text: /* Copyright 2014 Google Inc. All Rights Reserved.
  
     Distributed under MIT license.
     See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
  */
  
  /* Brotli bit stream functions to support the low level format. There are no
     compression algorithms here, just the right ordering of bits to match the
     specs. */
  
  #include "./brotli_bit_stream.h"
  
  #include <string.h>  /* memcpy, memset */
  
  #include "../common/constants.h"
  #include "../common/platform.h"
  #include <brotli/types.h>
  #include "./context.h"
  #include "./entropy_encode.h"
  #include "./entropy_encode_static.h"
  #include "./fast_log.h"
  #include "./memory.h"
  #include "./write_bits.h"
  
  #if defined(__cplusplus) || defined(c_plusplus)
  extern "C" {
  #endif
  
  #define MAX_HUFFMAN_TREE_SIZE (2 * BROTLI_NUM_COMMAND_SYMBOLS + 1)
  /* The size of Huffman dictionary for distances assuming that NPOSTFIX = 0 and
   NDIRECT = 0. */
  #define SIMPLE_DISTANCE_ALPHABET_SIZE (BROTLI_NUM_DISTANCE_SHORT_CODES + \
                                         (2 * BROTLI_MAX_DISTANCE_BITS))
  /* SIMPLE_DISTANCE_ALPHABET_SIZE == 64 */
  #define SIMPLE_DISTANCE_ALPHABET_BITS 6
  
  /* Represents the range of values belonging to a prefix code:
     [offset, offset + 2^nbits) */
  typedef struct PrefixCodeRange {
    uint32_t offset;
    uint32_t nbits;
  } PrefixCodeRange;
  
  static const PrefixCodeRange
      kBlockLengthPrefixCode[BROTLI_NUM_BLOCK_LEN_SYMBOLS] = {
    { 1, 2}, { 5, 2}, { 9, 2}, {13, 2}, {17, 3}, { 25, 3}, { 33, 3},
    {41, 3}, {49, 4}, {65, 4}, {81, 4}, {97, 4}, {113, 5}, {145, 5},
    {177, 5}, { 209,  5}, { 241,  6}, { 305,  6}, { 369,  7}, {  497,  8},
    {753, 9}, {1265, 10}, {2289, 11}, {4337, 12}, {8433, 13}, {16625, 24}
  };
  
  static BROTLI_INLINE uint32_t BlockLengthPrefixCode(uint32_t len) {
    uint32_t code = (len >= 177) ? (len >= 753 ? 20 : 14) : (len >= 41 ? 7 : 0);
    while (code < (BROTLI_NUM_BLOCK_LEN_SYMBOLS - 1) &&
        len >= kBlockLengthPrefixCode[code + 1].offset) ++code;
    return code;
  }
  
  static BROTLI_INLINE void GetBlockLengthPrefixCode(uint32_t len, size_t* code,
      uint32_t* n_extra, uint32_t* extra) {
    *code = BlockLengthPrefixCode(len);
    *n_extra = kBlockLengthPrefixCode[*code].nbits;
    *extra = len - kBlockLengthPrefixCode[*code].offset;
  }
  
  typedef struct BlockTypeCodeCalculator {
    size_t last_type;
    size_t second_last_type;
  } BlockTypeCodeCalculator;
  
  static void InitBlockTypeCodeCalculator(BlockTypeCodeCalculator* self) {
    self->last_type = 1;
    self->second_last_type = 0;
  }
  
  static BROTLI_INLINE size_t NextBlockTypeCode(
      BlockTypeCodeCalculator* calculator, uint8_t type) {
    size_t type_code = (type == calculator->last_type + 1) ? 1u :
        (type == calculator->second_last_type) ? 0u : type + 2u;
    calculator->second_last_type = calculator->last_type;
    calculator->last_type = type;
    return type_code;
  }
  
  /* |nibblesbits| represents the 2 bits to encode MNIBBLES (0-3)
     REQUIRES: length > 0
     REQUIRES: length <= (1 << 24) */
  static void BrotliEncodeMlen(size_t length, uint64_t* bits,
                               size_t* numbits, uint64_t* nibblesbits) {
    size_t lg = (length == 1) ? 1 : Log2FloorNonZero((uint32_t)(length - 1)) + 1;
    size_t mnibbles = (lg < 16 ? 16 : (lg + 3)) / 4;
    BROTLI_DCHECK(length > 0);
    BROTLI_DCHECK(length <= (1 << 24));
    BROTLI_DCHECK(lg <= 24);
    *nibblesbits = mnibbles - 4;
    *numbits = mnibbles * 4;
    *bits = length - 1;
  }
  
  static BROTLI_INLINE void StoreCommandExtra(
      const Command* cmd, size_t* storage_ix, uint8_t* storage) {
    uint32_t copylen_code = CommandCopyLenCode(cmd);
    uint16_t inscode = GetInsertLengthCode(cmd->insert_len_);
    uint16_t copycode = GetCopyLengthCode(copylen_code);
    uint32_t insnumextra = GetInsertExtra(inscode);
    uint64_t insextraval = cmd->insert_len_ - GetInsertBase(inscode);
    uint64_t copyextraval = copylen_code - GetCopyBase(copycode);
    uint64_t bits = (copyextraval << insnumextra) | insextraval;
    BrotliWriteBits(
        insnumextra + GetCopyExtra(copycode), bits, storage_ix, storage);
  }
  
  /* Data structure that stores almost everything that is needed to encode each
     block switch command. */
  typedef struct BlockSplitCode {
    BlockTypeCodeCalculator type_code_calculator;
    uint8_t type_depths[BROTLI_MAX_BLOCK_TYPE_SYMBOLS];
    uint16_t type_bits[BROTLI_MAX_BLOCK_TYPE_SYMBOLS];
    uint8_t length_depths[BROTLI_NUM_BLOCK_LEN_SYMBOLS];
    uint16_t length_bits[BROTLI_NUM_BLOCK_LEN_SYMBOLS];
  } BlockSplitCode;
  
  /* Stores a number between 0 and 255. */
  static void StoreVarLenUint8(size_t n, size_t* storage_ix, uint8_t* storage) {
    if (n == 0) {
      BrotliWriteBits(1, 0, storage_ix, storage);
    } else {
      size_t nbits = Log2FloorNonZero(n);
      BrotliWriteBits(1, 1, storage_ix, storage);
      BrotliWriteBits(3, nbits, storage_ix, storage);
      BrotliWriteBits(nbits, n - ((size_t)1 << nbits), storage_ix, storage);
    }
  }
  
  /* Stores the compressed meta-block header.
     REQUIRES: length > 0
     REQUIRES: length <= (1 << 24) */
  static void StoreCompressedMetaBlockHeader(BROTLI_BOOL is_final_block,
                                             size_t length,
                                             size_t* storage_ix,
                                             uint8_t* storage) {
    uint64_t lenbits;
    size_t nlenbits;
    uint64_t nibblesbits;
  
    /* Write ISLAST bit. */
    BrotliWriteBits(1, (uint64_t)is_final_block, storage_ix, storage);
    /* Write ISEMPTY bit. */
    if (is_final_block) {
      BrotliWriteBits(1, 0, storage_ix, storage);
    }
  
