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Viewing changes to thirdparty/brotli/enc/histogram.c

  • Committer: Jose Fonseca
  • Date: 2018-04-05 10:04:29 UTC
  • Revision ID: git-v1:da5c63cc6f90b1a407bb25b0d9ec7867346088e2
brotli: Update to 1.0.2.

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thirdparty/brotli/enc/histogram.c
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/* Copyright 2013 Google Inc. All Rights Reserved.
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   Distributed under MIT license.
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   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Build per-context histograms of literals, commands and distance codes. */
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#include "./histogram.h"
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#include "./block_splitter.h"
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#include "./command.h"
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#include "./context.h"
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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typedef struct BlockSplitIterator {
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  const BlockSplit* split_;  /* Not owned. */
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  size_t idx_;
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  size_t type_;
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  size_t length_;
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} BlockSplitIterator;
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static void InitBlockSplitIterator(BlockSplitIterator* self,
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    const BlockSplit* split) {
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  self->split_ = split;
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  self->idx_ = 0;
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  self->type_ = 0;
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  self->length_ = split->lengths ? split->lengths[0] : 0;
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}
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static void BlockSplitIteratorNext(BlockSplitIterator* self) {
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  if (self->length_ == 0) {
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    ++self->idx_;
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    self->type_ = self->split_->types[self->idx_];
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    self->length_ = self->split_->lengths[self->idx_];
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  }
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  --self->length_;
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}
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void BrotliBuildHistogramsWithContext(
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    const Command* cmds, const size_t num_commands,
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    const BlockSplit* literal_split, const BlockSplit* insert_and_copy_split,
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    const BlockSplit* dist_split, const uint8_t* ringbuffer, size_t start_pos,
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    size_t mask, uint8_t prev_byte, uint8_t prev_byte2,
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    const ContextType* context_modes, HistogramLiteral* literal_histograms,
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    HistogramCommand* insert_and_copy_histograms,
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    HistogramDistance* copy_dist_histograms) {
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  size_t pos = start_pos;
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  BlockSplitIterator literal_it;
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  BlockSplitIterator insert_and_copy_it;
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  BlockSplitIterator dist_it;
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  size_t i;
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  InitBlockSplitIterator(&literal_it, literal_split);
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  InitBlockSplitIterator(&insert_and_copy_it, insert_and_copy_split);
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  InitBlockSplitIterator(&dist_it, dist_split);
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  for (i = 0; i < num_commands; ++i) {
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    const Command* cmd = &cmds[i];
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    size_t j;
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    BlockSplitIteratorNext(&insert_and_copy_it);
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    HistogramAddCommand(&insert_and_copy_histograms[insert_and_copy_it.type_],
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        cmd->cmd_prefix_);
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    for (j = cmd->insert_len_; j != 0; --j) {
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      size_t context;
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      BlockSplitIteratorNext(&literal_it);
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      context = (literal_it.type_ << BROTLI_LITERAL_CONTEXT_BITS) +
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          Context(prev_byte, prev_byte2, context_modes[literal_it.type_]);
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      HistogramAddLiteral(&literal_histograms[context],
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          ringbuffer[pos & mask]);
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      prev_byte2 = prev_byte;
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      prev_byte = ringbuffer[pos & mask];
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      ++pos;
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    }
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    pos += CommandCopyLen(cmd);
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    if (CommandCopyLen(cmd)) {
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      prev_byte2 = ringbuffer[(pos - 2) & mask];
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      prev_byte = ringbuffer[(pos - 1) & mask];
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      if (cmd->cmd_prefix_ >= 128) {
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        size_t context;
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        BlockSplitIteratorNext(&dist_it);
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        context = (dist_it.type_ << BROTLI_DISTANCE_CONTEXT_BITS) +
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            CommandDistanceContext(cmd);
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        HistogramAddDistance(&copy_dist_histograms[context],
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            cmd->dist_prefix_);
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      }
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    }
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  }
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}
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#if defined(__cplusplus) || defined(c_plusplus)
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}  /* extern "C" */
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#endif