4ba9b64b |
1 | /* |
2 | * Zlib (RFC1950 / RFC1951) compression for PuTTY. |
3 | * |
4 | * There will no doubt be criticism of my decision to reimplement |
5 | * Zlib compression from scratch instead of using the existing zlib |
6 | * code. People will cry `reinventing the wheel'; they'll claim |
7 | * that the `fundamental basis of OSS' is code reuse; they'll want |
8 | * to see a really good reason for me having chosen not to use the |
9 | * existing code. |
10 | * |
11 | * Well, here are my reasons. Firstly, I don't want to link the |
12 | * whole of zlib into the PuTTY binary; PuTTY is justifiably proud |
13 | * of its small size and I think zlib contains a lot of unnecessary |
14 | * baggage for the kind of compression that SSH requires. |
15 | * |
16 | * Secondly, I also don't like the alternative of using zlib.dll. |
17 | * Another thing PuTTY is justifiably proud of is its ease of |
18 | * installation, and the last thing I want to do is to start |
19 | * mandating DLLs. Not only that, but there are two _kinds_ of |
20 | * zlib.dll kicking around, one with C calling conventions on the |
21 | * exported functions and another with WINAPI conventions, and |
22 | * there would be a significant danger of getting the wrong one. |
23 | * |
24 | * Thirdly, there seems to be a difference of opinion on the IETF |
25 | * secsh mailing list about the correct way to round off a |
26 | * compressed packet and start the next. In particular, there's |
27 | * some talk of switching to a mechanism zlib isn't currently |
28 | * capable of supporting (see below for an explanation). Given that |
29 | * sort of uncertainty, I thought it might be better to have code |
30 | * that will support even the zlib-incompatible worst case. |
31 | * |
32 | * Fourthly, it's a _second implementation_. Second implementations |
33 | * are fundamentally a Good Thing in standardisation efforts. The |
34 | * difference of opinion mentioned above has arisen _precisely_ |
35 | * because there has been only one zlib implementation and |
36 | * everybody has used it. I don't intend that this should happen |
37 | * again. |
38 | */ |
39 | |
40 | #include <stdlib.h> |
41 | #include <assert.h> |
42 | |
43 | /* FIXME */ |
44 | #include <windows.h> |
45 | #include <stdio.h> |
46 | #include "putty.h" |
47 | |
48 | #include "ssh.h" |
49 | |
50 | /* ---------------------------------------------------------------------- |
51 | * Basic LZ77 code. This bit is designed modularly, so it could be |
52 | * ripped out and used in a different LZ77 compressor. Go to it, |
53 | * and good luck :-) |
54 | */ |
55 | |
56 | struct LZ77InternalContext; |
57 | struct LZ77Context { |
58 | struct LZ77InternalContext *ictx; |
59 | void *userdata; |
60 | void (*literal)(struct LZ77Context *ctx, unsigned char c); |
61 | void (*match)(struct LZ77Context *ctx, int distance, int len); |
62 | }; |
63 | |
64 | /* |
65 | * Initialise the private fields of an LZ77Context. It's up to the |
66 | * user to initialise the public fields. |
67 | */ |
68 | static int lz77_init(struct LZ77Context *ctx); |
69 | |
70 | /* |
71 | * Supply data to be compressed. Will update the private fields of |
72 | * the LZ77Context, and will call literal() and match() to output. |
6e9e9520 |
73 | * If `compress' is FALSE, it will never emit a match, but will |
74 | * instead call literal() for everything. |
4ba9b64b |
75 | */ |
76 | static void lz77_compress(struct LZ77Context *ctx, |
6e9e9520 |
77 | unsigned char *data, int len, int compress); |
4ba9b64b |
78 | |
79 | /* |
80 | * Modifiable parameters. |
81 | */ |
82 | #define WINSIZE 32768 /* window size. Must be power of 2! */ |
83 | #define HASHMAX 2039 /* one more than max hash value */ |
84 | #define MAXMATCH 32 /* how many matches we track */ |
85 | #define HASHCHARS 3 /* how many chars make a hash */ |
86 | |
87 | /* |
88 | * This compressor takes a less slapdash approach than the |
89 | * gzip/zlib one. Rather than allowing our hash chains to fall into |
90 | * disuse near the far end, we keep them doubly linked so we can |
91 | * _find_ the far end, and then every time we add a new byte to the |
92 | * window (thus rolling round by one and removing the previous |
93 | * byte), we can carefully remove the hash chain entry. |
94 | */ |
95 | |
96 | #define INVALID -1 /* invalid hash _and_ invalid offset */ |
97 | struct WindowEntry { |
d2371c81 |
98 | short next, prev; /* array indices within the window */ |
99 | short hashval; |
4ba9b64b |
100 | }; |
101 | |
102 | struct HashEntry { |
d2371c81 |
103 | short first; /* window index of first in chain */ |
4ba9b64b |
104 | }; |
105 | |
106 | struct Match { |
107 | int distance, len; |
108 | }; |
109 | |
110 | struct LZ77InternalContext { |
111 | struct WindowEntry win[WINSIZE]; |
112 | unsigned char data[WINSIZE]; |
113 | int winpos; |
114 | struct HashEntry hashtab[HASHMAX]; |
115 | unsigned char pending[HASHCHARS]; |
116 | int npending; |
117 | }; |
