Hash :
8a7201c6
Author :
Date :
2025-08-05T02:49:08
fix some includes PiperOrigin-RevId: 791124445
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646
/* Copyright 2015 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Function for fast encoding of an input fragment, independently from the input
history. This function uses two-pass processing: in the first pass we save
the found backward matches and literal bytes into a buffer, and in the
second pass we emit them into the bit stream using prefix codes built based
on the actual command and literal byte histograms. */
#include "compress_fragment_two_pass.h"
#include "../common/constants.h"
#include "../common/platform.h"
#include "bit_cost.h"
#include "brotli_bit_stream.h"
#include "entropy_encode.h"
#include "fast_log.h"
#include "find_match_length.h"
#include "hash_base.h"
#include "write_bits.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
#define MAX_DISTANCE (long)BROTLI_MAX_BACKWARD_LIMIT(18)
static BROTLI_INLINE uint32_t Hash(const uint8_t* p,
size_t shift, size_t length) {
const uint64_t h =
(BROTLI_UNALIGNED_LOAD64LE(p) << ((8 - length) * 8)) * kHashMul32;
return (uint32_t)(h >> shift);
}
static BROTLI_INLINE uint32_t HashBytesAtOffset(uint64_t v, size_t offset,
size_t shift, size_t length) {
BROTLI_DCHECK(offset <= 8 - length);
{
const uint64_t h = ((v >> (8 * offset)) << ((8 - length) * 8)) * kHashMul32;
return (uint32_t)(h >> shift);
}
}
static BROTLI_INLINE BROTLI_BOOL IsMatch(const uint8_t* p1, const uint8_t* p2,
size_t length) {
if (BrotliUnalignedRead32(p1) == BrotliUnalignedRead32(p2)) {
if (length == 4) return BROTLI_TRUE;
return TO_BROTLI_BOOL(p1[4] == p2[4] && p1[5] == p2[5]);
}
return BROTLI_FALSE;
}
/* Builds a command and distance prefix code (each 64 symbols) into "depth" and
"bits" based on "histogram" and stores it into the bit stream. */
static void BuildAndStoreCommandPrefixCode(BrotliTwoPassArena* s,
size_t* storage_ix,
uint8_t* storage) {
/* Tree size for building a tree over 64 symbols is 2 * 64 + 1. */
/* TODO(eustas): initialize once. */
memset(s->tmp_depth, 0, sizeof(s->tmp_depth));
BrotliCreateHuffmanTree(s->cmd_histo, 64, 15, s->tmp_tree, s->cmd_depth);
BrotliCreateHuffmanTree(&s->cmd_histo[64], 64, 14, s->tmp_tree,
&s->cmd_depth[64]);
/* We have to jump through a few hoops here in order to compute
the command bits because the symbols are in a different order than in
the full alphabet. This looks complicated, but having the symbols
in this order in the command bits saves a few branches in the Emit*
functions. */
memcpy(s->tmp_depth, s->cmd_depth + 24, 24);
memcpy(s->tmp_depth + 24, s->cmd_depth, 8);
memcpy(s->tmp_depth + 32, s->cmd_depth + 48, 8);
memcpy(s->tmp_depth + 40, s->cmd_depth + 8, 8);
memcpy(s->tmp_depth + 48, s->cmd_depth + 56, 8);
memcpy(s->tmp_depth + 56, s->cmd_depth + 16, 8);
BrotliConvertBitDepthsToSymbols(s->tmp_depth, 64, s->tmp_bits);
memcpy(s->cmd_bits, s->tmp_bits + 24, 16);
memcpy(s->cmd_bits + 8, s->tmp_bits + 40, 16);
memcpy(s->cmd_bits + 16, s->tmp_bits + 56, 16);
memcpy(s->cmd_bits + 24, s->tmp_bits, 48);
memcpy(s->cmd_bits + 48, s->tmp_bits + 32, 16);
memcpy(s->cmd_bits + 56, s->tmp_bits + 48, 16);
BrotliConvertBitDepthsToSymbols(&s->cmd_depth[64], 64, &s->cmd_bits[64]);
{
/* Create the bit length array for the full command alphabet. */
size_t i;
memset(s->tmp_depth, 0, 64); /* only 64 first values were used */
memcpy(s->tmp_depth, s->cmd_depth + 24, 8);
memcpy(s->tmp_depth + 64, s->cmd_depth + 32, 8);
memcpy(s->tmp_depth + 128, s->cmd_depth + 40, 8);
