kc3-lang/brotli/research/durchschlag.h

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• Hash : 35e69fc7
  Author :
  Date : 2018-02-26T09:04:36
  

  New feature: "Large Window Brotli" (#640)
  
  * New feature: "Large Window Brotli"
  
  By setting special encoder/decoder flag it is now possible to extend
  LZ-window up to 30 bits; though produced stream will not be RFC7932
  compliant.
  
  Added new dictionary generator - "DSH". It combines speed of "Sieve"
  and quality of "DM". Plus utilities to prepare train corpora
  (remove unique strings).
  
  Improved compression ratio: now two sub-blocks could be stitched:
  the last copy command could be extended to span the next sub-block.
  
  Fixed compression ineffectiveness caused by floating numbers rounding and
  wrong cost heuristic.
  
  Other C changes:
   - combined / moved `context.h` to `common`
   - moved transforms to `common`
   - unified some aspects of code formatting
   - added an abstraction for encoder (static) dictionary
   - moved default allocator/deallocator functions to `common`
  
  brotli CLI:
   - window size is auto-adjusted if not specified explicitly
  
  Java:
   - added "eager" decoding both to JNI wrapper and pure decoder
   - huge speed-up of `DictionaryData` initialization
  
  * Add dictionaryless compressed dictionary
  
  * Fix `sources.lst`
  
  * Fix `sources.lst` and add a note that `libtool` is also required.
  
  * Update setup.py
  
  * Fix `EagerStreamTest`
  
  * Fix BUILD file
  
  * Add missing `libdivsufsort` dependency
  
  * Fix "unused parameter" warning.
  

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• research/durchschlag.h

• #ifndef BROTLI_RESEARCH_DURCHSCHLAG_H_
  #define BROTLI_RESEARCH_DURCHSCHLAG_H_
  
  #include <cstddef>
  #include <cstdint>
  #include <string>
  #include <vector>
  
  /**
   * Generate a dictionary for given samples.
   *
   * @param dictionary_size_limit maximal dictionary size
   * @param slice_len text slice size
   * @param block_len score block length
   * @param sample_sizes vector with sample sizes
   * @param sample_data concatenated samples
   * @return generated dictionary
   */
  std::string durchschlag_generate(
      size_t dictionary_size_limit, size_t slice_len, size_t block_len,
      const std::vector<size_t>& sample_sizes, const uint8_t* sample_data);
  
  //------------------------------------------------------------------------------
  // Lower level API for repetitive dictionary generation.
  //------------------------------------------------------------------------------
  
  /* Pointer to position in text. */
  typedef uint32_t DurchschlagTextIdx;
  
  /* Context is made public for flexible serialization / deserialization. */
  typedef struct DurchschlagContext {
    DurchschlagTextIdx dataSize;
    DurchschlagTextIdx sliceLen;
    DurchschlagTextIdx numUniqueSlices;
    std::vector<DurchschlagTextIdx> offsets;
    std::vector<DurchschlagTextIdx> sliceMap;
  } DurchschlagContext;
  
  DurchschlagContext durchschlag_prepare(size_t slice_len,
      const std::vector<size_t>& sample_sizes, const uint8_t* sample_data);
  
  typedef enum DurchschalgResourceStrategy {
    // Faster
    DURCHSCHLAG_EXCLUSIVE = 0,
    // Uses much less memory
    DURCHSCHLAG_COLLABORATIVE = 1
  } DurchschalgResourceStrategy;
  
  std::string durchschlag_generate(DurchschalgResourceStrategy strategy,
      size_t dictionary_size_limit, size_t block_len,
      const DurchschlagContext& context, const uint8_t* sample_data);
  
  //------------------------------------------------------------------------------
  // Suffix Array based preparation.
  //------------------------------------------------------------------------------
  
  typedef struct DurchschlagIndex {
    std::vector<DurchschlagTextIdx> lcp;
    std::vector<DurchschlagTextIdx> sa;
  } DurchschlagIndex;
  
  DurchschlagIndex durchschlag_index(const std::vector<uint8_t>& data);
  
  DurchschlagContext durchschlag_prepare(size_t slice_len,
      const std::vector<size_t>& sample_sizes, const DurchschlagIndex& index);
  
  //------------------------------------------------------------------------------
  // Data preparation.
  //------------------------------------------------------------------------------
  
  /**
   * Cut out unique slices.
   *
   * Both @p sample_sizes and @p sample_data are modified in-place. Number of
   * samples remains unchanged, but some samples become shorter.
   *
   * @param slice_len (unique) slice size
   * @param minimum_population minimum non-unique slice occurrence
   * @param sample_sizes [in / out] vector with sample sizes
   * @param sample_data [in / out] concatenated samples
   */
  void durchschlag_distill(size_t slice_len, size_t minimum_population,
      std::vector<size_t>* sample_sizes, uint8_t* sample_data);
  
  /**
   * Replace unique slices with zeroes.
   *
   * @p sample_data is modified in-place. Number of samples and their length
   * remain unchanged.
   *
   * @param slice_len (unique) slice size
   * @param minimum_population minimum non-unique slice occurrence
   * @param sample_sizes vector with sample sizes
   * @param sample_data [in / out] concatenated samples
   */
  void durchschlag_purify(size_t slice_len, size_t minimum_population,
      const std::vector<size_t>& sample_sizes, uint8_t* sample_data);
  
  #endif  // BROTLI_RESEARCH_DURCHSCHLAG_H_
  

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