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

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• Hash : 8a7201c6
  Author :
  Date : 2025-08-05T02:49:08
  

  fix some includes
  
  PiperOrigin-RevId: 791124445
  

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• c/enc/histogram.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
  */
  
  /* Build per-context histograms of literals, commands and distance codes. */
  
  #include "histogram.h"
  
  #include "../common/context.h"
  #include "../common/platform.h"
  #include "block_splitter.h"
  #include "command.h"
  
  #if defined(__cplusplus) || defined(c_plusplus)
  extern "C" {
  #endif
  
  typedef struct BlockSplitIterator {
    const BlockSplit* split_;  /* Not owned. */
    size_t idx_;
    size_t type_;
    size_t length_;
  } BlockSplitIterator;
  
  static void InitBlockSplitIterator(BlockSplitIterator* self,
      const BlockSplit* split) {
    self->split_ = split;
    self->idx_ = 0;
    self->type_ = 0;
    self->length_ = split->lengths ? split->lengths[0] : 0;
  }
  
  static void BlockSplitIteratorNext(BlockSplitIterator* self) {
    if (self->length_ == 0) {
      ++self->idx_;
      self->type_ = self->split_->types[self->idx_];
      self->length_ = self->split_->lengths[self->idx_];
    }
    --self->length_;
  }
  
  void BrotliBuildHistogramsWithContext(
      const Command* cmds, const size_t num_commands,
      const BlockSplit* literal_split, const BlockSplit* insert_and_copy_split,
      const BlockSplit* dist_split, const uint8_t* ringbuffer, size_t start_pos,
      size_t mask, uint8_t prev_byte, uint8_t prev_byte2,
      const ContextType* context_modes, HistogramLiteral* literal_histograms,
      HistogramCommand* insert_and_copy_histograms,
      HistogramDistance* copy_dist_histograms) {
    size_t pos = start_pos;
    BlockSplitIterator literal_it;
    BlockSplitIterator insert_and_copy_it;
    BlockSplitIterator dist_it;
    size_t i;
  
    InitBlockSplitIterator(&literal_it, literal_split);
    InitBlockSplitIterator(&insert_and_copy_it, insert_and_copy_split);
    InitBlockSplitIterator(&dist_it, dist_split);
    for (i = 0; i < num_commands; ++i) {
      const Command* cmd = &cmds[i];
      size_t j;
      BlockSplitIteratorNext(&insert_and_copy_it);
      HistogramAddCommand(&insert_and_copy_histograms[insert_and_copy_it.type_],
          cmd->cmd_prefix_);
      /* TODO(eustas): unwrap iterator blocks. */
      for (j = cmd->insert_len_; j != 0; --j) {
        size_t context;
        BlockSplitIteratorNext(&literal_it);
        context = literal_it.type_;
        if (context_modes) {
          ContextLut lut = BROTLI_CONTEXT_LUT(context_modes[context]);
          context = (context << BROTLI_LITERAL_CONTEXT_BITS) +
              BROTLI_CONTEXT(prev_byte, prev_byte2, lut);
        }
        HistogramAddLiteral(&literal_histograms[context],
            ringbuffer[pos & mask]);
        prev_byte2 = prev_byte;
        prev_byte = ringbuffer[pos & mask];
        ++pos;
      }
      pos += CommandCopyLen(cmd);
      if (CommandCopyLen(cmd)) {
        prev_byte2 = ringbuffer[(pos - 2) & mask];
        prev_byte = ringbuffer[(pos - 1) & mask];
        if (cmd->cmd_prefix_ >= 128) {
          size_t context;
          BlockSplitIteratorNext(&dist_it);
          context = (dist_it.type_ << BROTLI_DISTANCE_CONTEXT_BITS) +
              CommandDistanceContext(cmd);
          HistogramAddDistance(&copy_dist_histograms[context],
              cmd->dist_prefix_ & 0x3FF);
        }
      }
    }
  }
  
  #if defined(__cplusplus) || defined(c_plusplus)
  }  /* extern "C" */
  #endif
  

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