| 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 | #include "ssh.h" |
| 44 | |
| 45 | #ifndef FALSE |
| 46 | #define FALSE 0 |
| 47 | #define TRUE (!FALSE) |
| 48 | #endif |
| 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. |
| 73 | * If `compress' is FALSE, it will never emit a match, but will |
| 74 | * instead call literal() for everything. |
| 75 | */ |
| 76 | static void lz77_compress(struct LZ77Context *ctx, |
| 77 | unsigned char *data, int len, int compress); |
| 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 { |
| 98 | short next, prev; /* array indices within the window */ |
| 99 | short hashval; |
| 100 | }; |
| 101 | |
| 102 | struct HashEntry { |
| 103 | short first; /* window index of first in chain */ |
| 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 | { |
| 121 | return (257 * data[0] + 263 * data[1] + 269 * data[2]) % HASHMAX; |
| 122 | } |
| 123 | |
| 124 | static int lz77_init(struct LZ77Context *ctx) |
| 125 | { |
| 126 | struct LZ77InternalContext *st; |
| 127 | int i; |
| 128 | |
| 129 | st = snew(struct LZ77InternalContext); |
| 130 | if (!st) |
| 131 | return 0; |
| 132 | |
| 133 | ctx->ictx = st; |
| 134 | |
| 135 | for (i = 0; i < WINSIZE; i++) |
| 136 | st->win[i].next = st->win[i].prev = st->win[i].hashval = INVALID; |
| 137 | for (i = 0; i < HASHMAX; i++) |
| 138 | st->hashtab[i].first = INVALID; |
| 139 | st->winpos = 0; |
| 140 | |
| 141 | st->npending = 0; |
| 142 | |
| 143 | return 1; |
| 144 | } |
| 145 | |
| 146 | static void lz77_advance(struct LZ77InternalContext *st, |
| 147 | unsigned char c, int hash) |
| 148 | { |
| 149 | int off; |
| 150 | |
| 151 | /* |
| 152 | * Remove the hash entry at winpos from the tail of its chain, |
| 153 | * or empty the chain if it's the only thing on the chain. |
| 154 | */ |
| 155 | if (st->win[st->winpos].prev != INVALID) { |
| 156 | st->win[st->win[st->winpos].prev].next = INVALID; |
| 157 | } else if (st->win[st->winpos].hashval != INVALID) { |
| 158 | st->hashtab[st->win[st->winpos].hashval].first = INVALID; |
| 159 | } |
| 160 | |
| 161 | /* |
| 162 | * Create a new entry at winpos and add it to the head of its |
| 163 | * hash chain. |
| 164 | */ |
| 165 | st->win[st->winpos].hashval = hash; |
| 166 | st->win[st->winpos].prev = INVALID; |
| 167 | off = st->win[st->winpos].next = st->hashtab[hash].first; |
| 168 | st->hashtab[hash].first = st->winpos; |
| 169 | if (off != INVALID) |
| 170 | st->win[off].prev = st->winpos; |
| 171 | st->data[st->winpos] = c; |
| 172 | |
| 173 | /* |
| 174 | * Advance the window pointer. |
| 175 | */ |
| 176 | st->winpos = (st->winpos + 1) & (WINSIZE - 1); |
| 177 | } |
| 178 | |
| 179 | #define CHARAT(k) ( (k)<0 ? st->data[(st->winpos+k)&(WINSIZE-1)] : data[k] ) |
| 180 | |
| 181 | static void lz77_compress(struct LZ77Context *ctx, |
| 182 | unsigned char *data, int len, int compress) |
| 183 | { |
| 184 | struct LZ77InternalContext *st = ctx->ictx; |
| 185 | int i, hash, distance, off, nmatch, matchlen, advance; |
| 186 | struct Match defermatch, matches[MAXMATCH]; |
| 187 | int deferchr; |
| 188 | |
| 189 | /* |
| 190 | * Add any pending characters from last time to the window. (We |
| 191 | * might not be able to.) |
| 192 | */ |
| 193 | for (i = 0; i < st->npending; i++) { |
| 194 | unsigned char foo[HASHCHARS]; |
| 195 | int j; |
| 196 | if (len + st->npending - i < HASHCHARS) { |
| 197 | /* Update the pending array. */ |
| 198 | for (j = i; j < st->npending; j++) |
| 199 | st->pending[j - i] = st->pending[j]; |
| 200 | break; |
| 201 | } |
| 202 | for (j = 0; j < HASHCHARS; j++) |
| 203 | foo[j] = (i + j < st->npending ? st->pending[i + j] : |
| 204 | data[i + j - st->npending]); |
| 205 | lz77_advance(st, foo[0], lz77_hash(foo)); |
| 206 | } |
| 207 | st->npending -= i; |
| 208 | |
| 209 | defermatch.len = 0; |
| 210 | deferchr = '\0'; |
| 211 | while (len > 0) { |
| 212 | |
| 213 | /* Don't even look for a match, if we're not compressing. */ |
| 214 | if (compress && len >= HASHCHARS) { |
| 215 | /* |
| 216 | * Hash the next few characters. |
| 217 | */ |
| 218 | hash = lz77_hash(data); |
| 219 | |
| 220 | /* |
| 221 | * Look the hash up in the corresponding hash chain and see |
| 222 | * what we can find. |
| 223 | */ |
| 224 | nmatch = 0; |
| 225 | for (off = st->hashtab[hash].first; |
| 226 | off != INVALID; off = st->win[off].next) { |
| 227 | /* distance = 1 if off == st->winpos-1 */ |
| 228 | /* distance = WINSIZE if off == st->winpos */ |
| 229 | distance = |
| 230 | WINSIZE - (off + WINSIZE - st->winpos) % WINSIZE; |
| 231 | for (i = 0; i < HASHCHARS; i++) |
| 232 | if (CHARAT(i) != CHARAT(i - distance)) |
| 233 | break; |
| 234 | if (i == HASHCHARS) { |
| 235 | matches[nmatch].distance = distance; |
| 236 | matches[nmatch].len = 3; |
| 237 | if (++nmatch >= MAXMATCH) |
| 238 | break; |
| 239 | } |
| 240 | } |
| 241 | } else { |
| 242 | nmatch = 0; |
| 243 | hash = INVALID; |
| 244 | } |
| 245 | |
| 246 | if (nmatch > 0) { |
