Added brotli enc/ and tools/ directories.

third_party/brotli/enc/encode.cc

+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+// Implementation of Brotli compressor.
+
+#include "./encode.h"
+
+#include <algorithm>
+#include <cstdlib>  /* free, malloc */
+#include <cstring>  /* memset */
+#include <limits>
+
+#include "./backward_references.h"
+#include "./bit_cost.h"
+#include "./block_splitter.h"
+#include "./brotli_bit_stream.h"
+#include "./cluster.h"
+#include "./context.h"
+#include "./metablock.h"
+#include "./transform.h"
+#include "./compress_fragment.h"
+#include "./compress_fragment_two_pass.h"
+#include "./entropy_encode.h"
+#include "./fast_log.h"
+#include "./hash.h"
+#include "./histogram.h"
+#include "./prefix.h"
+#include "./utf8_util.h"
+#include "./write_bits.h"
+
+namespace brotli {
+
+static const int kMinQualityForBlockSplit = 4;
+static const int kMinQualityForContextModeling = 5;
+static const int kMinQualityForOptimizeHistograms = 4;
+// For quality 2 there is no block splitting, so we buffer at most this much
+// literals and commands.
+static const size_t kMaxNumDelayedSymbols = 0x2fff;
+
+#define COPY_ARRAY(dst, src) memcpy(dst, src, sizeof(src));
+
+static void RecomputeDistancePrefixes(Command* cmds,
+                                      size_t num_commands,
+                                      uint32_t num_direct_distance_codes,
+                                      uint32_t distance_postfix_bits) {
+  if (num_direct_distance_codes == 0 && distance_postfix_bits == 0) {
+    return;
+  }
+  for (size_t i = 0; i < num_commands; ++i) {
+    Command* cmd = &cmds[i];
+    if (cmd->copy_len() && cmd->cmd_prefix_ >= 128) {
+      PrefixEncodeCopyDistance(cmd->DistanceCode(),
+                               num_direct_distance_codes,
+                               distance_postfix_bits,
+                               &cmd->dist_prefix_,
+                               &cmd->dist_extra_);
+    }
+  }
+}
+
+/* Wraps 64-bit input position to 32-bit ringbuffer position preserving
+   "not-a-first-lap" feature. */
+static uint32_t WrapPosition(uint64_t position) {
+  uint32_t result = static_cast<uint32_t>(position);
+  if (position > (1u << 30)) {
+    result = (result & ((1u << 30) - 1)) | (1u << 30);
+  }
+  return result;
+}
+
+uint8_t* BrotliCompressor::GetBrotliStorage(size_t size) {
+  if (storage_size_ < size) {
+    delete[] storage_;
+    storage_ = new uint8_t[size];
+    storage_size_ = size;
+  }
+  return storage_;
+}
+
+static size_t MaxHashTableSize(int quality) {
+  return quality == 0 ? 1 << 15 : 1 << 17;
+}
+
+static size_t HashTableSize(size_t max_table_size, size_t input_size) {
+  size_t htsize = 256;
+  while (htsize < max_table_size && htsize < input_size) {
+    htsize <<= 1;
+  }
+  return htsize;
+}
+
+int* BrotliCompressor::GetHashTable(int quality,
+                                    size_t input_size,
+                                    size_t* table_size) {
+  // Use smaller hash table when input.size() is smaller, since we
+  // fill the table, incurring O(hash table size) overhead for
+  // compression, and if the input is short, we won't need that
+  // many hash table entries anyway.
+  const size_t max_table_size = MaxHashTableSize(quality);
+  assert(max_table_size >= 256);
+  size_t htsize = HashTableSize(max_table_size, input_size);
+
+  int* table;
+  if (htsize <= sizeof(small_table_) / sizeof(small_table_[0])) {
+    table = small_table_;
+  } else {
+    if (large_table_ == NULL) {
+      large_table_ = new int[max_table_size];
+    }
+    table = large_table_;
+  }
+
+  *table_size = htsize;
+  memset(table, 0, htsize * sizeof(*table));
+  return table;
+}
+
+static void EncodeWindowBits(int lgwin, uint8_t* last_byte,
+                             uint8_t* last_byte_bits) {
+  if (lgwin == 16) {
+    *last_byte = 0;
+    *last_byte_bits = 1;
+  } else if (lgwin == 17) {
+    *last_byte = 1;
+    *last_byte_bits = 7;
+  } else if (lgwin > 17) {
+    *last_byte = static_cast<uint8_t>(((lgwin - 17) << 1) | 1);
+    *last_byte_bits = 4;
+  } else {
+    *last_byte = static_cast<uint8_t>(((lgwin - 8) << 4) | 1);
+    *last_byte_bits = 7;
+  }
+}
+
+// Initializes the command and distance prefix codes for the first block.
+static void InitCommandPrefixCodes(uint8_t cmd_depths[128],
+                                   uint16_t cmd_bits[128],
+                                   uint8_t cmd_code[512],
+                                   size_t* cmd_code_numbits) {
+  static const uint8_t kDefaultCommandDepths[128] = {
+    0, 4, 4, 5, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8,
+    0, 0, 0, 4, 4, 4, 4, 4, 5, 5, 6, 6, 6, 6, 7, 7,
+    7, 7, 10, 10, 10, 10, 10, 10, 0, 4, 4, 5, 5, 5, 6, 6,
+    7, 8, 8, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
+    5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    6, 6, 6, 6, 6, 6, 5, 5, 5, 5, 5, 5, 4, 4, 4, 4,
+    4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 7, 7, 7, 8, 10,
+    12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
+  };
+  static const uint16_t kDefaultCommandBits[128] = {
+    0,   0,   8,   9,   3,  35,   7,   71,
+    39, 103,  23,  47, 175, 111, 239,   31,
+    0,   0,   0,   4,  12,   2,  10,    6,
+    13,  29,  11,  43,  27,  59,  87,   55,
+    15,  79, 319, 831, 191, 703, 447,  959,
+    0,  14,   1,  25,   5,  21,  19,   51,
+    119, 159,  95, 223, 479, 991,  63,  575,
+    127, 639, 383, 895, 255, 767, 511, 1023,
+    14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    27, 59, 7, 39, 23, 55, 30, 1, 17, 9, 25, 5, 0, 8, 4, 12,
+    2, 10, 6, 21, 13, 29, 3, 19, 11, 15, 47, 31, 95, 63, 127, 255,
+    767, 2815, 1791, 3839, 511, 2559, 1535, 3583, 1023, 3071, 2047, 4095,
+  };
+  COPY_ARRAY(cmd_depths, kDefaultCommandDepths);
+  COPY_ARRAY(cmd_bits, kDefaultCommandBits);
+
+  // Initialize the pre-compressed form of the command and distance prefix
+  // codes.
