rsc | b6afd33 | 2003-11-23 18:19:18 +0000 | [diff] [blame] | 1 | #include <u.h> |
| 2 | #include <libc.h> |
| 3 | #include <flate.h> |
| 4 | |
| 5 | typedef struct Chain Chain; |
| 6 | typedef struct Chains Chains; |
| 7 | typedef struct Dyncode Dyncode; |
| 8 | typedef struct Huff Huff; |
| 9 | typedef struct LZblock LZblock; |
| 10 | typedef struct LZstate LZstate; |
| 11 | |
| 12 | enum |
| 13 | { |
| 14 | /* |
| 15 | * deflate format paramaters |
| 16 | */ |
| 17 | DeflateUnc = 0, /* uncompressed block */ |
| 18 | DeflateFix = 1, /* fixed huffman codes */ |
| 19 | DeflateDyn = 2, /* dynamic huffman codes */ |
| 20 | |
| 21 | DeflateEob = 256, /* end of block code in lit/len book */ |
| 22 | DeflateMaxBlock = 64*1024-1, /* maximum size of uncompressed block */ |
| 23 | |
| 24 | DeflateMaxExp = 10, /* maximum expansion for a block */ |
| 25 | |
| 26 | LenStart = 257, /* start of length codes in litlen */ |
| 27 | Nlitlen = 288, /* number of litlen codes */ |
| 28 | Noff = 30, /* number of offset codes */ |
| 29 | Nclen = 19, /* number of codelen codes */ |
| 30 | |
| 31 | MaxOff = 32*1024, |
| 32 | MinMatch = 3, /* shortest match possible */ |
| 33 | MaxMatch = 258, /* longest match possible */ |
| 34 | |
| 35 | /* |
| 36 | * huffman code paramaters |
| 37 | */ |
| 38 | MaxLeaf = Nlitlen, |
| 39 | MaxHuffBits = 16, /* max bits in a huffman code */ |
| 40 | ChainMem = 2 * (MaxHuffBits - 1) * MaxHuffBits, |
| 41 | |
| 42 | /* |
| 43 | * coding of the lz parse |
| 44 | */ |
| 45 | LenFlag = 1 << 3, |
| 46 | LenShift = 4, /* leaves enough space for MinMatchMaxOff */ |
| 47 | MaxLitRun = LenFlag - 1, |
| 48 | |
| 49 | /* |
| 50 | * internal lz paramaters |
| 51 | */ |
| 52 | DeflateOut = 4096, /* output buffer size */ |
| 53 | BlockSize = 8192, /* attempted input read quanta */ |
| 54 | DeflateBlock = DeflateMaxBlock & ~(BlockSize - 1), |
| 55 | MinMatchMaxOff = 4096, /* max profitable offset for small match; |
| 56 | * assumes 8 bits for len, 5+10 for offset |
| 57 | * DONT CHANGE WITHOUT CHANGING LZPARSE CONSTANTS |
| 58 | */ |
| 59 | HistSlop = 512, /* must be at lead MaxMatch */ |
| 60 | HistBlock = 64*1024, |
| 61 | HistSize = HistBlock + HistSlop, |
| 62 | |
| 63 | HashLog = 13, |
| 64 | HashSize = 1<<HashLog, |
| 65 | |
| 66 | MaxOffCode = 256, /* biggest offset looked up in direct table */ |
| 67 | |
| 68 | EstLitBits = 8, |
| 69 | EstLenBits = 4, |
rsc | cbeb0b2 | 2006-04-01 19:24:03 +0000 | [diff] [blame] | 70 | EstOffBits = 5 |
rsc | b6afd33 | 2003-11-23 18:19:18 +0000 | [diff] [blame] | 71 | }; |
| 72 | |
| 73 | /* |
| 74 | * knuth vol. 3 multiplicative hashing |
| 75 | * each byte x chosen according to rules |
| 76 | * 1/4 < x < 3/10, 1/3 x < < 3/7, 4/7 < x < 2/3, 7/10 < x < 3/4 |
| 77 | * with reasonable spread between the bytes & their complements |
| 78 | * |
| 79 | * the 3 byte value appears to be as almost good as the 4 byte value, |
| 80 | * and might be faster on some machines |
| 81 | */ |
| 82 | /* |
rsc | 00c6cee | 2006-06-07 23:25:39 +0000 | [diff] [blame] | 83 | #define hashit(c) ((u32int)((c) * 0x6b43a9) >> (24 - HashLog)) |
rsc | b6afd33 | 2003-11-23 18:19:18 +0000 | [diff] [blame] | 84 | */ |
rsc | 00c6cee | 2006-06-07 23:25:39 +0000 | [diff] [blame] | 85 | #define hashit(c) ((u32int)(((c) & 0xffffff) * 0x6b43a9b5) >> (32 - HashLog)) |
rsc | b6afd33 | 2003-11-23 18:19:18 +0000 | [diff] [blame] | 86 | |
| 87 | /* |
| 88 | * lempel-ziv style compression state |
| 89 | */ |
| 90 | struct LZstate |
| 91 | { |
| 92 | uchar hist[HistSize]; |
| 93 | ulong pos; /* current location in history buffer */ |
| 94 | ulong avail; /* data available after pos */ |
| 95 | int eof; |
| 96 | ushort hash[HashSize]; /* hash chains */ |
| 97 | ushort nexts[MaxOff]; |
| 98 | int now; /* pos in hash chains */ |
| 99 | int dot; /* dawn of time in history */ |
| 100 | int prevlen; /* lazy matching state */ |
| 101 | int prevoff; |
| 102 | int maxcheck; /* compressor tuning */ |
| 103 | |
| 104 | uchar obuf[DeflateOut]; |
| 105 | uchar *out; /* current position in the output buffer */ |
| 106 | uchar *eout; |
| 107 | ulong bits; /* bit shift register */ |
| 108 | int nbits; |
| 109 | int rbad; /* got an error reading the buffer */ |
| 110 | int wbad; /* got an error writing the buffer */ |
| 111 | int (*w)(void*, void*, int); |
| 112 | void *wr; |
| 113 | |
| 114 | ulong totr; /* total input size */ |
| 115 | ulong totw; /* total output size */ |
| 116 | int debug; |
| 117 | }; |
| 118 | |
| 119 | struct LZblock |
| 120 | { |
| 121 | ushort parse[DeflateMaxBlock / 2 + 1]; |
| 122 | int lastv; /* value being constucted for parse */ |
| 123 | ulong litlencount[Nlitlen]; |
| 124 | ulong offcount[Noff]; |
| 125 | ushort *eparse; /* limit for parse table */ |
| 126 | int bytes; /* consumed from the input */ |
| 127 | int excost; /* cost of encoding extra len & off bits */ |
| 128 | }; |
| 129 | |
| 130 | /* |
| 131 | * huffman code table |
| 132 | */ |
| 133 | struct Huff |
| 134 | { |
| 135 | short bits; /* length of the code */ |
| 136 | ushort encode; /* the code */ |
| 137 | }; |
| 138 | |
| 139 | /* |
| 140 | * encoding of dynamic huffman trees |
| 141 | */ |
| 142 | struct Dyncode |
| 143 | { |
| 144 | int nlit; |
| 145 | int noff; |
| 146 | int nclen; |
| 147 | int ncode; |
| 148 | Huff codetab[Nclen]; |
| 149 | uchar codes[Nlitlen+Noff]; |