| 247 | /* |
| 248 | * We've now filled up matches[] with nmatch potential |
| 249 | * matches. Follow them down to find the longest. (We |
| 250 | * assume here that it's always worth favouring a |
| 251 | * longer match over a shorter one.) |
| 252 | */ |
| 253 | matchlen = HASHCHARS; |
| 254 | while (matchlen < len) { |
| 255 | int j; |
| 256 | for (i = j = 0; i < nmatch; i++) { |
| 257 | if (CHARAT(matchlen) == |
| 258 | CHARAT(matchlen - matches[i].distance)) { |
| 259 | matches[j++] = matches[i]; |
| 260 | } |
| 261 | } |
| 262 | if (j == 0) |
| 263 | break; |
| 264 | matchlen++; |
| 265 | nmatch = j; |
| 266 | } |
| 267 | |
| 268 | /* |
| 269 | * We've now got all the longest matches. We favour the |
| 270 | * shorter distances, which means we go with matches[0]. |
| 271 | * So see if we want to defer it or throw it away. |
| 272 | */ |
| 273 | matches[0].len = matchlen; |
| 274 | if (defermatch.len > 0) { |
| 275 | if (matches[0].len > defermatch.len + 1) { |
| 276 | /* We have a better match. Emit the deferred char, |
| 277 | * and defer this match. */ |
| 278 | ctx->literal(ctx, (unsigned char) deferchr); |
| 279 | defermatch = matches[0]; |
| 280 | deferchr = data[0]; |
| 281 | advance = 1; |
| 282 | } else { |
| 283 | /* We don't have a better match. Do the deferred one. */ |
| 284 | ctx->match(ctx, defermatch.distance, defermatch.len); |
| 285 | advance = defermatch.len - 1; |
| 286 | defermatch.len = 0; |
| 287 | } |
| 288 | } else { |
| 289 | /* There was no deferred match. Defer this one. */ |
| 290 | defermatch = matches[0]; |
| 291 | deferchr = data[0]; |
| 292 | advance = 1; |
| 293 | } |
| 294 | } else { |
| 295 | /* |
| 296 | * We found no matches. Emit the deferred match, if |
| 297 | * any; otherwise emit a literal. |
| 298 | */ |
| 299 | if (defermatch.len > 0) { |
| 300 | ctx->match(ctx, defermatch.distance, defermatch.len); |
| 301 | advance = defermatch.len - 1; |
| 302 | defermatch.len = 0; |
| 303 | } else { |
| 304 | ctx->literal(ctx, data[0]); |
| 305 | advance = 1; |
| 306 | } |
| 307 | } |
| 308 | |
| 309 | /* |
| 310 | * Now advance the position by `advance' characters, |
| 311 | * keeping the window and hash chains consistent. |
| 312 | */ |
| 313 | while (advance > 0) { |
| 314 | if (len >= HASHCHARS) { |
| 315 | lz77_advance(st, *data, lz77_hash(data)); |
| 316 | } else { |
| 317 | st->pending[st->npending++] = *data; |
| 318 | } |
| 319 | data++; |
| 320 | len--; |
| 321 | advance--; |
| 322 | } |
| 323 | } |
| 324 | } |
| 325 | |
| 326 | /* ---------------------------------------------------------------------- |
| 327 | * Zlib compression. We always use the static Huffman tree option. |
| 328 | * Mostly this is because it's hard to scan a block in advance to |
| 329 | * work out better trees; dynamic trees are great when you're |
| 330 | * compressing a large file under no significant time constraint, |
| 331 | * but when you're compressing little bits in real time, things get |
| 332 | * hairier. |
| 333 | * |
| 334 | * I suppose it's possible that I could compute Huffman trees based |
| 335 | * on the frequencies in the _previous_ block, as a sort of |
| 336 | * heuristic, but I'm not confident that the gain would balance out |
| 337 | * having to transmit the trees. |
| 338 | */ |
| 339 | |
| 340 | struct Outbuf { |
| 341 | unsigned char *outbuf; |
| 342 | int outlen, outsize; |
| 343 | unsigned long outbits; |
| 344 | int noutbits; |
| 345 | int firstblock; |
| 346 | int comp_disabled; |
| 347 | }; |
| 348 | |
| 349 | static void outbits(struct Outbuf *out, unsigned long bits, int nbits) |
| 350 | { |
| 351 | assert(out->noutbits + nbits <= 32); |
| 352 | out->outbits |= bits << out->noutbits; |
| 353 | out->noutbits += nbits; |
| 354 | while (out->noutbits >= 8) { |
| 355 | if (out->outlen >= out->outsize) { |
| 356 | out->outsize = out->outlen + 64; |
| 357 | out->outbuf = sresize(out->outbuf, out->outsize, unsigned char); |
| 358 | } |
| 359 | out->outbuf[out->outlen++] = (unsigned char) (out->outbits & 0xFF); |
| 360 | out->outbits >>= 8; |
| 361 | out->noutbits -= 8; |
| 362 | } |
| 363 | } |
| 364 | |
| 365 | static const unsigned char mirrorbytes[256] = { |
| 366 | 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, |
| 367 | 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0, |
| 368 | 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, |
| 369 | 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8, |
| 370 | 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, |
| 371 | 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4, |
| 372 | 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, |
| 373 | 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc, |
| 374 | 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, |
| 375 | 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2, |
| 376 | 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea, |
| 377 | 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa, |