+  static const uint8_t kDefaultCommandCode[] = {
+    0xff, 0x77, 0xd5, 0xbf, 0xe7, 0xde, 0xea, 0x9e, 0x51, 0x5d, 0xde, 0xc6,
+    0x70, 0x57, 0xbc, 0x58, 0x58, 0x58, 0xd8, 0xd8, 0x58, 0xd5, 0xcb, 0x8c,
+    0xea, 0xe0, 0xc3, 0x87, 0x1f, 0x83, 0xc1, 0x60, 0x1c, 0x67, 0xb2, 0xaa,
+    0x06, 0x83, 0xc1, 0x60, 0x30, 0x18, 0xcc, 0xa1, 0xce, 0x88, 0x54, 0x94,
+    0x46, 0xe1, 0xb0, 0xd0, 0x4e, 0xb2, 0xf7, 0x04, 0x00,
+  };
+  static const int kDefaultCommandCodeNumBits = 448;
+  COPY_ARRAY(cmd_code, kDefaultCommandCode);
+  *cmd_code_numbits = kDefaultCommandCodeNumBits;
+}
+
+// Decide about the context map based on the ability of the prediction
+// ability of the previous byte UTF8-prefix on the next byte. The
+// prediction ability is calculated as shannon entropy. Here we need
+// shannon entropy instead of 'BitsEntropy' since the prefix will be
+// encoded with the remaining 6 bits of the following byte, and
+// BitsEntropy will assume that symbol to be stored alone using Huffman
+// coding.
+static void ChooseContextMap(int quality,
+                             uint32_t* bigram_histo,
+                             size_t* num_literal_contexts,
+                             const uint32_t** literal_context_map) {
+  uint32_t monogram_histo[3] = { 0 };
+  uint32_t two_prefix_histo[6] = { 0 };
+  size_t total = 0;
+  for (size_t i = 0; i < 9; ++i) {
+    total += bigram_histo[i];
+    monogram_histo[i % 3] += bigram_histo[i];
+    size_t j = i;
+    if (j >= 6) {
+      j -= 6;
+    }
+    two_prefix_histo[j] += bigram_histo[i];
+  }
+  size_t dummy;
+  double entropy1 = ShannonEntropy(monogram_histo, 3, &dummy);
+  double entropy2 = (ShannonEntropy(two_prefix_histo, 3, &dummy) +
+                     ShannonEntropy(two_prefix_histo + 3, 3, &dummy));
+  double entropy3 = 0;
+  for (size_t k = 0; k < 3; ++k) {
+    entropy3 += ShannonEntropy(bigram_histo + 3 * k, 3, &dummy);
+  }
+
+  assert(total != 0);
+  double scale = 1.0 / static_cast<double>(total);
+  entropy1 *= scale;
+  entropy2 *= scale;
+  entropy3 *= scale;
+
+  static const uint32_t kStaticContextMapContinuation[64] = {
+    1, 1, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  };
+  static const uint32_t kStaticContextMapSimpleUTF8[64] = {
+    0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  };
+  if (quality < 7) {
+    // 3 context models is a bit slower, don't use it at lower qualities.
+    entropy3 = entropy1 * 10;
+  }
+  // If expected savings by symbol are less than 0.2 bits, skip the
+  // context modeling -- in exchange for faster decoding speed.
+  if (entropy1 - entropy2 < 0.2 &&
+      entropy1 - entropy3 < 0.2) {
+    *num_literal_contexts = 1;
+  } else if (entropy2 - entropy3 < 0.02) {
+    *num_literal_contexts = 2;
+    *literal_context_map = kStaticContextMapSimpleUTF8;
+  } else {
+    *num_literal_contexts = 3;
+    *literal_context_map = kStaticContextMapContinuation;
+  }
+}
+
+static void DecideOverLiteralContextModeling(
+    const uint8_t* input,
+    size_t start_pos,
+    size_t length,
+    size_t mask,
+    int quality,
+    ContextType* literal_context_mode,
+    size_t* num_literal_contexts,
+    const uint32_t** literal_context_map) {
+  if (quality < kMinQualityForContextModeling || length < 64) {
+    return;
+  }
+  // Gather bigram data of the UTF8 byte prefixes. To make the analysis of
+  // UTF8 data faster we only examine 64 byte long strides at every 4kB
+  // intervals.