118 | |
119 | static int lz77_hash(unsigned char *data) { |
120 | return (257*data[0] + 263*data[1] + 269*data[2]) % HASHMAX; |
121 | } |
122 | |
123 | static int lz77_init(struct LZ77Context *ctx) { |
124 | struct LZ77InternalContext *st; |
125 | int i; |
126 | |
dcbde236 |
127 | st = (struct LZ77InternalContext *)smalloc(sizeof(*st)); |
4ba9b64b |
128 | if (!st) |
129 | return 0; |
130 | |
131 | ctx->ictx = st; |
132 | |
133 | for (i = 0; i < WINSIZE; i++) |
134 | st->win[i].next = st->win[i].prev = st->win[i].hashval = INVALID; |
135 | for (i = 0; i < HASHMAX; i++) |
136 | st->hashtab[i].first = INVALID; |
137 | st->winpos = 0; |
138 | |
139 | st->npending = 0; |
140 | |
141 | return 1; |
142 | } |
143 | |
144 | static void lz77_advance(struct LZ77InternalContext *st, |
145 | unsigned char c, int hash) { |
146 | int off; |
147 | |
148 | /* |
149 | * Remove the hash entry at winpos from the tail of its chain, |
150 | * or empty the chain if it's the only thing on the chain. |
151 | */ |
152 | if (st->win[st->winpos].prev != INVALID) { |
153 | st->win[st->win[st->winpos].prev].next = INVALID; |
154 | } else if (st->win[st->winpos].hashval != INVALID) { |
155 | st->hashtab[st->win[st->winpos].hashval].first = INVALID; |
156 | } |
157 | |
158 | /* |
159 | * Create a new entry at winpos and add it to the head of its |
160 | * hash chain. |
161 | */ |
162 | st->win[st->winpos].hashval = hash; |
163 | st->win[st->winpos].prev = INVALID; |
164 | off = st->win[st->winpos].next = st->hashtab[hash].first; |
165 | st->hashtab[hash].first = st->winpos; |
166 | if (off != INVALID) |
167 | st->win[off].prev = st->winpos; |
168 | st->data[st->winpos] = c; |
169 | |
170 | /* |
171 | * Advance the window pointer. |
172 | */ |
173 | st->winpos = (st->winpos + 1) & (WINSIZE-1); |
174 | } |
175 | |
176 | #define CHARAT(k) ( (k)<0 ? st->data[(st->winpos+k)&(WINSIZE-1)] : data[k] ) |
177 | |
178 | static void lz77_compress(struct LZ77Context *ctx, |
6e9e9520 |
179 | unsigned char *data, int len, int compress) { |
4ba9b64b |
180 | struct LZ77InternalContext *st = ctx->ictx; |
181 | int i, hash, distance, off, nmatch, matchlen, advance; |
182 | struct Match defermatch, matches[MAXMATCH]; |
183 | int deferchr; |
184 | |
185 | /* |
186 | * Add any pending characters from last time to the window. (We |
187 | * might not be able to.) |
188 | */ |
189 | for (i = 0; i < st->npending; i++) { |
190 | unsigned char foo[HASHCHARS]; |
191 | int j; |
192 | if (len + st->npending - i < HASHCHARS) { |
193 | /* Update the pending array. */ |
194 | for (j = i; j < st->npending; j++) |
195 | st->pending[j-i] = st->pending[j]; |
196 | break; |
197 | } |
198 | for (j = 0; j < HASHCHARS; j++) |
199 | foo[j] = (i + j < st->npending ? st->pending[i+j] : |
200 | data[i + j - st->npending]); |
201 | lz77_advance(st, foo[0], lz77_hash(foo)); |
202 | } |
203 | st->npending -= i; |
204 | |
205 | defermatch.len = 0; |
206 | while (len > 0) { |
207 | |
6e9e9520 |
208 | /* Don't even look for a match, if we're not compressing. */ |
209 | if (compress && len >= HASHCHARS) { |
4ba9b64b |
210 | /* |
211 | * Hash the next few characters. |
212 | */ |
213 | hash = lz77_hash(data); |
214 | |
215 | /* |
216 | * Look the hash up in the corresponding hash chain and see |
217 | * what we can find. |
218 | */ |
219 | nmatch = 0; |
220 | for (off = st->hashtab[hash].first; |
221 | off != INVALID; off = st->win[off].next) { |
222 | /* distance = 1 if off == st->winpos-1 */ |
223 | /* distance = WINSIZE if off == st->winpos */ |
224 | distance = WINSIZE - (off + WINSIZE - st->winpos) % WINSIZE; |
225 | for (i = 0; i < HASHCHARS; i++) |
226 | if (CHARAT(i) != CHARAT(i-distance)) |
227 | break; |
228 | if (i == HASHCHARS) { |
229 | matches[nmatch].distance = distance; |
230 | matches[nmatch].len = 3; |
231 | if (++nmatch >= MAXMATCH) |
232 | break; |
233 | } |
234 | } |
235 | } else { |
236 | nmatch = 0; |
237 | hash = INVALID; |
238 | } |
239 | |
240 | if (nmatch > 0) { |
241 | /* |
242 | * We've now filled up matches[] with nmatch potential |
243 | * matches. Follow them down to find the longest. (We |
244 | * assume here that it's always worth favouring a |
245 | * longer match over a shorter one.) |
246 | */ |
247 | matchlen = HASHCHARS; |
248 | while (matchlen < len) { |
249 | int j; |
250 | for (i = j = 0; i < nmatch; i++) { |
251 | if (CHARAT(matchlen) == |
252 | CHARAT(matchlen - matches[i].distance)) { |
253 | matches[j++] = matches[i]; |
254 | } |
255 | } |
256 | if (j == 0) |
257 | break; |
258 | matchlen++; |
259 | nmatch = j; |
260 | } |
261 | |
262 | /* |
263 | * We've now got all the longest matches. We favour the |
264 | * shorter distances, which means we go with matches[0]. |
265 | * So see if we want to defer it or throw it away. |
266 | */ |
267 | matches[0].len = matchlen; |
268 | if (defermatch.len > 0) { |
269 | if (matches[0].len > defermatch.len + 1) { |
270 | /* We have a better match. Emit the deferred char, |