| 150 | uchar codeaux[Nlitlen+Noff]; |
| 151 | }; |
| 152 | |
| 153 | static int deflateb(LZstate *lz, LZblock *lzb, void *rr, int (*r)(void*, void*, int)); |
| 154 | static int lzcomp(LZstate*, LZblock*, uchar*, ushort*, int finish); |
| 155 | static void wrblock(LZstate*, int, ushort*, ushort*, Huff*, Huff*); |
| 156 | static int bitcost(Huff*, ulong*, int); |
| 157 | static int huffcodes(Dyncode*, Huff*, Huff*); |
| 158 | static void wrdyncode(LZstate*, Dyncode*); |
| 159 | static void lzput(LZstate*, ulong bits, int nbits); |
| 160 | static void lzflushbits(LZstate*); |
| 161 | static void lzflush(LZstate *lz); |
| 162 | static void lzwrite(LZstate *lz, void *buf, int n); |
| 163 | |
| 164 | static int hufftabinit(Huff*, int, ulong*, int); |
| 165 | static int mkgzprecode(Huff*, ulong *, int, int); |
| 166 | |
| 167 | static int mkprecode(Huff*, ulong *, int, int, ulong*); |
| 168 | static void nextchain(Chains*, int); |
| 169 | static void leafsort(ulong*, ushort*, int, int); |
| 170 | |
| 171 | /* conversion from len to code word */ |
| 172 | static int lencode[MaxMatch]; |
| 173 | |
| 174 | /* |
| 175 | * conversion from off to code word |
| 176 | * off <= MaxOffCode ? offcode[off] : bigoffcode[off >> 7] |
| 177 | */ |
| 178 | static int offcode[MaxOffCode]; |
| 179 | static int bigoffcode[256]; |
| 180 | |
| 181 | /* litlen code words LenStart-285 extra bits */ |
| 182 | static int litlenbase[Nlitlen-LenStart]; |
| 183 | static int litlenextra[Nlitlen-LenStart] = |
| 184 | { |
| 185 | /* 257 */ 0, 0, 0, |
| 186 | /* 260 */ 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, |
| 187 | /* 270 */ 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, |
| 188 | /* 280 */ 4, 5, 5, 5, 5, 0, 0, 0 |
| 189 | }; |
| 190 | |
| 191 | /* offset code word extra bits */ |
| 192 | static int offbase[Noff]; |
| 193 | static int offextra[] = |
| 194 | { |
| 195 | 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, |
| 196 | 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, |
| 197 | 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, |
| 198 | 0, 0, |
| 199 | }; |
| 200 | |
| 201 | /* order code lengths */ |
| 202 | static int clenorder[Nclen] = |
| 203 | { |
| 204 | 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 |
| 205 | }; |
| 206 | |
| 207 | /* static huffman tables */ |
| 208 | static Huff litlentab[Nlitlen]; |
| 209 | static Huff offtab[Noff]; |
| 210 | static Huff hofftab[Noff]; |
| 211 | |
| 212 | /* bit reversal for brain dead endian swap in huffman codes */ |
| 213 | static uchar revtab[256]; |
| 214 | static ulong nlits; |
| 215 | static ulong nmatches; |
| 216 | |
| 217 | int |
| 218 | deflateinit(void) |
| 219 | { |
| 220 | ulong bitcount[MaxHuffBits]; |
| 221 | int i, j, ci, n; |
| 222 | |
| 223 | /* byte reverse table */ |
| 224 | for(i=0; i<256; i++) |
| 225 | for(j=0; j<8; j++) |
| 226 | if(i & (1<<j)) |
| 227 | revtab[i] |= 0x80 >> j; |
| 228 | |
| 229 | /* static Litlen bit lengths */ |
| 230 | for(i=0; i<144; i++) |
| 231 | litlentab[i].bits = 8; |
| 232 | for(i=144; i<256; i++) |
| 233 | litlentab[i].bits = 9; |
| 234 | for(i=256; i<280; i++) |
| 235 | litlentab[i].bits = 7; |
| 236 | for(i=280; i<Nlitlen; i++) |
| 237 | litlentab[i].bits = 8; |
| 238 | |
| 239 | memset(bitcount, 0, sizeof(bitcount)); |
| 240 | bitcount[8] += 144 - 0; |
| 241 | bitcount[9] += 256 - 144; |
| 242 | bitcount[7] += 280 - 256; |
| 243 | bitcount[8] += Nlitlen - 280; |
| 244 | |
| 245 | if(!hufftabinit(litlentab, Nlitlen, bitcount, 9)) |
| 246 | return FlateInternal; |
| 247 | |
| 248 | /* static offset bit lengths */ |
| 249 | for(i = 0; i < Noff; i++) |
| 250 | offtab[i].bits = 5; |
| 251 | |
| 252 | memset(bitcount, 0, sizeof(bitcount)); |
| 253 | bitcount[5] = Noff; |
| 254 | |
| 255 | if(!hufftabinit(offtab, Noff, bitcount, 5)) |
| 256 | return FlateInternal; |
| 257 | |
| 258 | bitcount[0] = 0; |
| 259 | bitcount[1] = 0; |
| 260 | if(!mkgzprecode(hofftab, bitcount, 2, MaxHuffBits)) |
| 261 | return FlateInternal; |
| 262 | |
| 263 | /* conversion tables for lens & offs to codes */ |
| 264 | ci = 0; |
| 265 | for(i = LenStart; i < 286; i++){ |
| 266 | n = ci + (1 << litlenextra[i - LenStart]); |
| 267 | litlenbase[i - LenStart] = ci; |
| 268 | for(; ci < n; ci++) |
| 269 | lencode[ci] = i; |
| 270 | } |
| 271 | /* patch up special case for len MaxMatch */ |
| 272 | lencode[MaxMatch-MinMatch] = 285; |
| 273 | litlenbase[285-LenStart] = MaxMatch-MinMatch; |
| 274 | |
| 275 | ci = 0; |
| 276 | for(i = 0; i < 16; i++){ |
| 277 | n = ci + (1 << offextra[i]); |
| 278 | offbase[i] = ci; |
| 279 | for(; ci < n; ci++) |
| 280 | offcode[ci] = i; |
| 281 | } |
| 282 | |
| 283 | ci = ci >> 7; |
| 284 | for(; i < 30; i++){ |
| 285 | n = ci + (1 << (offextra[i] - 7)); |
| 286 | offbase[i] = ci << 7; |
| 287 | for(; ci < n; ci++) |
| 288 | bigoffcode[ci] = i; |
| 289 | } |
| 290 | return FlateOk; |
| 291 | } |
| 292 | |
| 293 | static void |
| 294 | deflatereset(LZstate *lz, int level, int debug) |
| 295 | { |
| 296 | memset(lz->nexts, 0, sizeof lz->nexts); |
| 297 | memset(lz->hash, 0, sizeof lz->hash); |
| 298 | lz->totr = 0; |
| 299 | lz->totw = 0; |
| 300 | lz->pos = 0; |
| 301 | lz->avail = 0; |
| 302 | lz->out = lz->obuf; |
| 303 | lz->eout = &lz->obuf[DeflateOut]; |
| 304 | lz->prevlen = MinMatch - 1; |
| 305 | lz->prevoff = 0; |
| 306 | lz->now = MaxOff + 1; |