+  const size_t end_pos = start_pos + length;
+  uint32_t bigram_prefix_histo[9] = { 0 };
+  for (; start_pos + 64 <= end_pos; start_pos += 4096) {
+      static const int lut[4] = { 0, 0, 1, 2 };
+    const size_t stride_end_pos = start_pos + 64;
+    int prev = lut[input[start_pos & mask] >> 6] * 3;
+    for (size_t pos = start_pos + 1; pos < stride_end_pos; ++pos) {
+      const uint8_t literal = input[pos & mask];
+      ++bigram_prefix_histo[prev + lut[literal >> 6]];
+      prev = lut[literal >> 6] * 3;
+    }
+  }
+  *literal_context_mode = CONTEXT_UTF8;
+  ChooseContextMap(quality, &bigram_prefix_histo[0], num_literal_contexts,
+                   literal_context_map);
+}
+
+static bool ShouldCompress(const uint8_t* data,
+                           const size_t mask,
+                           const uint64_t last_flush_pos,
+                           const size_t bytes,
+                           const size_t num_literals,
+                           const size_t num_commands) {
+  if (num_commands < (bytes >> 8) + 2) {
+    if (num_literals > 0.99 * static_cast<double>(bytes)) {
+      uint32_t literal_histo[256] = { 0 };
+      static const uint32_t kSampleRate = 13;
+      static const double kMinEntropy = 7.92;
+      const double bit_cost_threshold =
+          static_cast<double>(bytes) * kMinEntropy / kSampleRate;
+      size_t t = (bytes + kSampleRate - 1) / kSampleRate;
+      uint32_t pos = static_cast<uint32_t>(last_flush_pos);
+      for (size_t i = 0; i < t; i++) {
+        ++literal_histo[data[pos & mask]];
+        pos += kSampleRate;
+      }
+      if (BitsEntropy(literal_histo, 256) > bit_cost_threshold) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+static void WriteMetaBlockInternal(const uint8_t* data,
+                                   const size_t mask,
+                                   const uint64_t last_flush_pos,
+                                   const size_t bytes,
+                                   const bool is_last,
+                                   const int quality,
+                                   const bool font_mode,
+                                   const uint8_t prev_byte,
+                                   const uint8_t prev_byte2,
+                                   const size_t num_literals,
+                                   const size_t num_commands,
+                                   Command* commands,
+                                   const int* saved_dist_cache,
+                                   int* dist_cache,
+                                   size_t* storage_ix,
+                                   uint8_t* storage) {
+  if (bytes == 0) {
+    // Write the ISLAST and ISEMPTY bits.
+    WriteBits(2, 3, storage_ix, storage);
+    *storage_ix = (*storage_ix + 7u) & ~7u;
+    return;
+  }
+
+  if (!ShouldCompress(data, mask, last_flush_pos, bytes,
+                      num_literals, num_commands)) {
+    // Restore the distance cache, as its last update by
+    // CreateBackwardReferences is now unused.
+    memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
+    StoreUncompressedMetaBlock(is_last, data,
+                               WrapPosition(last_flush_pos), mask, bytes,
+                               storage_ix, storage);
+    return;
+  }
+
+  const uint8_t last_byte = storage[0];
+  const uint8_t last_byte_bits = static_cast<uint8_t>(*storage_ix & 0xff);
+  uint32_t num_direct_distance_codes = 0;
+  uint32_t distance_postfix_bits = 0;
+  if (quality > 9 && font_mode) {
+    num_direct_distance_codes = 12;
+    distance_postfix_bits = 1;
+    RecomputeDistancePrefixes(commands,
+                              num_commands,
+                              num_direct_distance_codes,
+                              distance_postfix_bits);
+  }
+  if (quality == 2) {
+    StoreMetaBlockFast(data, WrapPosition(last_flush_pos),
+                       bytes, mask, is_last,
+                       commands, num_commands,
+                       storage_ix, storage);
+  } else if (quality < kMinQualityForBlockSplit) {
+    StoreMetaBlockTrivial(data, WrapPosition(last_flush_pos),
+                          bytes, mask, is_last,
+                          commands, num_commands,
+                          storage_ix, storage);
+  } else {
+    MetaBlockSplit mb;
+    ContextType literal_context_mode = CONTEXT_UTF8;
+    if (quality <= 9) {
+      size_t num_literal_contexts = 1;
+      const uint32_t* literal_context_map = NULL;
+      DecideOverLiteralContextModeling(data, WrapPosition(last_flush_pos),
+                                       bytes, mask,
+                                       quality,
+                                       &literal_context_mode,
+                                       &num_literal_contexts,
+                                       &literal_context_map);
+      if (literal_context_map == NULL) {
+        BuildMetaBlockGreedy(data, WrapPosition(last_flush_pos), mask,
+                             commands, num_commands, &mb);
+      } else {
+        BuildMetaBlockGreedyWithContexts(data, WrapPosition(last_flush_pos),
+                                         mask,
+                                         prev_byte, prev_byte2,
+                                         literal_context_mode,
+                                         num_literal_contexts,
+                                         literal_context_map,
+                                         commands, num_commands,
+                                         &mb);
+      }
+    } else {
+      if (!IsMostlyUTF8(data, WrapPosition(last_flush_pos), mask, bytes,
+                        kMinUTF8Ratio)) {
+        literal_context_mode = CONTEXT_SIGNED;
+      }
+      BuildMetaBlock(data, WrapPosition(last_flush_pos), mask,
+                     prev_byte, prev_byte2,
+                     commands, num_commands,
+                     literal_context_mode,
+                     &mb);
+    }
+    if (quality >= kMinQualityForOptimizeHistograms) {
+      OptimizeHistograms(num_direct_distance_codes,
+                         distance_postfix_bits,
+                         &mb);
+    }
+    StoreMetaBlock(data, WrapPosition(last_flush_pos), bytes, mask,
+                   prev_byte, prev_byte2,
+                   is_last,
+                   num_direct_distance_codes,
+                   distance_postfix_bits,
+                   literal_context_mode,
+                   commands, num_commands,
+                   mb,
+                   storage_ix, storage);
+  }
+  if (bytes + 4 < (*storage_ix >> 3)) {
+    // Restore the distance cache and last byte.
+    memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
+    storage[0] = last_byte;
+    *storage_ix = last_byte_bits;
+    StoreUncompressedMetaBlock(is_last, data,
+                               WrapPosition(last_flush_pos), mask,
+                               bytes, storage_ix, storage);
+  }
+}
+
+BrotliCompressor::BrotliCompressor(BrotliParams params)
+    : params_(params),
+      hashers_(new Hashers()),
+      input_pos_(0),
+      num_commands_(0),
+      num_literals_(0),
+      last_insert_len_(0),
+      last_flush_pos_(0),
+      last_processed_pos_(0),
+      prev_byte_(0),
+      prev_byte2_(0),
+      storage_size_(0),
+      storage_(0),
+      large_table_(NULL),
+      cmd_code_numbits_(0),
+      command_buf_(NULL),
+      literal_buf_(NULL) {
+  // Sanitize params.