    BrotliEncodeMlen(length, &lenbits, &nlenbits, &nibblesbits);
    BrotliWriteBits(2, nibblesbits, storage_ix, storage);
    BrotliWriteBits(nlenbits, lenbits, storage_ix, storage);
  
    if (!is_final_block) {
      /* Write ISUNCOMPRESSED bit. */
      BrotliWriteBits(1, 0, storage_ix, storage);
    }
  }
  
  /* Stores the uncompressed meta-block header.
     REQUIRES: length > 0
     REQUIRES: length <= (1 << 24) */
  static void BrotliStoreUncompressedMetaBlockHeader(size_t length,
                                                     size_t* storage_ix,
                                                     uint8_t* storage) {
    uint64_t lenbits;
    size_t nlenbits;
    uint64_t nibblesbits;
  
    /* Write ISLAST bit.
       Uncompressed block cannot be the last one, so set to 0. */
    BrotliWriteBits(1, 0, storage_ix, storage);
    BrotliEncodeMlen(length, &lenbits, &nlenbits, &nibblesbits);
    BrotliWriteBits(2, nibblesbits, storage_ix, storage);
    BrotliWriteBits(nlenbits, lenbits, storage_ix, storage);
    /* Write ISUNCOMPRESSED bit. */
    BrotliWriteBits(1, 1, storage_ix, storage);
  }
  
  static void BrotliStoreHuffmanTreeOfHuffmanTreeToBitMask(
      const int num_codes, const uint8_t* code_length_bitdepth,
      size_t* storage_ix, uint8_t* storage) {
    static const uint8_t kStorageOrder[BROTLI_CODE_LENGTH_CODES] = {
      1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15
    };
    /* The bit lengths of the Huffman code over the code length alphabet
       are compressed with the following static Huffman code:
         Symbol   Code
         ------   ----
         0          00
         1        1110
         2         110
         3          01
         4          10
         5        1111 */
    static const uint8_t kHuffmanBitLengthHuffmanCodeSymbols[6] = {
       0, 7, 3, 2, 1, 15
    };
    static const uint8_t kHuffmanBitLengthHuffmanCodeBitLengths[6] = {
      2, 4, 3, 2, 2, 4
    };
  
    size_t skip_some = 0;  /* skips none. */
  
    /* Throw away trailing zeros: */
    size_t codes_to_store = BROTLI_CODE_LENGTH_CODES;
    if (num_codes > 1) {
      for (; codes_to_store > 0; --codes_to_store) {
        if (code_length_bitdepth[kStorageOrder[codes_to_store - 1]] != 0) {
          break;
        }
      }
    }
    if (code_length_bitdepth[kStorageOrder[0]] == 0 &&
        code_length_bitdepth[kStorageOrder[1]] == 0) {
      skip_some = 2;  /* skips two. */
      if (code_length_bitdepth[kStorageOrder[2]] == 0) {
        skip_some = 3;  /* skips three. */
      }
    }
    BrotliWriteBits(2, skip_some, storage_ix, storage);
    {
      size_t i;
      for (i = skip_some; i < codes_to_store; ++i) {
        size_t l = code_length_bitdepth[kStorageOrder[i]];
        BrotliWriteBits(kHuffmanBitLengthHuffmanCodeBitLengths[l],
            kHuffmanBitLengthHuffmanCodeSymbols[l], storage_ix, storage);
      }
    }
  }
  
  static void BrotliStoreHuffmanTreeToBitMask(
      const size_t huffman_tree_size, const uint8_t* huffman_tree,
      const uint8_t* huffman_tree_extra_bits, const uint8_t* code_length_bitdepth,
      const uint16_t* code_length_bitdepth_symbols,
      size_t* BROTLI_RESTRICT storage_ix, uint8_t* BROTLI_RESTRICT storage) {
    size_t i;
    for (i = 0; i < huffman_tree_size; ++i) {
      size_t ix = huffman_tree[i];
      BrotliWriteBits(code_length_bitdepth[ix], code_length_bitdepth_symbols[ix],
                      storage_ix, storage);
      /* Extra bits */
      switch (ix) {
        case BROTLI_REPEAT_PREVIOUS_CODE_LENGTH:
          BrotliWriteBits(2, huffman_tree_extra_bits[i], storage_ix, storage);
          break;
        case BROTLI_REPEAT_ZERO_CODE_LENGTH:
          BrotliWriteBits(3, huffman_tree_extra_bits[i], storage_ix, storage);
          break;
      }
    }
  }
  
  static void StoreSimpleHuffmanTree(const uint8_t* depths,
                                     size_t symbols[4],
                                     size_t num_symbols,
                                     size_t max_bits,
                                     size_t *storage_ix, uint8_t *storage) {
    /* value of 1 indicates a simple Huffman code */
    BrotliWriteBits(2, 1, storage_ix, storage);
    BrotliWriteBits(2, num_symbols - 1, storage_ix, storage);  /* NSYM - 1 */
  
    {
      /* Sort */
      size_t i;
      for (i = 0; i < num_symbols; i++) {
        size_t j;
        for (j = i + 1; j < num_symbols; j++) {
          if (depths[symbols[j]] < depths[symbols[i]]) {
            BROTLI_SWAP(size_t, symbols, j, i);
          }
        }
      }
    }
  
    if (num_symbols == 2) {
      BrotliWriteBits(max_bits, symbols[0], storage_ix, storage);
      BrotliWriteBits(max_bits, symbols[1], storage_ix, storage);
    } else if (num_symbols == 3) {
      BrotliWriteBits(max_bits, symbols[0], storage_ix, storage);
      BrotliWriteBits(max_bits, symbols[1], storage_ix, storage);
      BrotliWriteBits(max_bits, symbols[2], storage_ix, storage);
    } else {
      BrotliWriteBits(max_bits, symbols[0], storage_ix, storage);
      BrotliWriteBits(max_bits, symbols[1], storage_ix, storage);
      BrotliWriteBits(max_bits, symbols[2], storage_ix, storage);
      BrotliWriteBits(max_bits, symbols[3], storage_ix, storage);
      /* tree-select */
      BrotliWriteBits(1, depths[symbols[0]] == 1 ? 1 : 0, storage_ix, storage);
    }
  }
  
  /* num = alphabet size
     depths = symbol depths */
  void BrotliStoreHuffmanTree(const uint8_t* depths, size_t num,
                              HuffmanTree* tree,
                              size_t *storage_ix, uint8_t *storage) {
    /* Write the Huffman tree into the brotli-representation.
       The command alphabet is the largest, so this allocation will fit all
       alphabets. */
    uint8_t huffman_tree[BROTLI_NUM_COMMAND_SYMBOLS];
    uint8_t huffman_tree_extra_bits[BROTLI_NUM_COMMAND_SYMBOLS];
    size_t huffman_tree_size = 0;
    uint8_t code_length_bitdepth[BROTLI_CODE_LENGTH_CODES] = { 0 };
    uint16_t code_length_bitdepth_symbols[BROTLI_CODE_LENGTH_CODES];
    uint32_t huffman_tree_histogram[BROTLI_CODE_LENGTH_CODES] = { 0 };
    size_t i;
    int num_codes = 0;
    size_t code = 0;
  