271 | * and defer this match. */ |
272 | ctx->literal(ctx, (unsigned char)deferchr); |
273 | defermatch = matches[0]; |
274 | deferchr = data[0]; |
275 | advance = 1; |
276 | } else { |
277 | /* We don't have a better match. Do the deferred one. */ |
278 | ctx->match(ctx, defermatch.distance, defermatch.len); |
279 | advance = defermatch.len - 1; |
280 | defermatch.len = 0; |
281 | } |
282 | } else { |
283 | /* There was no deferred match. Defer this one. */ |
284 | defermatch = matches[0]; |
285 | deferchr = data[0]; |
286 | advance = 1; |
287 | } |
288 | } else { |
289 | /* |
290 | * We found no matches. Emit the deferred match, if |
291 | * any; otherwise emit a literal. |
292 | */ |
293 | if (defermatch.len > 0) { |
294 | ctx->match(ctx, defermatch.distance, defermatch.len); |
295 | advance = defermatch.len - 1; |
296 | defermatch.len = 0; |
297 | } else { |
298 | ctx->literal(ctx, data[0]); |
299 | advance = 1; |
300 | } |
301 | } |
302 | |
303 | /* |
304 | * Now advance the position by `advance' characters, |
305 | * keeping the window and hash chains consistent. |
306 | */ |
307 | while (advance > 0) { |
308 | if (len >= HASHCHARS) { |
309 | lz77_advance(st, *data, lz77_hash(data)); |
310 | } else { |
311 | st->pending[st->npending++] = *data; |
312 | } |
313 | data++; |
314 | len--; |
315 | advance--; |
316 | } |
317 | } |
318 | } |
319 | |
320 | /* ---------------------------------------------------------------------- |
321 | * Zlib compression. We always use the static Huffman tree option. |
322 | * Mostly this is because it's hard to scan a block in advance to |
323 | * work out better trees; dynamic trees are great when you're |
324 | * compressing a large file under no significant time constraint, |
325 | * but when you're compressing little bits in real time, things get |
326 | * hairier. |
327 | * |
328 | * I suppose it's possible that I could compute Huffman trees based |
329 | * on the frequencies in the _previous_ block, as a sort of |
330 | * heuristic, but I'm not confident that the gain would balance out |
331 | * having to transmit the trees. |
332 | */ |
333 | |
334 | static struct LZ77Context ectx; |
335 | |
336 | struct Outbuf { |
337 | unsigned char *outbuf; |
338 | int outlen, outsize; |
339 | unsigned long outbits; |
340 | int noutbits; |
341 | int firstblock; |
6e9e9520 |
342 | int comp_disabled; |
4ba9b64b |
343 | }; |
344 | |
345 | static void outbits(struct Outbuf *out, unsigned long bits, int nbits) { |
346 | assert(out->noutbits + nbits <= 32); |
347 | out->outbits |= bits << out->noutbits; |
348 | out->noutbits += nbits; |
349 | while (out->noutbits >= 8) { |
350 | if (out->outlen >= out->outsize) { |
351 | out->outsize = out->outlen + 64; |
dcbde236 |
352 | out->outbuf = srealloc(out->outbuf, out->outsize); |
4ba9b64b |
353 | } |
354 | out->outbuf[out->outlen++] = (unsigned char)(out->outbits & 0xFF); |
355 | out->outbits >>= 8; |
356 | out->noutbits -= 8; |
357 | } |
358 | } |
359 | |
360 | static const unsigned char mirrorbytes[256] = { |
361 | 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, |
362 | 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0, |
363 | 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, |
364 | 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8, |
365 | 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, |
366 | 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4, |
367 | 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, |
368 | 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc, |
369 | 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, |
370 | 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2, |
371 | 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea, |
372 | 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa, |
373 | 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, |
374 | 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6, |
375 | 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, |
376 | 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe, |
377 | 0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1, |
378 | 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1, |
379 | 0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, |
380 | 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9, |
381 | 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5, |
382 | 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5, |
383 | 0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed, |
384 | 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd, |
385 | 0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, |
386 | 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3, |
387 | 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb, |
388 | 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb, |
389 | 0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7, |
390 | 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7, |