+  params_.quality = std::max(0, params_.quality);
+  if (params_.lgwin < kMinWindowBits) {
+    params_.lgwin = kMinWindowBits;
+  } else if (params_.lgwin > kMaxWindowBits) {
+    params_.lgwin = kMaxWindowBits;
+  }
+  if (params_.quality <= 1) {
+    params_.lgblock = params_.lgwin;
+  } else if (params_.quality < kMinQualityForBlockSplit) {
+    params_.lgblock = 14;
+  } else if (params_.lgblock == 0) {
+    params_.lgblock = 16;
+    if (params_.quality >= 9 && params_.lgwin > params_.lgblock) {
+      params_.lgblock = std::min(18, params_.lgwin);
+    }
+  } else {
+    params_.lgblock = std::min(kMaxInputBlockBits,
+                               std::max(kMinInputBlockBits, params_.lgblock));
+  }
+
+  // Initialize input and literal cost ring buffers.
+  // We allocate at least lgwin + 1 bits for the ring buffer so that the newly
+  // added block fits there completely and we still get lgwin bits and at least
+  // read_block_size_bits + 1 bits because the copy tail length needs to be
+  // smaller than ringbuffer size.
+  int ringbuffer_bits = std::max(params_.lgwin + 1, params_.lgblock + 1);
+  ringbuffer_ = new RingBuffer(ringbuffer_bits, params_.lgblock);
+
+  commands_ = 0;
+  cmd_alloc_size_ = 0;
+
+  // Initialize last byte with stream header.
+  EncodeWindowBits(params_.lgwin, &last_byte_, &last_byte_bits_);
+
+  // Initialize distance cache.
+  dist_cache_[0] = 4;
+  dist_cache_[1] = 11;
+  dist_cache_[2] = 15;
+  dist_cache_[3] = 16;
+  // Save the state of the distance cache in case we need to restore it for
+  // emitting an uncompressed block.
+  memcpy(saved_dist_cache_, dist_cache_, sizeof(dist_cache_));
+
+  if (params_.quality == 0) {
+    InitCommandPrefixCodes(cmd_depths_, cmd_bits_,
+                           cmd_code_, &cmd_code_numbits_);
+  } else if (params_.quality == 1) {
+    command_buf_ = new uint32_t[kCompressFragmentTwoPassBlockSize];
+    literal_buf_ = new uint8_t[kCompressFragmentTwoPassBlockSize];
+  }
+
+  // Initialize hashers.
+  hash_type_ = std::min(10, params_.quality);
+  hashers_->Init(hash_type_);
+}
+
+BrotliCompressor::~BrotliCompressor(void) {
+  delete[] storage_;
+  free(commands_);
+  delete ringbuffer_;
+  delete hashers_;
+  delete[] large_table_;
+  delete[] command_buf_;
+  delete[] literal_buf_;
+}
+
+void BrotliCompressor::CopyInputToRingBuffer(const size_t input_size,
+                                             const uint8_t* input_buffer) {
+  ringbuffer_->Write(input_buffer, input_size);
+  input_pos_ += input_size;
+
+  // TL;DR: If needed, initialize 7 more bytes in the ring buffer to make the
+  // hashing not depend on uninitialized data. This makes compression
+  // deterministic and it prevents uninitialized memory warnings in Valgrind.
+  // Even without erasing, the output would be valid (but nondeterministic).
+  //
+  // Background information: The compressor stores short (at most 8 bytes)
+  // substrings of the input already read in a hash table, and detects
+  // repetitions by looking up such substrings in the hash table. If it
+  // can find a substring, it checks whether the substring is really there
+  // in the ring buffer (or it's just a hash collision). Should the hash
+  // table become corrupt, this check makes sure that the output is
+  // still valid, albeit the compression ratio would be bad.
+  //
+  // The compressor populates the hash table from the ring buffer as it's
+  // reading new bytes from the input. However, at the last few indexes of
+  // the ring buffer, there are not enough bytes to build full-length
+  // substrings from. Since the hash table always contains full-length
+  // substrings, we erase with dummy 0s here to make sure that those
+  // substrings will contain 0s at the end instead of uninitialized
+  // data.
+  //
+  // Please note that erasing is not necessary (because the
+  // memory region is already initialized since he ring buffer
+  // has a `tail' that holds a copy of the beginning,) so we
+  // skip erasing if we have already gone around at least once in
+  // the ring buffer.
+  size_t pos = ringbuffer_->position();
+  // Only clear during the first round of ringbuffer writes. On
+  // subsequent rounds data in the ringbuffer would be affected.
+  if (pos <= ringbuffer_->mask()) {
+    // This is the first time when the ring buffer is being written.
+    // We clear 7 bytes just after the bytes that have been copied from
+    // the input buffer.
+    //
+    // The ringbuffer has a "tail" that holds a copy of the beginning,
+    // but only once the ring buffer has been fully written once, i.e.,
+    // pos <= mask. For the first time, we need to write values
+    // in this tail (where index may be larger than mask), so that
+    // we have exactly defined behavior and don't read un-initialized
+    // memory. Due to performance reasons, hashing reads data using a
+    // LOAD64, which can go 7 bytes beyond the bytes written in the
+    // ringbuffer.
+    memset(ringbuffer_->start() + pos, 0, 7);
+  }
+}
+
+void BrotliCompressor::BrotliSetCustomDictionary(
+    const size_t size, const uint8_t* dict) {
+  CopyInputToRingBuffer(size, dict);
+  last_flush_pos_ = size;
+  last_processed_pos_ = size;
+  if (size > 0) {
+    prev_byte_ = dict[size - 1];
+  }
+  if (size > 1) {
+    prev_byte2_ = dict[size - 2];
+  }
+  hashers_->PrependCustomDictionary(hash_type_, params_.lgwin, size, dict);
+}
+
+bool BrotliCompressor::WriteBrotliData(const bool is_last,
+                                       const bool force_flush,
+                                       size_t* out_size,
+                                       uint8_t** output) {
+  const uint64_t delta = input_pos_ - last_processed_pos_;
+  const uint8_t* data = ringbuffer_->start();
+  const uint32_t mask = ringbuffer_->mask();
+
+  if (delta > input_block_size()) {
+    return false;
+  }
+  const uint32_t bytes = static_cast<uint32_t>(delta);
+
+  if (params_.quality <= 1) {
+    if (delta == 0 && !is_last) {
+      // We have no new input data and we don't have to finish the stream, so
+      // nothing to do.