    BROTLI_DCHECK(num <= BROTLI_NUM_COMMAND_SYMBOLS);
  
    BrotliWriteHuffmanTree(depths, num, &huffman_tree_size, huffman_tree,
                           huffman_tree_extra_bits);
  
    /* Calculate the statistics of the Huffman tree in brotli-representation. */
    for (i = 0; i < huffman_tree_size; ++i) {
      ++huffman_tree_histogram[huffman_tree[i]];
    }
  
    for (i = 0; i < BROTLI_CODE_LENGTH_CODES; ++i) {
      if (huffman_tree_histogram[i]) {
        if (num_codes == 0) {
          code = i;
          num_codes = 1;
        } else if (num_codes == 1) {
          num_codes = 2;
          break;
        }
      }
    }
  
    /* Calculate another Huffman tree to use for compressing both the
       earlier Huffman tree with. */
    BrotliCreateHuffmanTree(huffman_tree_histogram, BROTLI_CODE_LENGTH_CODES,
                            5, tree, code_length_bitdepth);
    BrotliConvertBitDepthsToSymbols(code_length_bitdepth,
                                    BROTLI_CODE_LENGTH_CODES,
                                    code_length_bitdepth_symbols);
  
    /* Now, we have all the data, let's start storing it */
    BrotliStoreHuffmanTreeOfHuffmanTreeToBitMask(num_codes, code_length_bitdepth,
                                                 storage_ix, storage);
  
    if (num_codes == 1) {
      code_length_bitdepth[code] = 0;
    }
  
    /* Store the real Huffman tree now. */
    BrotliStoreHuffmanTreeToBitMask(huffman_tree_size,
                                    huffman_tree,
                                    huffman_tree_extra_bits,
                                    code_length_bitdepth,
                                    code_length_bitdepth_symbols,
                                    storage_ix, storage);
  }
  
  /* Builds a Huffman tree from histogram[0:length] into depth[0:length] and
     bits[0:length] and stores the encoded tree to the bit stream. */
  static void BuildAndStoreHuffmanTree(const uint32_t *histogram,
                                       const size_t length,
                                       HuffmanTree* tree,
                                       uint8_t* depth,
                                       uint16_t* bits,
                                       size_t* storage_ix,
                                       uint8_t* storage) {
    size_t count = 0;
    size_t s4[4] = { 0 };
    size_t i;
    size_t max_bits = 0;
    for (i = 0; i < length; i++) {
      if (histogram[i]) {
        if (count < 4) {
          s4[count] = i;
        } else if (count > 4) {
          break;
        }
        count++;
      }
    }
  
    {
      size_t max_bits_counter = length - 1;
      while (max_bits_counter) {
        max_bits_counter >>= 1;
        ++max_bits;
      }
    }
  
    if (count <= 1) {
      BrotliWriteBits(4, 1, storage_ix, storage);
      BrotliWriteBits(max_bits, s4[0], storage_ix, storage);
      depth[s4[0]] = 0;
      bits[s4[0]] = 0;
      return;
    }
  
    memset(depth, 0, length * sizeof(depth[0]));
    BrotliCreateHuffmanTree(histogram, length, 15, tree, depth);
    BrotliConvertBitDepthsToSymbols(depth, length, bits);
  
    if (count <= 4) {
      StoreSimpleHuffmanTree(depth, s4, count, max_bits, storage_ix, storage);
    } else {
      BrotliStoreHuffmanTree(depth, length, tree, storage_ix, storage);
    }
  }
  
  static BROTLI_INLINE BROTLI_BOOL SortHuffmanTree(
      const HuffmanTree* v0, const HuffmanTree* v1) {
    return TO_BROTLI_BOOL(v0->total_count_ < v1->total_count_);
  }
  
  void BrotliBuildAndStoreHuffmanTreeFast(MemoryManager* m,
                                          const uint32_t* histogram,
                                          const size_t histogram_total,
                                          const size_t max_bits,
                                          uint8_t* depth, uint16_t* bits,
                                          size_t* storage_ix,
                                          uint8_t* storage) {
    size_t count = 0;
    size_t symbols[4] = { 0 };
    size_t length = 0;
    size_t total = histogram_total;
    while (total != 0) {
      if (histogram[length]) {
        if (count < 4) {
          symbols[count] = length;
        }
        ++count;
        total -= histogram[length];
      }
      ++length;
    }
  
    if (count <= 1) {
      BrotliWriteBits(4, 1, storage_ix, storage);
      BrotliWriteBits(max_bits, symbols[0], storage_ix, storage);
      depth[symbols[0]] = 0;
      bits[symbols[0]] = 0;
      return;
    }
  
    memset(depth, 0, length * sizeof(depth[0]));
    {
      const size_t max_tree_size = 2 * length + 1;
      HuffmanTree* tree = BROTLI_ALLOC(m, HuffmanTree, max_tree_size);
      uint32_t count_limit;
      if (BROTLI_IS_OOM(m)) return;
      for (count_limit = 1; ; count_limit *= 2) {
        HuffmanTree* node = tree;
        size_t l;
        for (l = length; l != 0;) {
          --l;
          if (histogram[l]) {
            if (BROTLI_PREDICT_TRUE(histogram[l] >= count_limit)) {
              InitHuffmanTree(node, histogram[l], -1, (int16_t)l);
            } else {
              InitHuffmanTree(node, count_limit, -1, (int16_t)l);
            }
            ++node;
          }
        }
        {
          const int n = (int)(node - tree);
          HuffmanTree sentinel;
          int i = 0;      /* Points to the next leaf node. */
          int j = n + 1;  /* Points to the next non-leaf node. */
          int k;
  
          SortHuffmanTreeItems(tree, (size_t)n, SortHuffmanTree);
          /* The nodes are:
             [0, n): the sorted leaf nodes that we start with.
             [n]: we add a sentinel here.
             [n + 1, 2n): new parent nodes are added here, starting from
                          (n+1). These are naturally in ascending order.
             [2n]: we add a sentinel at the end as well.
             There will be (2n+1) elements at the end. */
          InitHuffmanTree(&sentinel, BROTLI_UINT32_MAX, -1, -1);
          *node++ = sentinel;
          *node++ = sentinel;
  
          for (k = n - 1; k > 0; --k) {
            int left, right;
            if (tree[i].total_count_ <= tree[j].total_count_) {
              left = i;
              ++i;
            } else {
              left = j;
              ++j;
            }
            if (tree[i].total_count_ <= tree[j].total_count_) {
              right = i;
              ++i;
            } else {
              right = j;
              ++j;
            }
            /* The sentinel node becomes the parent node. */
            node[-1].total_count_ =
                tree[left].total_count_ + tree[right].total_count_;
            node[-1].index_left_ = (int16_t)left;
            node[-1].index_right_or_value_ = (int16_t)right;
            /* Add back the last sentinel node. */
            *node++ = sentinel;
          }
          if (BrotliSetDepth(2 * n - 1, tree, depth, 14)) {
            /* We need to pack the Huffman tree in 14 bits. If this was not
               successful, add fake entities to the lowest values and retry. */
            break;
          }
        }
      }
      BROTLI_FREE(m, tree);
    }
    BrotliConvertBitDepthsToSymbols(depth, length, bits);
    if (count <= 4) {
      size_t i;
      /* value of 1 indicates a simple Huffman code */
      BrotliWriteBits(2, 1, storage_ix, storage);
      BrotliWriteBits(2, count - 1, storage_ix, storage);  /* NSYM - 1 */
  
