_HIST_LEN];
52 uint16_t histptr;
53 uint16_t hash[MPPE_HIST_LEN];
54 };
55
56 /* Inserts 1 to 8 bits into the output buffer. */
57 static void __inline
58 putbits8(uint8_t *buf, uint32_t val, const uint32_t n, uint32_t *i, uint32_t *l)
59 {
60 buf += *i;
61 if (*l >= n) {
62 *l = (*l) - n;
63 val <<= *l;
64 *buf = *buf | (val & 0xff);
65 if (*l == 0) {
66 *l = 8;
67 (*i)++;
68 *(++buf) = 0;
69 }
70 } else {
71 (*i)++;
72 *l = 8 - n + (*l);
73 val <<= *l;
74 *buf = *buf | ((val >> 8) & 0xff);
75 *(++buf) = val & 0xff;
76 }
77 }
78
79 /* Inserts 9 to 16 bits into the output buffer. */
80 static void __inline
81 putbits16(uint8_t *buf, uint32_t val, const uint32_t n, uint32_t *i, uint32_t *l)
82 {
83 buf += *i;
84 if (*l >= n - 8) {
85 (*i)++;
86 *l = 8 - n + (*l);
87 val <<= *l;
88 *buf = *buf | ((val >> 8) & 0xff);
89 *(++buf) = val & 0xff;
90 if (*l == 0) {
91 *l = 8;
92 (*i)++;
93 *(++buf) = 0;
94 }
95 } else {
96 (*i)++; (*i)++;
97 *l = 16 - n + (*l);
98 val <<= *l;
99 *buf = *buf | ((val >> 16) & 0xff);
100 *(++buf) = (val >> 8) & 0xff;
101 *(++buf) = val & 0xff;
102 }
103 }
104
105 /* Inserts 17 to 24 bits into the output buffer. */
106 static void __inline
107 putbits24(uint8_t *buf, uint32_t val, const uint32_t n, uint32_t *i, uint32_t *l)
108 {
109 buf += *i;
110 if (*l >= n - 16) {
111 (*i)++; (*i)++;
112 *l = 16 - n + (*l);
113 val <<= *l;
114 *buf = *buf | ((val >> 16) & 0xff);
115 *(++buf) = (val >> 8) & 0xff;
116 *(++buf) = val & 0xff;
117 if (*l == 0) {
118 *l = 8;
119 (*i)++;
120 *(++buf) = 0;
121 }
122 } else {
123 (*i)++; (*i)++; (*i)++;
124 *l = 24 - n + (*l);
125 val <<= *l;
126 *buf = *buf | ((val >> 24) & 0xff);
127 *(++buf) = (val >> 16) & 0xff;
128 *(++buf) = (val >> 8) & 0xff;
129 *(++buf) = val & 0xff;
130 }
131 }
132
133 size_t MPPC_SizeOfCompressionHistory(void)
134 {
135 return (sizeof(struct MPPC_comp_state));
136 }
137
138 void MPPC_InitCompressionHistory(char *history)
139 {
140 struct MPPC_comp_state *state = (struct MPPC_comp_state*)history;
141
142 bzero(history, sizeof(struct MPPC_comp_state));
143 state->histptr = MPPE_HIST_LEN;
144 }
145
146 int MPPC_Compress(u_char **src, u_char **dst, u_long *srcCnt, u_long *dstCnt, char *history, int flags, int undef)
147 {
148 struct MPPC_comp_state *state = (struct MPPC_comp_state*)history;
149 uint32_t olen, off, len, idx, i, l;
150 uint8_t *hist, *sbuf, *p, *q, *r, *s;
151 int rtn = MPPC_OK;
152
153 /*
154 * At this point, to avoid possible buffer overflow caused by packet
155 * expansion during/after compression, we should make sure we have
156 * space for the worst case.
157
158 * Maximum MPPC packet expansion is 12.5%. This is the worst case when
159 * all octets in the input buffer are >= 0x80 and we cannot find any
160 * repeated tokens.