+      *out_size = 0;
+      return true;
+    }
+    const size_t max_out_size = 2 * bytes + 500;
+    uint8_t* storage = GetBrotliStorage(max_out_size);
+    storage[0] = last_byte_;
+    size_t storage_ix = last_byte_bits_;
+    size_t table_size;
+    int* table = GetHashTable(params_.quality, bytes, &table_size);
+    if (params_.quality == 0) {
+      BrotliCompressFragmentFast(
+          &data[WrapPosition(last_processed_pos_) & mask],
+          bytes, is_last,
+          table, table_size,
+          cmd_depths_, cmd_bits_,
+          &cmd_code_numbits_, cmd_code_,
+          &storage_ix, storage);
+    } else {
+      BrotliCompressFragmentTwoPass(
+          &data[WrapPosition(last_processed_pos_) & mask],
+          bytes, is_last,
+          command_buf_, literal_buf_,
+          table, table_size,
+          &storage_ix, storage);
+    }
+    last_byte_ = storage[storage_ix >> 3];
+    last_byte_bits_ = storage_ix & 7u;
+    last_processed_pos_ = input_pos_;
+    *output = &storage[0];
+    *out_size = storage_ix >> 3;
+    return true;
+  }
+
+  // Theoretical max number of commands is 1 per 2 bytes.
+  size_t newsize = num_commands_ + bytes / 2 + 1;
+  if (newsize > cmd_alloc_size_) {
+    // Reserve a bit more memory to allow merging with a next block
+    // without realloc: that would impact speed.
+    newsize += (bytes / 4) + 16;
+    cmd_alloc_size_ = newsize;
+    commands_ =
+        static_cast<Command*>(realloc(commands_, sizeof(Command) * newsize));
+  }
+
+  CreateBackwardReferences(bytes, WrapPosition(last_processed_pos_),
+                           is_last, data, mask,
+                           params_.quality,
+                           params_.lgwin,
+                           hashers_,
+                           hash_type_,
+                           dist_cache_,
+                           &last_insert_len_,
+                           &commands_[num_commands_],
+                           &num_commands_,
+                           &num_literals_);
+
+  size_t max_length = std::min<size_t>(mask + 1, 1u << kMaxInputBlockBits);
+  const size_t max_literals = max_length / 8;
+  const size_t max_commands = max_length / 8;
+  if (!is_last && !force_flush &&
+      (params_.quality >= kMinQualityForBlockSplit ||
+       (num_literals_ + num_commands_ < kMaxNumDelayedSymbols)) &&
+      num_literals_ < max_literals &&
+      num_commands_ < max_commands &&
+      input_pos_ + input_block_size() <= last_flush_pos_ + max_length) {
+    // Merge with next input block. Everything will happen later.
+    last_processed_pos_ = input_pos_;
+    *out_size = 0;
+    return true;
+  }
+
+  // Create the last insert-only command.
+  if (last_insert_len_ > 0) {
+    brotli::Command cmd(last_insert_len_);
+    commands_[num_commands_++] = cmd;
+    num_literals_ += last_insert_len_;
+    last_insert_len_ = 0;
+  }
+
+  if (!is_last && input_pos_ == last_flush_pos_) {
+    // We have no new input data and we don't have to finish the stream, so
+    // nothing to do.
+    *out_size = 0;
+    return true;
+  }
+  assert(input_pos_ >= last_flush_pos_);
+  assert(input_pos_ > last_flush_pos_ || is_last);
+  assert(input_pos_ - last_flush_pos_ <= 1u << 24);
+  const uint32_t metablock_size =
+      static_cast<uint32_t>(input_pos_ - last_flush_pos_);
+  const size_t max_out_size = 2 * metablock_size + 500;
+  uint8_t* storage = GetBrotliStorage(max_out_size);
+  storage[0] = last_byte_;
+  size_t storage_ix = last_byte_bits_;
+  bool font_mode = params_.mode == BrotliParams::MODE_FONT;
+  WriteMetaBlockInternal(
+      data, mask, last_flush_pos_, metablock_size, is_last, params_.quality,
+      font_mode, prev_byte_, prev_byte2_, num_literals_, num_commands_,
+      commands_, saved_dist_cache_, dist_cache_, &storage_ix, storage);
+  last_byte_ = storage[storage_ix >> 3];
+  last_byte_bits_ = storage_ix & 7u;
+  last_flush_pos_ = input_pos_;
+  last_processed_pos_ = input_pos_;
+  if (last_flush_pos_ > 0) {
+    prev_byte_ = data[(static_cast<uint32_t>(last_flush_pos_) - 1) & mask];
+  }
+  if (last_flush_pos_ > 1) {
+    prev_byte2_ = data[(static_cast<uint32_t>(last_flush_pos_) - 2) & mask];
+  }
+  num_commands_ = 0;
+  num_literals_ = 0;
+  // Save the state of the distance cache in case we need to restore it for
+  // emitting an uncompressed block.