      /* Sort */
      for (i = 0; i < count; i++) {
        size_t j;
        for (j = i + 1; j < count; j++) {
          if (depth[symbols[j]] < depth[symbols[i]]) {
            BROTLI_SWAP(size_t, symbols, j, i);
          }
        }
      }
  
      if (count == 2) {
        BrotliWriteBits(max_bits, symbols[0], storage_ix, storage);
        BrotliWriteBits(max_bits, symbols[1], storage_ix, storage);
      } else if (count == 3) {
        BrotliWriteBits(max_bits, symbols[0], storage_ix, storage);
        BrotliWriteBits(max_bits, symbols[1], storage_ix, storage);
        BrotliWriteBits(max_bits, symbols[2], storage_ix, storage);
      } else {
        BrotliWriteBits(max_bits, symbols[0], storage_ix, storage);
        BrotliWriteBits(max_bits, symbols[1], storage_ix, storage);
        BrotliWriteBits(max_bits, symbols[2], storage_ix, storage);
        BrotliWriteBits(max_bits, symbols[3], storage_ix, storage);
        /* tree-select */
        BrotliWriteBits(1, depth[symbols[0]] == 1 ? 1 : 0, storage_ix, storage);
      }
    } else {
      uint8_t previous_value = 8;
      size_t i;
      /* Complex Huffman Tree */
      StoreStaticCodeLengthCode(storage_ix, storage);
  
      /* Actual RLE coding. */
      for (i = 0; i < length;) {
        const uint8_t value = depth[i];
        size_t reps = 1;
        size_t k;
        for (k = i + 1; k < length && depth[k] == value; ++k) {
          ++reps;
        }
        i += reps;
        if (value == 0) {
          BrotliWriteBits(kZeroRepsDepth[reps], kZeroRepsBits[reps],
                          storage_ix, storage);
        } else {
          if (previous_value != value) {
            BrotliWriteBits(kCodeLengthDepth[value], kCodeLengthBits[value],
                            storage_ix, storage);
            --reps;
          }
          if (reps < 3) {
            while (reps != 0) {
              reps--;
              BrotliWriteBits(kCodeLengthDepth[value], kCodeLengthBits[value],
                              storage_ix, storage);
            }
          } else {
            reps -= 3;
            BrotliWriteBits(kNonZeroRepsDepth[reps], kNonZeroRepsBits[reps],
                            storage_ix, storage);
          }
          previous_value = value;
        }
      }
    }
  }
  
  static size_t IndexOf(const uint8_t* v, size_t v_size, uint8_t value) {
    size_t i = 0;
    for (; i < v_size; ++i) {
      if (v[i] == value) return i;
    }
    return i;
  }
  
  static void MoveToFront(uint8_t* v, size_t index) {
    uint8_t value = v[index];
    size_t i;
    for (i = index; i != 0; --i) {
      v[i] = v[i - 1];
    }
    v[0] = value;
  }
  
  static void MoveToFrontTransform(const uint32_t* BROTLI_RESTRICT v_in,
                                   const size_t v_size,
                                   uint32_t* v_out) {
    size_t i;
    uint8_t mtf[256];
    uint32_t max_value;
    if (v_size == 0) {
      return;
    }
    max_value = v_in[0];
    for (i = 1; i < v_size; ++i) {
      if (v_in[i] > max_value) max_value = v_in[i];
    }
    BROTLI_DCHECK(max_value < 256u);
    for (i = 0; i <= max_value; ++i) {
      mtf[i] = (uint8_t)i;
    }
    {
      size_t mtf_size = max_value + 1;
      for (i = 0; i < v_size; ++i) {
        size_t index = IndexOf(mtf, mtf_size, (uint8_t)v_in[i]);
        BROTLI_DCHECK(index < mtf_size);
        v_out[i] = (uint32_t)index;
        MoveToFront(mtf, index);
      }
    }
  }
  
  /* Finds runs of zeros in v[0..in_size) and replaces them with a prefix code of
     the run length plus extra bits (lower 9 bits is the prefix code and the rest
     are the extra bits). Non-zero values in v[] are shifted by
     *max_length_prefix. Will not create prefix codes bigger than the initial
     value of *max_run_length_prefix. The prefix code of run length L is simply
     Log2Floor(L) and the number of extra bits is the same as the prefix code. */
  static void RunLengthCodeZeros(const size_t in_size,
      uint32_t* BROTLI_RESTRICT v, size_t* BROTLI_RESTRICT out_size,
      uint32_t* BROTLI_RESTRICT max_run_length_prefix) {
    uint32_t max_reps = 0;
    size_t i;
    uint32_t max_prefix;
    for (i = 0; i < in_size;) {
      uint32_t reps = 0;
      for (; i < in_size && v[i] != 0; ++i) ;
      for (; i < in_size && v[i] == 0; ++i) {
        ++reps;
      }
      max_reps = BROTLI_MAX(uint32_t, reps, max_reps);
    }
    max_prefix = max_reps > 0 ? Log2FloorNonZero(max_reps) : 0;
    max_prefix = BROTLI_MIN(uint32_t, max_prefix, *max_run_length_prefix);
    *max_run_length_prefix = max_prefix;
    *out_size = 0;
    for (i = 0; i < in_size;) {
      BROTLI_DCHECK(*out_size <= i);
      if (v[i] != 0) {
        v[*out_size] = v[i] + *max_run_length_prefix;
        ++i;
        ++(*out_size);
      } else {
        uint32_t reps = 1;
        size_t k;
        for (k = i + 1; k < in_size && v[k] == 0; ++k) {
          ++reps;
        }
        i += reps;
        while (reps != 0) {
          if (reps < (2u << max_prefix)) {
            uint32_t run_length_prefix = Log2FloorNonZero(reps);
            const uint32_t extra_bits = reps - (1u << run_length_prefix);
            v[*out_size] = run_length_prefix + (extra_bits << 9);
            ++(*out_size);
            break;
          } else {
            const uint32_t extra_bits = (1u << max_prefix) - 1u;
            v[*out_size] = max_prefix + (extra_bits << 9);
            reps -= (2u << max_prefix) - 1u;
            ++(*out_size);
          }
        }
      }
    }
  }
  
  #define SYMBOL_BITS 9
  
  static void EncodeContextMap(MemoryManager* m,
                               const uint32_t* context_map,
                               size_t context_map_size,
                               size_t num_clusters,
                               HuffmanTree* tree,
                               size_t* storage_ix, uint8_t* storage) {
    size_t i;
    uint32_t* rle_symbols;
    uint32_t max_run_length_prefix = 6;
    size_t num_rle_symbols = 0;
    uint32_t histogram[BROTLI_MAX_CONTEXT_MAP_SYMBOLS];
    static const uint32_t kSymbolMask = (1u << SYMBOL_BITS) - 1u;
    uint8_t depths[BROTLI_MAX_CONTEXT_MAP_SYMBOLS];
    uint16_t bits[BROTLI_MAX_CONTEXT_MAP_SYMBOLS];
  
