src/zopfli/deflate.c

/*
Copyright 2011 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Author: lode.vandevenne@gmail.com (Lode Vandevenne)
Author: jyrki.alakuijala@gmail.com (Jyrki Alakuijala)
*/

#include "deflate.h"

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

#include "blocksplitter.h"
#include "lz77.h"
#include "squeeze.h"
#include "tree.h"

/*
bp = bitpointer, always in range [0, 7].
The outsize is number of necessary bytes to encode the bits.
Given the value of bp and the amount of bytes, the amount of bits represented
is not simply bytesize * 8 + bp because even representing one bit requires a
whole byte. It is: (bp == 0) ? (bytesize * 8) : ((bytesize - 1) * 8 + bp)
*/
static void AddBit(int bit,
                   unsigned char* bp, unsigned char** out, size_t* outsize) {
  if (*bp == 0) ZOPFLI_APPEND_DATA(0, out, outsize);
  (*out)[*outsize - 1] |= bit << *bp;
  *bp = (*bp + 1) & 7;
}

static void AddBits(unsigned symbol, unsigned length,
                    unsigned char* bp, unsigned char** out, size_t* outsize) {
  /* TODO(lode): make more efficient (add more bits at once). */
  unsigned i;
  for (i = 0; i < length; i++) {
    unsigned bit = (symbol >> i) & 1;
    if (*bp == 0) ZOPFLI_APPEND_DATA(0, out, outsize);
    (*out)[*outsize - 1] |= bit << *bp;
    *bp = (*bp + 1) & 7;
  }
}

/*
Adds bits, like AddBits, but the order is inverted. The deflate specification
uses both orders in one standard.
*/
static void AddHuffmanBits(unsigned symbol, unsigned length,
                           unsigned char* bp, unsigned char** out,
                           size_t* outsize) {
  /* TODO(lode): make more efficient (add more bits at once). */
  unsigned i;
  for (i = 0; i < length; i++) {
    unsigned bit = (symbol >> (length - i - 1)) & 1;
    if (*bp == 0) ZOPFLI_APPEND_DATA(0, out, outsize);
    (*out)[*outsize - 1] |= bit << *bp;
    *bp = (*bp + 1) & 7;
  }
}

/*
Ensures there are at least 2 distance codes to support buggy decoders.
Zlib 1.2.1 and below have a bug where it fails if there isn't at least 1
distance code (with length > 0), even though it's valid according to the
deflate spec to have 0 distance codes. On top of that, some mobile phones
require at least two distance codes. To support these decoders too (but
potentially at the cost of a few bytes), add dummy code lengths of 1.
References to this bug can be found in the changelog of
Zlib 1.2.2 and here: http://www.jonof.id.au/forum/index.php?topic=515.0.

d_lengths: the 32 lengths of the distance codes.
*/
static void PatchDistanceCodesForBuggyDecoders(unsigned* d_lengths) {
  int num_dist_codes = 0; /* Amount of non-zero distance codes */
  int i;
  for (i = 0; i < 30 /* Ignore the two unused codes from the spec */; i++) {
    if (d_lengths[i]) num_dist_codes++;
    if (num_dist_codes >= 2) return; /* Two or more codes is fine. */
  }

  if (num_dist_codes == 0) {
    d_lengths[0] = d_lengths[1] = 1;
  } else if (num_dist_codes == 1) {
    d_lengths[d_lengths[0] ? 1 : 0] = 1;
  }
}