| 307 | lz->dot = lz->now; |
| 308 | lz->bits = 0; |
| 309 | lz->nbits = 0; |
| 310 | lz->maxcheck = (1 << level); |
| 311 | lz->maxcheck -= lz->maxcheck >> 2; |
| 312 | if(lz->maxcheck < 2) |
| 313 | lz->maxcheck = 2; |
| 314 | else if(lz->maxcheck > 1024) |
| 315 | lz->maxcheck = 1024; |
| 316 | |
| 317 | lz->debug = debug; |
| 318 | } |
| 319 | |
| 320 | int |
| 321 | deflate(void *wr, int (*w)(void*, void*, int), void *rr, int (*r)(void*, void*, int), int level, int debug) |
| 322 | { |
| 323 | LZstate *lz; |
| 324 | LZblock *lzb; |
| 325 | int ok; |
| 326 | |
| 327 | lz = malloc(sizeof *lz + sizeof *lzb); |
| 328 | if(lz == nil) |
| 329 | return FlateNoMem; |
| 330 | lzb = (LZblock*)&lz[1]; |
| 331 | |
| 332 | deflatereset(lz, level, debug); |
| 333 | lz->w = w; |
| 334 | lz->wr = wr; |
| 335 | lz->wbad = 0; |
| 336 | lz->rbad = 0; |
| 337 | lz->eof = 0; |
| 338 | ok = FlateOk; |
| 339 | while(!lz->eof || lz->avail){ |
| 340 | ok = deflateb(lz, lzb, rr, r); |
| 341 | if(ok != FlateOk) |
| 342 | break; |
| 343 | } |
| 344 | if(ok == FlateOk && lz->rbad) |
| 345 | ok = FlateInputFail; |
| 346 | if(ok == FlateOk && lz->wbad) |
| 347 | ok = FlateOutputFail; |
| 348 | free(lz); |
| 349 | return ok; |
| 350 | } |
| 351 | |
| 352 | static int |
| 353 | deflateb(LZstate *lz, LZblock *lzb, void *rr, int (*r)(void*, void*, int)) |
| 354 | { |
| 355 | Dyncode dyncode, hdyncode; |
| 356 | Huff dlitlentab[Nlitlen], dofftab[Noff], hlitlentab[Nlitlen]; |
| 357 | ulong litcount[Nlitlen]; |
| 358 | long nunc, ndyn, nfix, nhuff; |
| 359 | uchar *slop, *hslop; |
| 360 | ulong ep; |
| 361 | int i, n, m, mm, nslop; |
| 362 | |
| 363 | memset(lzb->litlencount, 0, sizeof lzb->litlencount); |
| 364 | memset(lzb->offcount, 0, sizeof lzb->offcount); |
| 365 | lzb->litlencount[DeflateEob]++; |
| 366 | |
| 367 | lzb->bytes = 0; |
| 368 | lzb->eparse = lzb->parse; |
| 369 | lzb->lastv = 0; |
| 370 | lzb->excost = 0; |
| 371 | |
| 372 | slop = &lz->hist[lz->pos]; |
| 373 | n = lz->avail; |
| 374 | while(n < DeflateBlock && (!lz->eof || lz->avail)){ |
| 375 | /* |
| 376 | * fill the buffer as much as possible, |
| 377 | * while leaving room for MaxOff history behind lz->pos, |
| 378 | * and not reading more than we can handle. |
| 379 | * |
| 380 | * make sure we read at least HistSlop bytes. |
| 381 | */ |
| 382 | if(!lz->eof){ |
| 383 | ep = lz->pos + lz->avail; |
| 384 | if(ep >= HistBlock) |
| 385 | ep -= HistBlock; |
| 386 | m = HistBlock - MaxOff - lz->avail; |
| 387 | if(m > HistBlock - n) |
| 388 | m = HistBlock - n; |
| 389 | if(m > (HistBlock + HistSlop) - ep) |
| 390 | m = (HistBlock + HistSlop) - ep; |
| 391 | if(m & ~(BlockSize - 1)) |
| 392 | m &= ~(BlockSize - 1); |
| 393 | |
| 394 | /* |
| 395 | * be nice to the caller: stop reads that are too small. |
| 396 | * can only get here when we've already filled the buffer some |
| 397 | */ |
| 398 | if(m < HistSlop){ |
| 399 | if(!m || !lzb->bytes) |
| 400 | return FlateInternal; |
| 401 | break; |
| 402 | } |
| 403 | |
| 404 | mm = (*r)(rr, &lz->hist[ep], m); |
| 405 | if(mm > 0){ |
| 406 | /* |
| 407 | * wrap data to end if we're read it from the beginning |
| 408 | * this way, we don't have to wrap searches. |
| 409 | * |
| 410 | * wrap reads past the end to the beginning. |
| 411 | * this way, we can guarantee minimum size reads. |
| 412 | */ |
| 413 | if(ep < HistSlop) |
| 414 | memmove(&lz->hist[ep + HistBlock], &lz->hist[ep], HistSlop - ep); |
| 415 | else if(ep + mm > HistBlock) |
| 416 | memmove(&lz->hist[0], &lz->hist[HistBlock], ep + mm - HistBlock); |
| 417 | |
| 418 | lz->totr += mm; |
| 419 | n += mm; |
| 420 | lz->avail += mm; |
| 421 | }else{ |
| 422 | if(mm < 0) |
| 423 | lz->rbad = 1; |
| 424 | lz->eof = 1; |
| 425 | } |
| 426 | } |
| 427 | ep = lz->pos + lz->avail; |
| 428 | if(ep > HistSize) |
| 429 | ep = HistSize; |
| 430 | if(lzb->bytes + ep - lz->pos > DeflateMaxBlock) |
| 431 | ep = lz->pos + DeflateMaxBlock - lzb->bytes; |
| 432 | m = lzcomp(lz, lzb, &lz->hist[ep], lzb->eparse, lz->eof); |
| 433 | lzb->bytes += m; |
| 434 | lz->pos = (lz->pos + m) & (HistBlock - 1); |
| 435 | lz->avail -= m; |
| 436 | } |
| 437 | if(lzb->lastv) |
| 438 | *lzb->eparse++ = lzb->lastv; |
| 439 | if(lzb->eparse > lzb->parse + nelem(lzb->parse)) |
| 440 | return FlateInternal; |
| 441 | nunc = lzb->bytes; |
| 442 | |
| 443 | if(!mkgzprecode(dlitlentab, lzb->litlencount, Nlitlen, MaxHuffBits) |
| 444 | || !mkgzprecode(dofftab, lzb->offcount, Noff, MaxHuffBits)) |
| 445 | return FlateInternal; |
| 446 | |
| 447 | ndyn = huffcodes(&dyncode, dlitlentab, dofftab); |
| 448 | if(ndyn < 0) |
| 449 | return FlateInternal; |
| 450 | ndyn += bitcost(dlitlentab, lzb->litlencount, Nlitlen) |
| 451 | + bitcost(dofftab, lzb->offcount, Noff) |
| 452 | + lzb->excost; |
| 453 | |
| 454 | memset(litcount, 0, sizeof litcount); |
| 455 | |
| 456 | nslop = nunc; |
| 457 | if(nslop > &lz->hist[HistSize] - slop) |
| 458 | nslop = &lz->hist[HistSize] - slop; |
| 459 | |
| 460 | for(i = 0; i < nslop; i++) |
| 461 | litcount[slop[i]]++; |
| 462 | hslop = &lz->hist[HistSlop - nslop]; |
| 463 | for(; i < nunc; i++) |
| 464 | litcount[hslop[i]]++; |
| 465 | litcount[DeflateEob]++; |
| 466 | |
| 467 | if(!mkgzprecode(hlitlentab, litcount, Nlitlen, MaxHuffBits)) |
| 468 | return FlateInternal; |