+  memcpy(saved_dist_cache_, dist_cache_, sizeof(dist_cache_));
+  *output = &storage[0];
+  *out_size = storage_ix >> 3;
+  return true;
+}
+
+bool BrotliCompressor::WriteMetaBlock(const size_t input_size,
+                                      const uint8_t* input_buffer,
+                                      const bool is_last,
+                                      size_t* encoded_size,
+                                      uint8_t* encoded_buffer) {
+  CopyInputToRingBuffer(input_size, input_buffer);
+  size_t out_size = 0;
+  uint8_t* output;
+  if (!WriteBrotliData(is_last, /* force_flush = */ true, &out_size, &output) ||
+      out_size > *encoded_size) {
+    return false;
+  }
+  if (out_size > 0) {
+    memcpy(encoded_buffer, output, out_size);
+  }
+  *encoded_size = out_size;
+  return true;
+}
+
+bool BrotliCompressor::WriteMetadata(const size_t input_size,
+                                     const uint8_t* input_buffer,
+                                     const bool is_last,
+                                     size_t* encoded_size,
+                                     uint8_t* encoded_buffer) {
+  if (input_size > (1 << 24) || input_size + 6 > *encoded_size) {
+    return false;
+  }
+  uint64_t hdr_buffer_data[2];
+  uint8_t* hdr_buffer = reinterpret_cast<uint8_t*>(&hdr_buffer_data[0]);
+  size_t storage_ix = last_byte_bits_;
+  hdr_buffer[0] = last_byte_;
+  WriteBits(1, 0, &storage_ix, hdr_buffer);
+  WriteBits(2, 3, &storage_ix, hdr_buffer);
+  WriteBits(1, 0, &storage_ix, hdr_buffer);
+  if (input_size == 0) {
+    WriteBits(2, 0, &storage_ix, hdr_buffer);
+    *encoded_size = (storage_ix + 7u) >> 3;
+    memcpy(encoded_buffer, hdr_buffer, *encoded_size);
+  } else {
+    uint32_t nbits = (input_size == 1) ? 0 : (Log2FloorNonZero(
+        static_cast<uint32_t>(input_size) - 1) + 1);
+    uint32_t nbytes = (nbits + 7) / 8;
+    WriteBits(2, nbytes, &storage_ix, hdr_buffer);
+    WriteBits(8 * nbytes, input_size - 1, &storage_ix, hdr_buffer);
+    size_t hdr_size = (storage_ix + 7u) >> 3;
+    memcpy(encoded_buffer, hdr_buffer, hdr_size);
+    memcpy(&encoded_buffer[hdr_size], input_buffer, input_size);
+    *encoded_size = hdr_size + input_size;
+  }
+  if (is_last) {
+    encoded_buffer[(*encoded_size)++] = 3;
+  }
+  last_byte_ = 0;
+  last_byte_bits_ = 0;
+  return true;
+}
+
+bool BrotliCompressor::FinishStream(
+    size_t* encoded_size, uint8_t* encoded_buffer) {
+  return WriteMetaBlock(0, NULL, true, encoded_size, encoded_buffer);
+}
+
+static int BrotliCompressBufferQuality10(int lgwin,
+                                         size_t input_size,
+                                         const uint8_t* input_buffer,
+                                         size_t* encoded_size,
+                                         uint8_t* encoded_buffer) {
+  const size_t mask = std::numeric_limits<size_t>::max() >> 1;
+  assert(input_size <= mask + 1);
+  const size_t max_backward_limit = (1 << lgwin) - 16;
+  int dist_cache[4] = { 4, 11, 15, 16 };
+  int saved_dist_cache[4] = { 4, 11, 15, 16 };
+  int ok = 1;
+  const size_t max_out_size = *encoded_size;
+  size_t total_out_size = 0;
+  uint8_t last_byte;
+  uint8_t last_byte_bits;
+  EncodeWindowBits(lgwin, &last_byte, &last_byte_bits);
+
+  Hashers::H10* hasher = new Hashers::H10;
+  const size_t hasher_eff_size = std::min(input_size, max_backward_limit + 16);
+  hasher->Init(lgwin, 0, hasher_eff_size, true);
+
+  const int lgblock = std::min(18, lgwin);
+  const int lgmetablock = std::min(24, lgwin + 1);
+  const size_t max_block_size = static_cast<size_t>(1) << lgblock;
+  const size_t max_metablock_size = static_cast<size_t>(1) << lgmetablock;
+  const size_t max_literals_per_metablock = max_metablock_size / 8;
+  const size_t max_commands_per_metablock = max_metablock_size / 8;
+  size_t metablock_start = 0;
+  uint8_t prev_byte = 0;
+  uint8_t prev_byte2 = 0;
+  while (ok && metablock_start < input_size) {
+    const size_t metablock_end =
+        std::min(input_size, metablock_start + max_metablock_size);
+    const size_t expected_num_commands =
+        (metablock_end - metablock_start) / 12 + 16;
+    Command* commands = 0;
+    size_t num_commands = 0;
+    size_t last_insert_len = 0;
+    size_t num_literals = 0;
+    size_t metablock_size = 0;
+    size_t cmd_alloc_size = 0;
+
+    for (size_t block_start = metablock_start; block_start < metablock_end; ) {
+      size_t block_size = std::min(metablock_end - block_start, max_block_size);
+      ZopfliNode* nodes = new ZopfliNode[block_size + 1];
+      std::vector<uint32_t> path;
+      hasher->StitchToPreviousBlock(block_size, block_start,
+                                    input_buffer, mask);
+      ZopfliComputeShortestPath(block_size, block_start, input_buffer, mask,
+                                max_backward_limit, dist_cache,
+                                hasher, nodes, &path);
+      // We allocate a command buffer in the first iteration of this loop that
+      // will be likely big enough for the whole metablock, so that for most
+      // inputs we will not have to reallocate in later iterations. We do the
+      // allocation here and not before the loop, because if the input is small,
+      // this will be allocated after the zopfli cost model is freed, so this
+      // will not increase peak memory usage.
+      // TODO: If the first allocation is too small, increase command
+      // buffer size exponentially.
+      size_t new_cmd_alloc_size = std::max(expected_num_commands,
+                                           num_commands + path.size() + 1);
+      if (cmd_alloc_size != new_cmd_alloc_size) {
+        cmd_alloc_size = new_cmd_alloc_size;
+        commands = static_cast<Command*>(
+            realloc(commands, cmd_alloc_size * sizeof(Command)));
+      }
+      ZopfliCreateCommands(block_size, block_start, max_backward_limit, path,
+                           &nodes[0], dist_cache, &last_insert_len,
+                           &commands[num_commands], &num_literals);
+      num_commands += path.size();
+      block_start += block_size;
+      metablock_size += block_size;
+      delete[] nodes;
+      if (num_literals > max_literals_per_metablock ||
+          num_commands > max_commands_per_metablock) {
+        break;
+      }
+    }
+
+    if (last_insert_len > 0) {
+      Command cmd(last_insert_len);
+      commands[num_commands++] = cmd;
+      num_literals += last_insert_len;
+    }
+
+    const bool is_last = (metablock_start + metablock_size == input_size);
+    uint8_t* storage = NULL;
+    size_t storage_ix = last_byte_bits;
+
+    if (metablock_size == 0) {
+      // Write the ISLAST and ISEMPTY bits.