/*
Encodes the Huffman tree and returns how many bits its encoding takes. If out
is a null pointer, only returns the size and runs faster.
*/
static size_t EncodeTree(const unsigned* ll_lengths,
                         const unsigned* d_lengths,
                         int use_16, int use_17, int use_18,
                         unsigned char* bp,
                         unsigned char** out, size_t* outsize) {
  unsigned lld_total;  /* Total amount of literal, length, distance codes. */
  /* Runlength encoded version of lengths of litlen and dist trees. */
  unsigned* rle = 0;
  unsigned* rle_bits = 0;  /* Extra bits for rle values 16, 17 and 18. */
  size_t rle_size = 0;  /* Size of rle array. */
  size_t rle_bits_size = 0;  /* Should have same value as rle_size. */
  unsigned hlit = 29;  /* 286 - 257 */
  unsigned hdist = 29;  /* 32 - 1, but gzip does not like hdist > 29.*/
  unsigned hclen;
  unsigned hlit2;
  size_t i, j;
  size_t clcounts[19];
  unsigned clcl[19];  /* Code length code lengths. */
  unsigned clsymbols[19];
  /* The order in which code length code lengths are encoded as per deflate. */
  static const unsigned order[19] = {
    16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
  };
  int size_only = !out;
  size_t result_size = 0;

  for(i = 0; i < 19; i++) clcounts[i] = 0;

  /* Trim zeros. */
  while (hlit > 0 && ll_lengths[257 + hlit - 1] == 0) hlit--;
  while (hdist > 0 && d_lengths[1 + hdist - 1] == 0) hdist--;
  hlit2 = hlit + 257;

  lld_total = hlit2 + hdist + 1;

  for (i = 0; i < lld_total; i++) {
    /* This is an encoding of a huffman tree, so now the length is a symbol */
    unsigned char symbol = i < hlit2 ? ll_lengths[i] : d_lengths[i - hlit2];
    unsigned count = 1;
    if(use_16 || (symbol == 0 && (use_17 || use_18))) {
      for (j = i + 1; j < lld_total && symbol ==
          (j < hlit2 ? ll_lengths[j] : d_lengths[j - hlit2]); j++) {
        count++;
      }
    }
    i += count - 1;

    /* Repetitions of zeroes */
    if (symbol == 0 && count >= 3) {
      if (use_18) {
        while (count >= 11) {
          unsigned count2 = count > 138 ? 138 : count;
          if (!size_only) {
            ZOPFLI_APPEND_DATA(18, &rle, &rle_size);
            ZOPFLI_APPEND_DATA(count2 - 11, &rle_bits, &rle_bits_size);
          }
          clcounts[18]++;
          count -= count2;
        }
      }
      if (use_17) {
        while (count >= 3) {
          unsigned count2 = count > 10 ? 10 : count;
          if (!size_only) {
            ZOPFLI_APPEND_DATA(17, &rle, &rle_size);
            ZOPFLI_APPEND_DATA(count2 - 3, &rle_bits, &rle_bits_size);
          }
          clcounts[17]++;
          count -= count2;
        }
      }
    }

    /* Repetitions of any symbol */
    if (use_16 && count >= 4) {
      count--;  /* Since the first one is hardcoded. */
      clcounts[symbol]++;
      if (!size_only) {
        ZOPFLI_APPEND_DATA(symbol, &rle, &rle_size);
        ZOPFLI_APPEND_DATA(0, &rle_bits, &rle_bits_size);
      }
      while (count >= 3) {
        unsigned count2 = count > 6 ? 6 : count;
        if (!size_only) {
          ZOPFLI_APPEND_DATA(16, &rle, &rle_size);
          ZOPFLI_APPEND_DATA(count2 - 3, &rle_bits, &rle_bits_size);
        }
        clcounts[16]++;
        count -= count2;
      }
    }

    /* No or insufficient repetition */
    clcounts[symbol] += count;
    while (count > 0) {
      if (!size_only) {
        ZOPFLI_APPEND_DATA(symbol, &rle, &rle_size);
        ZOPFLI_APPEND_DATA(0, &rle_bits, &rle_bits_size);
      }
      count--;
    }
  }