| 378 | 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, |
| 379 | 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6, |
| 380 | 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, |
| 381 | 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe, |
| 382 | 0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1, |
| 383 | 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1, |
| 384 | 0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, |
| 385 | 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9, |
| 386 | 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5, |
| 387 | 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5, |
| 388 | 0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed, |
| 389 | 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd, |
| 390 | 0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, |
| 391 | 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3, |
| 392 | 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb, |
| 393 | 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb, |
| 394 | 0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7, |
| 395 | 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7, |
| 396 | 0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, |
| 397 | 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff, |
| 398 | }; |
| 399 | |
| 400 | typedef struct { |
| 401 | short code, extrabits; |
| 402 | int min, max; |
| 403 | } coderecord; |
| 404 | |
| 405 | static const coderecord lencodes[] = { |
| 406 | {257, 0, 3, 3}, |
| 407 | {258, 0, 4, 4}, |
| 408 | {259, 0, 5, 5}, |
| 409 | {260, 0, 6, 6}, |
| 410 | {261, 0, 7, 7}, |
| 411 | {262, 0, 8, 8}, |
| 412 | {263, 0, 9, 9}, |
| 413 | {264, 0, 10, 10}, |
| 414 | {265, 1, 11, 12}, |
| 415 | {266, 1, 13, 14}, |
| 416 | {267, 1, 15, 16}, |
| 417 | {268, 1, 17, 18}, |
| 418 | {269, 2, 19, 22}, |
| 419 | {270, 2, 23, 26}, |
| 420 | {271, 2, 27, 30}, |
| 421 | {272, 2, 31, 34}, |
| 422 | {273, 3, 35, 42}, |
| 423 | {274, 3, 43, 50}, |
| 424 | {275, 3, 51, 58}, |
| 425 | {276, 3, 59, 66}, |
| 426 | {277, 4, 67, 82}, |
| 427 | {278, 4, 83, 98}, |
| 428 | {279, 4, 99, 114}, |
| 429 | {280, 4, 115, 130}, |
| 430 | {281, 5, 131, 162}, |
| 431 | {282, 5, 163, 194}, |
| 432 | {283, 5, 195, 226}, |
| 433 | {284, 5, 227, 257}, |
| 434 | {285, 0, 258, 258}, |
| 435 | }; |
| 436 | |
| 437 | static const coderecord distcodes[] = { |
| 438 | {0, 0, 1, 1}, |
| 439 | {1, 0, 2, 2}, |
| 440 | {2, 0, 3, 3}, |
| 441 | {3, 0, 4, 4}, |
| 442 | {4, 1, 5, 6}, |
| 443 | {5, 1, 7, 8}, |
| 444 | {6, 2, 9, 12}, |
| 445 | {7, 2, 13, 16}, |
| 446 | {8, 3, 17, 24}, |
| 447 | {9, 3, 25, 32}, |
| 448 | {10, 4, 33, 48}, |
| 449 | {11, 4, 49, 64}, |
| 450 | {12, 5, 65, 96}, |
| 451 | {13, 5, 97, 128}, |
| 452 | {14, 6, 129, 192}, |
| 453 | {15, 6, 193, 256}, |
| 454 | {16, 7, 257, 384}, |
| 455 | {17, 7, 385, 512}, |
| 456 | {18, 8, 513, 768}, |
| 457 | {19, 8, 769, 1024}, |
| 458 | {20, 9, 1025, 1536}, |
| 459 | {21, 9, 1537, 2048}, |
| 460 | {22, 10, 2049, 3072}, |
| 461 | {23, 10, 3073, 4096}, |
| 462 | {24, 11, 4097, 6144}, |
| 463 | {25, 11, 6145, 8192}, |
| 464 | {26, 12, 8193, 12288}, |
| 465 | {27, 12, 12289, 16384}, |
| 466 | {28, 13, 16385, 24576}, |
| 467 | {29, 13, 24577, 32768}, |
| 468 | }; |
| 469 | |
| 470 | static void zlib_literal(struct LZ77Context *ectx, unsigned char c) |
| 471 | { |
| 472 | struct Outbuf *out = (struct Outbuf *) ectx->userdata; |
| 473 | |
| 474 | if (out->comp_disabled) { |
| 475 | /* |
| 476 | * We're in an uncompressed block, so just output the byte. |
| 477 | */ |
| 478 | outbits(out, c, 8); |
| 479 | return; |
| 480 | } |
| 481 | |
| 482 | if (c <= 143) { |
| 483 | /* 0 through 143 are 8 bits long starting at 00110000. */ |
| 484 | outbits(out, mirrorbytes[0x30 + c], 8); |
| 485 | } else { |
| 486 | /* 144 through 255 are 9 bits long starting at 110010000. */ |
| 487 | outbits(out, 1 + 2 * mirrorbytes[0x90 - 144 + c], 9); |
| 488 | } |
| 489 | } |
| 490 | |
| 491 | static void zlib_match(struct LZ77Context *ectx, int distance, int len) |
| 492 | { |
| 493 | const coderecord *d, *l; |
| 494 | int i, j, k; |
| 495 | struct Outbuf *out = (struct Outbuf *) ectx->userdata; |
| 496 | |
| 497 | assert(!out->comp_disabled); |
| 498 | |
| 499 | while (len > 0) { |
| 500 | int thislen; |
| 501 | |
| 502 | /* |
| 503 | * We can transmit matches of lengths 3 through 258 |
| 504 | * inclusive. So if len exceeds 258, we must transmit in |
| 505 | * several steps, with 258 or less in each step. |
| 506 | * |
| 507 | * Specifically: if len >= 261, we can transmit 258 and be |
| 508 | * sure of having at least 3 left for the next step. And if |
| 509 | * len <= 258, we can just transmit len. But if len == 259 |
| 510 | * or 260, we must transmit len-3. |
| 511 | */ |
| 512 | thislen = (len > 260 ? 258 : len <= 258 ? len : len - 3); |
| 513 | len -= thislen; |
| 514 | |
| 515 | /* |
| 516 | * Binary-search to find which length code we're |
| 517 | * transmitting. |