391 | 0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, |
392 | 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff, |
393 | }; |
394 | |
395 | typedef struct { |
d2371c81 |
396 | short code, extrabits; |
397 | int min, max; |
4ba9b64b |
398 | } coderecord; |
399 | |
400 | static const coderecord lencodes[] = { |
401 | {257, 0, 3,3}, |
402 | {258, 0, 4,4}, |
403 | {259, 0, 5,5}, |
404 | {260, 0, 6,6}, |
405 | {261, 0, 7,7}, |
406 | {262, 0, 8,8}, |
407 | {263, 0, 9,9}, |
408 | {264, 0, 10,10}, |
409 | {265, 1, 11,12}, |
410 | {266, 1, 13,14}, |
411 | {267, 1, 15,16}, |
412 | {268, 1, 17,18}, |
413 | {269, 2, 19,22}, |
414 | {270, 2, 23,26}, |
415 | {271, 2, 27,30}, |
416 | {272, 2, 31,34}, |
417 | {273, 3, 35,42}, |
418 | {274, 3, 43,50}, |
419 | {275, 3, 51,58}, |
420 | {276, 3, 59,66}, |
421 | {277, 4, 67,82}, |
422 | {278, 4, 83,98}, |
423 | {279, 4, 99,114}, |
424 | {280, 4, 115,130}, |
425 | {281, 5, 131,162}, |
426 | {282, 5, 163,194}, |
427 | {283, 5, 195,226}, |
428 | {284, 5, 227,257}, |
429 | {285, 0, 258,258}, |
430 | }; |
431 | |
432 | static const coderecord distcodes[] = { |
433 | {0, 0, 1,1}, |
434 | {1, 0, 2,2}, |
435 | {2, 0, 3,3}, |
436 | {3, 0, 4,4}, |
437 | {4, 1, 5,6}, |
438 | {5, 1, 7,8}, |
439 | {6, 2, 9,12}, |
440 | {7, 2, 13,16}, |
441 | {8, 3, 17,24}, |
442 | {9, 3, 25,32}, |
443 | {10, 4, 33,48}, |
444 | {11, 4, 49,64}, |
445 | {12, 5, 65,96}, |
446 | {13, 5, 97,128}, |
447 | {14, 6, 129,192}, |
448 | {15, 6, 193,256}, |
449 | {16, 7, 257,384}, |
450 | {17, 7, 385,512}, |
451 | {18, 8, 513,768}, |
452 | {19, 8, 769,1024}, |
453 | {20, 9, 1025,1536}, |
454 | {21, 9, 1537,2048}, |
455 | {22, 10, 2049,3072}, |
456 | {23, 10, 3073,4096}, |
457 | {24, 11, 4097,6144}, |
458 | {25, 11, 6145,8192}, |
459 | {26, 12, 8193,12288}, |
460 | {27, 12, 12289,16384}, |
461 | {28, 13, 16385,24576}, |
462 | {29, 13, 24577,32768}, |
463 | }; |
464 | |
465 | static void zlib_literal(struct LZ77Context *ectx, unsigned char c) { |
466 | struct Outbuf *out = (struct Outbuf *)ectx->userdata; |
467 | |
6e9e9520 |
468 | if (out->comp_disabled) { |
469 | /* |
470 | * We're in an uncompressed block, so just output the byte. |
471 | */ |
472 | outbits(out, c, 8); |
473 | return; |
474 | } |
475 | |
4ba9b64b |
476 | if (c <= 143) { |
477 | /* 0 through 143 are 8 bits long starting at 00110000. */ |
478 | outbits(out, mirrorbytes[0x30 + c], 8); |
479 | } else { |
480 | /* 144 through 255 are 9 bits long starting at 110010000. */ |
481 | outbits(out, 1 + 2*mirrorbytes[0x90 - 144 + c], 9); |
482 | } |
483 | } |
484 | |
485 | static void zlib_match(struct LZ77Context *ectx, int distance, int len) { |
486 | const coderecord *d, *l; |
487 | int i, j, k; |
488 | struct Outbuf *out = (struct Outbuf *)ectx->userdata; |
6e9e9520 |
489 | |
490 | assert(!out->comp_disabled); |
491 | |
4ba9b64b |
492 | while (len > 0) { |
493 | int thislen; |
494 | |
495 | /* |
496 | * We can transmit matches of lengths 3 through 258 |
497 | * inclusive. So if len exceeds 258, we must transmit in |
498 | * several steps, with 258 or less in each step. |
499 | * |
500 | * Specifically: if len >= 261, we can transmit 258 and be |
501 | * sure of having at least 3 left for the next step. And if |
502 | * len <= 258, we can just transmit len. But if len == 259 |
503 | * or 260, we must transmit len-3. |
504 | */ |
505 | thislen = (len > 260 ? 258 : len <= 258 ? len : len-3); |
506 | len -= thislen; |
507 | |
508 | /* |
509 | * Binary-search to find which length code we're |
510 | * transmitting. |
511 | */ |
512 | i = -1; j = sizeof(lencodes)/sizeof(*lencodes); |
513 | while (j - i >= 2) { |
514 | k = (j+i)/2; |
515 | if (thislen < lencodes[k].min) |
516 | j = k; |
517 | else if (thislen > lencodes[k].max) |
518 | i = k; |
519 | else { |
520 | l = &lencodes[k]; |
521 | break; /* found it! */ |
522 | } |
523 | } |
524 | |
525 | /* |
526 | * Transmit the length code. 256-279 are seven bits |
527 | * starting at 0000000; 280-287 are eight bits starting at |
528 | * 11000000. |
529 | */ |
530 | if (l->code <= 279) { |
531 | outbits(out, mirrorbytes[(l->code-256)*2], 7); |
532 | } else { |
533 | outbits(out, mirrorbytes[0xc0 - 280 + l->code], 8); |
534 | } |
535 | |
536 | /* |
537 | * Transmit the extra bits. |
538 | */ |
539 | if (l->extrabits) |
540 | outbits(out, thislen - l->min, l->extrabits); |
541 | |
542 | /* |
543 | * Binary-search to find which distance code we're |
544 | * transmitting. |
545 | */ |
546 | i = -1; j = sizeof(distcodes)/sizeof(*distcodes); |
547 | while (j - i >= 2) { |
548 | k = (j+i)/2; |
549 | if (distance < distcodes[k].min) |
550 | j = k; |
551 | else if (distance > distcodes[k].max) |
552 | i = k; |
553 | else { |
554 | d = &distcodes[k]; |
555 | break; /* found it! */ |
556 | } |
557 | } |
558 | |
559 | /* |
560 | * Transmit the distance code. Five bits starting at 00000. |
561 | */ |
562 | outbits(out, mirrorbytes[d->code*8], 5); |