memcpy(s->tmp_depth + 192, s->cmd_depth + 48, 8);
memcpy(s->tmp_depth + 384, s->cmd_depth + 56, 8);
for (i = 0; i < 8; ++i) {
s->tmp_depth[128 + 8 * i] = s->cmd_depth[i];
s->tmp_depth[256 + 8 * i] = s->cmd_depth[8 + i];
s->tmp_depth[448 + 8 * i] = s->cmd_depth[16 + i];
}
BrotliStoreHuffmanTree(s->tmp_depth, BROTLI_NUM_COMMAND_SYMBOLS,
s->tmp_tree, storage_ix, storage);
}
BrotliStoreHuffmanTree(&s->cmd_depth[64], 64, s->tmp_tree, storage_ix,
storage);
}
static BROTLI_INLINE void EmitInsertLen(
uint32_t insertlen, uint32_t** commands) {
if (insertlen < 6) {
**commands = insertlen;
} else if (insertlen < 130) {
const uint32_t tail = insertlen - 2;
const uint32_t nbits = Log2FloorNonZero(tail) - 1u;
const uint32_t prefix = tail >> nbits;
const uint32_t inscode = (nbits << 1) + prefix + 2;
const uint32_t extra = tail - (prefix << nbits);
**commands = inscode | (extra << 8);
} else if (insertlen < 2114) {
const uint32_t tail = insertlen - 66;
const uint32_t nbits = Log2FloorNonZero(tail);
const uint32_t code = nbits + 10;
const uint32_t extra = tail - (1u << nbits);
**commands = code | (extra << 8);
} else if (insertlen < 6210) {
const uint32_t extra = insertlen - 2114;
**commands = 21 | (extra << 8);
} else if (insertlen < 22594) {
const uint32_t extra = insertlen - 6210;
**commands = 22 | (extra << 8);
} else {
const uint32_t extra = insertlen - 22594;
**commands = 23 | (extra << 8);
}
++(*commands);
}
static BROTLI_INLINE void EmitCopyLen(size_t copylen, uint32_t** commands) {
if (copylen < 10) {
**commands = (uint32_t)(copylen + 38);
} else if (copylen < 134) {
const size_t tail = copylen - 6;
const size_t nbits = Log2FloorNonZero(tail) - 1;
const size_t prefix = tail >> nbits;
const size_t code = (nbits << 1) + prefix + 44;
const size_t extra = tail - (prefix << nbits);
**commands = (uint32_t)(code | (extra << 8));
} else if (copylen < 2118) {
const size_t tail = copylen - 70;
const size_t nbits = Log2FloorNonZero(tail);
const size_t code = nbits + 52;
const size_t extra = tail - ((size_t)1 << nbits);
**commands = (uint32_t)(code | (extra << 8));
} else {
const size_t extra = copylen - 2118;
**commands = (uint32_t)(63 | (extra << 8));
}
++(*commands);
}
static BROTLI_INLINE void EmitCopyLenLastDistance(
size_t copylen, uint32_t** commands) {
if (copylen < 12) {
**commands = (uint32_t)(copylen + 20);
++(*commands);
} else if (copylen < 72) {
const size_t tail = copylen - 8;
const size_t nbits = Log2FloorNonZero(tail) - 1;
const size_t prefix = tail >> nbits;
const size_t code = (nbits << 1) + prefix + 28;
const size_t extra = tail - (prefix << nbits);
**commands = (uint32_t)(code | (extra << 8));
++(*commands);
} else if (copylen < 136) {
const size_t tail = copylen - 8;
const size_t code = (tail >> 5) + 54;
const size_t extra = tail & 31;
**commands = (uint32_t)(code | (extra << 8));
++(*commands);
**commands = 64;
++(*commands);
} else if (copylen < 2120) {
const size_t tail = copylen - 72;
const size_t nbits = Log2FloorNonZero(tail);
const size_t code = nbits + 52;
const size_t extra = tail - ((size_t)1 << nbits);
**commands = (uint32_t)(code | (extra << 8));
++(*commands);
**commands = 64;
++(*commands);
} else {
const size_t extra = copylen - 2120;
**commands = (uint32_t)(63 | (extra << 8));
++(*commands);
**commands = 64;
++(*commands);
}
}
static BROTLI_INLINE void EmitDistance(uint32_t distance, uint32_t** commands) {
uint32_t d = distance + 3;
uint32_t nbits = Log2FloorNonZero(d) - 1;
const uint32_t prefix = (d >> nbits) & 1;
const uint32_t offset = (2 + prefix) << nbits;