| 518 | */ |
| 519 | i = -1; |
| 520 | j = sizeof(lencodes) / sizeof(*lencodes); |
| 521 | while (1) { |
| 522 | assert(j - i >= 2); |
| 523 | k = (j + i) / 2; |
| 524 | if (thislen < lencodes[k].min) |
| 525 | j = k; |
| 526 | else if (thislen > lencodes[k].max) |
| 527 | i = k; |
| 528 | else { |
| 529 | l = &lencodes[k]; |
| 530 | break; /* found it! */ |
| 531 | } |
| 532 | } |
| 533 | |
| 534 | /* |
| 535 | * Transmit the length code. 256-279 are seven bits |
| 536 | * starting at 0000000; 280-287 are eight bits starting at |
| 537 | * 11000000. |
| 538 | */ |
| 539 | if (l->code <= 279) { |
| 540 | outbits(out, mirrorbytes[(l->code - 256) * 2], 7); |
| 541 | } else { |
| 542 | outbits(out, mirrorbytes[0xc0 - 280 + l->code], 8); |
| 543 | } |
| 544 | |
| 545 | /* |
| 546 | * Transmit the extra bits. |
| 547 | */ |
| 548 | if (l->extrabits) |
| 549 | outbits(out, thislen - l->min, l->extrabits); |
| 550 | |
| 551 | /* |
| 552 | * Binary-search to find which distance code we're |
| 553 | * transmitting. |
| 554 | */ |
| 555 | i = -1; |
| 556 | j = sizeof(distcodes) / sizeof(*distcodes); |
| 557 | while (1) { |
| 558 | assert(j - i >= 2); |
| 559 | k = (j + i) / 2; |
| 560 | if (distance < distcodes[k].min) |
| 561 | j = k; |
| 562 | else if (distance > distcodes[k].max) |
| 563 | i = k; |
| 564 | else { |
| 565 | d = &distcodes[k]; |
| 566 | break; /* found it! */ |
| 567 | } |
| 568 | } |
| 569 | |
| 570 | /* |
| 571 | * Transmit the distance code. Five bits starting at 00000. |
| 572 | */ |
| 573 | outbits(out, mirrorbytes[d->code * 8], 5); |
| 574 | |
| 575 | /* |
| 576 | * Transmit the extra bits. |
| 577 | */ |
| 578 | if (d->extrabits) |
| 579 | outbits(out, distance - d->min, d->extrabits); |
| 580 | } |
| 581 | } |
| 582 | |
| 583 | void *zlib_compress_init(void) |
| 584 | { |
| 585 | struct Outbuf *out; |
| 586 | struct LZ77Context *ectx = snew(struct LZ77Context); |
| 587 | |
| 588 | lz77_init(ectx); |
| 589 | ectx->literal = zlib_literal; |
| 590 | ectx->match = zlib_match; |
| 591 | |
| 592 | out = snew(struct Outbuf); |
| 593 | out->outbits = out->noutbits = 0; |
| 594 | out->firstblock = 1; |
| 595 | out->comp_disabled = FALSE; |
| 596 | ectx->userdata = out; |
| 597 | |
| 598 | return ectx; |
| 599 | } |
| 600 | |
| 601 | void zlib_compress_cleanup(void *handle) |
| 602 | { |
| 603 | struct LZ77Context *ectx = (struct LZ77Context *)handle; |
| 604 | sfree(ectx->userdata); |
| 605 | } |
| 606 | |
| 607 | /* |
| 608 | * Turn off actual LZ77 analysis for one block, to facilitate |
| 609 | * construction of a precise-length IGNORE packet. Returns the |
| 610 | * length adjustment (which is only valid for packets < 65536 |
| 611 | * bytes, but that seems reasonable enough). |
| 612 | */ |
| 613 | static int zlib_disable_compression(void *handle) |
| 614 | { |
| 615 | struct LZ77Context *ectx = (struct LZ77Context *)handle; |
| 616 | struct Outbuf *out = (struct Outbuf *) ectx->userdata; |
| 617 | int n; |
| 618 | |
| 619 | out->comp_disabled = TRUE; |
| 620 | |
| 621 | n = 0; |
| 622 | /* |
| 623 | * If this is the first block, we will start by outputting two |
| 624 | * header bytes, and then three bits to begin an uncompressed |
| 625 | * block. This will cost three bytes (because we will start on |
| 626 | * a byte boundary, this is certain). |
| 627 | */ |
| 628 | if (out->firstblock) { |
| 629 | n = 3; |
| 630 | } else { |
| 631 | /* |
| 632 | * Otherwise, we will output seven bits to close the |
| 633 | * previous static block, and _then_ three bits to begin an |
| 634 | * uncompressed block, and then flush the current byte. |
| 635 | * This may cost two bytes or three, depending on noutbits. |
| 636 | */ |
| 637 | n += (out->noutbits + 10) / 8; |
| 638 | } |
| 639 | |
| 640 | /* |
| 641 | * Now we output four bytes for the length / ~length pair in |
| 642 | * the uncompressed block. |
| 643 | */ |
| 644 | n += 4; |
| 645 | |
| 646 | return n; |
| 647 | } |
| 648 | |
| 649 | int zlib_compress_block(void *handle, unsigned char *block, int len, |
| 650 | unsigned char **outblock, int *outlen) |
| 651 | { |
| 652 | struct LZ77Context *ectx = (struct LZ77Context *)handle; |
| 653 | struct Outbuf *out = (struct Outbuf *) ectx->userdata; |
| 654 | int in_block; |
| 655 | |
| 656 | out->outbuf = NULL; |
| 657 | out->outlen = out->outsize = 0; |
| 658 | |
| 659 | /* |
| 660 | * If this is the first block, output the Zlib (RFC1950) header |
| 661 | * bytes 78 9C. (Deflate compression, 32K window size, default |
| 662 | * algorithm.) |
| 663 | */ |
| 664 | if (out->firstblock) { |
| 665 | outbits(out, 0x9C78, 16); |
| 666 | out->firstblock = 0; |
| 667 | |
| 668 | in_block = FALSE; |
| 669 | } else |
| 670 | in_block = TRUE; |
| 671 | |
| 672 | if (out->comp_disabled) { |
| 673 | if (in_block) |
| 674 | outbits(out, 0, 7); /* close static block */ |
| 675 | |
| 676 | while (len > 0) { |
| 677 | int blen = (len < 65535 ? len : 65535); |
| 678 | |
| 679 | /* |