161 */
162 if (*dstCnt < (*srcCnt * 9 / 8 + 2)) {
163 rtn &= ~MPPC_OK;
164 return (rtn);
165 }
166
167 /* We can't compress more then MPPE_HIST_LEN bytes in a call. */
168 if (*srcCnt > MPPE_HIST_LEN) {
169 rtn &= ~MPPC_OK;
170 return (rtn);
171 }
172
173 hist = state->hist + MPPE_HIST_LEN;
174 /* check if there is enough room at the end of the history */
175 if (state->histptr + *srcCnt >= 2*MPPE_HIST_LEN) {
176 rtn |= MPPC_RESTART_HISTORY;
177 state->histptr = MPPE_HIST_LEN;
178 memcpy(state->hist, hist, MPPE_HIST_LEN);
179 }
180 /* Add packet to the history. */
181 sbuf = state->hist + state->histptr;
182 memcpy(sbuf, *src, *srcCnt);
183 state->histptr += *srcCnt;
184
185 /* compress data */
186 r = sbuf + *srcCnt;
187 **dst = olen = i = 0;
188 l = 8;
189 while (i < *srcCnt - 2) {
190 s = q = sbuf + i;
191
192 /* Prognose matching position using hash function. */
193 idx = HASH(s);
194 p = hist + state->hash[idx];
195 state->hash[idx] = (uint16_t) (s - hist);
196 if (p > s) /* It was before MPPC_RESTART_HISTORY. */
197 p -= MPPE_HIST_LEN; /* Try previous history buffer. */
198 off = s - p;
199
200 /* Check our prognosis. */
201 if (off > MPPE_HIST_LEN - 1 || off < 1 || *p++ != *s++ ||
202 *p++ != *s++ || *p++ != *s++) {
203 /* No match found; encode literal byte. */
204 if ((*src)[i] < 0x80) { /* literal byte < 0x80 */
205 putbits8(*dst, (uint32_t) (*src)[i], 8, &olen, &l);
206 } else { /* literal byte >= 0x80 */
207 putbits16(*dst, (uint32_t) (0x100|((*src)[i]&0x7f)), 9,
208 &olen, &l);
209 }
210 ++i;
211 continue;
212 }
213
214 /* Find length of the matching fragment */
215 #if defined(__amd64__) || defined(__i386__)
216 /* Optimization for CPUs without strict data aligning requirements */
217 while ((*((uint32_t*)p) == *((uint32_t*)s)) && (s < (r - 3))) {
218 p+=4;
219 s+=4;
220 }
221 #endif
222 while((*p++ == *s++) && (s <= r));
223 len = s - q - 1;
224 i += len;
225
226 /* At least 3 character match found; code data. */
227 /* Encode offset. */
228 if (off < 64) { /* 10-bit offset; 0 <= offset < 64 */
229 putbits16(*dst, 0x3c0|off, 10, &olen, &l);
230 } else if (off < 320) { /* 12-bit offset; 64 <= offset < 320 */
231 putbits16(*dst, 0xe00|(off-64), 12, &olen, &l);
232 } else if (off < 8192) { /* 16-bit offset; 320 <= offset < 8192 */
233 putbits16(*dst, 0xc000|(off-320), 16, &olen, &l);
234 } else { /* NOTREACHED */
235 __unreachable();
236 rtn &= ~MPPC_OK;
237 return (rtn);
238 }
239
240 /* Encode length of match. */
241 if (len < 4) { /* length = 3 */
242 putbits8(*dst, 0, 1, &olen, &l);
243 } else if (len < 8) { /* 4 <= length < 8 */
244 putbits8(*dst, 0x08|(len&0x03), 4, &olen, &l);
245 } else if (len < 16) { /* 8 <= length < 16 */
246 putbits8(*dst, 0x30|(len&0x07), 6, &olen, &l);
247 } else if (len < 32) { /* 16 <= length < 32 */
248 putbits8(*dst, 0xe0|(len&0x0f), 8, &olen, &l);
249 } else if (len < 64) { /* 32 <= length < 64 */
250 putbits16(*dst, 0x3c0|(len&0x1f), 10, &olen, &l);
251 } else if (len < 128) { /* 64 <= length < 128 */
252 putbits16(*dst, 0xf80|(len&0x3f), 12, &olen, &l);
253 } else if (len < 256) { /* 128 <= length < 256 */
254 putbits16(*dst, 0x3f00|(len&0x7f), 14, &olen, &l);
255 } else if (len < 512) { /* 256 <= length < 512 */
256 putbits16(*dst, 0xfe00|(len&0xff), 16, &olen, &l);
257 } else if (len < 1024) { /* 512 <= length < 1024 */
258 putbits24(*dst, 0x3fc00|(len&0x1ff), 18, &olen, &l);
259 } else if (len < 2048) { /* 1024 <= length < 2048 */
260 putbits24(*dst, 0xff800|(len&0x3ff), 20, &olen, &l);
261 } else if (len < 4096) { /* 2048 <= length < 4096 */
262 putbits24(*dst, 0x3ff000|(len&0x7ff), 22, &olen, &l);
263 } else if (len < 8192) { /* 4096 <= length < 8192 */
264 putbits24(*dst, 0xffe000|(len&0xfff), 24, &olen, &l);
265 } else { /* NOTREACHED */
266 rtn &= ~MPPC_OK;
267 return (rtn);
268 }
269 }
270
271 /* Add remaining octets to the output. */
272 while(*srcCnt - i > 0) {
273 if ((*src)[i] < 0x80) { /* literal byte < 0x80 */
274 putbits8(*dst, (uint32_t) (*src)[i++], 8, &olen, &l);
275 } else { /* literal byte >= 0x80 */
276 putbits16(*dst, (uint32_t) (0x100|((*src)[i++]&0x7f)), 9, &olen,
277 &l);
278 }
279 }
280
281 /* Reset unused bits of the last output octet. */
282 if ((l != 0) && (l != 8)) {
283 putbits8(*dst, 0, l, &olen, &l);
284 }
285
286 /* If result is bigger then original, set flag and flush history. */
287 if ((*srcCnt < olen) || ((flags & MPPC_SAVE_HISTORY) == 0)) {
288 if (*srcCnt < olen)
289 rtn |= MPPC_EXPANDED;
290 bzero(history, sizeof(struct MPPC_comp_state));
291 state->histptr = MPPE_HIST_LEN;
292 }
293
294 *src += *srcCnt;
295 *srcCnt = 0;
296 *dst += olen;
297 *dstCnt -= olen;
298
299 return (rtn);
300 }
Cache object: 811b495d1523e28a671404537eaf3645
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