    StoreVarLenUint8(num_clusters - 1, storage_ix, storage);
  
    if (num_clusters == 1) {
      return;
    }
  
    rle_symbols = BROTLI_ALLOC(m, uint32_t, context_map_size);
    if (BROTLI_IS_OOM(m)) return;
    MoveToFrontTransform(context_map, context_map_size, rle_symbols);
    RunLengthCodeZeros(context_map_size, rle_symbols,
                       &num_rle_symbols, &max_run_length_prefix);
    memset(histogram, 0, sizeof(histogram));
    for (i = 0; i < num_rle_symbols; ++i) {
      ++histogram[rle_symbols[i] & kSymbolMask];
    }
    {
      BROTLI_BOOL use_rle = TO_BROTLI_BOOL(max_run_length_prefix > 0);
      BrotliWriteBits(1, (uint64_t)use_rle, storage_ix, storage);
      if (use_rle) {
        BrotliWriteBits(4, max_run_length_prefix - 1, storage_ix, storage);
      }
    }
    BuildAndStoreHuffmanTree(histogram, num_clusters + max_run_length_prefix,
                             tree, depths, bits, storage_ix, storage);
    for (i = 0; i < num_rle_symbols; ++i) {
      const uint32_t rle_symbol = rle_symbols[i] & kSymbolMask;
      const uint32_t extra_bits_val = rle_symbols[i] >> SYMBOL_BITS;
      BrotliWriteBits(depths[rle_symbol], bits[rle_symbol], storage_ix, storage);
      if (rle_symbol > 0 && rle_symbol <= max_run_length_prefix) {
        BrotliWriteBits(rle_symbol, extra_bits_val, storage_ix, storage);
      }
    }
    BrotliWriteBits(1, 1, storage_ix, storage);  /* use move-to-front */
    BROTLI_FREE(m, rle_symbols);
  }
  
  /* Stores the block switch command with index block_ix to the bit stream. */
  static BROTLI_INLINE void StoreBlockSwitch(BlockSplitCode* code,
                                             const uint32_t block_len,
                                             const uint8_t block_type,
                                             BROTLI_BOOL is_first_block,
                                             size_t* storage_ix,
                                             uint8_t* storage) {
    size_t typecode = NextBlockTypeCode(&code->type_code_calculator, block_type);
    size_t lencode;
    uint32_t len_nextra;
    uint32_t len_extra;
    if (!is_first_block) {
      BrotliWriteBits(code->type_depths[typecode], code->type_bits[typecode],
                      storage_ix, storage);
    }
    GetBlockLengthPrefixCode(block_len, &lencode, &len_nextra, &len_extra);
  
    BrotliWriteBits(code->length_depths[lencode], code->length_bits[lencode],
                    storage_ix, storage);
    BrotliWriteBits(len_nextra, len_extra, storage_ix, storage);
  }
  
  /* Builds a BlockSplitCode data structure from the block split given by the
     vector of block types and block lengths and stores it to the bit stream. */
  static void BuildAndStoreBlockSplitCode(const uint8_t* types,
                                          const uint32_t* lengths,
                                          const size_t num_blocks,
                                          const size_t num_types,
                                          HuffmanTree* tree,
                                          BlockSplitCode* code,
                                          size_t* storage_ix,
                                          uint8_t* storage) {
    uint32_t type_histo[BROTLI_MAX_BLOCK_TYPE_SYMBOLS];
    uint32_t length_histo[BROTLI_NUM_BLOCK_LEN_SYMBOLS];
    size_t i;
    BlockTypeCodeCalculator type_code_calculator;
    memset(type_histo, 0, (num_types + 2) * sizeof(type_histo[0]));
    memset(length_histo, 0, sizeof(length_histo));
    InitBlockTypeCodeCalculator(&type_code_calculator);
    for (i = 0; i < num_blocks; ++i) {
      size_t type_code = NextBlockTypeCode(&type_code_calculator, types[i]);
      if (i != 0) ++type_histo[type_code];
      ++length_histo[BlockLengthPrefixCode(lengths[i])];
    }
    StoreVarLenUint8(num_types - 1, storage_ix, storage);
    if (num_types > 1) {  /* TODO: else? could StoreBlockSwitch occur? */
      BuildAndStoreHuffmanTree(&type_histo[0], num_types + 2, tree,
                               &code->type_depths[0], &code->type_bits[0],
                               storage_ix, storage);
      BuildAndStoreHuffmanTree(&length_histo[0], BROTLI_NUM_BLOCK_LEN_SYMBOLS,
                               tree, &code->length_depths[0],
                               &code->length_bits[0], storage_ix, storage);
      StoreBlockSwitch(code, lengths[0], types[0], 1, storage_ix, storage);
    }
  }
  
  /* Stores a context map where the histogram type is always the block type. */
  static void StoreTrivialContextMap(size_t num_types,
                                     size_t context_bits,
                                     HuffmanTree* tree,
                                     size_t* storage_ix,
                                     uint8_t* storage) {
    StoreVarLenUint8(num_types - 1, storage_ix, storage);
    if (num_types > 1) {
      size_t repeat_code = context_bits - 1u;
      size_t repeat_bits = (1u << repeat_code) - 1u;
      size_t alphabet_size = num_types + repeat_code;
      uint32_t histogram[BROTLI_MAX_CONTEXT_MAP_SYMBOLS];
      uint8_t depths[BROTLI_MAX_CONTEXT_MAP_SYMBOLS];
      uint16_t bits[BROTLI_MAX_CONTEXT_MAP_SYMBOLS];
      size_t i;
      memset(histogram, 0, alphabet_size * sizeof(histogram[0]));
      /* Write RLEMAX. */
      BrotliWriteBits(1, 1, storage_ix, storage);
      BrotliWriteBits(4, repeat_code - 1, storage_ix, storage);
      histogram[repeat_code] = (uint32_t)num_types;
      histogram[0] = 1;
      for (i = context_bits; i < alphabet_size; ++i) {
        histogram[i] = 1;
      }
      BuildAndStoreHuffmanTree(histogram, alphabet_size, tree,
                               depths, bits, storage_ix, storage);
      for (i = 0; i < num_types; ++i) {
        size_t code = (i == 0 ? 0 : i + context_bits - 1);
        BrotliWriteBits(depths[code], bits[code], storage_ix, storage);
        BrotliWriteBits(
            depths[repeat_code], bits[repeat_code], storage_ix, storage);
        BrotliWriteBits(repeat_code, repeat_bits, storage_ix, storage);
      }
      /* Write IMTF (inverse-move-to-front) bit. */
      BrotliWriteBits(1, 1, storage_ix, storage);
    }
  }
  