const uint32_t distcode = 2 * (nbits - 1) + prefix + 80;
uint32_t extra = d - offset;
**commands = distcode | (extra << 8);
++(*commands);
}
/* REQUIRES: len <= 1 << 24. */
static void BrotliStoreMetaBlockHeader(
size_t len, BROTLI_BOOL is_uncompressed, size_t* storage_ix,
uint8_t* storage) {
size_t nibbles = 6;
/* ISLAST */
BrotliWriteBits(1, 0, storage_ix, storage);
if (len <= (1U << 16)) {
nibbles = 4;
} else if (len <= (1U << 20)) {
nibbles = 5;
}
BrotliWriteBits(2, nibbles - 4, storage_ix, storage);
BrotliWriteBits(nibbles * 4, len - 1, storage_ix, storage);
/* ISUNCOMPRESSED */
BrotliWriteBits(1, (uint64_t)is_uncompressed, storage_ix, storage);
}
static BROTLI_INLINE void CreateCommands(const uint8_t* input,
size_t block_size, size_t input_size, const uint8_t* base_ip, int* table,
size_t table_bits, size_t min_match,
uint8_t** literals, uint32_t** commands) {
/* "ip" is the input pointer. */
const uint8_t* ip = input;
const size_t shift = 64u - table_bits;
const uint8_t* ip_end = input + block_size;
/* "next_emit" is a pointer to the first byte that is not covered by a
previous copy. Bytes between "next_emit" and the start of the next copy or
the end of the input will be emitted as literal bytes. */
const uint8_t* next_emit = input;
int last_distance = -1;
const size_t kInputMarginBytes = BROTLI_WINDOW_GAP;
if (BROTLI_PREDICT_TRUE(block_size >= kInputMarginBytes)) {
/* For the last block, we need to keep a 16 bytes margin so that we can be
sure that all distances are at most window size - 16.
For all other blocks, we only need to keep a margin of 5 bytes so that
we don't go over the block size with a copy. */
const size_t len_limit = BROTLI_MIN(size_t, block_size - min_match,
input_size - kInputMarginBytes);
const uint8_t* ip_limit = input + len_limit;
uint32_t next_hash;
for (next_hash = Hash(++ip, shift, min_match); ; ) {
/* Step 1: Scan forward in the input looking for a 6-byte-long match.
If we get close to exhausting the input then goto emit_remainder.
Heuristic match skipping: If 32 bytes are scanned with no matches
found, start looking only at every other byte. If 32 more bytes are
scanned, look at every third byte, etc.. When a match is found,
immediately go back to looking at every byte. This is a small loss
(~5% performance, ~0.1% density) for compressible data due to more
bookkeeping, but for non-compressible data (such as JPEG) it's a huge
win since the compressor quickly "realizes" the data is incompressible
and doesn't bother looking for matches everywhere.
The "skip" variable keeps track of how many bytes there are since the
last match; dividing it by 32 (ie. right-shifting by five) gives the
number of bytes to move ahead for each iteration. */
uint32_t skip = 32;
const uint8_t* next_ip = ip;
const uint8_t* candidate;
BROTLI_DCHECK(next_emit < ip);
trawl:
do {
uint32_t hash = next_hash;
uint32_t bytes_between_hash_lookups = skip++ >> 5;
ip = next_ip;
BROTLI_DCHECK(hash == Hash(ip, shift, min_match));
next_ip = ip + bytes_between_hash_lookups;
if (BROTLI_PREDICT_FALSE(next_ip > ip_limit)) {
goto emit_remainder;
}
next_hash = Hash(next_ip, shift, min_match);
candidate = ip - last_distance;
if (IsMatch(ip, candidate, min_match)) {
if (BROTLI_PREDICT_TRUE(candidate < ip)) {
table[hash] = (int)(ip - base_ip);
break;
}
}
candidate = base_ip + table[hash];
BROTLI_DCHECK(candidate >= base_ip);
BROTLI_DCHECK(candidate < ip);
table[hash] = (int)(ip - base_ip);
} while (BROTLI_PREDICT_TRUE(!IsMatch(ip, candidate, min_match)));
/* Check copy distance. If candidate is not feasible, continue search.