| 469 | nhuff = huffcodes(&hdyncode, hlitlentab, hofftab); |
| 470 | if(nhuff < 0) |
| 471 | return FlateInternal; |
| 472 | nhuff += bitcost(hlitlentab, litcount, Nlitlen); |
| 473 | |
| 474 | nfix = bitcost(litlentab, lzb->litlencount, Nlitlen) |
| 475 | + bitcost(offtab, lzb->offcount, Noff) |
| 476 | + lzb->excost; |
| 477 | |
| 478 | lzput(lz, lz->eof && !lz->avail, 1); |
| 479 | |
| 480 | if(lz->debug){ |
| 481 | fprint(2, "block: bytes=%lud entries=%ld extra bits=%d\n\tuncompressed=%lud fixed=%lud dynamic=%lud huffman=%lud\n", |
| 482 | nunc, lzb->eparse - lzb->parse, lzb->excost, (nunc + 4) * 8, nfix, ndyn, nhuff); |
| 483 | fprint(2, "\tnlit=%lud matches=%lud eof=%d\n", nlits, nmatches, lz->eof && !lz->avail); |
| 484 | } |
| 485 | |
| 486 | if((nunc + 4) * 8 < ndyn && (nunc + 4) * 8 < nfix && (nunc + 4) * 8 < nhuff){ |
| 487 | lzput(lz, DeflateUnc, 2); |
| 488 | lzflushbits(lz); |
| 489 | |
| 490 | lzput(lz, nunc & 0xff, 8); |
| 491 | lzput(lz, (nunc >> 8) & 0xff, 8); |
| 492 | lzput(lz, ~nunc & 0xff, 8); |
| 493 | lzput(lz, (~nunc >> 8) & 0xff, 8); |
| 494 | lzflush(lz); |
| 495 | |
| 496 | lzwrite(lz, slop, nslop); |
| 497 | lzwrite(lz, &lz->hist[HistSlop], nunc - nslop); |
| 498 | }else if(ndyn < nfix && ndyn < nhuff){ |
| 499 | lzput(lz, DeflateDyn, 2); |
| 500 | |
| 501 | wrdyncode(lz, &dyncode); |
| 502 | wrblock(lz, slop - lz->hist, lzb->parse, lzb->eparse, dlitlentab, dofftab); |
| 503 | lzput(lz, dlitlentab[DeflateEob].encode, dlitlentab[DeflateEob].bits); |
| 504 | }else if(nhuff < nfix){ |
| 505 | lzput(lz, DeflateDyn, 2); |
| 506 | |
| 507 | wrdyncode(lz, &hdyncode); |
| 508 | |
| 509 | m = 0; |
| 510 | for(i = nunc; i > MaxLitRun; i -= MaxLitRun) |
| 511 | lzb->parse[m++] = MaxLitRun; |
| 512 | lzb->parse[m++] = i; |
| 513 | |
| 514 | wrblock(lz, slop - lz->hist, lzb->parse, lzb->parse + m, hlitlentab, hofftab); |
| 515 | lzput(lz, hlitlentab[DeflateEob].encode, hlitlentab[DeflateEob].bits); |
| 516 | }else{ |
| 517 | lzput(lz, DeflateFix, 2); |
| 518 | |
| 519 | wrblock(lz, slop - lz->hist, lzb->parse, lzb->eparse, litlentab, offtab); |
| 520 | lzput(lz, litlentab[DeflateEob].encode, litlentab[DeflateEob].bits); |
| 521 | } |
| 522 | |
| 523 | if(lz->eof && !lz->avail){ |
| 524 | lzflushbits(lz); |
| 525 | lzflush(lz); |
| 526 | } |
| 527 | return FlateOk; |
| 528 | } |
| 529 | |
| 530 | static void |
| 531 | lzwrite(LZstate *lz, void *buf, int n) |
| 532 | { |
| 533 | int nw; |
| 534 | |
| 535 | if(n && lz->w){ |
| 536 | nw = (*lz->w)(lz->wr, buf, n); |
| 537 | if(nw != n){ |
rsc | a0f1e21 | 2004-04-20 02:03:38 +0000 | [diff] [blame] | 538 | lz->w = 0; |
rsc | b6afd33 | 2003-11-23 18:19:18 +0000 | [diff] [blame] | 539 | lz->wbad = 1; |
| 540 | }else |
| 541 | lz->totw += n; |
| 542 | } |
| 543 | } |
| 544 | |
| 545 | static void |
| 546 | lzflush(LZstate *lz) |
| 547 | { |
| 548 | lzwrite(lz, lz->obuf, lz->out - lz->obuf); |
| 549 | lz->out = lz->obuf; |
| 550 | } |
| 551 | |
| 552 | static void |
| 553 | lzput(LZstate *lz, ulong bits, int nbits) |
| 554 | { |
| 555 | bits = (bits << lz->nbits) | lz->bits; |
| 556 | for(nbits += lz->nbits; nbits >= 8; nbits -= 8){ |
| 557 | *lz->out++ = bits; |
| 558 | if(lz->out == lz->eout) |
| 559 | lzflush(lz); |
| 560 | bits >>= 8; |
| 561 | } |
| 562 | lz->bits = bits; |
| 563 | lz->nbits = nbits; |
| 564 | } |
| 565 | |
| 566 | static void |
| 567 | lzflushbits(LZstate *lz) |
| 568 | { |
| 569 | if(lz->nbits) |
| 570 | lzput(lz, 0, 8 - (lz->nbits & 7)); |
| 571 | } |
| 572 | |
| 573 | /* |
| 574 | * write out a block of n samples, |
| 575 | * given lz encoding and counts for huffman tables |
| 576 | */ |
| 577 | static void |
| 578 | wrblock(LZstate *out, int litoff, ushort *soff, ushort *eoff, Huff *litlentab, Huff *offtab) |
| 579 | { |
| 580 | ushort *off; |
| 581 | int i, run, offset, lit, len, c; |
| 582 | |
| 583 | if(out->debug > 2){ |
| 584 | for(off = soff; off < eoff; ){ |
| 585 | offset = *off++; |
| 586 | run = offset & MaxLitRun; |
| 587 | if(run){ |
| 588 | for(i = 0; i < run; i++){ |
| 589 | lit = out->hist[litoff & (HistBlock - 1)]; |
| 590 | litoff++; |
| 591 | fprint(2, "\tlit %.2ux %c\n", lit, lit); |
| 592 | } |
| 593 | if(!(offset & LenFlag)) |
| 594 | continue; |
| 595 | len = offset >> LenShift; |
| 596 | offset = *off++; |
| 597 | }else if(offset & LenFlag){ |
| 598 | len = offset >> LenShift; |
| 599 | offset = *off++; |
| 600 | }else{ |
| 601 | len = 0; |
| 602 | offset >>= LenShift; |
| 603 | } |
| 604 | litoff += len + MinMatch; |
| 605 | fprint(2, "\t<%d, %d>\n", offset + 1, len + MinMatch); |
| 606 | } |
| 607 | } |
| 608 | |
| 609 | for(off = soff; off < eoff; ){ |
| 610 | offset = *off++; |
| 611 | run = offset & MaxLitRun; |
| 612 | if(run){ |
| 613 | for(i = 0; i < run; i++){ |
| 614 | lit = out->hist[litoff & (HistBlock - 1)]; |
| 615 | litoff++; |
| 616 | lzput(out, litlentab[lit].encode, litlentab[lit].bits); |
| 617 | } |
| 618 | if(!(offset & LenFlag)) |
| 619 | continue; |
| 620 | len = offset >> LenShift; |
| 621 | offset = *off++; |
| 622 | }else if(offset & LenFlag){ |
| 623 | len = offset >> LenShift; |
| 624 | offset = *off++; |
| 625 | }else{ |
| 626 | len = 0; |
| 627 | offset >>= LenShift; |
| 628 | } |
| 629 | litoff += len + MinMatch; |
| 630 | c = lencode[len]; |
| 631 | lzput(out, litlentab[c].encode, litlentab[c].bits); |
| 632 | c -= LenStart; |