  /* Manages the encoding of one block category (literal, command or distance). */
  typedef struct BlockEncoder {
    size_t alphabet_size_;
    size_t num_block_types_;
    const uint8_t* block_types_;  /* Not owned. */
    const uint32_t* block_lengths_;  /* Not owned. */
    size_t num_blocks_;
    BlockSplitCode block_split_code_;
    size_t block_ix_;
    size_t block_len_;
    size_t entropy_ix_;
    uint8_t* depths_;
    uint16_t* bits_;
  } BlockEncoder;
  
  static void InitBlockEncoder(BlockEncoder* self, size_t alphabet_size,
      size_t num_block_types, const uint8_t* block_types,
      const uint32_t* block_lengths, const size_t num_blocks) {
    self->alphabet_size_ = alphabet_size;
    self->num_block_types_ = num_block_types;
    self->block_types_ = block_types;
    self->block_lengths_ = block_lengths;
    self->num_blocks_ = num_blocks;
    InitBlockTypeCodeCalculator(&self->block_split_code_.type_code_calculator);
    self->block_ix_ = 0;
    self->block_len_ = num_blocks == 0 ? 0 : block_lengths[0];
    self->entropy_ix_ = 0;
    self->depths_ = 0;
    self->bits_ = 0;
  }
  
  static void CleanupBlockEncoder(MemoryManager* m, BlockEncoder* self) {
    BROTLI_FREE(m, self->depths_);
    BROTLI_FREE(m, self->bits_);
  }
  
  /* Creates entropy codes of block lengths and block types and stores them
     to the bit stream. */
  static void BuildAndStoreBlockSwitchEntropyCodes(BlockEncoder* self,
      HuffmanTree* tree, size_t* storage_ix, uint8_t* storage) {
    BuildAndStoreBlockSplitCode(self->block_types_, self->block_lengths_,
        self->num_blocks_, self->num_block_types_, tree, &self->block_split_code_,
        storage_ix, storage);
  }
  
  /* Stores the next symbol with the entropy code of the current block type.
     Updates the block type and block length at block boundaries. */
  static void StoreSymbol(BlockEncoder* self, size_t symbol, size_t* storage_ix,
      uint8_t* storage) {
    if (self->block_len_ == 0) {
      size_t block_ix = ++self->block_ix_;
      uint32_t block_len = self->block_lengths_[block_ix];
      uint8_t block_type = self->block_types_[block_ix];
      self->block_len_ = block_len;
      self->entropy_ix_ = block_type * self->alphabet_size_;
      StoreBlockSwitch(&self->block_split_code_, block_len, block_type, 0,
          storage_ix, storage);
    }
    --self->block_len_;
    {
      size_t ix = self->entropy_ix_ + symbol;
      BrotliWriteBits(self->depths_[ix], self->bits_[ix], storage_ix, storage);
    }
  }
  
  /* Stores the next symbol with the entropy code of the current block type and
     context value.
     Updates the block type and block length at block boundaries. */
  static void StoreSymbolWithContext(BlockEncoder* self, size_t symbol,
      size_t context, const uint32_t* context_map, size_t* storage_ix,
      uint8_t* storage, const size_t context_bits) {
    if (self->block_len_ == 0) {
      size_t block_ix = ++self->block_ix_;
      uint32_t block_len = self->block_lengths_[block_ix];
      uint8_t block_type = self->block_types_[block_ix];
      self->block_len_ = block_len;
      self->entropy_ix_ = (size_t)block_type << context_bits;
      StoreBlockSwitch(&self->block_split_code_, block_len, block_type, 0,
          storage_ix, storage);
    }
    --self->block_len_;
    {
      size_t histo_ix = context_map[self->entropy_ix_ + context];
      size_t ix = histo_ix * self->alphabet_size_ + symbol;
      BrotliWriteBits(self->depths_[ix], self->bits_[ix], storage_ix, storage);
    }
  }
  
  #define FN(X) X ## Literal
  /* NOLINTNEXTLINE(build/include) */
  #include "./block_encoder_inc.h"
  #undef FN
  
  #define FN(X) X ## Command
  /* NOLINTNEXTLINE(build/include) */
  #include "./block_encoder_inc.h"
  #undef FN
  
  #define FN(X) X ## Distance
  /* NOLINTNEXTLINE(build/include) */
  #include "./block_encoder_inc.h"
  #undef FN
  
  static void JumpToByteBoundary(size_t* storage_ix, uint8_t* storage) {
    *storage_ix = (*storage_ix + 7u) & ~7u;
    storage[*storage_ix >> 3] = 0;
  }
  
  void BrotliStoreMetaBlock(MemoryManager* m,
                            const uint8_t* input,
                            size_t start_pos,
                            size_t length,
                            size_t mask,
                            uint8_t prev_byte,
                            uint8_t prev_byte2,
                            BROTLI_BOOL is_last,
                            uint32_t num_direct_distance_codes,
                            uint32_t distance_postfix_bits,
                            ContextType literal_context_mode,
                            const Command *commands,
                            size_t n_commands,
                            const MetaBlockSplit* mb,
                            size_t *storage_ix,
                            uint8_t *storage) {
    size_t pos = start_pos;
    size_t i;
    size_t num_distance_codes =
        BROTLI_NUM_DISTANCE_SHORT_CODES + num_direct_distance_codes +
        (48u << distance_postfix_bits);
    HuffmanTree* tree;
    BlockEncoder literal_enc;
    BlockEncoder command_enc;
    BlockEncoder distance_enc;
  
    StoreCompressedMetaBlockHeader(is_last, length, storage_ix, storage);
  
    tree = BROTLI_ALLOC(m, HuffmanTree, MAX_HUFFMAN_TREE_SIZE);
    if (BROTLI_IS_OOM(m)) return;
    InitBlockEncoder(&literal_enc, 256, mb->literal_split.num_types,
        mb->literal_split.types, mb->literal_split.lengths,
        mb->literal_split.num_blocks);
    InitBlockEncoder(&command_enc, BROTLI_NUM_COMMAND_SYMBOLS,
        mb->command_split.num_types, mb->command_split.types,
        mb->command_split.lengths, mb->command_split.num_blocks);
    InitBlockEncoder(&distance_enc, num_distance_codes,
        mb->distance_split.num_types, mb->distance_split.types,
        mb->distance_split.lengths, mb->distance_split.num_blocks);
  
    BuildAndStoreBlockSwitchEntropyCodes(&literal_enc, tree, storage_ix, storage);
    BuildAndStoreBlockSwitchEntropyCodes(&command_enc, tree, storage_ix, storage);
    BuildAndStoreBlockSwitchEntropyCodes(
        &distance_enc, tree, storage_ix, storage);
  
    BrotliWriteBits(2, distance_postfix_bits, storage_ix, storage);
    BrotliWriteBits(4, num_direct_distance_codes >> distance_postfix_bits,
                    storage_ix, storage);
    for (i = 0; i < mb->literal_split.num_types; ++i) {
      BrotliWriteBits(2, literal_context_mode, storage_ix, storage);
    }
  
    if (mb->literal_context_map_size == 0) {
      StoreTrivialContextMap(mb->literal_histograms_size,
          BROTLI_LITERAL_CONTEXT_BITS, tree, storage_ix, storage);
    } else {
      EncodeContextMap(m,
          mb->literal_context_map, mb->literal_context_map_size,
          mb->literal_histograms_size, tree, storage_ix, storage);
      if (BROTLI_IS_OOM(m)) return;
    }
  
    if (mb->distance_context_map_size == 0) {
      StoreTrivialContextMap(mb->distance_histograms_size,
          BROTLI_DISTANCE_CONTEXT_BITS, tree, storage_ix, storage);
    } else {
      EncodeContextMap(m,
          mb->distance_context_map, mb->distance_context_map_size,
          mb->distance_histograms_size, tree, storage_ix, storage);
      if (BROTLI_IS_OOM(m)) return;
    }
  