  ZopfliCalculateBitLengths(clcounts, 19, 7, clcl);
  if (!size_only) ZopfliLengthsToSymbols(clcl, 19, 7, clsymbols);

  hclen = 15;
  /* Trim zeros. */
  while (hclen > 0 && clcounts[order[hclen + 4 - 1]] == 0) hclen--;

  if (!size_only) {
    AddBits(hlit, 5, bp, out, outsize);
    AddBits(hdist, 5, bp, out, outsize);
    AddBits(hclen, 4, bp, out, outsize);

    for (i = 0; i < hclen + 4; i++) {
      AddBits(clcl[order[i]], 3, bp, out, outsize);
    }

    for (i = 0; i < rle_size; i++) {
      unsigned symbol = clsymbols[rle[i]];
      AddHuffmanBits(symbol, clcl[rle[i]], bp, out, outsize);
      /* Extra bits. */
      if (rle[i] == 16) AddBits(rle_bits[i], 2, bp, out, outsize);
      else if (rle[i] == 17) AddBits(rle_bits[i], 3, bp, out, outsize);
      else if (rle[i] == 18) AddBits(rle_bits[i], 7, bp, out, outsize);
    }
  }

  result_size += 14;  /* hlit, hdist, hclen bits */
  result_size += (hclen + 4) * 3;  /* clcl bits */
  for(i = 0; i < 19; i++) {
    result_size += clcl[i] * clcounts[i];
  }
  /* Extra bits. */
  result_size += clcounts[16] * 2;
  result_size += clcounts[17] * 3;
  result_size += clcounts[18] * 7;

  /* Note: in case of "size_only" these are null pointers so no effect. */
  free(rle);
  free(rle_bits);

  return result_size;
}

static void AddDynamicTree(const unsigned* ll_lengths,
                           const unsigned* d_lengths,
                           unsigned char* bp,
                           unsigned char** out, size_t* outsize) {
  int i;
  int best = 0;
  size_t bestsize = 0;

  for(i = 0; i < 8; i++) {
    size_t size = EncodeTree(ll_lengths, d_lengths,
                             i & 1, i & 2, i & 4,
                             0, 0, 0);
    if (bestsize == 0 || size < bestsize) {
      bestsize = size;
      best = i;
    }
  }

  EncodeTree(ll_lengths, d_lengths,
             best & 1, best & 2, best & 4,
             bp, out, outsize);
}

/*
Gives the exact size of the tree, in bits, as it will be encoded in DEFLATE.
*/
static size_t CalculateTreeSize(const unsigned* ll_lengths,
                                const unsigned* d_lengths) {
  size_t result = 0;
  int i;

  for(i = 0; i < 8; i++) {
    size_t size = EncodeTree(ll_lengths, d_lengths,
                             i & 1, i & 2, i & 4,
                             0, 0, 0);
    if (result == 0 || size < result) result = size;
  }

  return result;
}

/*
Adds all lit/len and dist codes from the lists as huffman symbols. Does not add
end code 256. expected_data_size is the uncompressed block size, used for
assert, but you can set it to 0 to not do the assertion.
*/
static void AddLZ77Data(const unsigned short* litlens,
                        const unsigned short* dists,
                        size_t lstart, size_t lend,
                        size_t expected_data_size,
                        const unsigned* ll_symbols, const unsigned* ll_lengths,
                        const unsigned* d_symbols, const unsigned* d_lengths,
                        unsigned char* bp,
                        unsigned char** out, size_t* outsize) {
  size_t testlength = 0;
  size_t i;

  for (i = lstart; i < lend; i++) {
    unsigned dist = dists[i];
    unsigned litlen = litlens[i];
    if (dist == 0) {
      assert(litlen < 256);
      assert(ll_lengths[litlen] > 0);
      AddHuffmanBits(ll_symbols[litlen], ll_lengths[litlen], bp, out, outsize);
      testlength++;
    } else {
      unsigned lls = ZopfliGetLengthSymbol(litlen);
      unsigned ds = ZopfliGetDistSymbol(dist);
      assert(litlen >= 3 && litlen <= 288);
      assert(ll_lengths[lls] > 0);
      assert(d_lengths[ds] > 0);
      AddHuffmanBits(ll_symbols[lls], ll_lengths[lls], bp, out, outsize);
      AddBits(ZopfliGetLengthExtraBitsValue(litlen),
              ZopfliGetLengthExtraBits(litlen),
              bp, out, outsize);
      AddHuffmanBits(d_symbols[ds], d_lengths[ds], bp, out, outsize);
      AddBits(ZopfliGetDistExtraBitsValue(dist),
              ZopfliGetDistExtraBits(dist),
              bp, out, outsize);
      testlength += litlen;
    }
  }
  assert(expected_data_size == 0 || testlength == expected_data_size);
}