| 633 | if(litlenextra[c]) |
| 634 | lzput(out, len - litlenbase[c], litlenextra[c]); |
| 635 | |
| 636 | if(offset < MaxOffCode) |
| 637 | c = offcode[offset]; |
| 638 | else |
| 639 | c = bigoffcode[offset >> 7]; |
| 640 | lzput(out, offtab[c].encode, offtab[c].bits); |
| 641 | if(offextra[c]) |
| 642 | lzput(out, offset - offbase[c], offextra[c]); |
| 643 | } |
| 644 | } |
| 645 | |
| 646 | /* |
| 647 | * look for the longest, closest string which matches |
| 648 | * the next prefix. the clever part here is looking for |
| 649 | * a string 1 longer than the previous best match. |
| 650 | * |
| 651 | * follows the recommendation of limiting number of chains |
| 652 | * which are checked. this appears to be the best heuristic. |
| 653 | */ |
| 654 | static int |
| 655 | lzmatch(int now, int then, uchar *p, uchar *es, ushort *nexts, uchar *hist, int runlen, int check, int *m) |
| 656 | { |
| 657 | uchar *s, *t; |
| 658 | int ml, off, last; |
| 659 | |
| 660 | ml = check; |
| 661 | if(runlen >= 8) |
| 662 | check >>= 2; |
| 663 | *m = 0; |
| 664 | if(p + runlen >= es) |
| 665 | return runlen; |
| 666 | last = 0; |
| 667 | for(; check-- > 0; then = nexts[then & (MaxOff-1)]){ |
| 668 | off = (ushort)(now - then); |
| 669 | if(off <= last || off > MaxOff) |
| 670 | break; |
| 671 | s = p + runlen; |
| 672 | t = hist + (((p - hist) - off) & (HistBlock-1)); |
| 673 | t += runlen; |
| 674 | for(; s >= p; s--){ |
| 675 | if(*s != *t) |
| 676 | goto matchloop; |
| 677 | t--; |
| 678 | } |
| 679 | |
| 680 | /* |
| 681 | * we have a new best match. |
| 682 | * extend it to it's maximum length |
| 683 | */ |
| 684 | t += runlen + 2; |
| 685 | s += runlen + 2; |
| 686 | for(; s < es; s++){ |
| 687 | if(*s != *t) |
| 688 | break; |
| 689 | t++; |
| 690 | } |
| 691 | runlen = s - p; |
| 692 | *m = off - 1; |
| 693 | if(s == es || runlen > ml) |
| 694 | break; |
| 695 | matchloop:; |
| 696 | last = off; |
| 697 | } |
| 698 | return runlen; |
| 699 | } |
| 700 | |
| 701 | static int |
| 702 | lzcomp(LZstate *lz, LZblock *lzb, uchar *ep, ushort *parse, int finish) |
| 703 | { |
| 704 | ulong cont, excost, *litlencount, *offcount; |
| 705 | uchar *p, *q, *s, *es; |
| 706 | ushort *nexts, *hash; |
| 707 | int v, i, h, runlen, n, now, then, m, prevlen, prevoff, maxdefer; |
| 708 | |
| 709 | litlencount = lzb->litlencount; |
| 710 | offcount = lzb->offcount; |
| 711 | nexts = lz->nexts; |
| 712 | hash = lz->hash; |
| 713 | now = lz->now; |
| 714 | |
| 715 | p = &lz->hist[lz->pos]; |
| 716 | if(lz->prevlen != MinMatch - 1) |
| 717 | p++; |
| 718 | |
| 719 | /* |
| 720 | * hash in the links for any hanging link positions, |
| 721 | * and calculate the hash for the current position. |
| 722 | */ |
| 723 | n = MinMatch; |
| 724 | if(n > ep - p) |
| 725 | n = ep - p; |
| 726 | cont = 0; |
| 727 | for(i = 0; i < n - 1; i++){ |
| 728 | m = now - ((MinMatch-1) - i); |
| 729 | if(m < lz->dot) |
| 730 | continue; |
| 731 | s = lz->hist + (((p - lz->hist) - (now - m)) & (HistBlock-1)); |
| 732 | |
| 733 | cont = (s[0] << 16) | (s[1] << 8) | s[2]; |
| 734 | h = hashit(cont); |
| 735 | prevoff = 0; |
| 736 | for(then = hash[h]; ; then = nexts[then & (MaxOff-1)]){ |
| 737 | v = (ushort)(now - then); |
| 738 | if(v <= prevoff || v >= (MinMatch-1) - i) |
| 739 | break; |
| 740 | prevoff = v; |
| 741 | } |
| 742 | if(then == (ushort)m) |
| 743 | continue; |
| 744 | nexts[m & (MaxOff-1)] = hash[h]; |
| 745 | hash[h] = m; |
| 746 | } |
| 747 | for(i = 0; i < n; i++) |
| 748 | cont = (cont << 8) | p[i]; |
| 749 | |
| 750 | /* |
| 751 | * now must point to the index in the nexts array |
| 752 | * corresponding to p's position in the history |
| 753 | */ |
| 754 | prevlen = lz->prevlen; |
| 755 | prevoff = lz->prevoff; |
| 756 | maxdefer = lz->maxcheck >> 2; |
| 757 | excost = 0; |
| 758 | v = lzb->lastv; |
| 759 | for(;;){ |
| 760 | es = p + MaxMatch; |
| 761 | if(es > ep){ |
| 762 | if(!finish || p >= ep) |
| 763 | break; |
| 764 | es = ep; |
| 765 | } |
| 766 | |
| 767 | h = hashit(cont); |
| 768 | runlen = lzmatch(now, hash[h], p, es, nexts, lz->hist, prevlen, lz->maxcheck, &m); |
| 769 | |
| 770 | /* |
| 771 | * back out of small matches too far in the past |
| 772 | */ |
| 773 | if(runlen == MinMatch && m >= MinMatchMaxOff){ |
| 774 | runlen = MinMatch - 1; |
| 775 | m = 0; |
| 776 | } |
| 777 | |
| 778 | /* |
| 779 | * record the encoding and increment counts for huffman trees |
| 780 | * if we get a match, defer selecting it until we check for |
| 781 | * a longer match at the next position. |
| 782 | */ |
| 783 | if(prevlen >= runlen && prevlen != MinMatch - 1){ |
| 784 | /* |
| 785 | * old match at least as good; use that one |
| 786 | */ |
| 787 | n = prevlen - MinMatch; |
| 788 | if(v || n){ |
| 789 | *parse++ = v | LenFlag | (n << LenShift); |
| 790 | *parse++ = prevoff; |
| 791 | }else |
| 792 | *parse++ = prevoff << LenShift; |
| 793 | v = 0; |
| 794 | |
| 795 | n = lencode[n]; |
| 796 | litlencount[n]++; |
| 797 | excost += litlenextra[n - LenStart]; |
| 798 | |
| 799 | if(prevoff < MaxOffCode) |
| 800 | n = offcode[prevoff]; |
| 801 | else |
| 802 | n = bigoffcode[prevoff >> 7]; |
| 803 | offcount[n]++; |
| 804 | excost += offextra[n]; |
| 805 | |
| 806 | runlen = prevlen - 1; |
| 807 | prevlen = MinMatch - 1; |
| 808 | nmatches++; |
| 809 | }else if(runlen == MinMatch - 1){ |