    BuildAndStoreEntropyCodesLiteral(m, &literal_enc, mb->literal_histograms,
        mb->literal_histograms_size, tree, storage_ix, storage);
    if (BROTLI_IS_OOM(m)) return;
    BuildAndStoreEntropyCodesCommand(m, &command_enc, mb->command_histograms,
        mb->command_histograms_size, tree, storage_ix, storage);
    if (BROTLI_IS_OOM(m)) return;
    BuildAndStoreEntropyCodesDistance(m, &distance_enc, mb->distance_histograms,
        mb->distance_histograms_size, tree, storage_ix, storage);
    if (BROTLI_IS_OOM(m)) return;
    BROTLI_FREE(m, tree);
  
    for (i = 0; i < n_commands; ++i) {
      const Command cmd = commands[i];
      size_t cmd_code = cmd.cmd_prefix_;
      StoreSymbol(&command_enc, cmd_code, storage_ix, storage);
      StoreCommandExtra(&cmd, storage_ix, storage);
      if (mb->literal_context_map_size == 0) {
        size_t j;
        for (j = cmd.insert_len_; j != 0; --j) {
          StoreSymbol(&literal_enc, input[pos & mask], storage_ix, storage);
          ++pos;
        }
      } else {
        size_t j;
        for (j = cmd.insert_len_; j != 0; --j) {
          size_t context = Context(prev_byte, prev_byte2, literal_context_mode);
          uint8_t literal = input[pos & mask];
          StoreSymbolWithContext(&literal_enc, literal, context,
              mb->literal_context_map, storage_ix, storage,
              BROTLI_LITERAL_CONTEXT_BITS);
          prev_byte2 = prev_byte;
          prev_byte = literal;
          ++pos;
        }
      }
      pos += CommandCopyLen(&cmd);
      if (CommandCopyLen(&cmd)) {
        prev_byte2 = input[(pos - 2) & mask];
        prev_byte = input[(pos - 1) & mask];
        if (cmd.cmd_prefix_ >= 128) {
          size_t dist_code = cmd.dist_prefix_;
          uint32_t distnumextra = cmd.dist_extra_ >> 24;
          uint64_t distextra = cmd.dist_extra_ & 0xffffff;
          if (mb->distance_context_map_size == 0) {
            StoreSymbol(&distance_enc, dist_code, storage_ix, storage);
          } else {
            size_t context = CommandDistanceContext(&cmd);
            StoreSymbolWithContext(&distance_enc, dist_code, context,
                mb->distance_context_map, storage_ix, storage,
                BROTLI_DISTANCE_CONTEXT_BITS);
          }
          BrotliWriteBits(distnumextra, distextra, storage_ix, storage);
        }
      }
    }
    CleanupBlockEncoder(m, &distance_enc);
    CleanupBlockEncoder(m, &command_enc);
    CleanupBlockEncoder(m, &literal_enc);
    if (is_last) {
      JumpToByteBoundary(storage_ix, storage);
    }
  }
  
  static void BuildHistograms(const uint8_t* input,
                              size_t start_pos,
                              size_t mask,
                              const Command *commands,
                              size_t n_commands,
                              HistogramLiteral* lit_histo,
                              HistogramCommand* cmd_histo,
                              HistogramDistance* dist_histo) {
    size_t pos = start_pos;
    size_t i;
    for (i = 0; i < n_commands; ++i) {
      const Command cmd = commands[i];
      size_t j;
      HistogramAddCommand(cmd_histo, cmd.cmd_prefix_);
      for (j = cmd.insert_len_; j != 0; --j) {
        HistogramAddLiteral(lit_histo, input[pos & mask]);
        ++pos;
      }
      pos += CommandCopyLen(&cmd);
      if (CommandCopyLen(&cmd) && cmd.cmd_prefix_ >= 128) {
        HistogramAddDistance(dist_histo, cmd.dist_prefix_);
      }
    }
  }
  
  static void StoreDataWithHuffmanCodes(const uint8_t* input,
                                        size_t start_pos,
                                        size_t mask,
                                        const Command *commands,
                                        size_t n_commands,
                                        const uint8_t* lit_depth,
                                        const uint16_t* lit_bits,
                                        const uint8_t* cmd_depth,
                                        const uint16_t* cmd_bits,
                                        const uint8_t* dist_depth,
                                        const uint16_t* dist_bits,
                                        size_t* storage_ix,
                                        uint8_t* storage) {
    size_t pos = start_pos;
    size_t i;
    for (i = 0; i < n_commands; ++i) {
      const Command cmd = commands[i];
      const size_t cmd_code = cmd.cmd_prefix_;
      size_t j;
      BrotliWriteBits(
          cmd_depth[cmd_code], cmd_bits[cmd_code], storage_ix, storage);
      StoreCommandExtra(&cmd, storage_ix, storage);
      for (j = cmd.insert_len_; j != 0; --j) {
        const uint8_t literal = input[pos & mask];
        BrotliWriteBits(
            lit_depth[literal], lit_bits[literal], storage_ix, storage);
        ++pos;
      }
      pos += CommandCopyLen(&cmd);
      if (CommandCopyLen(&cmd) && cmd.cmd_prefix_ >= 128) {
        const size_t dist_code = cmd.dist_prefix_;
        const uint32_t distnumextra = cmd.dist_extra_ >> 24;
        const uint32_t distextra = cmd.dist_extra_ & 0xffffff;
        BrotliWriteBits(dist_depth[dist_code], dist_bits[dist_code],
                        storage_ix, storage);
        BrotliWriteBits(distnumextra, distextra, storage_ix, storage);
      }
    }
  }
  
  void BrotliStoreMetaBlockTrivial(MemoryManager* m,
                                   const uint8_t* input,
                                   size_t start_pos,
                                   size_t length,
                                   size_t mask,
                                   BROTLI_BOOL is_last,
                                   const Command *commands,
                                   size_t n_commands,
                                   size_t *storage_ix,
                                   uint8_t *storage) {
    HistogramLiteral lit_histo;
    HistogramCommand cmd_histo;
    HistogramDistance dist_histo;
    uint8_t lit_depth[BROTLI_NUM_LITERAL_SYMBOLS];
    uint16_t lit_bits[BROTLI_NUM_LITERAL_SYMBOLS];
    uint8_t cmd_depth[BROTLI_NUM_COMMAND_SYMBOLS];
    uint16_t cmd_bits[BROTLI_NUM_COMMAND_SYMBOLS];
    uint8_t dist_depth[SIMPLE_DISTANCE_ALPHABET_SIZE];
    uint16_t dist_bits[SIMPLE_DISTANCE_ALPHABET_SIZE];
    HuffmanTree* tree;
  
    StoreCompressedMetaBlockHeader(is_last, length, storage_ix, storage);
  
    HistogramClearLiteral(&lit_histo);
    HistogramClearCommand(&cmd_histo);
    HistogramClearDistance(&dist_histo);
  