+      storage = new uint8_t[16];
+      storage[0] = last_byte;
+      WriteBits(2, 3, &storage_ix, storage);
+      storage_ix = (storage_ix + 7u) & ~7u;
+    } else if (!ShouldCompress(input_buffer, mask, metablock_start,
+                               metablock_size, num_literals, num_commands)) {
+      // Restore the distance cache, as its last update by
+      // CreateBackwardReferences is now unused.
+      memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
+      storage = new uint8_t[metablock_size + 16];
+      storage[0] = last_byte;
+      StoreUncompressedMetaBlock(is_last, input_buffer,
+                                 metablock_start, mask, metablock_size,
+                                 &storage_ix, storage);
+    } else {
+      uint32_t num_direct_distance_codes = 0;
+      uint32_t distance_postfix_bits = 0;
+      MetaBlockSplit mb;
+      ContextType literal_context_mode = CONTEXT_UTF8;
+      if (!IsMostlyUTF8(
+              input_buffer, metablock_start, mask, metablock_size,
+              kMinUTF8Ratio)) {
+        literal_context_mode = CONTEXT_SIGNED;
+      }
+      BuildMetaBlock(input_buffer, metablock_start, mask,
+                     prev_byte, prev_byte2,
+                     commands, num_commands,
+                     literal_context_mode,
+                     &mb);
+      OptimizeHistograms(num_direct_distance_codes,
+                         distance_postfix_bits,
+                         &mb);
+      const size_t max_out_metablock_size = 2 * metablock_size + 500;
+      storage = new uint8_t[max_out_metablock_size];
+      storage[0] = last_byte;
+      StoreMetaBlock(input_buffer, metablock_start, metablock_size, mask,
+                     prev_byte, prev_byte2,
+                     is_last,
+                     num_direct_distance_codes,
+                     distance_postfix_bits,
+                     literal_context_mode,
+                     commands, num_commands,
+                     mb,
+                     &storage_ix, storage);
+      if (metablock_size + 4 < (storage_ix >> 3)) {
+        // Restore the distance cache and last byte.
+        memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
+        storage[0] = last_byte;
+        storage_ix = last_byte_bits;
+        StoreUncompressedMetaBlock(is_last, input_buffer,
+                                   metablock_start, mask,
+                                   metablock_size, &storage_ix, storage);
+      }
+    }
+    last_byte = storage[storage_ix >> 3];
+    last_byte_bits = storage_ix & 7u;
+    metablock_start += metablock_size;
+    prev_byte = input_buffer[metablock_start - 1];
+    prev_byte2 = input_buffer[metablock_start - 2];
+    // Save the state of the distance cache in case we need to restore it for
+    // emitting an uncompressed block.
+    memcpy(saved_dist_cache, dist_cache, 4 * sizeof(dist_cache[0]));
+
+    const size_t out_size = storage_ix >> 3;
+    total_out_size += out_size;
+    if (total_out_size <= max_out_size) {
+      memcpy(encoded_buffer, storage, out_size);
+      encoded_buffer += out_size;
+    } else {
+      ok = 0;
+    }
+    delete[] storage;
+    free(commands);
+  }
+
+  *encoded_size = total_out_size;
+  delete hasher;
+  return ok;
+}
+
+int BrotliCompressBuffer(BrotliParams params,
+                         size_t input_size,
+                         const uint8_t* input_buffer,
+                         size_t* encoded_size,
+                         uint8_t* encoded_buffer) {
+  if (*encoded_size == 0) {
+    // Output buffer needs at least one byte.
+    return 0;
+  }
+  if (input_size == 0) {
+    // Handle the special case of empty input.
+    *encoded_size = 1;
+    *encoded_buffer = 6;
+    return 1;
+  }
+  if (params.quality == 10) {
+    // TODO: Implement this direct path for all quality levels.
+    const int lgwin = std::min(24, std::max(16, params.lgwin));
+    return BrotliCompressBufferQuality10(lgwin, input_size, input_buffer,
+                                         encoded_size, encoded_buffer);
+  }
+  BrotliMemIn in(input_buffer, input_size);
+  BrotliMemOut out(encoded_buffer, *encoded_size);
+  if (!BrotliCompress(params, &in, &out)) {
+    return 0;
+  }
+  *encoded_size = out.position();
+  return 1;
+}
+
+static bool BrotliInIsFinished(BrotliIn* r) {
+  size_t read_bytes;
+  return r->Read(0, &read_bytes) == NULL;
+}
+
+static const uint8_t* BrotliInReadAndCheckEnd(const size_t block_size,
+                                              BrotliIn* r,
+                                              size_t* bytes_read,
+                                              bool* is_last) {
+  *bytes_read = 0;
+  const uint8_t* data = reinterpret_cast<const uint8_t*>(
+      r->Read(block_size, bytes_read));
+  assert((data == NULL) == (*bytes_read == 0));
+  *is_last = BrotliInIsFinished(r);
+  return data;
+}
+
+static bool CopyOneBlockToRingBuffer(BrotliIn* r,
+                                     BrotliCompressor* compressor,
+                                     size_t* bytes_read,
+                                     bool* is_last) {
+  const size_t block_size = compressor->input_block_size();
+  const uint8_t* data = BrotliInReadAndCheckEnd(block_size, r,
+                                                bytes_read, is_last);
+  if (data == NULL) {
+    return *is_last;
+  }
+  compressor->CopyInputToRingBuffer(*bytes_read, data);
+
+  // Read more bytes until block_size is filled or an EOF (data == NULL) is
+  // received. This is useful to get deterministic compressed output for the
+  // same input no matter how r->Read splits the input to chunks.