| 810 | /* |
| 811 | * no match; just put out the literal |
| 812 | */ |
| 813 | if(++v == MaxLitRun){ |
| 814 | *parse++ = v; |
| 815 | v = 0; |
| 816 | } |
| 817 | litlencount[*p]++; |
| 818 | nlits++; |
| 819 | runlen = 1; |
| 820 | }else{ |
| 821 | if(prevlen != MinMatch - 1){ |
| 822 | /* |
| 823 | * longer match now. output previous literal, |
| 824 | * update current match, and try again |
| 825 | */ |
| 826 | if(++v == MaxLitRun){ |
| 827 | *parse++ = v; |
| 828 | v = 0; |
| 829 | } |
| 830 | litlencount[p[-1]]++; |
| 831 | nlits++; |
| 832 | } |
| 833 | |
| 834 | prevoff = m; |
| 835 | |
| 836 | if(runlen < maxdefer){ |
| 837 | prevlen = runlen; |
| 838 | runlen = 1; |
| 839 | }else{ |
| 840 | n = runlen - MinMatch; |
| 841 | if(v || n){ |
| 842 | *parse++ = v | LenFlag | (n << LenShift); |
| 843 | *parse++ = prevoff; |
| 844 | }else |
| 845 | *parse++ = prevoff << LenShift; |
| 846 | v = 0; |
| 847 | |
| 848 | n = lencode[n]; |
| 849 | litlencount[n]++; |
| 850 | excost += litlenextra[n - LenStart]; |
| 851 | |
| 852 | if(prevoff < MaxOffCode) |
| 853 | n = offcode[prevoff]; |
| 854 | else |
| 855 | n = bigoffcode[prevoff >> 7]; |
| 856 | offcount[n]++; |
| 857 | excost += offextra[n]; |
| 858 | |
| 859 | prevlen = MinMatch - 1; |
| 860 | nmatches++; |
| 861 | } |
| 862 | } |
| 863 | |
| 864 | /* |
| 865 | * update the hash for the newly matched data |
| 866 | * this is constructed so the link for the old |
| 867 | * match in this position must be at the end of a chain, |
| 868 | * and will expire when this match is added, ie it will |
| 869 | * never be examined by the match loop. |
| 870 | * add to the hash chain only if we have the real hash data. |
| 871 | */ |
| 872 | for(q = p + runlen; p != q; p++){ |
| 873 | if(p + MinMatch <= ep){ |
| 874 | h = hashit(cont); |
| 875 | nexts[now & (MaxOff-1)] = hash[h]; |
| 876 | hash[h] = now; |
| 877 | if(p + MinMatch < ep) |
| 878 | cont = (cont << 8) | p[MinMatch]; |
| 879 | } |
| 880 | now++; |
| 881 | } |
| 882 | } |
| 883 | |
| 884 | /* |
| 885 | * we can just store away the lazy state and |
| 886 | * pick it up next time. the last block will have finish set |
| 887 | * so we won't have any pending matches |
| 888 | * however, we need to correct for how much we've encoded |
| 889 | */ |
| 890 | if(prevlen != MinMatch - 1) |
| 891 | p--; |
| 892 | |
| 893 | lzb->excost += excost; |
| 894 | lzb->eparse = parse; |
| 895 | lzb->lastv = v; |
| 896 | |
| 897 | lz->now = now; |
| 898 | lz->prevlen = prevlen; |
| 899 | lz->prevoff = prevoff; |
| 900 | |
| 901 | return p - &lz->hist[lz->pos]; |
| 902 | } |
| 903 | |
| 904 | /* |
| 905 | * make up the dynamic code tables, and return the number of bits |
| 906 | * needed to transmit them. |
| 907 | */ |
| 908 | static int |
| 909 | huffcodes(Dyncode *dc, Huff *littab, Huff *offtab) |
| 910 | { |
| 911 | Huff *codetab; |
| 912 | uchar *codes, *codeaux; |
| 913 | ulong codecount[Nclen], excost; |
| 914 | int i, n, m, v, c, nlit, noff, ncode, nclen; |
| 915 | |
| 916 | codetab = dc->codetab; |
| 917 | codes = dc->codes; |
| 918 | codeaux = dc->codeaux; |
| 919 | |
| 920 | /* |
| 921 | * trim the sizes of the tables |
| 922 | */ |
| 923 | for(nlit = Nlitlen; nlit > 257 && littab[nlit-1].bits == 0; nlit--) |
| 924 | ; |
| 925 | for(noff = Noff; noff > 1 && offtab[noff-1].bits == 0; noff--) |
| 926 | ; |
| 927 | |
| 928 | /* |
| 929 | * make the code-length code |
| 930 | */ |
| 931 | for(i = 0; i < nlit; i++) |
| 932 | codes[i] = littab[i].bits; |
| 933 | for(i = 0; i < noff; i++) |
| 934 | codes[i + nlit] = offtab[i].bits; |
| 935 | |
| 936 | /* |
| 937 | * run-length compress the code-length code |
| 938 | */ |
| 939 | excost = 0; |
| 940 | c = 0; |
| 941 | ncode = nlit+noff; |
| 942 | for(i = 0; i < ncode; ){ |
| 943 | n = i + 1; |
| 944 | v = codes[i]; |
| 945 | while(n < ncode && v == codes[n]) |
| 946 | n++; |
| 947 | n -= i; |
| 948 | i += n; |
| 949 | if(v == 0){ |
| 950 | while(n >= 11){ |
| 951 | m = n; |
| 952 | if(m > 138) |
| 953 | m = 138; |
| 954 | codes[c] = 18; |
| 955 | codeaux[c++] = m - 11; |
| 956 | n -= m; |
| 957 | excost += 7; |
| 958 | } |
| 959 | if(n >= 3){ |
| 960 | codes[c] = 17; |
| 961 | codeaux[c++] = n - 3; |
| 962 | n = 0; |
| 963 | excost += 3; |
| 964 | } |
| 965 | } |
| 966 | while(n--){ |
| 967 | codes[c++] = v; |
| 968 | while(n >= 3){ |
| 969 | m = n; |
| 970 | if(m > 6) |
| 971 | m = 6; |
| 972 | codes[c] = 16; |
| 973 | codeaux[c++] = m - 3; |
| 974 | n -= m; |
| 975 | excost += 3; |
| 976 | } |
| 977 | } |
| 978 | } |
| 979 | |
| 980 | memset(codecount, 0, sizeof codecount); |
| 981 | for(i = 0; i < c; i++) |
| 982 | codecount[codes[i]]++; |
| 983 | if(!mkgzprecode(codetab, codecount, Nclen, 8)) |
| 984 | return -1; |
| 985 | |
| 986 | for(nclen = Nclen; nclen > 4 && codetab[clenorder[nclen-1]].bits == 0; nclen--) |
| 987 | ; |
| 988 | |
| 989 | dc->nlit = nlit; |
| 990 | dc->noff = noff; |
| 991 | dc->nclen = nclen; |
| 992 | dc->ncode = c; |
| 993 | |
| 994 | return 5 + 5 + 4 + nclen * 3 + bitcost(codetab, codecount, Nclen) + excost; |
| 995 | } |
| 996 | |
| 997 | static void |
| 998 | wrdyncode(LZstate *out, Dyncode *dc) |
| 999 | { |
| 1000 | Huff *codetab; |
| 1001 | uchar *codes, *codeaux; |
| 1002 | int i, v, c; |
| 1003 | |
| 1004 | /* |
| 1005 | * write out header, then code length code lengths, |