static void GetFixedTree(unsigned* ll_lengths, unsigned* d_lengths) {
  size_t i;
  for (i = 0; i < 144; i++) ll_lengths[i] = 8;
  for (i = 144; i < 256; i++) ll_lengths[i] = 9;
  for (i = 256; i < 280; i++) ll_lengths[i] = 7;
  for (i = 280; i < 288; i++) ll_lengths[i] = 8;
  for (i = 0; i < 32; i++) d_lengths[i] = 5;
}

/*
Calculates size of the part after the header and tree of an LZ77 block, in bits.
*/
static size_t CalculateBlockSymbolSize(const unsigned* ll_lengths,
                                       const unsigned* d_lengths,
                                       const unsigned short* litlens,
                                       const unsigned short* dists,
                                       size_t lstart, size_t lend) {
  size_t result = 0;
  size_t i;
  for (i = lstart; i < lend; i++) {
    if (dists[i] == 0) {
      result += ll_lengths[litlens[i]];
    } else {
      result += ll_lengths[ZopfliGetLengthSymbol(litlens[i])];
      result += d_lengths[ZopfliGetDistSymbol(dists[i])];
      result += ZopfliGetLengthExtraBits(litlens[i]);
      result += ZopfliGetDistExtraBits(dists[i]);
    }
  }
  result += ll_lengths[256]; /*end symbol*/
  return result;
}

static size_t AbsDiff(size_t x, size_t y) {
  if (x > y)
    return x - y;
  else
    return y - x;
}

/*
Change the population counts in a way that the consequent Hufmann tree
compression, especially its rle-part will be more likely to compress this data
more efficiently. length containts the size of the histogram.
*/
void OptimizeHuffmanForRle(int length, size_t* counts) {
  int i, k, stride;
  size_t symbol, sum, limit;
  int* good_for_rle;

  /* 1) We don't want to touch the trailing zeros. We may break the
  rules of the format by adding more data in the distance codes. */
  for (; length >= 0; --length) {
    if (length == 0) {
      return;
    }
    if (counts[length - 1] != 0) {
      /* Now counts[0..length - 1] does not have trailing zeros. */
      break;
    }
  }
  /* 2) Let's mark all population counts that already can be encoded
  with an rle code.*/
  good_for_rle = (int*)malloc(length * sizeof(int));
  for (i = 0; i < length; ++i) good_for_rle[i] = 0;

  /* Let's not spoil any of the existing good rle codes.
  Mark any seq of 0's that is longer than 5 as a good_for_rle.
  Mark any seq of non-0's that is longer than 7 as a good_for_rle.*/
  symbol = counts[0];
  stride = 0;
  for (i = 0; i < length + 1; ++i) {
    if (i == length || counts[i] != symbol) {
      if ((symbol == 0 && stride >= 5) || (symbol != 0 && stride >= 7)) {
        for (k = 0; k < stride; ++k) {
          good_for_rle[i - k - 1] = 1;
        }
      }
      stride = 1;
      if (i != length) {
        symbol = counts[i];
      }
    } else {
      ++stride;
    }
  }