+  for (size_t remaining = block_size - *bytes_read; remaining > 0; ) {
+    size_t more_bytes_read = 0;
+    data = BrotliInReadAndCheckEnd(remaining, r, &more_bytes_read, is_last);
+    if (data == NULL) {
+      return *is_last;
+    }
+    compressor->CopyInputToRingBuffer(more_bytes_read, data);
+    *bytes_read += more_bytes_read;
+    remaining -= more_bytes_read;
+  }
+  return true;
+}
+
+
+int BrotliCompress(BrotliParams params, BrotliIn* in, BrotliOut* out) {
+  return BrotliCompressWithCustomDictionary(0, 0, params, in, out);
+}
+
+// Reads the provided input in 'block_size' blocks. Only the last read can be
+// smaller than 'block_size'.
+class BrotliBlockReader {
+ public:
+  explicit BrotliBlockReader(size_t block_size)
+      : block_size_(block_size), buf_(NULL) {}
+  ~BrotliBlockReader(void) { delete[] buf_; }
+
+  const uint8_t* Read(BrotliIn* in, size_t* bytes_read, bool* is_last) {
+    *bytes_read = 0;
+    const uint8_t* data = BrotliInReadAndCheckEnd(block_size_, in,
+                                                  bytes_read, is_last);
+    if (data == NULL || *bytes_read == block_size_ || *is_last) {
+      // If we could get the whole block in one read, or it is the last block,
+      // we just return the pointer to the data without copying.
+      return data;
+    }
+    // If the data comes in smaller chunks, we need to copy it into an internal
+    // buffer until we get a whole block or reach the last chunk.
+    if (buf_ == NULL) {
+      buf_ = new uint8_t[block_size_];
+    }
+    memcpy(buf_, data, *bytes_read);
+    do {
+      size_t cur_bytes_read = 0;
+      data = BrotliInReadAndCheckEnd(block_size_ - *bytes_read, in,
+                                     &cur_bytes_read, is_last);
+      if (data == NULL) {
+        return *is_last ? buf_ : NULL;
+      }
+      memcpy(&buf_[*bytes_read], data, cur_bytes_read);
+      *bytes_read += cur_bytes_read;
+    } while (*bytes_read < block_size_ && !*is_last);
+    return buf_;
+  }
+
+ private:
+  const size_t block_size_;
+  uint8_t* buf_;
+};
+
+int BrotliCompressWithCustomDictionary(size_t dictsize, const uint8_t* dict,
+                                       BrotliParams params,
+                                       BrotliIn* in, BrotliOut* out) {
+  if (params.quality <= 1) {
+    const int quality = std::max(0, params.quality);
+    const int lgwin = std::min(kMaxWindowBits,
+                               std::max(kMinWindowBits, params.lgwin));
+    uint8_t* storage = NULL;
+    int* table = NULL;
+    uint32_t* command_buf = NULL;
+    uint8_t* literal_buf = NULL;
+    uint8_t cmd_depths[128];
+    uint16_t cmd_bits[128];
+    uint8_t cmd_code[512];
+    size_t cmd_code_numbits;
+    if (quality == 0) {
+      InitCommandPrefixCodes(cmd_depths, cmd_bits, cmd_code, &cmd_code_numbits);
+    }
+    uint8_t last_byte;
+    uint8_t last_byte_bits;
+    EncodeWindowBits(lgwin, &last_byte, &last_byte_bits);
+    BrotliBlockReader r(1u << lgwin);
+    int ok = 1;
+    bool is_last = false;
+    while (ok && !is_last) {
+      // Read next block of input.
+      size_t bytes;
+      const uint8_t* data = r.Read(in, &bytes, &is_last);
+      if (data == NULL) {
+        if (!is_last) {
+          ok = 0;
+          break;
+        }
+        assert(bytes == 0);
+      }
+      // Set up output storage.
+      const size_t max_out_size = 2 * bytes + 500;
+      if (storage == NULL) {
+        storage = new uint8_t[max_out_size];
+      }
+      storage[0] = last_byte;
+      size_t storage_ix = last_byte_bits;
+      // Set up hash table.
+      size_t htsize = HashTableSize(MaxHashTableSize(quality), bytes);
+      if (table == NULL) {
+        table = new int[htsize];
+      }
+      memset(table, 0, htsize * sizeof(table[0]));
+      // Set up command and literal buffers for two pass mode.
+      if (quality == 1 && command_buf == NULL) {
+        size_t buf_size = std::min(bytes, kCompressFragmentTwoPassBlockSize);
+        command_buf = new uint32_t[buf_size];
+        literal_buf = new uint8_t[buf_size];
+      }
+      // Do the actual compression.
+      if (quality == 0) {
+        BrotliCompressFragmentFast(data, bytes, is_last, table, htsize,
+                                   cmd_depths, cmd_bits,
+                                   &cmd_code_numbits, cmd_code,
+                                   &storage_ix, storage);
+      } else {
+        BrotliCompressFragmentTwoPass(data, bytes, is_last,
+                                      command_buf, literal_buf,
+                                      table, htsize,
+                                      &storage_ix, storage);
+      }
+      // Save last bytes to stitch it together with the next output block.
+      last_byte = storage[storage_ix >> 3];
+      last_byte_bits = storage_ix & 7u;
+      // Write output block.
+      size_t out_bytes = storage_ix >> 3;
+      if (out_bytes > 0 && !out->Write(storage, out_bytes)) {
+        ok = 0;
+        break;
+      }
+    }
+    delete[] storage;
+    delete[] table;
+    delete[] command_buf;
+    delete[] literal_buf;
+    return ok;
+  }
+
+  size_t in_bytes = 0;
+  size_t out_bytes = 0;
+  uint8_t* output;
+  bool final_block = false;
+  BrotliCompressor compressor(params);
+  if (dictsize != 0) compressor.BrotliSetCustomDictionary(dictsize, dict);
+  while (!final_block) {
+    if (!CopyOneBlockToRingBuffer(in, &compressor, &in_bytes, &final_block)) {
+      return false;
+    }
+    out_bytes = 0;
+    if (!compressor.WriteBrotliData(final_block,
+                                    /* force_flush = */ false,
+                                    &out_bytes, &output)) {
+      return false;
+    }
+    if (out_bytes > 0 && !out->Write(output, out_bytes)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+
+}  // namespace brotli