| 680 | * Start a Deflate (RFC1951) uncompressed block. We |
| 681 | * transmit a zero bit (BFINAL=0), followed by a zero |
| 682 | * bit and a one bit (BTYPE=00). Of course these are in |
| 683 | * the wrong order (00 0). |
| 684 | */ |
| 685 | outbits(out, 0, 3); |
| 686 | |
| 687 | /* |
| 688 | * Output zero bits to align to a byte boundary. |
| 689 | */ |
| 690 | if (out->noutbits) |
| 691 | outbits(out, 0, 8 - out->noutbits); |
| 692 | |
| 693 | /* |
| 694 | * Output the block length, and then its one's |
| 695 | * complement. They're little-endian, so all we need to |
| 696 | * do is pass them straight to outbits() with bit count |
| 697 | * 16. |
| 698 | */ |
| 699 | outbits(out, blen, 16); |
| 700 | outbits(out, blen ^ 0xFFFF, 16); |
| 701 | |
| 702 | /* |
| 703 | * Do the `compression': we need to pass the data to |
| 704 | * lz77_compress so that it will be taken into account |
| 705 | * for subsequent (distance,length) pairs. But |
| 706 | * lz77_compress is passed FALSE, which means it won't |
| 707 | * actually find (or even look for) any matches; so |
| 708 | * every character will be passed straight to |
| 709 | * zlib_literal which will spot out->comp_disabled and |
| 710 | * emit in the uncompressed format. |
| 711 | */ |
| 712 | lz77_compress(ectx, block, blen, FALSE); |
| 713 | |
| 714 | len -= blen; |
| 715 | block += blen; |
| 716 | } |
| 717 | outbits(out, 2, 3); /* open new block */ |
| 718 | } else { |
| 719 | if (!in_block) { |
| 720 | /* |
| 721 | * Start a Deflate (RFC1951) fixed-trees block. We |
| 722 | * transmit a zero bit (BFINAL=0), followed by a zero |
| 723 | * bit and a one bit (BTYPE=01). Of course these are in |
| 724 | * the wrong order (01 0). |
| 725 | */ |
| 726 | outbits(out, 2, 3); |
| 727 | } |
| 728 | |
| 729 | /* |
| 730 | * Do the compression. |
| 731 | */ |
| 732 | lz77_compress(ectx, block, len, TRUE); |
| 733 | |
| 734 | /* |
| 735 | * End the block (by transmitting code 256, which is |
| 736 | * 0000000 in fixed-tree mode), and transmit some empty |
| 737 | * blocks to ensure we have emitted the byte containing the |
| 738 | * last piece of genuine data. There are three ways we can |
| 739 | * do this: |
| 740 | * |
| 741 | * - Minimal flush. Output end-of-block and then open a |
| 742 | * new static block. This takes 9 bits, which is |
| 743 | * guaranteed to flush out the last genuine code in the |
| 744 | * closed block; but allegedly zlib can't handle it. |
| 745 | * |
| 746 | * - Zlib partial flush. Output EOB, open and close an |
| 747 | * empty static block, and _then_ open the new block. |
| 748 | * This is the best zlib can handle. |
| 749 | * |
| 750 | * - Zlib sync flush. Output EOB, then an empty |
| 751 | * _uncompressed_ block (000, then sync to byte |
| 752 | * boundary, then send bytes 00 00 FF FF). Then open the |
| 753 | * new block. |
| 754 | * |
| 755 | * For the moment, we will use Zlib partial flush. |
| 756 | */ |
| 757 | outbits(out, 0, 7); /* close block */ |
| 758 | outbits(out, 2, 3 + 7); /* empty static block */ |
| 759 | outbits(out, 2, 3); /* open new block */ |
| 760 | } |
| 761 | |
| 762 | out->comp_disabled = FALSE; |
| 763 | |
| 764 | *outblock = out->outbuf; |
| 765 | *outlen = out->outlen; |
| 766 | |
| 767 | return 1; |
| 768 | } |
| 769 | |
| 770 | /* ---------------------------------------------------------------------- |
| 771 | * Zlib decompression. Of course, even though our compressor always |
| 772 | * uses static trees, our _decompressor_ has to be capable of |
| 773 | * handling dynamic trees if it sees them. |
| 774 | */ |
| 775 | |
| 776 | /* |
| 777 | * The way we work the Huffman decode is to have a table lookup on |
| 778 | * the first N bits of the input stream (in the order they arrive, |
| 779 | * of course, i.e. the first bit of the Huffman code is in bit 0). |
| 780 | * Each table entry lists the number of bits to consume, plus |
| 781 | * either an output code or a pointer to a secondary table. |
| 782 | */ |
| 783 | struct zlib_table; |
| 784 | struct zlib_tableentry; |
| 785 | |
| 786 | struct zlib_tableentry { |
| 787 | unsigned char nbits; |
| 788 | short code; |
| 789 | struct zlib_table *nexttable; |
| 790 | }; |
| 791 | |
| 792 | struct zlib_table { |
| 793 | int mask; /* mask applied to input bit stream */ |
| 794 | struct zlib_tableentry *table; |
| 795 | }; |
| 796 | |
| 797 | #define MAXCODELEN 16 |
| 798 | #define MAXSYMS 288 |
| 799 | |
| 800 | /* |
| 801 | * Build a single-level decode table for elements |
| 802 | * [minlength,maxlength) of the provided code/length tables, and |
| 803 | * recurse to build subtables. |
| 804 | */ |
| 805 | static struct zlib_table *zlib_mkonetab(int *codes, unsigned char *lengths, |
| 806 | int nsyms, |
| 807 | int pfx, int pfxbits, int bits) |
| 808 | { |
| 809 | struct zlib_table *tab = snew(struct zlib_table); |
| 810 | int pfxmask = (1 << pfxbits) - 1; |
| 811 | int nbits, i, j, code; |
| 812 | |
| 813 | tab->table = snewn(1 << bits, struct zlib_tableentry); |
