kc3-lang/brotli/c/enc/backward_references.c

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• Hash : 4b2b2d4f
  Author :
  Date : 2019-04-12T13:57:42
  

  Update (#749)
  
  Update:
  
   * Bazel: fix MSVC configuration
   * C: common: extended documentation and helpers around distance codes
   * C: common: enable BROTLI_DCHECK in "debug" builds
   * C: common: fix implicit trailing zero in `kPrefixSuffix`
   * C: dec: fix possible bit reader discharge for "large-window" mode
   * C: dec: simplify distance decoding via lookup table
   * C: dec: reuse decoder state members memory via union with lookup table
   * C: dec: add decoder state diagram
   * C: enc: clarify access to static dictionary
   * C: enc: improve static dictionary hash
   * C: enc: add "stream offset" parameter for parallel encoding
   * C: enc: reorganize hasher; now Q2-Q3 require exactly 256KiB
             to avoid global TCMalloc lock
   * C: enc: fix rare access to uninitialized data in ring-buffer
   * C: enc: reorganize logging / checks in `write_bits.h`
   * Java: dec: add "large-window" support
   * Java: dec: improve speed
   * Java: dec: debug and 32-bit mode are now activated via system properties
   * Java: dec: demystify some state variables (use better names)
   * Dictionary generator: add single input mode
   * Java: dec: modernize tests
   * Bazel: js: pick working commit for closure rules
  

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• c/enc/backward_references.c

• /* Copyright 2013 Google Inc. All Rights Reserved.
  
     Distributed under MIT license.
     See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
  */
  
  /* Function to find backward reference copies. */
  
  #include "./backward_references.h"
  
  #include "../common/constants.h"
  #include "../common/context.h"
  #include "../common/dictionary.h"
  #include "../common/platform.h"
  #include <brotli/types.h>
  #include "./command.h"
  #include "./dictionary_hash.h"
  #include "./memory.h"
  #include "./quality.h"
  
  #if defined(__cplusplus) || defined(c_plusplus)
  extern "C" {
  #endif
  
  static BROTLI_INLINE size_t ComputeDistanceCode(size_t distance,
                                                  size_t max_distance,
                                                  const int* dist_cache) {
    if (distance <= max_distance) {
      size_t distance_plus_3 = distance + 3;
      size_t offset0 = distance_plus_3 - (size_t)dist_cache[0];
      size_t offset1 = distance_plus_3 - (size_t)dist_cache[1];
      if (distance == (size_t)dist_cache[0]) {
        return 0;
      } else if (distance == (size_t)dist_cache[1]) {
        return 1;
      } else if (offset0 < 7) {
        return (0x9750468 >> (4 * offset0)) & 0xF;
      } else if (offset1 < 7) {
        return (0xFDB1ACE >> (4 * offset1)) & 0xF;
      } else if (distance == (size_t)dist_cache[2]) {
        return 2;
      } else if (distance == (size_t)dist_cache[3]) {
        return 3;
      }
    }
    return distance + BROTLI_NUM_DISTANCE_SHORT_CODES - 1;
  }
  
  #define EXPAND_CAT(a, b) CAT(a, b)
  #define CAT(a, b) a ## b
  #define FN(X) EXPAND_CAT(X, HASHER())
  #define EXPORT_FN(X) EXPAND_CAT(X, EXPAND_CAT(PREFIX(), HASHER()))
  
  #define PREFIX() N
  
  #define HASHER() H2
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H3
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H4
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H5
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H6
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H40
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H41
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H42
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H54
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H35
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H55
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #define HASHER() H65
  /* NOLINTNEXTLINE(build/include) */
  #include "./backward_references_inc.h"
  #undef HASHER
  
  #undef PREFIX
  
  #undef EXPORT_FN
  #undef FN
  #undef CAT
  #undef EXPAND_CAT
  
  void BrotliCreateBackwardReferences(size_t num_bytes,
      size_t position, const uint8_t* ringbuffer, size_t ringbuffer_mask,
      ContextLut literal_context_lut, const BrotliEncoderParams* params,
      Hasher* hasher, int* dist_cache, size_t* last_insert_len,
      Command* commands, size_t* num_commands, size_t* num_literals) {
    switch (params->hasher.type) {
  #define CASE_(N)                                                  \
      case N:                                                       \
        CreateBackwardReferencesNH ## N(num_bytes,                  \
            position, ringbuffer, ringbuffer_mask,                  \
            literal_context_lut, params, hasher, dist_cache,        \
            last_insert_len, commands, num_commands, num_literals); \
        return;
      FOR_GENERIC_HASHERS(CASE_)
  #undef CASE_
      default:
        break;
    }
  }
  
  #if defined(__cplusplus) || defined(c_plusplus)
  }  /* extern "C" */
  #endif
  

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