| 1006 | * and code lengths |
| 1007 | */ |
| 1008 | lzput(out, dc->nlit-257, 5); |
| 1009 | lzput(out, dc->noff-1, 5); |
| 1010 | lzput(out, dc->nclen-4, 4); |
| 1011 | |
| 1012 | codetab = dc->codetab; |
| 1013 | for(i = 0; i < dc->nclen; i++) |
| 1014 | lzput(out, codetab[clenorder[i]].bits, 3); |
| 1015 | |
| 1016 | codes = dc->codes; |
| 1017 | codeaux = dc->codeaux; |
| 1018 | c = dc->ncode; |
| 1019 | for(i = 0; i < c; i++){ |
| 1020 | v = codes[i]; |
| 1021 | lzput(out, codetab[v].encode, codetab[v].bits); |
| 1022 | if(v >= 16){ |
| 1023 | if(v == 16) |
| 1024 | lzput(out, codeaux[i], 2); |
| 1025 | else if(v == 17) |
| 1026 | lzput(out, codeaux[i], 3); |
| 1027 | else /* v == 18 */ |
| 1028 | lzput(out, codeaux[i], 7); |
| 1029 | } |
| 1030 | } |
| 1031 | } |
| 1032 | |
| 1033 | static int |
| 1034 | bitcost(Huff *tab, ulong *count, int n) |
| 1035 | { |
| 1036 | ulong tot; |
| 1037 | int i; |
| 1038 | |
| 1039 | tot = 0; |
| 1040 | for(i = 0; i < n; i++) |
| 1041 | tot += count[i] * tab[i].bits; |
| 1042 | return tot; |
| 1043 | } |
| 1044 | |
| 1045 | static int |
| 1046 | mkgzprecode(Huff *tab, ulong *count, int n, int maxbits) |
| 1047 | { |
| 1048 | ulong bitcount[MaxHuffBits]; |
| 1049 | int i, nbits; |
| 1050 | |
| 1051 | nbits = mkprecode(tab, count, n, maxbits, bitcount); |
| 1052 | for(i = 0; i < n; i++){ |
| 1053 | if(tab[i].bits == -1) |
| 1054 | tab[i].bits = 0; |
| 1055 | else if(tab[i].bits == 0){ |
| 1056 | if(nbits != 0 || bitcount[0] != 1) |
| 1057 | return 0; |
| 1058 | bitcount[1] = 1; |
| 1059 | bitcount[0] = 0; |
| 1060 | nbits = 1; |
| 1061 | tab[i].bits = 1; |
| 1062 | } |
| 1063 | } |
| 1064 | if(bitcount[0] != 0) |
| 1065 | return 0; |
| 1066 | return hufftabinit(tab, n, bitcount, nbits); |
| 1067 | } |
| 1068 | |
| 1069 | static int |
| 1070 | hufftabinit(Huff *tab, int n, ulong *bitcount, int nbits) |
| 1071 | { |
| 1072 | ulong code, nc[MaxHuffBits]; |
| 1073 | int i, bits; |
| 1074 | |
| 1075 | code = 0; |
| 1076 | for(bits = 1; bits <= nbits; bits++){ |
| 1077 | code = (code + bitcount[bits-1]) << 1; |
| 1078 | nc[bits] = code; |
| 1079 | } |
| 1080 | |
| 1081 | for(i = 0; i < n; i++){ |
| 1082 | bits = tab[i].bits; |
| 1083 | if(bits){ |
| 1084 | code = nc[bits]++ << (16 - bits); |
| 1085 | if(code & ~0xffff) |
| 1086 | return 0; |
| 1087 | tab[i].encode = revtab[code >> 8] | (revtab[code & 0xff] << 8); |
| 1088 | } |
| 1089 | } |
| 1090 | return 1; |
| 1091 | } |
| 1092 | |
| 1093 | |
| 1094 | /* |
| 1095 | * this should be in a library |
| 1096 | */ |
| 1097 | struct Chain |
| 1098 | { |
| 1099 | ulong count; /* occurances of everything in the chain */ |
| 1100 | ushort leaf; /* leaves to the left of chain, or leaf value */ |
| 1101 | char col; /* ref count for collecting unused chains */ |
| 1102 | char gen; /* need to generate chains for next lower level */ |
| 1103 | Chain *up; /* Chain up in the lists */ |
| 1104 | }; |
| 1105 | |
| 1106 | struct Chains |
| 1107 | { |
| 1108 | Chain *lists[(MaxHuffBits - 1) * 2]; |
| 1109 | ulong leafcount[MaxLeaf]; /* sorted list of leaf counts */ |
| 1110 | ushort leafmap[MaxLeaf]; /* map to actual leaf number */ |
| 1111 | int nleaf; /* number of leaves */ |
| 1112 | Chain chains[ChainMem]; |
| 1113 | Chain *echains; |
| 1114 | Chain *free; |
| 1115 | char col; |
| 1116 | int nlists; |
| 1117 | }; |
| 1118 | |
| 1119 | /* |
| 1120 | * fast, low space overhead algorithm for max depth huffman type codes |
| 1121 | * |
| 1122 | * J. Katajainen, A. Moffat and A. Turpin, "A fast and space-economical |
| 1123 | * algorithm for length-limited coding," Proc. Intl. Symp. on Algorithms |
| 1124 | * and Computation, Cairns, Australia, Dec. 1995, Lecture Notes in Computer |
| 1125 | * Science, Vol 1004, J. Staples, P. Eades, N. Katoh, and A. Moffat, eds., |
| 1126 | * pp 12-21, Springer Verlag, New York, 1995. |
| 1127 | */ |
| 1128 | static int |
| 1129 | mkprecode(Huff *tab, ulong *count, int n, int maxbits, ulong *bitcount) |
| 1130 | { |
| 1131 | Chains cs; |
| 1132 | Chain *c; |
| 1133 | int i, m, em, bits; |
| 1134 | |
Russ Cox | 995e570 | 2009-04-30 07:24:53 -0700 | [diff] [blame] | 1135 | memset(&cs, 0, sizeof cs); |
| 1136 | |
rsc | b6afd33 | 2003-11-23 18:19:18 +0000 | [diff] [blame] | 1137 | /* |
| 1138 | * set up the sorted list of leaves |
| 1139 | */ |
| 1140 | m = 0; |
| 1141 | for(i = 0; i < n; i++){ |
| 1142 | tab[i].bits = -1; |
| 1143 | tab[i].encode = 0; |
| 1144 | if(count[i] != 0){ |
| 1145 | cs.leafcount[m] = count[i]; |
| 1146 | cs.leafmap[m] = i; |
| 1147 | m++; |
| 1148 | } |
| 1149 | } |
| 1150 | if(m < 2){ |
| 1151 | if(m != 0){ |
| 1152 | tab[cs.leafmap[0]].bits = 0; |
| 1153 | bitcount[0] = 1; |
| 1154 | }else |
| 1155 | bitcount[0] = 0; |
| 1156 | return 0; |
| 1157 | } |
| 1158 | cs.nleaf = m; |
| 1159 | leafsort(cs.leafcount, cs.leafmap, 0, m); |
| 1160 | |
| 1161 | for(i = 0; i < m; i++) |
| 1162 | cs.leafcount[i] = count[cs.leafmap[i]]; |
| 1163 | |
| 1164 | /* |
| 1165 | * set up free list |
| 1166 | */ |
| 1167 | cs.free = &cs.chains[2]; |
| 1168 | cs.echains = &cs.chains[ChainMem]; |
| 1169 | cs.col = 1; |
| 1170 | |
| 1171 | /* |
| 1172 | * initialize chains for each list |
| 1173 | */ |
| 1174 | c = &cs.chains[0]; |
| 1175 | c->count = cs.leafcount[0]; |
| 1176 | c->leaf = 1; |
| 1177 | c->col = cs.col; |
| 1178 | c->up = nil; |
| 1179 | c->gen = 0; |