Checking is done outside of hot loop to reduce overhead. */
if (ip - candidate > MAX_DISTANCE) goto trawl;
/* Step 2: Emit the found match together with the literal bytes from
"next_emit", and then see if we can find a next match immediately
afterwards. Repeat until we find no match for the input
without emitting some literal bytes. */
{
/* We have a 6-byte match at ip, and we need to emit bytes in
[next_emit, ip). */
const uint8_t* base = ip;
size_t matched = min_match + FindMatchLengthWithLimit(
candidate + min_match, ip + min_match,
(size_t)(ip_end - ip) - min_match);
int distance = (int)(base - candidate); /* > 0 */
int insert = (int)(base - next_emit);
ip += matched;
BROTLI_DCHECK(0 == memcmp(base, candidate, matched));
EmitInsertLen((uint32_t)insert, commands);
BROTLI_LOG(("[CompressFragment] pos = %d insert = %d copy = %d\n",
(int)(next_emit - base_ip), insert, 2));
memcpy(*literals, next_emit, (size_t)insert);
*literals += insert;
if (distance == last_distance) {
**commands = 64;
++(*commands);
} else {
EmitDistance((uint32_t)distance, commands);
last_distance = distance;
}
EmitCopyLenLastDistance(matched, commands);
BROTLI_LOG(("[CompressFragment] pos = %d distance = %d\n"
"[CompressFragment] pos = %d insert = %d copy = %d\n"
"[CompressFragment] pos = %d distance = %d\n",
(int)(base - base_ip), (int)distance,
(int)(base - base_ip) + 2, 0, (int)matched - 2,
(int)(base - base_ip) + 2, (int)distance));
next_emit = ip;
if (BROTLI_PREDICT_FALSE(ip >= ip_limit)) {
goto emit_remainder;
}
{
/* We could immediately start working at ip now, but to improve
compression we first update "table" with the hashes of some
positions within the last copy. */
uint64_t input_bytes;
uint32_t cur_hash;
uint32_t prev_hash;
if (min_match == 4) {
input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 3);
cur_hash = HashBytesAtOffset(input_bytes, 3, shift, min_match);
prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 3);
prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 2);
prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 1);
} else {
input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 5);
prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 5);
prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 4);
prev_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 3);
input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 2);
cur_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match);
prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 2);
prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 1);
}
candidate = base_ip + table[cur_hash];
table[cur_hash] = (int)(ip - base_ip);
}
}
while (ip - candidate <= MAX_DISTANCE &&
IsMatch(ip, candidate, min_match)) {
/* We have a 6-byte match at ip, and no need to emit any
literal bytes prior to ip. */
const uint8_t* base = ip;
size_t matched = min_match + FindMatchLengthWithLimit(
candidate + min_match, ip + min_match,
(size_t)(ip_end - ip) - min_match);
ip += matched;
last_distance = (int)(base - candidate); /* > 0 */
BROTLI_DCHECK(0 == memcmp(base, candidate, matched));
EmitCopyLen(matched, commands);
EmitDistance((uint32_t)last_distance, commands);
BROTLI_LOG(("[CompressFragment] pos = %d insert = %d copy = %d\n"
"[CompressFragment] pos = %d distance = %d\n",
(int)(base - base_ip), 0, (int)matched,
(int)(base - base_ip), (int)last_distance));
next_emit = ip;
if (BROTLI_PREDICT_FALSE(ip >= ip_limit)) {
goto emit_remainder;
}
{
/* We could immediately start working at ip now, but to improve
compression we first update "table" with the hashes of some
positions within the last copy. */
uint64_t input_bytes;
uint32_t cur_hash;
uint32_t prev_hash;
if (min_match == 4) {
input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 3);
cur_hash = HashBytesAtOffset(input_bytes, 3, shift, min_match);
prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 3);
prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 2);
prev_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 1);
} else {
input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 5);
prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 5);
prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 4);
prev_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 3);
input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 2);
cur_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match);
prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 2);
prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match);
table[prev_hash] = (int)(ip - base_ip - 1);
}
candidate = base_ip + table[cur_hash];
table[cur_hash] = (int)(ip - base_ip);
}
}
next_hash = Hash(++ip, shift, min_match);
}
}
emit_remainder:
BROTLI_DCHECK(next_emit <= ip_end);
/* Emit the remaining bytes as literals. */
if (next_emit < ip_end) {
const uint32_t insert = (uint32_t)(ip_end - next_emit);
EmitInsertLen(insert, commands);
BROTLI_LOG(("[CompressFragment] pos = %d insert = %d copy = %d\n",
(int)(next_emit - base_ip), insert, 2));
memcpy(*literals, next_emit, insert);
*literals += insert;
}
}
static void StoreCommands(BrotliTwoPassArena* s,
const uint8_t* literals, const size_t num_literals,
const uint32_t* commands, const size_t num_commands,
size_t* storage_ix, uint8_t* storage) {
static const uint32_t kNumExtraBits[128] = {
0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5,
6, 7, 8, 9, 10, 12, 14, 24, 0, 0, 0, 0, 0, 0, 0, 0,
1, 1, 2, 2, 3, 3, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0,
1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 7, 8, 9, 10, 24,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8,
9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16,
17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24,
};
static const uint32_t kInsertOffset[24] = {
0, 1, 2, 3, 4, 5, 6, 8, 10, 14, 18, 26,
34, 50, 66, 98, 130, 194, 322, 578, 1090, 2114, 6210, 22594,
};
size_t i;
memset(s->lit_histo, 0, sizeof(s->lit_histo));
/* TODO(eustas): is that necessary? */
memset(s->cmd_depth, 0, sizeof(s->cmd_depth));
/* TODO(eustas): is that necessary? */
memset(s->cmd_bits, 0, sizeof(s->cmd_bits));
memset(s->cmd_histo, 0, sizeof(s->cmd_histo));
for (i = 0; i < num_literals; ++i) {
++s->lit_histo[literals[i]];
}
BrotliBuildAndStoreHuffmanTreeFast(s->tmp_tree, s->lit_histo, num_literals,
/* max_bits = */ 8, s->lit_depth,
s->lit_bits, storage_ix, storage);
for (i = 0; i < num_commands; ++i) {
const uint32_t code = commands[i] & 0xFF;
BROTLI_DCHECK(code < 128);
++s->cmd_histo[code];
}
s->cmd_histo[1] += 1;
s->cmd_histo[2] += 1;
s->cmd_histo[64] += 1;
s->cmd_histo[84] += 1;
BuildAndStoreCommandPrefixCode(s, storage_ix, storage);
for (i = 0; i < num_commands; ++i) {
const uint32_t cmd = commands[i];
const uint32_t code = cmd & 0xFF;
const uint32_t extra = cmd >> 8;
BROTLI_DCHECK(code < 128);
BrotliWriteBits(s->cmd_depth[code], s->cmd_bits[code], storage_ix, storage);
BrotliWriteBits(kNumExtraBits[code], extra, storage_ix, storage);
if (code < 24) {
const uint32_t insert = kInsertOffset[code] + extra;
uint32_t j;
for (j = 0; j < insert; ++j) {
const uint8_t lit = *literals;
BrotliWriteBits(s->lit_depth[lit], s->lit_bits[lit], storage_ix,
storage);
++literals;
}
}
}
}
/* Acceptable loss for uncompressible speedup is 2% */
#define MIN_RATIO 0.98
#define SAMPLE_RATE 43
static BROTLI_BOOL ShouldCompress(BrotliTwoPassArena* s,
const uint8_t* input, size_t input_size, size_t num_literals) {
double corpus_size = (double)input_size;
if ((double)num_literals < MIN_RATIO * corpus_size) {
return BROTLI_TRUE;
} else {
const double max_total_bit_cost = corpus_size * 8 * MIN_RATIO / SAMPLE_RATE;
size_t i;
memset(s->lit_histo, 0, sizeof(s->lit_histo));
for (i = 0; i < input_size; i += SAMPLE_RATE) {
++s->lit_histo[input[i]];
}
return TO_BROTLI_BOOL(BitsEntropy(s->lit_histo, 256) < max_total_bit_cost);
}
}
static void RewindBitPosition(const size_t new_storage_ix,
size_t* storage_ix, uint8_t* storage) {
const size_t bitpos = new_storage_ix & 7;
const size_t mask = (1u << bitpos) - 1;
storage[new_storage_ix >> 3] &= (uint8_t)mask;
*storage_ix = new_storage_ix;
}
static void EmitUncompressedMetaBlock(const uint8_t* input, size_t input_size,
size_t* storage_ix, uint8_t* storage) {
BrotliStoreMetaBlockHeader(input_size, 1, storage_ix, storage);
*storage_ix = (*storage_ix + 7u) & ~7u;
memcpy(&storage[*storage_ix >> 3], input, input_size);
*storage_ix += input_size << 3;
storage[*storage_ix >> 3] = 0;
}
static BROTLI_INLINE void BrotliCompressFragmentTwoPassImpl(
BrotliTwoPassArena* s, const uint8_t* input, size_t input_size,
BROTLI_BOOL is_last, uint32_t* command_buf, uint8_t* literal_buf,
int* table, size_t table_bits, size_t min_match,
size_t* storage_ix, uint8_t* storage) {
/* Save the start of the first block for position and distance computations.