| 814 | tab->mask = (1 << bits) - 1; |
| 815 | |
| 816 | for (code = 0; code <= tab->mask; code++) { |
| 817 | tab->table[code].code = -1; |
| 818 | tab->table[code].nbits = 0; |
| 819 | tab->table[code].nexttable = NULL; |
| 820 | } |
| 821 | |
| 822 | for (i = 0; i < nsyms; i++) { |
| 823 | if (lengths[i] <= pfxbits || (codes[i] & pfxmask) != pfx) |
| 824 | continue; |
| 825 | code = (codes[i] >> pfxbits) & tab->mask; |
| 826 | for (j = code; j <= tab->mask; j += 1 << (lengths[i] - pfxbits)) { |
| 827 | tab->table[j].code = i; |
| 828 | nbits = lengths[i] - pfxbits; |
| 829 | if (tab->table[j].nbits < nbits) |
| 830 | tab->table[j].nbits = nbits; |
| 831 | } |
| 832 | } |
| 833 | for (code = 0; code <= tab->mask; code++) { |
| 834 | if (tab->table[code].nbits <= bits) |
| 835 | continue; |
| 836 | /* Generate a subtable. */ |
| 837 | tab->table[code].code = -1; |
| 838 | nbits = tab->table[code].nbits - bits; |
| 839 | if (nbits > 7) |
| 840 | nbits = 7; |
| 841 | tab->table[code].nbits = bits; |
| 842 | tab->table[code].nexttable = zlib_mkonetab(codes, lengths, nsyms, |
| 843 | pfx | (code << pfxbits), |
| 844 | pfxbits + bits, nbits); |
| 845 | } |
| 846 | |
| 847 | return tab; |
| 848 | } |
| 849 | |
| 850 | /* |
| 851 | * Build a decode table, given a set of Huffman tree lengths. |
| 852 | */ |
| 853 | static struct zlib_table *zlib_mktable(unsigned char *lengths, |
| 854 | int nlengths) |
| 855 | { |
| 856 | int count[MAXCODELEN], startcode[MAXCODELEN], codes[MAXSYMS]; |
| 857 | int code, maxlen; |
| 858 | int i, j; |
| 859 | |
| 860 | /* Count the codes of each length. */ |
| 861 | maxlen = 0; |
| 862 | for (i = 1; i < MAXCODELEN; i++) |
| 863 | count[i] = 0; |
| 864 | for (i = 0; i < nlengths; i++) { |
| 865 | count[lengths[i]]++; |
| 866 | if (maxlen < lengths[i]) |
| 867 | maxlen = lengths[i]; |
| 868 | } |
| 869 | /* Determine the starting code for each length block. */ |
| 870 | code = 0; |
| 871 | for (i = 1; i < MAXCODELEN; i++) { |
| 872 | startcode[i] = code; |
| 873 | code += count[i]; |
| 874 | code <<= 1; |
| 875 | } |
| 876 | /* Determine the code for each symbol. Mirrored, of course. */ |
| 877 | for (i = 0; i < nlengths; i++) { |
| 878 | code = startcode[lengths[i]]++; |
| 879 | codes[i] = 0; |
| 880 | for (j = 0; j < lengths[i]; j++) { |
| 881 | codes[i] = (codes[i] << 1) | (code & 1); |
| 882 | code >>= 1; |
| 883 | } |
| 884 | } |
| 885 | |
| 886 | /* |
| 887 | * Now we have the complete list of Huffman codes. Build a |
| 888 | * table. |
| 889 | */ |
| 890 | return zlib_mkonetab(codes, lengths, nlengths, 0, 0, |
| 891 | maxlen < 9 ? maxlen : 9); |
| 892 | } |
| 893 | |
| 894 | static int zlib_freetable(struct zlib_table **ztab) |
| 895 | { |
| 896 | struct zlib_table *tab; |
| 897 | int code; |
| 898 | |
| 899 | if (ztab == NULL) |
| 900 | return -1; |
| 901 | |
| 902 | if (*ztab == NULL) |
| 903 | return 0; |
| 904 | |
| 905 | tab = *ztab; |
| 906 | |
| 907 | for (code = 0; code <= tab->mask; code++) |
| 908 | if (tab->table[code].nexttable != NULL) |
| 909 | zlib_freetable(&tab->table[code].nexttable); |
| 910 | |
| 911 | sfree(tab->table); |
| 912 | tab->table = NULL; |
| 913 | |
| 914 | sfree(tab); |
| 915 | *ztab = NULL; |
| 916 | |
| 917 | return (0); |
| 918 | } |
| 919 | |
| 920 | struct zlib_decompress_ctx { |
| 921 | struct zlib_table *staticlentable, *staticdisttable; |
| 922 | struct zlib_table *currlentable, *currdisttable, *lenlentable; |
| 923 | enum { |
| 924 | START, OUTSIDEBLK, |
| 925 | TREES_HDR, TREES_LENLEN, TREES_LEN, TREES_LENREP, |
| 926 | INBLK, GOTLENSYM, GOTLEN, GOTDISTSYM, |
| 927 | UNCOMP_LEN, UNCOMP_NLEN, UNCOMP_DATA |
| 928 | } state; |
| 929 | int sym, hlit, hdist, hclen, lenptr, lenextrabits, lenaddon, len, |
| 930 | lenrep; |
| 931 | int uncomplen; |
| 932 | unsigned char lenlen[19]; |
| 933 | unsigned char lengths[286 + 32]; |
| 934 | unsigned long bits; |
| 935 | int nbits; |
| 936 | unsigned char window[WINSIZE]; |
| 937 | int winpos; |
| 938 | unsigned char *outblk; |
| 939 | int outlen, outsize; |
| 940 | }; |
| 941 | |
| 942 | void *zlib_decompress_init(void) |
| 943 | { |
| 944 | struct zlib_decompress_ctx *dctx = snew(struct zlib_decompress_ctx); |
| 945 | unsigned char lengths[288]; |
| 946 | |
| 947 | memset(lengths, 8, 144); |
| 948 | memset(lengths + 144, 9, 256 - 144); |
| 949 | memset(lengths + 256, 7, 280 - 256); |
| 950 | memset(lengths + 280, 8, 288 - 280); |
| 951 | dctx->staticlentable = zlib_mktable(lengths, 288); |
| 952 | memset(lengths, 5, 32); |
| 953 | dctx->staticdisttable = zlib_mktable(lengths, 32); |
| 954 | dctx->state = START; /* even before header */ |
| 955 | dctx->currlentable = dctx->currdisttable = dctx->lenlentable = NULL; |
| 956 | dctx->bits = 0; |
| 957 | dctx->nbits = 0; |
| 958 | dctx->winpos = 0; |
| 959 | |
| 960 | return dctx; |
| 961 | } |
| 962 | |
| 963 | void zlib_decompress_cleanup(void *handle) |
| 964 | { |
| 965 | struct zlib_decompress_ctx *dctx = (struct zlib_decompress_ctx *)handle; |