| 1180 | cs.chains[1] = cs.chains[0]; |
| 1181 | cs.chains[1].leaf = 2; |
| 1182 | cs.chains[1].count = cs.leafcount[1]; |
| 1183 | for(i = 0; i < maxbits-1; i++){ |
| 1184 | cs.lists[i * 2] = &cs.chains[0]; |
| 1185 | cs.lists[i * 2 + 1] = &cs.chains[1]; |
| 1186 | } |
| 1187 | |
| 1188 | cs.nlists = 2 * (maxbits - 1); |
| 1189 | m = 2 * m - 2; |
| 1190 | for(i = 2; i < m; i++) |
| 1191 | nextchain(&cs, cs.nlists - 2); |
| 1192 | |
| 1193 | bits = 0; |
| 1194 | bitcount[0] = cs.nleaf; |
| 1195 | for(c = cs.lists[cs.nlists - 1]; c != nil; c = c->up){ |
| 1196 | m = c->leaf; |
| 1197 | bitcount[bits++] -= m; |
| 1198 | bitcount[bits] = m; |
| 1199 | } |
| 1200 | m = 0; |
| 1201 | for(i = bits; i >= 0; i--) |
| 1202 | for(em = m + bitcount[i]; m < em; m++) |
| 1203 | tab[cs.leafmap[m]].bits = i; |
| 1204 | |
| 1205 | return bits; |
| 1206 | } |
| 1207 | |
| 1208 | /* |
| 1209 | * calculate the next chain on the list |
| 1210 | * we can always toss out the old chain |
| 1211 | */ |
| 1212 | static void |
| 1213 | nextchain(Chains *cs, int list) |
| 1214 | { |
| 1215 | Chain *c, *oc; |
| 1216 | int i, nleaf, sumc; |
| 1217 | |
| 1218 | oc = cs->lists[list + 1]; |
| 1219 | cs->lists[list] = oc; |
| 1220 | if(oc == nil) |
| 1221 | return; |
| 1222 | |
| 1223 | /* |
| 1224 | * make sure we have all chains needed to make sumc |
| 1225 | * note it is possible to generate only one of these, |
| 1226 | * use twice that value for sumc, and then generate |
| 1227 | * the second if that preliminary sumc would be chosen. |
| 1228 | * however, this appears to be slower on current tests |
| 1229 | */ |
| 1230 | if(oc->gen){ |
| 1231 | nextchain(cs, list - 2); |
| 1232 | nextchain(cs, list - 2); |
| 1233 | oc->gen = 0; |
| 1234 | } |
| 1235 | |
| 1236 | /* |
| 1237 | * pick up the chain we're going to add; |
| 1238 | * collect unused chains no free ones are left |
| 1239 | */ |
| 1240 | for(c = cs->free; ; c++){ |
| 1241 | if(c >= cs->echains){ |
| 1242 | cs->col++; |
| 1243 | for(i = 0; i < cs->nlists; i++) |
| 1244 | for(c = cs->lists[i]; c != nil; c = c->up) |
| 1245 | c->col = cs->col; |
| 1246 | c = cs->chains; |
| 1247 | } |
| 1248 | if(c->col != cs->col) |
| 1249 | break; |
| 1250 | } |
| 1251 | |
| 1252 | /* |
| 1253 | * pick the cheapest of |
| 1254 | * 1) the next package from the previous list |
| 1255 | * 2) the next leaf |
| 1256 | */ |
| 1257 | nleaf = oc->leaf; |
| 1258 | sumc = 0; |
| 1259 | if(list > 0 && cs->lists[list-1] != nil) |
| 1260 | sumc = cs->lists[list-2]->count + cs->lists[list-1]->count; |
| 1261 | if(sumc != 0 && (nleaf >= cs->nleaf || cs->leafcount[nleaf] > sumc)){ |
| 1262 | c->count = sumc; |
| 1263 | c->leaf = oc->leaf; |
| 1264 | c->up = cs->lists[list-1]; |
| 1265 | c->gen = 1; |
| 1266 | }else if(nleaf >= cs->nleaf){ |
| 1267 | cs->lists[list + 1] = nil; |
| 1268 | return; |
| 1269 | }else{ |
| 1270 | c->leaf = nleaf + 1; |
| 1271 | c->count = cs->leafcount[nleaf]; |
| 1272 | c->up = oc->up; |
| 1273 | c->gen = 0; |
| 1274 | } |
| 1275 | cs->free = c + 1; |
| 1276 | |
| 1277 | cs->lists[list + 1] = c; |
| 1278 | c->col = cs->col; |
| 1279 | } |
| 1280 | |
| 1281 | static int |
| 1282 | pivot(ulong *c, int a, int n) |
| 1283 | { |
| 1284 | int j, pi, pj, pk; |
| 1285 | |
| 1286 | j = n/6; |
| 1287 | pi = a + j; /* 1/6 */ |
| 1288 | j += j; |
| 1289 | pj = pi + j; /* 1/2 */ |
| 1290 | pk = pj + j; /* 5/6 */ |
| 1291 | if(c[pi] < c[pj]){ |
| 1292 | if(c[pi] < c[pk]){ |
| 1293 | if(c[pj] < c[pk]) |
| 1294 | return pj; |
| 1295 | return pk; |
| 1296 | } |
| 1297 | return pi; |
| 1298 | } |
| 1299 | if(c[pj] < c[pk]){ |
| 1300 | if(c[pi] < c[pk]) |
| 1301 | return pi; |
| 1302 | return pk; |
| 1303 | } |
| 1304 | return pj; |
| 1305 | } |
| 1306 | |
| 1307 | static void |
| 1308 | leafsort(ulong *leafcount, ushort *leafmap, int a, int n) |
| 1309 | { |
| 1310 | ulong t; |
| 1311 | int j, pi, pj, pn; |
| 1312 | |
| 1313 | while(n > 1){ |
| 1314 | if(n > 10){ |
| 1315 | pi = pivot(leafcount, a, n); |
| 1316 | }else |
| 1317 | pi = a + (n>>1); |
| 1318 | |
| 1319 | t = leafcount[pi]; |
| 1320 | leafcount[pi] = leafcount[a]; |
| 1321 | leafcount[a] = t; |
| 1322 | t = leafmap[pi]; |
| 1323 | leafmap[pi] = leafmap[a]; |
| 1324 | leafmap[a] = t; |
| 1325 | pi = a; |
| 1326 | pn = a + n; |
| 1327 | pj = pn; |
| 1328 | for(;;){ |
| 1329 | do |
| 1330 | pi++; |
| 1331 | while(pi < pn && (leafcount[pi] < leafcount[a] || leafcount[pi] == leafcount[a] && leafmap[pi] > leafmap[a])); |
| 1332 | do |
| 1333 | pj--; |
| 1334 | while(pj > a && (leafcount[pj] > leafcount[a] || leafcount[pj] == leafcount[a] && leafmap[pj] < leafmap[a])); |
| 1335 | if(pj < pi) |
| 1336 | break; |
| 1337 | t = leafcount[pi]; |
| 1338 | leafcount[pi] = leafcount[pj]; |
| 1339 | leafcount[pj] = t; |
| 1340 | t = leafmap[pi]; |
| 1341 | leafmap[pi] = leafmap[pj]; |
| 1342 | leafmap[pj] = t; |
| 1343 | } |
| 1344 | t = leafcount[a]; |
| 1345 | leafcount[a] = leafcount[pj]; |
| 1346 | leafcount[pj] = t; |
| 1347 | t = leafmap[a]; |
| 1348 | leafmap[a] = leafmap[pj]; |
| 1349 | leafmap[pj] = t; |
| 1350 | j = pj - a; |
| 1351 | |
| 1352 | n = n-j-1; |
| 1353 | if(j >= n){ |
| 1354 | leafsort(leafcount, leafmap, a, j); |
| 1355 | a += j+1; |
| 1356 | }else{ |
| 1357 | leafsort(leafcount, leafmap, a + (j+1), n); |
| 1358 | n = j; |
| 1359 | } |
| 1360 | } |
| 1361 | } |