563 | |
564 | /* |
565 | * Transmit the extra bits. |
566 | */ |
567 | if (d->extrabits) |
568 | outbits(out, distance - d->min, d->extrabits); |
569 | } |
570 | } |
571 | |
572 | void zlib_compress_init(void) { |
573 | struct Outbuf *out; |
574 | |
575 | lz77_init(&ectx); |
576 | ectx.literal = zlib_literal; |
577 | ectx.match = zlib_match; |
578 | |
dcbde236 |
579 | out = smalloc(sizeof(struct Outbuf)); |
4ba9b64b |
580 | out->outbits = out->noutbits = 0; |
581 | out->firstblock = 1; |
6e9e9520 |
582 | out->comp_disabled = FALSE; |
4ba9b64b |
583 | ectx.userdata = out; |
584 | |
585 | logevent("Initialised zlib (RFC1950) compression"); |
586 | } |
587 | |
6e9e9520 |
588 | /* |
589 | * Turn off actual LZ77 analysis for one block, to facilitate |
590 | * construction of a precise-length IGNORE packet. Returns the |
591 | * length adjustment (which is only valid for packets < 65536 |
592 | * bytes, but that seems reasonable enough). |
593 | */ |
594 | int zlib_disable_compression(void) { |
595 | struct Outbuf *out = (struct Outbuf *)ectx.userdata; |
dae2b91f |
596 | int n; |
6e9e9520 |
597 | |
598 | out->comp_disabled = TRUE; |
599 | |
600 | n = 0; |
601 | /* |
602 | * If this is the first block, we will start by outputting two |
603 | * header bytes, and then three bits to begin an uncompressed |
604 | * block. This will cost three bytes (because we will start on |
605 | * a byte boundary, this is certain). |
606 | */ |
607 | if (out->firstblock) { |
608 | n = 3; |
609 | } else { |
610 | /* |
611 | * Otherwise, we will output seven bits to close the |
612 | * previous static block, and _then_ three bits to begin an |
613 | * uncompressed block, and then flush the current byte. |
614 | * This may cost two bytes or three, depending on noutbits. |
615 | */ |
616 | n += (out->noutbits + 10) / 8; |
617 | } |
618 | |
619 | /* |
620 | * Now we output four bytes for the length / ~length pair in |
621 | * the uncompressed block. |
622 | */ |
623 | n += 4; |
624 | |
625 | return n; |
626 | } |
627 | |
4ba9b64b |
628 | int zlib_compress_block(unsigned char *block, int len, |
629 | unsigned char **outblock, int *outlen) { |
630 | struct Outbuf *out = (struct Outbuf *)ectx.userdata; |
6e9e9520 |
631 | int in_block; |
4ba9b64b |
632 | |
633 | out->outbuf = NULL; |
634 | out->outlen = out->outsize = 0; |
635 | |
636 | /* |
637 | * If this is the first block, output the Zlib (RFC1950) header |
638 | * bytes 78 9C. (Deflate compression, 32K window size, default |
639 | * algorithm.) |
640 | */ |
641 | if (out->firstblock) { |
642 | outbits(out, 0x9C78, 16); |
643 | out->firstblock = 0; |
6e9e9520 |
644 | |
645 | in_block = FALSE; |
4ba9b64b |
646 | } |
647 | |
6e9e9520 |
648 | if (out->comp_disabled) { |
649 | if (in_block) |
650 | outbits(out, 0, 7); /* close static block */ |
651 | |
652 | while (len > 0) { |
653 | int blen = (len < 65535 ? len : 65535); |
654 | |
655 | /* |
656 | * Start a Deflate (RFC1951) uncompressed block. We |
657 | * transmit a zero bit (BFINAL=0), followed by a zero |
658 | * bit and a one bit (BTYPE=00). Of course these are in |
659 | * the wrong order (00 0). |
660 | */ |
661 | outbits(out, 0, 3); |
662 | |
663 | /* |
664 | * Output zero bits to align to a byte boundary. |
665 | */ |
666 | if (out->noutbits) |
667 | outbits(out, 0, 8 - out->noutbits); |
668 | |
669 | /* |
670 | * Output the block length, and then its one's |
671 | * complement. They're little-endian, so all we need to |
672 | * do is pass them straight to outbits() with bit count |
673 | * 16. |
674 | */ |
675 | outbits(out, blen, 16); |
676 | outbits(out, blen ^ 0xFFFF, 16); |
677 | |
678 | /* |
679 | * Do the `compression': we need to pass the data to |
680 | * lz77_compress so that it will be taken into account |
681 | * for subsequent (distance,length) pairs. But |
682 | * lz77_compress is passed FALSE, which means it won't |
683 | * actually find (or even look for) any matches; so |
684 | * every character will be passed straight to |
685 | * zlib_literal which will spot out->comp_disabled and |
686 | * emit in the uncompressed format. |
687 | */ |
688 | lz77_compress(&ectx, block, blen, FALSE); |
689 | |
690 | len -= blen; |
691 | block += blen; |
692 | } |
693 | outbits(out, 2, 3); /* open new block */ |
694 | } else { |
695 | if (!in_block) { |
696 | /* |
697 | * Start a Deflate (RFC1951) fixed-trees block. We |
698 | * transmit a zero bit (BFINAL=0), followed by a zero |
699 | * bit and a one bit (BTYPE=01). Of course these are in |
700 | * the wrong order (01 0). |
701 | */ |
702 | outbits(out, 2, 3); |
703 | } |
704 | |
705 | /* |
706 | * Do the compression. |
707 | */ |
708 | lz77_compress(&ectx, block, len, TRUE); |
709 | |
710 | /* |
711 | * End the block (by transmitting code 256, which is |
712 | * 0000000 in fixed-tree mode), and transmit some empty |
713 | * blocks to ensure we have emitted the byte containing the |
714 | * last piece of genuine data. There are three ways we can |