  /* 3) Let's replace those population counts that lead to more rle codes. */
  stride = 0;
  limit = counts[0];
  sum = 0;
  for (i = 0; i < length + 1; ++i) {
    if (i == length || good_for_rle[i]
        /* Heuristic for selecting the stride ranges to collapse. */
        || AbsDiff(counts[i], limit) >= 4) {
      if (stride >= 4 || (stride >= 3 && sum == 0)) {
        /* The stride must end, collapse what we have, if we have enough (4). */
        int count = (sum + stride / 2) / stride;
        if (count < 1) count = 1;
        if (sum == 0) {
          /* Don't make an all zeros stride to be upgraded to ones. */
          count = 0;
        }
        for (k = 0; k < stride; ++k) {
          /* We don't want to change value at counts[i],
          that is already belonging to the next stride. Thus - 1. */
          counts[i - k - 1] = count;
        }
      }
      stride = 0;
      sum = 0;
      if (i < length - 3) {
        /* All interesting strides have a count of at least 4,
        at least when non-zeros. */
        limit = (counts[i] + counts[i + 1] +
                 counts[i + 2] + counts[i + 3] + 2) / 4;
      } else if (i < length) {
        limit = counts[i];
      } else {
        limit = 0;
      }
    }
    ++stride;
    if (i != length) {
      sum += counts[i];
    }
  }

  free(good_for_rle);
}

/*
Calculates the bit lengths for the symbols for dynamic blocks. Chooses bit
lengths that give the smallest size of tree encoding + encoding of all the
symbols to have smallest output size. This are not necessarily the ideal Huffman
bit lengths.
*/
static void GetDynamicLengths(const unsigned short* litlens,
                              const unsigned short* dists,
                              size_t lstart, size_t lend,
                              unsigned* ll_lengths, unsigned* d_lengths) {
  size_t ll_counts[288];
  size_t d_counts[32];

  ZopfliLZ77Counts(litlens, dists, lstart, lend, ll_counts, d_counts);
  OptimizeHuffmanForRle(288, ll_counts);
  OptimizeHuffmanForRle(32, d_counts);
  ZopfliCalculateBitLengths(ll_counts, 288, 15, ll_lengths);
  ZopfliCalculateBitLengths(d_counts, 32, 15, d_lengths);
  PatchDistanceCodesForBuggyDecoders(d_lengths);
}

double ZopfliCalculateBlockSize(const unsigned short* litlens,
                                const unsigned short* dists,
                                size_t lstart, size_t lend, int btype) {
  unsigned ll_lengths[288];
  unsigned d_lengths[32];

  double result = 3; /* bfinal and btype bits */

  assert(btype == 1 || btype == 2); /* This is not for uncompressed blocks. */

  if(btype == 1) {
    GetFixedTree(ll_lengths, d_lengths);
  } else {
    GetDynamicLengths(litlens, dists, lstart, lend, ll_lengths, d_lengths);
    result += CalculateTreeSize(ll_lengths, d_lengths);
  }

  result += CalculateBlockSymbolSize(
      ll_lengths, d_lengths, litlens, dists, lstart, lend);

  return result;
}

/*
Adds a deflate block with the given LZ77 data to the output.
options: global program options
btype: the block type, must be 1 or 2
final: whether to set the "final" bit on this block, must be the last block
litlens: literal/length array of the LZ77 data, in the same format as in
    ZopfliLZ77Store.
dists: distance array of the LZ77 data, in the same format as in
    ZopfliLZ77Store.
lstart: where to start in the LZ77 data
lend: where to end in the LZ77 data (not inclusive)
expected_data_size: the uncompressed block size, used for assert, but you can
  set it to 0 to not do the assertion.
bp: output bit pointer
out: dynamic output array to append to
outsize: dynamic output array size
*/
static void AddLZ77Block(const ZopfliOptions* options, int btype, int final,
                         const unsigned short* litlens,
                         const unsigned short* dists,
                         size_t lstart, size_t lend,
                         size_t expected_data_size,
                         unsigned char* bp,
                         unsigned char** out, size_t* outsize) {
  unsigned ll_lengths[288];
  unsigned d_lengths[32];
  unsigned ll_symbols[288];
  unsigned d_symbols[32];
  size_t detect_block_size = *outsize;
  size_t compressed_size;
  size_t uncompressed_size = 0;
  size_t i;

  AddBit(final, bp, out, outsize);
  AddBit(btype & 1, bp, out, outsize);
  AddBit((btype & 2) >> 1, bp, out, outsize);

  if (btype == 1) {
    /* Fixed block. */
    GetFixedTree(ll_lengths, d_lengths);
  } else {
    /* Dynamic block. */
    unsigned detect_tree_size;
    assert(btype == 2);