    BuildHistograms(input, start_pos, mask, commands, n_commands,
                    &lit_histo, &cmd_histo, &dist_histo);
  
    BrotliWriteBits(13, 0, storage_ix, storage);
  
    tree = BROTLI_ALLOC(m, HuffmanTree, MAX_HUFFMAN_TREE_SIZE);
    if (BROTLI_IS_OOM(m)) return;
    BuildAndStoreHuffmanTree(lit_histo.data_, BROTLI_NUM_LITERAL_SYMBOLS, tree,
                             lit_depth, lit_bits,
                             storage_ix, storage);
    BuildAndStoreHuffmanTree(cmd_histo.data_, BROTLI_NUM_COMMAND_SYMBOLS, tree,
                             cmd_depth, cmd_bits,
                             storage_ix, storage);
    BuildAndStoreHuffmanTree(dist_histo.data_, SIMPLE_DISTANCE_ALPHABET_SIZE,
                             tree,
                             dist_depth, dist_bits,
                             storage_ix, storage);
    BROTLI_FREE(m, tree);
    StoreDataWithHuffmanCodes(input, start_pos, mask, commands,
                              n_commands, lit_depth, lit_bits,
                              cmd_depth, cmd_bits,
                              dist_depth, dist_bits,
                              storage_ix, storage);
    if (is_last) {
      JumpToByteBoundary(storage_ix, storage);
    }
  }
  
  void BrotliStoreMetaBlockFast(MemoryManager* m,
                                const uint8_t* input,
                                size_t start_pos,
                                size_t length,
                                size_t mask,
                                BROTLI_BOOL is_last,
                                const Command *commands,
                                size_t n_commands,
                                size_t *storage_ix,
                                uint8_t *storage) {
    StoreCompressedMetaBlockHeader(is_last, length, storage_ix, storage);
  
    BrotliWriteBits(13, 0, storage_ix, storage);
  
    if (n_commands <= 128) {
      uint32_t histogram[BROTLI_NUM_LITERAL_SYMBOLS] = { 0 };
      size_t pos = start_pos;
      size_t num_literals = 0;
      size_t i;
      uint8_t lit_depth[BROTLI_NUM_LITERAL_SYMBOLS];
      uint16_t lit_bits[BROTLI_NUM_LITERAL_SYMBOLS];
      for (i = 0; i < n_commands; ++i) {
        const Command cmd = commands[i];
        size_t j;
        for (j = cmd.insert_len_; j != 0; --j) {
          ++histogram[input[pos & mask]];
          ++pos;
        }
        num_literals += cmd.insert_len_;
        pos += CommandCopyLen(&cmd);
      }
      BrotliBuildAndStoreHuffmanTreeFast(m, histogram, num_literals,
                                         /* max_bits = */ 8,
                                         lit_depth, lit_bits,
                                         storage_ix, storage);
      if (BROTLI_IS_OOM(m)) return;
      StoreStaticCommandHuffmanTree(storage_ix, storage);
      StoreStaticDistanceHuffmanTree(storage_ix, storage);
      StoreDataWithHuffmanCodes(input, start_pos, mask, commands,
                                n_commands, lit_depth, lit_bits,
                                kStaticCommandCodeDepth,
                                kStaticCommandCodeBits,
                                kStaticDistanceCodeDepth,
                                kStaticDistanceCodeBits,
                                storage_ix, storage);
    } else {
      HistogramLiteral lit_histo;
      HistogramCommand cmd_histo;
      HistogramDistance dist_histo;
      uint8_t lit_depth[BROTLI_NUM_LITERAL_SYMBOLS];
      uint16_t lit_bits[BROTLI_NUM_LITERAL_SYMBOLS];
      uint8_t cmd_depth[BROTLI_NUM_COMMAND_SYMBOLS];
      uint16_t cmd_bits[BROTLI_NUM_COMMAND_SYMBOLS];
      uint8_t dist_depth[SIMPLE_DISTANCE_ALPHABET_SIZE];
      uint16_t dist_bits[SIMPLE_DISTANCE_ALPHABET_SIZE];
      HistogramClearLiteral(&lit_histo);
      HistogramClearCommand(&cmd_histo);
      HistogramClearDistance(&dist_histo);
      BuildHistograms(input, start_pos, mask, commands, n_commands,
                      &lit_histo, &cmd_histo, &dist_histo);
      BrotliBuildAndStoreHuffmanTreeFast(m, lit_histo.data_,
                                         lit_histo.total_count_,
                                         /* max_bits = */ 8,
                                         lit_depth, lit_bits,
                                         storage_ix, storage);
      if (BROTLI_IS_OOM(m)) return;
      BrotliBuildAndStoreHuffmanTreeFast(m, cmd_histo.data_,
                                         cmd_histo.total_count_,
                                         /* max_bits = */ 10,
                                         cmd_depth, cmd_bits,
                                         storage_ix, storage);
      if (BROTLI_IS_OOM(m)) return;
      BrotliBuildAndStoreHuffmanTreeFast(m, dist_histo.data_,
                                         dist_histo.total_count_,
                                         /* max_bits = */
                                         SIMPLE_DISTANCE_ALPHABET_BITS,
                                         dist_depth, dist_bits,
                                         storage_ix, storage);
      if (BROTLI_IS_OOM(m)) return;
      StoreDataWithHuffmanCodes(input, start_pos, mask, commands,
                                n_commands, lit_depth, lit_bits,
                                cmd_depth, cmd_bits,
                                dist_depth, dist_bits,
                                storage_ix, storage);
    }
  
    if (is_last) {
      JumpToByteBoundary(storage_ix, storage);
    }
  }
  
  /* This is for storing uncompressed blocks (simple raw storage of
     bytes-as-bytes). */
  void BrotliStoreUncompressedMetaBlock(BROTLI_BOOL is_final_block,
                                        const uint8_t * BROTLI_RESTRICT input,
                                        size_t position, size_t mask,
                                        size_t len,
                                        size_t * BROTLI_RESTRICT storage_ix,
                                        uint8_t * BROTLI_RESTRICT storage) {
    size_t masked_pos = position & mask;
    BrotliStoreUncompressedMetaBlockHeader(len, storage_ix, storage);
    JumpToByteBoundary(storage_ix, storage);
  
    if (masked_pos + len > mask + 1) {
      size_t len1 = mask + 1 - masked_pos;
      memcpy(&storage[*storage_ix >> 3], &input[masked_pos], len1);
      *storage_ix += len1 << 3;
      len -= len1;
      masked_pos = 0;
    }
    memcpy(&storage[*storage_ix >> 3], &input[masked_pos], len);
    *storage_ix += len << 3;
  
    /* We need to clear the next 4 bytes to continue to be
       compatible with BrotliWriteBits. */
    BrotliWriteBitsPrepareStorage(*storage_ix, storage);
  
    /* Since the uncompressed block itself may not be the final block, add an
       empty one after this. */
    if (is_final_block) {
      BrotliWriteBits(1, 1, storage_ix, storage);  /* islast */
      BrotliWriteBits(1, 1, storage_ix, storage);  /* isempty */
      JumpToByteBoundary(storage_ix, storage);
    }
  }
  
  #if defined(__cplusplus) || defined(c_plusplus)
  }  /* extern "C" */
  #endif
  