*/
const uint8_t* base_ip = input;
BROTLI_UNUSED(is_last);
while (input_size > 0) {
size_t block_size =
BROTLI_MIN(size_t, input_size, kCompressFragmentTwoPassBlockSize);
uint32_t* commands = command_buf;
uint8_t* literals = literal_buf;
size_t num_literals;
CreateCommands(input, block_size, input_size, base_ip, table,
table_bits, min_match, &literals, &commands);
num_literals = (size_t)(literals - literal_buf);
if (ShouldCompress(s, input, block_size, num_literals)) {
const size_t num_commands = (size_t)(commands - command_buf);
BrotliStoreMetaBlockHeader(block_size, 0, storage_ix, storage);
/* No block splits, no contexts. */
BrotliWriteBits(13, 0, storage_ix, storage);
StoreCommands(s, literal_buf, num_literals, command_buf, num_commands,
storage_ix, storage);
} else {
/* Since we did not find many backward references and the entropy of
the data is close to 8 bits, we can simply emit an uncompressed block.
This makes compression speed of uncompressible data about 3x faster. */
EmitUncompressedMetaBlock(input, block_size, storage_ix, storage);
}
input += block_size;
input_size -= block_size;
}
}
#define FOR_TABLE_BITS_(X) \
X(8) X(9) X(10) X(11) X(12) X(13) X(14) X(15) X(16) X(17)
#define BAKE_METHOD_PARAM_(B) \
static BROTLI_NOINLINE void BrotliCompressFragmentTwoPassImpl ## B( \
BrotliTwoPassArena* s, const uint8_t* input, size_t input_size, \
BROTLI_BOOL is_last, uint32_t* command_buf, uint8_t* literal_buf, \
int* table, size_t* storage_ix, uint8_t* storage) { \
size_t min_match = (B <= 15) ? 4 : 6; \
BrotliCompressFragmentTwoPassImpl(s, input, input_size, is_last, command_buf,\
literal_buf, table, B, min_match, storage_ix, storage); \
}
FOR_TABLE_BITS_(BAKE_METHOD_PARAM_)
#undef BAKE_METHOD_PARAM_
void BrotliCompressFragmentTwoPass(
BrotliTwoPassArena* s, const uint8_t* input, size_t input_size,
BROTLI_BOOL is_last, uint32_t* command_buf, uint8_t* literal_buf,
int* table, size_t table_size, size_t* storage_ix, uint8_t* storage) {
const size_t initial_storage_ix = *storage_ix;
const size_t table_bits = Log2FloorNonZero(table_size);
switch (table_bits) {
#define CASE_(B) \
case B: \
BrotliCompressFragmentTwoPassImpl ## B( \
s, input, input_size, is_last, command_buf, \
literal_buf, table, storage_ix, storage); \
break;
FOR_TABLE_BITS_(CASE_)
#undef CASE_
default: BROTLI_DCHECK(0); break;
}
/* If output is larger than single uncompressed block, rewrite it. */
if (*storage_ix - initial_storage_ix > 31 + (input_size << 3)) {
RewindBitPosition(initial_storage_ix, storage_ix, storage);
EmitUncompressedMetaBlock(input, input_size, storage_ix, storage);
}
if (is_last) {
BrotliWriteBits(1, 1, storage_ix, storage); /* islast */
BrotliWriteBits(1, 1, storage_ix, storage); /* isempty */
*storage_ix = (*storage_ix + 7u) & ~7u;
}
}
#undef FOR_TABLE_BITS_
#if defined(__cplusplus) || defined(c_plusplus)
} /* extern "C" */
#endif