715 | * do this: |
716 | * |
717 | * - Minimal flush. Output end-of-block and then open a |
718 | * new static block. This takes 9 bits, which is |
719 | * guaranteed to flush out the last genuine code in the |
720 | * closed block; but allegedly zlib can't handle it. |
721 | * |
722 | * - Zlib partial flush. Output EOB, open and close an |
723 | * empty static block, and _then_ open the new block. |
724 | * This is the best zlib can handle. |
725 | * |
726 | * - Zlib sync flush. Output EOB, then an empty |
727 | * _uncompressed_ block (000, then sync to byte |
728 | * boundary, then send bytes 00 00 FF FF). Then open the |
729 | * new block. |
730 | * |
731 | * For the moment, we will use Zlib partial flush. |
732 | */ |
733 | outbits(out, 0, 7); /* close block */ |
734 | outbits(out, 2, 3+7); /* empty static block */ |
735 | outbits(out, 2, 3); /* open new block */ |
736 | } |
737 | |
738 | out->comp_disabled = FALSE; |
4ba9b64b |
739 | |
740 | *outblock = out->outbuf; |
741 | *outlen = out->outlen; |
742 | |
743 | return 1; |
744 | } |
745 | |
746 | /* ---------------------------------------------------------------------- |
747 | * Zlib decompression. Of course, even though our compressor always |
748 | * uses static trees, our _decompressor_ has to be capable of |
749 | * handling dynamic trees if it sees them. |
750 | */ |
751 | |
752 | /* |
753 | * The way we work the Huffman decode is to have a table lookup on |
754 | * the first N bits of the input stream (in the order they arrive, |
755 | * of course, i.e. the first bit of the Huffman code is in bit 0). |
756 | * Each table entry lists the number of bits to consume, plus |
757 | * either an output code or a pointer to a secondary table. |
758 | */ |
759 | struct zlib_table; |
760 | struct zlib_tableentry; |
761 | |
762 | struct zlib_tableentry { |
763 | unsigned char nbits; |
d2371c81 |
764 | short code; |
4ba9b64b |
765 | struct zlib_table *nexttable; |
766 | }; |
767 | |
768 | struct zlib_table { |
769 | int mask; /* mask applied to input bit stream */ |
770 | struct zlib_tableentry *table; |
771 | }; |
772 | |
773 | #define MAXCODELEN 16 |
774 | #define MAXSYMS 288 |
775 | |
776 | /* |
777 | * Build a single-level decode table for elements |
778 | * [minlength,maxlength) of the provided code/length tables, and |
779 | * recurse to build subtables. |
780 | */ |
781 | static struct zlib_table *zlib_mkonetab(int *codes, unsigned char *lengths, |
782 | int nsyms, |
783 | int pfx, int pfxbits, int bits) { |
dcbde236 |
784 | struct zlib_table *tab = smalloc(sizeof(struct zlib_table)); |
4ba9b64b |
785 | int pfxmask = (1 << pfxbits) - 1; |
786 | int nbits, i, j, code; |
787 | |
dcbde236 |
788 | tab->table = smalloc((1 << bits) * sizeof(struct zlib_tableentry)); |
4ba9b64b |
789 | tab->mask = (1 << bits) - 1; |
790 | |
791 | for (code = 0; code <= tab->mask; code++) { |
792 | tab->table[code].code = -1; |
793 | tab->table[code].nbits = 0; |
794 | tab->table[code].nexttable = NULL; |
795 | } |
796 | |
797 | for (i = 0; i < nsyms; i++) { |
798 | if (lengths[i] <= pfxbits || (codes[i] & pfxmask) != pfx) |
799 | continue; |
800 | code = (codes[i] >> pfxbits) & tab->mask; |
801 | for (j = code; j <= tab->mask; j += 1 << (lengths[i]-pfxbits)) { |
802 | tab->table[j].code = i; |
803 | nbits = lengths[i] - pfxbits; |
804 | if (tab->table[j].nbits < nbits) |
805 | tab->table[j].nbits = nbits; |
806 | } |
807 | } |
808 | for (code = 0; code <= tab->mask; code++) { |
809 | if (tab->table[code].nbits <= bits) |
810 | continue; |
811 | /* Generate a subtable. */ |
812 | tab->table[code].code = -1; |
813 | nbits = tab->table[code].nbits - bits; |
814 | if (nbits > 7) |
815 | nbits = 7; |
816 | tab->table[code].nbits = bits; |
817 | tab->table[code].nexttable = zlib_mkonetab(codes, lengths, nsyms, |
818 | pfx | (code << pfxbits), |
819 | pfxbits + bits, nbits); |
820 | } |
821 | |
822 | return tab; |
823 | } |
824 | |
825 | /* |
826 | * Build a decode table, given a set of Huffman tree lengths. |
827 | */ |
828 | static struct zlib_table *zlib_mktable(unsigned char *lengths, int nlengths) { |
829 | int count[MAXCODELEN], startcode[MAXCODELEN], codes[MAXSYMS]; |
830 | int code, maxlen; |
831 | int i, j; |
832 | |
833 | /* Count the codes of each length. */ |
834 | maxlen = 0; |
835 | for (i = 1; i < MAXCODELEN; i++) count[i] = 0; |
836 | for (i = 0; i < nlengths; i++) { |
837 | count[lengths[i]]++; |
838 | if (maxlen < lengths[i]) |
839 | maxlen = lengths[i]; |
840 | } |
841 | /* Determine the starting code for each length block. */ |
842 | code = 0; |
843 | for (i = 1; i < MAXCODELEN; i++) { |
844 | startcode[i] = code; |
845 | code += count[i]; |
846 | code <<= 1; |
847 | } |
848 | /* Determine the code for each symbol. Mirrored, of course. */ |
849 | for (i = 0; i < nlengths; i++) { |
850 | code = startcode[lengths[i]]++; |
851 | codes[i] = 0; |
852 | for (j = 0; j < lengths[i]; j++) { |