    GetDynamicLengths(litlens, dists, lstart, lend, ll_lengths, d_lengths);

    detect_tree_size = *outsize;
    AddDynamicTree(ll_lengths, d_lengths, bp, out, outsize);
    if (options->verbose) {
      fprintf(stderr, "treesize: %d\n", (int)(*outsize - detect_tree_size));
    }
  }

  ZopfliLengthsToSymbols(ll_lengths, 288, 15, ll_symbols);
  ZopfliLengthsToSymbols(d_lengths, 32, 15, d_symbols);

  detect_block_size = *outsize;
  AddLZ77Data(litlens, dists, lstart, lend, expected_data_size,
              ll_symbols, ll_lengths, d_symbols, d_lengths,
              bp, out, outsize);
  /* End symbol. */
  AddHuffmanBits(ll_symbols[256], ll_lengths[256], bp, out, outsize);

  for (i = lstart; i < lend; i++) {
    uncompressed_size += dists[i] == 0 ? 1 : litlens[i];
  }
  compressed_size = *outsize - detect_block_size;
  if (options->verbose) {
    fprintf(stderr, "compressed block size: %d (%dk) (unc: %d)\n",
           (int)compressed_size, (int)(compressed_size / 1024),
           (int)(uncompressed_size));
  }
}

static void DeflateDynamicBlock(const ZopfliOptions* options, int final,
                                const unsigned char* in,
                                size_t instart, size_t inend,
                                unsigned char* bp,
                                unsigned char** out, size_t* outsize) {
  ZopfliBlockState s;
  size_t blocksize = inend - instart;
  ZopfliLZ77Store store;
  int btype = 2;

  ZopfliInitLZ77Store(&store);

  s.options = options;
  s.blockstart = instart;
  s.blockend = inend;
#ifdef ZOPFLI_LONGEST_MATCH_CACHE
  s.lmc = (ZopfliLongestMatchCache*)malloc(sizeof(ZopfliLongestMatchCache));
  ZopfliInitCache(blocksize, s.lmc);
#endif

  ZopfliLZ77Optimal(&s, in, instart, inend, &store);

  /* For small block, encoding with fixed tree can be smaller. For large block,
  don't bother doing this expensive test, dynamic tree will be better.*/
  if (store.size < 1000) {
    double dyncost, fixedcost;
    ZopfliLZ77Store fixedstore;
    ZopfliInitLZ77Store(&fixedstore);
    ZopfliLZ77OptimalFixed(&s, in, instart, inend, &fixedstore);
    dyncost = ZopfliCalculateBlockSize(store.litlens, store.dists,
        0, store.size, 2);
    fixedcost = ZopfliCalculateBlockSize(fixedstore.litlens, fixedstore.dists,
        0, fixedstore.size, 1);
    if (fixedcost < dyncost) {
      btype = 1;
      ZopfliCleanLZ77Store(&store);
      store = fixedstore;
    } else {
      ZopfliCleanLZ77Store(&fixedstore);
    }
  }

  AddLZ77Block(s.options, btype, final,
               store.litlens, store.dists, 0, store.size,
               blocksize, bp, out, outsize);

#ifdef ZOPFLI_LONGEST_MATCH_CACHE
  ZopfliCleanCache(s.lmc);
  free(s.lmc);
#endif
  ZopfliCleanLZ77Store(&store);
}

static void DeflateFixedBlock(const ZopfliOptions* options, int final,
                              const unsigned char* in,
                              size_t instart, size_t inend,
                              unsigned char* bp,
                              unsigned char** out, size_t* outsize) {
  ZopfliBlockState s;
  size_t blocksize = inend - instart;
  ZopfliLZ77Store store;

  ZopfliInitLZ77Store(&store);

  s.options = options;
  s.blockstart = instart;
  s.blockend = inend;
#ifdef ZOPFLI_LONGEST_MATCH_CACHE
  s.lmc = (ZopfliLongestMatchCache*)malloc(sizeof(ZopfliLongestMatchCache));
  ZopfliInitCache(blocksize, s.lmc);
#endif