| 966 | |
| 967 | if (dctx->currlentable && dctx->currlentable != dctx->staticlentable) |
| 968 | zlib_freetable(&dctx->currlentable); |
| 969 | if (dctx->currdisttable && dctx->currdisttable != dctx->staticdisttable) |
| 970 | zlib_freetable(&dctx->currdisttable); |
| 971 | if (dctx->lenlentable) |
| 972 | zlib_freetable(&dctx->lenlentable); |
| 973 | sfree(dctx); |
| 974 | } |
| 975 | |
| 976 | static int zlib_huflookup(unsigned long *bitsp, int *nbitsp, |
| 977 | struct zlib_table *tab) |
| 978 | { |
| 979 | unsigned long bits = *bitsp; |
| 980 | int nbits = *nbitsp; |
| 981 | while (1) { |
| 982 | struct zlib_tableentry *ent; |
| 983 | ent = &tab->table[bits & tab->mask]; |
| 984 | if (ent->nbits > nbits) |
| 985 | return -1; /* not enough data */ |
| 986 | bits >>= ent->nbits; |
| 987 | nbits -= ent->nbits; |
| 988 | if (ent->code == -1) |
| 989 | tab = ent->nexttable; |
| 990 | else { |
| 991 | *bitsp = bits; |
| 992 | *nbitsp = nbits; |
| 993 | return ent->code; |
| 994 | } |
| 995 | |
| 996 | if (!tab) { |
| 997 | /* |
| 998 | * There was a missing entry in the table, presumably |
| 999 | * due to an invalid Huffman table description, and the |
| 1000 | * subsequent data has attempted to use the missing |
| 1001 | * entry. Return a decoding failure. |
| 1002 | */ |
| 1003 | return -2; |
| 1004 | } |
| 1005 | } |
| 1006 | } |
| 1007 | |
| 1008 | static void zlib_emit_char(struct zlib_decompress_ctx *dctx, int c) |
| 1009 | { |
| 1010 | dctx->window[dctx->winpos] = c; |
| 1011 | dctx->winpos = (dctx->winpos + 1) & (WINSIZE - 1); |
| 1012 | if (dctx->outlen >= dctx->outsize) { |
| 1013 | dctx->outsize = dctx->outlen + 512; |
| 1014 | dctx->outblk = sresize(dctx->outblk, dctx->outsize, unsigned char); |
| 1015 | } |
| 1016 | dctx->outblk[dctx->outlen++] = c; |
| 1017 | } |
| 1018 | |
| 1019 | #define EATBITS(n) ( dctx->nbits -= (n), dctx->bits >>= (n) ) |
| 1020 | |
| 1021 | int zlib_decompress_block(void *handle, unsigned char *block, int len, |
| 1022 | unsigned char **outblock, int *outlen) |
| 1023 | { |
| 1024 | struct zlib_decompress_ctx *dctx = (struct zlib_decompress_ctx *)handle; |
| 1025 | const coderecord *rec; |
| 1026 | int code, blktype, rep, dist, nlen; |
| 1027 | static const unsigned char lenlenmap[] = { |
| 1028 | 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 |
| 1029 | }; |
| 1030 | |
| 1031 | dctx->outblk = NULL; |
| 1032 | dctx->outsize = dctx->outlen = 0; |
| 1033 | |
| 1034 | while (len > 0 || dctx->nbits > 0) { |
| 1035 | while (dctx->nbits < 24 && len > 0) { |
| 1036 | dctx->bits |= (*block++) << dctx->nbits; |
| 1037 | dctx->nbits += 8; |
| 1038 | len--; |
| 1039 | } |
| 1040 | switch (dctx->state) { |
| 1041 | case START: |
| 1042 | /* Expect 16-bit zlib header, which we'll dishonourably ignore. */ |
| 1043 | if (dctx->nbits < 16) |
| 1044 | goto finished; /* done all we can */ |
| 1045 | EATBITS(16); |
| 1046 | dctx->state = OUTSIDEBLK; |
| 1047 | break; |
| 1048 | case OUTSIDEBLK: |
| 1049 | /* Expect 3-bit block header. */ |
| 1050 | if (dctx->nbits < 3) |
| 1051 | goto finished; /* done all we can */ |
| 1052 | EATBITS(1); |
| 1053 | blktype = dctx->bits & 3; |
| 1054 | EATBITS(2); |
| 1055 | if (blktype == 0) { |
| 1056 | int to_eat = dctx->nbits & 7; |
| 1057 | dctx->state = UNCOMP_LEN; |
| 1058 | EATBITS(to_eat); /* align to byte boundary */ |
| 1059 | } else if (blktype == 1) { |
| 1060 | dctx->currlentable = dctx->staticlentable; |
| 1061 | dctx->currdisttable = dctx->staticdisttable; |
| 1062 | dctx->state = INBLK; |
| 1063 | } else if (blktype == 2) { |
| 1064 | dctx->state = TREES_HDR; |
| 1065 | } |
| 1066 | break; |
| 1067 | case TREES_HDR: |
| 1068 | /* |
| 1069 | * Dynamic block header. Five bits of HLIT, five of |
| 1070 | * HDIST, four of HCLEN. |
| 1071 | */ |
| 1072 | if (dctx->nbits < 5 + 5 + 4) |
| 1073 | goto finished; /* done all we can */ |
| 1074 | dctx->hlit = 257 + (dctx->bits & 31); |
| 1075 | EATBITS(5); |
| 1076 | dctx->hdist = 1 + (dctx->bits & 31); |
| 1077 | EATBITS(5); |
| 1078 | dctx->hclen = 4 + (dctx->bits & 15); |
| 1079 | EATBITS(4); |
| 1080 | dctx->lenptr = 0; |
| 1081 | dctx->state = TREES_LENLEN; |
| 1082 | memset(dctx->lenlen, 0, sizeof(dctx->lenlen)); |
| 1083 | break; |
| 1084 | case TREES_LENLEN: |
| 1085 | if (dctx->nbits < 3) |
| 1086 | goto finished; |
| 1087 | while (dctx->lenptr < dctx->hclen && dctx->nbits >= 3) { |
| 1088 | dctx->lenlen[lenlenmap[dctx->lenptr++]] = |
| 1089 | (unsigned char) (dctx->bits & 7); |
| 1090 | EATBITS(3); |
| 1091 | } |
| 1092 | if (dctx->lenptr == dctx->hclen) { |
| 1093 | dctx->lenlentable = zlib_mktable(dctx->lenlen, 19); |
| 1094 | dctx->state = TREES_LEN; |
| 1095 | dctx->lenptr = 0; |
| 1096 | } |
| 1097 | break; |
| 1098 | case TREES_LEN: |
| 1099 | if (dctx->lenptr >= dctx->hlit + dctx->hdist) { |
| 1100 | dctx->currlentable = zlib_mktable(dctx->lengths, dctx->hlit); |
| 1101 | dctx->currdisttable = zlib_mktable(dctx->lengths + dctx->hlit, |