853 | codes[i] = (codes[i] << 1) | (code & 1); |
854 | code >>= 1; |
855 | } |
856 | } |
857 | |
858 | /* |
859 | * Now we have the complete list of Huffman codes. Build a |
860 | * table. |
861 | */ |
862 | return zlib_mkonetab(codes, lengths, nlengths, 0, 0, |
863 | maxlen < 9 ? maxlen : 9); |
864 | } |
865 | |
dda46d54 |
866 | static int zlib_freetable(struct zlib_table ** ztab) { |
867 | struct zlib_table *tab; |
868 | int code; |
869 | |
870 | if (ztab == NULL) |
871 | return -1; |
872 | |
873 | if (*ztab == NULL) |
874 | return 0; |
875 | |
876 | tab = *ztab; |
877 | |
878 | for (code = 0; code <= tab->mask; code++) |
879 | if (tab->table[code].nexttable != NULL) |
880 | zlib_freetable(&tab->table[code].nexttable); |
881 | |
882 | sfree(tab->table); |
883 | tab->table = NULL; |
884 | |
885 | sfree(tab); |
886 | *ztab = NULL; |
887 | |
888 | return(0); |
889 | } |
890 | |
4ba9b64b |
891 | static struct zlib_decompress_ctx { |
892 | struct zlib_table *staticlentable, *staticdisttable; |
893 | struct zlib_table *currlentable, *currdisttable, *lenlentable; |
894 | enum { |
895 | START, OUTSIDEBLK, |
896 | TREES_HDR, TREES_LENLEN, TREES_LEN, TREES_LENREP, |
897 | INBLK, GOTLENSYM, GOTLEN, GOTDISTSYM, |
898 | UNCOMP_LEN, UNCOMP_NLEN, UNCOMP_DATA |
899 | } state; |
900 | int sym, hlit, hdist, hclen, lenptr, lenextrabits, lenaddon, len, lenrep; |
901 | int uncomplen; |
902 | unsigned char lenlen[19]; |
903 | unsigned char lengths[286+32]; |
904 | unsigned long bits; |
905 | int nbits; |
906 | unsigned char window[WINSIZE]; |
907 | int winpos; |
908 | unsigned char *outblk; |
909 | int outlen, outsize; |
910 | } dctx; |
911 | |
912 | void zlib_decompress_init(void) { |
913 | unsigned char lengths[288]; |
914 | memset(lengths, 8, 144); |
915 | memset(lengths+144, 9, 256-144); |
916 | memset(lengths+256, 7, 280-256); |
917 | memset(lengths+280, 8, 288-280); |
918 | dctx.staticlentable = zlib_mktable(lengths, 288); |
919 | memset(lengths, 5, 32); |
920 | dctx.staticdisttable = zlib_mktable(lengths, 32); |
921 | dctx.state = START; /* even before header */ |
dcbde236 |
922 | dctx.currlentable = dctx.currdisttable = dctx.lenlentable = NULL; |
4ba9b64b |
923 | dctx.bits = 0; |
924 | dctx.nbits = 0; |
925 | logevent("Initialised zlib (RFC1950) decompression"); |
926 | } |
927 | |
928 | int zlib_huflookup(unsigned long *bitsp, int *nbitsp, struct zlib_table *tab) { |
929 | unsigned long bits = *bitsp; |
930 | int nbits = *nbitsp; |
931 | while (1) { |
932 | struct zlib_tableentry *ent; |
933 | ent = &tab->table[bits & tab->mask]; |
934 | if (ent->nbits > nbits) |
935 | return -1; /* not enough data */ |
936 | bits >>= ent->nbits; |
937 | nbits -= ent->nbits; |
938 | if (ent->code == -1) |
939 | tab = ent->nexttable; |
940 | else { |
941 | *bitsp = bits; |
942 | *nbitsp = nbits; |
943 | return ent->code; |
944 | } |
945 | } |
946 | } |
947 | |
948 | static void zlib_emit_char(int c) { |
949 | dctx.window[dctx.winpos] = c; |
950 | dctx.winpos = (dctx.winpos + 1) & (WINSIZE-1); |
951 | if (dctx.outlen >= dctx.outsize) { |
952 | dctx.outsize = dctx.outlen + 512; |
dcbde236 |
953 | dctx.outblk = srealloc(dctx.outblk, dctx.outsize); |
4ba9b64b |
954 | } |
955 | dctx.outblk[dctx.outlen++] = c; |
956 | } |
957 | |
958 | #define EATBITS(n) ( dctx.nbits -= (n), dctx.bits >>= (n) ) |
959 | |
960 | int zlib_decompress_block(unsigned char *block, int len, |
961 | unsigned char **outblock, int *outlen) { |
962 | const coderecord *rec; |
963 | int code, blktype, rep, dist, nlen; |
964 | static const unsigned char lenlenmap[] = { |
965 | 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 |
966 | }; |
967 | |
968 | dctx.outblk = NULL; |
969 | dctx.outsize = dctx.outlen = 0; |
970 | |
971 | while (len > 0 || dctx.nbits > 0) { |
972 | while (dctx.nbits < 24 && len > 0) { |
973 | dctx.bits |= (*block++) << dctx.nbits; |
974 | dctx.nbits += 8; |
975 | len--; |
976 | } |
977 | switch (dctx.state) { |
978 | case START: |
979 | /* Expect 16-bit zlib header, which we'll dishonourably ignore. */ |
980 | if (dctx.nbits < 16) |
981 | goto finished; /* done all we can */ |
982 | EATBITS(16); |
983 | dctx.state = OUTSIDEBLK; |
984 | break; |
985 | case OUTSIDEBLK: |
986 | /* Expect 3-bit block header. */ |
987 | if (dctx.nbits < 3) |
988 | goto finished; /* done all we can */ |
989 | EATBITS(1); |
990 | blktype = dctx.bits & 3; |
991 | EATBITS(2); |
992 | if (blktype == 0) { |
993 | int to_eat = dctx.nbits & 7; |
994 | dctx.state = UNCOMP_LEN; |
995 | EATBITS(to_eat); /* align to byte boundary */ |
996 | } else if (blktype == 1) { |
997 | dctx.currlentable = dctx.staticlentable; |
998 | dctx.currdisttable = dctx.staticdisttable; |
999 | dctx.state = INBLK; |
1000 | } else if (blktype == 2) { |
1001 | dctx.state = TREES_HDR; |
1002 | } |
1003 | break; |
1004 | case TREES_HDR: |
1005 | /* |
1006 | * Dynamic block header. Five bits of HLIT, five of |
1007 | * HDIST, four of HCLEN. |
1008 | */ |