  ZopfliLZ77OptimalFixed(&s, in, instart, inend, &store);

  AddLZ77Block(s.options, 1, final, store.litlens, store.dists, 0, store.size,
               blocksize, bp, out, outsize);

#ifdef ZOPFLI_LONGEST_MATCH_CACHE
  ZopfliCleanCache(s.lmc);
  free(s.lmc);
#endif
  ZopfliCleanLZ77Store(&store);
}

static void DeflateNonCompressedBlock(const ZopfliOptions* options, int final,
                                      const unsigned char* in, size_t instart,
                                      size_t inend,
                                      unsigned char* bp,
                                      unsigned char** out, size_t* outsize) {
  size_t i;
  size_t blocksize = inend - instart;
  unsigned short nlen = ~blocksize;

  (void)options;
  assert(blocksize < 65536);  /* Non compressed blocks are max this size. */

  AddBit(final, bp, out, outsize);
  /* BTYPE 00 */
  AddBit(0, bp, out, outsize);
  AddBit(0, bp, out, outsize);

  /* Any bits of input up to the next byte boundary are ignored. */
  *bp = 0;

  ZOPFLI_APPEND_DATA(blocksize % 256, out, outsize);
  ZOPFLI_APPEND_DATA((blocksize / 256) % 256, out, outsize);
  ZOPFLI_APPEND_DATA(nlen % 256, out, outsize);
  ZOPFLI_APPEND_DATA((nlen / 256) % 256, out, outsize);

  for (i = instart; i < inend; i++) {
    ZOPFLI_APPEND_DATA(in[i], out, outsize);
  }
}

static void DeflateBlock(const ZopfliOptions* options,
                         int btype, int final,
                         const unsigned char* in, size_t instart, size_t inend,
                         unsigned char* bp,
                         unsigned char** out, size_t* outsize) {
  if (btype == 0) {
    DeflateNonCompressedBlock(
        options, final, in, instart, inend, bp, out, outsize);
  } else if (btype == 1) {
     DeflateFixedBlock(options, final, in, instart, inend, bp, out, outsize);
  } else {
    assert (btype == 2);
    DeflateDynamicBlock(options, final, in, instart, inend, bp, out, outsize);
  }
}

/*
Does squeeze strategy where first block splitting is done, then each block is
squeezed.
Parameters: see description of the ZopfliDeflate function.
*/
static void DeflateSplittingFirst(const ZopfliOptions* options,
                                  int btype, int final,
                                  const unsigned char* in,
                                  size_t instart, size_t inend,
                                  unsigned char* bp,
                                  unsigned char** out, size_t* outsize) {
  size_t i;
  size_t* splitpoints = 0;
  size_t npoints = 0;
  if (btype == 0) {
    ZopfliBlockSplitSimple(in, instart, inend, 65535, &splitpoints, &npoints);
  } else if (btype == 1) {
    /* If all blocks are fixed tree, splitting into separate blocks only
    increases the total size. Leave npoints at 0, this represents 1 block. */
  } else {
    ZopfliBlockSplit(options, in, instart, inend,
                     options->blocksplittingmax, &splitpoints, &npoints);
  }

  for (i = 0; i <= npoints; i++) {
    size_t start = i == 0 ? instart : splitpoints[i - 1];
    size_t end = i == npoints ? inend : splitpoints[i];
    DeflateBlock(options, btype, i == npoints && final, in, start, end,
                 bp, out, outsize);
  }

  free(splitpoints);
}

/*
Does squeeze strategy where first the best possible lz77 is done, and then based
on that data, block splitting is done.
Parameters: see description of the ZopfliDeflate function.
*/
static void DeflateSplittingLast(const ZopfliOptions* options,
                                 int btype, int final,
                                 const unsigned char* in,
                                 size_t instart, size_t inend,
                                 unsigned char* bp,
                                 unsigned char** out, size_t* outsize) {
  size_t i;
  ZopfliBlockState s;
  ZopfliLZ77Store store;
  size_t* splitpoints = 0;
  size_t npoints = 0;

  if (btype == 0) {
    /* This function only supports LZ77 compression. DeflateSplittingFirst
       supports the special case of noncompressed data. Punt it to that one. */
    DeflateSplittingFirst(options, btype, final,
                          in, instart, inend,
                          bp, out, outsize);
  }
  assert(btype == 1 || btype == 2);