| 1102 | dctx->hdist); |
| 1103 | zlib_freetable(&dctx->lenlentable); |
| 1104 | dctx->lenlentable = NULL; |
| 1105 | dctx->state = INBLK; |
| 1106 | break; |
| 1107 | } |
| 1108 | code = |
| 1109 | zlib_huflookup(&dctx->bits, &dctx->nbits, dctx->lenlentable); |
| 1110 | if (code == -1) |
| 1111 | goto finished; |
| 1112 | if (code == -2) |
| 1113 | goto decode_error; |
| 1114 | if (code < 16) |
| 1115 | dctx->lengths[dctx->lenptr++] = code; |
| 1116 | else { |
| 1117 | dctx->lenextrabits = (code == 16 ? 2 : code == 17 ? 3 : 7); |
| 1118 | dctx->lenaddon = (code == 18 ? 11 : 3); |
| 1119 | dctx->lenrep = (code == 16 && dctx->lenptr > 0 ? |
| 1120 | dctx->lengths[dctx->lenptr - 1] : 0); |
| 1121 | dctx->state = TREES_LENREP; |
| 1122 | } |
| 1123 | break; |
| 1124 | case TREES_LENREP: |
| 1125 | if (dctx->nbits < dctx->lenextrabits) |
| 1126 | goto finished; |
| 1127 | rep = |
| 1128 | dctx->lenaddon + |
| 1129 | (dctx->bits & ((1 << dctx->lenextrabits) - 1)); |
| 1130 | EATBITS(dctx->lenextrabits); |
| 1131 | while (rep > 0 && dctx->lenptr < dctx->hlit + dctx->hdist) { |
| 1132 | dctx->lengths[dctx->lenptr] = dctx->lenrep; |
| 1133 | dctx->lenptr++; |
| 1134 | rep--; |
| 1135 | } |
| 1136 | dctx->state = TREES_LEN; |
| 1137 | break; |
| 1138 | case INBLK: |
| 1139 | code = |
| 1140 | zlib_huflookup(&dctx->bits, &dctx->nbits, dctx->currlentable); |
| 1141 | if (code == -1) |
| 1142 | goto finished; |
| 1143 | if (code == -2) |
| 1144 | goto decode_error; |
| 1145 | if (code < 256) |
| 1146 | zlib_emit_char(dctx, code); |
| 1147 | else if (code == 256) { |
| 1148 | dctx->state = OUTSIDEBLK; |
| 1149 | if (dctx->currlentable != dctx->staticlentable) { |
| 1150 | zlib_freetable(&dctx->currlentable); |
| 1151 | dctx->currlentable = NULL; |
| 1152 | } |
| 1153 | if (dctx->currdisttable != dctx->staticdisttable) { |
| 1154 | zlib_freetable(&dctx->currdisttable); |
| 1155 | dctx->currdisttable = NULL; |
| 1156 | } |
| 1157 | } else if (code < 286) { /* static tree can give >285; ignore */ |
| 1158 | dctx->state = GOTLENSYM; |
| 1159 | dctx->sym = code; |
| 1160 | } |
| 1161 | break; |
| 1162 | case GOTLENSYM: |
| 1163 | rec = &lencodes[dctx->sym - 257]; |
| 1164 | if (dctx->nbits < rec->extrabits) |
| 1165 | goto finished; |
| 1166 | dctx->len = |
| 1167 | rec->min + (dctx->bits & ((1 << rec->extrabits) - 1)); |
| 1168 | EATBITS(rec->extrabits); |
| 1169 | dctx->state = GOTLEN; |
| 1170 | break; |
| 1171 | case GOTLEN: |
| 1172 | code = |
| 1173 | zlib_huflookup(&dctx->bits, &dctx->nbits, |
| 1174 | dctx->currdisttable); |
| 1175 | if (code == -1) |
| 1176 | goto finished; |
| 1177 | if (code == -2) |
| 1178 | goto decode_error; |
| 1179 | dctx->state = GOTDISTSYM; |
| 1180 | dctx->sym = code; |
| 1181 | break; |
| 1182 | case GOTDISTSYM: |
| 1183 | rec = &distcodes[dctx->sym]; |
| 1184 | if (dctx->nbits < rec->extrabits) |
| 1185 | goto finished; |
| 1186 | dist = rec->min + (dctx->bits & ((1 << rec->extrabits) - 1)); |
| 1187 | EATBITS(rec->extrabits); |
| 1188 | dctx->state = INBLK; |
| 1189 | while (dctx->len--) |
| 1190 | zlib_emit_char(dctx, dctx->window[(dctx->winpos - dist) & |
| 1191 | (WINSIZE - 1)]); |
| 1192 | break; |
| 1193 | case UNCOMP_LEN: |
| 1194 | /* |
| 1195 | * Uncompressed block. We expect to see a 16-bit LEN. |
| 1196 | */ |
| 1197 | if (dctx->nbits < 16) |
| 1198 | goto finished; |
| 1199 | dctx->uncomplen = dctx->bits & 0xFFFF; |
| 1200 | EATBITS(16); |
| 1201 | dctx->state = UNCOMP_NLEN; |
| 1202 | break; |
| 1203 | case UNCOMP_NLEN: |
| 1204 | /* |
| 1205 | * Uncompressed block. We expect to see a 16-bit NLEN, |
| 1206 | * which should be the one's complement of the previous |
| 1207 | * LEN. |
| 1208 | */ |
| 1209 | if (dctx->nbits < 16) |
| 1210 | goto finished; |
| 1211 | nlen = dctx->bits & 0xFFFF; |
| 1212 | EATBITS(16); |
| 1213 | if (dctx->uncomplen == 0) |
| 1214 | dctx->state = OUTSIDEBLK; /* block is empty */ |
| 1215 | else |
| 1216 | dctx->state = UNCOMP_DATA; |
| 1217 | break; |
| 1218 | case UNCOMP_DATA: |
| 1219 | if (dctx->nbits < 8) |
| 1220 | goto finished; |
| 1221 | zlib_emit_char(dctx, dctx->bits & 0xFF); |
| 1222 | EATBITS(8); |
| 1223 | if (--dctx->uncomplen == 0) |
| 1224 | dctx->state = OUTSIDEBLK; /* end of uncompressed block */ |
| 1225 | break; |
| 1226 | } |
| 1227 | } |
| 1228 | |
| 1229 | finished: |
| 1230 | *outblock = dctx->outblk; |
| 1231 | *outlen = dctx->outlen; |
| 1232 | return 1; |
| 1233 | |
| 1234 | decode_error: |
| 1235 | sfree(dctx->outblk); |
| 1236 | *outblock = dctx->outblk = NULL; |
| 1237 | *outlen = 0; |
| 1238 | return 0; |
| 1239 | } |
| 1240 | |
| 1241 | const struct ssh_compress ssh_zlib = { |
| 1242 | "zlib", |
| 1243 | zlib_compress_init, |
| 1244 | zlib_compress_cleanup, |
| 1245 | zlib_compress_block, |
| 1246 | zlib_decompress_init, |
| 1247 | zlib_decompress_cleanup, |
| 1248 | zlib_decompress_block, |
| 1249 | zlib_disable_compression, |
| 1250 | "zlib (RFC1950)" |
| 1251 | }; |