1009 | if (dctx.nbits < 5+5+4) |
1010 | goto finished; /* done all we can */ |
1011 | dctx.hlit = 257 + (dctx.bits & 31); EATBITS(5); |
1012 | dctx.hdist = 1 + (dctx.bits & 31); EATBITS(5); |
1013 | dctx.hclen = 4 + (dctx.bits & 15); EATBITS(4); |
1014 | dctx.lenptr = 0; |
1015 | dctx.state = TREES_LENLEN; |
1016 | memset(dctx.lenlen, 0, sizeof(dctx.lenlen)); |
1017 | break; |
1018 | case TREES_LENLEN: |
1019 | if (dctx.nbits < 3) |
1020 | goto finished; |
1021 | while (dctx.lenptr < dctx.hclen && dctx.nbits >= 3) { |
1022 | dctx.lenlen[lenlenmap[dctx.lenptr++]] = |
1023 | (unsigned char)(dctx.bits & 7); |
1024 | EATBITS(3); |
1025 | } |
1026 | if (dctx.lenptr == dctx.hclen) { |
1027 | dctx.lenlentable = zlib_mktable(dctx.lenlen, 19); |
1028 | dctx.state = TREES_LEN; |
1029 | dctx.lenptr = 0; |
1030 | } |
1031 | break; |
1032 | case TREES_LEN: |
1033 | if (dctx.lenptr >= dctx.hlit+dctx.hdist) { |
1034 | dctx.currlentable = zlib_mktable(dctx.lengths, dctx.hlit); |
1035 | dctx.currdisttable = zlib_mktable(dctx.lengths + dctx.hlit, |
1036 | dctx.hdist); |
dda46d54 |
1037 | zlib_freetable(&dctx.lenlentable); |
1038 | dctx.state = INBLK; |
4ba9b64b |
1039 | break; |
1040 | } |
1041 | code = zlib_huflookup(&dctx.bits, &dctx.nbits, dctx.lenlentable); |
1042 | if (code == -1) |
1043 | goto finished; |
1044 | if (code < 16) |
1045 | dctx.lengths[dctx.lenptr++] = code; |
1046 | else { |
1047 | dctx.lenextrabits = (code == 16 ? 2 : code == 17 ? 3 : 7); |
1048 | dctx.lenaddon = (code == 18 ? 11 : 3); |
1049 | dctx.lenrep = (code == 16 && dctx.lenptr > 0 ? |
1050 | dctx.lengths[dctx.lenptr-1] : 0); |
1051 | dctx.state = TREES_LENREP; |
1052 | } |
1053 | break; |
1054 | case TREES_LENREP: |
1055 | if (dctx.nbits < dctx.lenextrabits) |
1056 | goto finished; |
1057 | rep = dctx.lenaddon + (dctx.bits & ((1<<dctx.lenextrabits)-1)); |
1058 | EATBITS(dctx.lenextrabits); |
1059 | while (rep > 0 && dctx.lenptr < dctx.hlit+dctx.hdist) { |
1060 | dctx.lengths[dctx.lenptr] = dctx.lenrep; |
1061 | dctx.lenptr++; |
1062 | rep--; |
1063 | } |
1064 | dctx.state = TREES_LEN; |
1065 | break; |
1066 | case INBLK: |
1067 | code = zlib_huflookup(&dctx.bits, &dctx.nbits, dctx.currlentable); |
1068 | if (code == -1) |
1069 | goto finished; |
1070 | if (code < 256) |
1071 | zlib_emit_char(code); |
1072 | else if (code == 256) { |
1073 | dctx.state = OUTSIDEBLK; |
dda46d54 |
1074 | if (dctx.currlentable != dctx.staticlentable) |
1075 | zlib_freetable(&dctx.currlentable); |
1076 | if (dctx.currdisttable != dctx.staticdisttable) |
1077 | zlib_freetable(&dctx.currdisttable); |
4ba9b64b |
1078 | } else if (code < 286) { /* static tree can give >285; ignore */ |
1079 | dctx.state = GOTLENSYM; |
1080 | dctx.sym = code; |
1081 | } |
1082 | break; |
1083 | case GOTLENSYM: |
1084 | rec = &lencodes[dctx.sym - 257]; |
1085 | if (dctx.nbits < rec->extrabits) |
1086 | goto finished; |
1087 | dctx.len = rec->min + (dctx.bits & ((1<<rec->extrabits)-1)); |
1088 | EATBITS(rec->extrabits); |
1089 | dctx.state = GOTLEN; |
1090 | break; |
1091 | case GOTLEN: |
1092 | code = zlib_huflookup(&dctx.bits, &dctx.nbits, dctx.currdisttable); |
1093 | if (code == -1) |
1094 | goto finished; |
1095 | dctx.state = GOTDISTSYM; |
1096 | dctx.sym = code; |
1097 | break; |
1098 | case GOTDISTSYM: |
1099 | rec = &distcodes[dctx.sym]; |
1100 | if (dctx.nbits < rec->extrabits) |
1101 | goto finished; |
1102 | dist = rec->min + (dctx.bits & ((1<<rec->extrabits)-1)); |
1103 | EATBITS(rec->extrabits); |
1104 | dctx.state = INBLK; |
1105 | while (dctx.len--) |
1106 | zlib_emit_char(dctx.window[(dctx.winpos-dist) & (WINSIZE-1)]); |
1107 | break; |
1108 | case UNCOMP_LEN: |
1109 | /* |
1110 | * Uncompressed block. We expect to see a 16-bit LEN. |
1111 | */ |
1112 | if (dctx.nbits < 16) |
1113 | goto finished; |
1114 | dctx.uncomplen = dctx.bits & 0xFFFF; |
1115 | EATBITS(16); |
1116 | dctx.state = UNCOMP_NLEN; |
1117 | break; |
1118 | case UNCOMP_NLEN: |
1119 | /* |
1120 | * Uncompressed block. We expect to see a 16-bit NLEN, |
1121 | * which should be the one's complement of the previous |
1122 | * LEN. |
1123 | */ |
1124 | if (dctx.nbits < 16) |
1125 | goto finished; |
1126 | nlen = dctx.bits & 0xFFFF; |
1127 | EATBITS(16); |
1128 | dctx.state = UNCOMP_DATA; |
1129 | break; |
1130 | case UNCOMP_DATA: |
1131 | if (dctx.nbits < 8) |
1132 | goto finished; |
1133 | zlib_emit_char(dctx.bits & 0xFF); |
1134 | EATBITS(8); |
1135 | if (--dctx.uncomplen == 0) |
1136 | dctx.state = OUTSIDEBLK; /* end of uncompressed block */ |
1137 | break; |
1138 | } |
1139 | } |
1140 | |
1141 | finished: |
1142 | *outblock = dctx.outblk; |
1143 | *outlen = dctx.outlen; |
1144 | |
1145 | return 1; |
1146 | } |
1147 | |
1148 | const struct ssh_compress ssh_zlib = { |
1149 | "zlib", |
1150 | zlib_compress_init, |
1151 | zlib_compress_block, |
1152 | zlib_decompress_init, |
6e9e9520 |
1153 | zlib_decompress_block, |
1154 | zlib_disable_compression |
4ba9b64b |
1155 | }; |