  ZopfliInitLZ77Store(&store);

  s.options = options;
  s.blockstart = instart;
  s.blockend = inend;
#ifdef ZOPFLI_LONGEST_MATCH_CACHE
  s.lmc = (ZopfliLongestMatchCache*)malloc(sizeof(ZopfliLongestMatchCache));
  ZopfliInitCache(inend - instart, s.lmc);
#endif

  if (btype == 2) {
    ZopfliLZ77Optimal(&s, in, instart, inend, &store);
  } else {
    assert (btype == 1);
    ZopfliLZ77OptimalFixed(&s, in, instart, inend, &store);
  }

  if (btype == 1) {
    /* If all blocks are fixed tree, splitting into separate blocks only
    increases the total size. Leave npoints at 0, this represents 1 block. */
  } else {
    ZopfliBlockSplitLZ77(options, store.litlens, store.dists, store.size,
                         options->blocksplittingmax, &splitpoints, &npoints);
  }

  for (i = 0; i <= npoints; i++) {
    size_t start = i == 0 ? 0 : splitpoints[i - 1];
    size_t end = i == npoints ? store.size : splitpoints[i];
    AddLZ77Block(options, btype, i == npoints && final,
                 store.litlens, store.dists, start, end, 0,
                 bp, out, outsize);
  }

#ifdef ZOPFLI_LONGEST_MATCH_CACHE
  ZopfliCleanCache(s.lmc);
  free(s.lmc);
#endif

  ZopfliCleanLZ77Store(&store);
  free(splitpoints);
}

/*
Deflate a part, to allow ZopfliDeflate() to use multiple master blocks if
needed.
It is possible to call this function multiple times in a row, shifting
instart and inend to next bytes of the data. If instart is larger than 0, then
previous bytes are used as the initial dictionary for LZ77.
This function will usually output multiple deflate blocks. If final is 1, then
the final bit will be set on the last block.
*/
void ZopfliDeflatePart(const ZopfliOptions* options, int btype, int final,
                       const unsigned char* in, size_t instart, size_t inend,
                       unsigned char* bp, unsigned char** out,
                       size_t* outsize) {
  if (options->blocksplitting) {
    if (options->blocksplittinglast) {
      DeflateSplittingLast(options, btype, final, in, instart, inend,
                           bp, out, outsize);
    } else {
      DeflateSplittingFirst(options, btype, final, in, instart, inend,
                            bp, out, outsize);
    }
  } else {
    DeflateBlock(options, btype, final, in, instart, inend, bp, out, outsize);
  }
}

void ZopfliDeflate(const ZopfliOptions* options, int btype, int final,
                   const unsigned char* in, size_t insize,
                   unsigned char* bp, unsigned char** out, size_t* outsize) {
#if ZOPFLI_MASTER_BLOCK_SIZE == 0
  ZopfliDeflatePart(options, btype, final, in, 0, insize, bp, out, outsize);
#else
  size_t i = 0;
  while (i < insize) {
    int masterfinal = (i + ZOPFLI_MASTER_BLOCK_SIZE >= insize);
    int final2 = final && masterfinal;
    size_t size = masterfinal ? insize - i : ZOPFLI_MASTER_BLOCK_SIZE;
    ZopfliDeflatePart(options, btype, final2,
                      in, i, i + size, bp, out, outsize);
    i += size;
  }
#endif
  if (options->verbose) {
    fprintf(stderr,
            "Original Size: %d, Deflate: %d, Compression: %f%% Removed\n",
            (int)insize, (int)*outsize,
            100.0 * (double)(insize - *outsize) / (double)insize);
  }
}