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76 lines
2.5 KiB
76 lines
2.5 KiB
// Copyright 2013 Google Inc. All Rights Reserved. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// http://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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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 <stdint.h> |
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#include <cmath> |
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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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#include "./prefix.h" |
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namespace brotli { |
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void BuildHistograms( |
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const Command* cmds, |
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const size_t num_commands, |
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const BlockSplit& literal_split, |
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const BlockSplit& insert_and_copy_split, |
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const BlockSplit& dist_split, |
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const uint8_t* ringbuffer, |
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size_t start_pos, |
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size_t mask, |
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uint8_t prev_byte, |
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uint8_t prev_byte2, |
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const std::vector<int>& context_modes, |
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std::vector<HistogramLiteral>* literal_histograms, |
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std::vector<HistogramCommand>* insert_and_copy_histograms, |
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std::vector<HistogramDistance>* copy_dist_histograms) { |
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size_t pos = start_pos; |
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BlockSplitIterator literal_it(literal_split); |
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BlockSplitIterator insert_and_copy_it(insert_and_copy_split); |
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BlockSplitIterator dist_it(dist_split); |
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for (int i = 0; i < num_commands; ++i) { |
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const Command &cmd = cmds[i]; |
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insert_and_copy_it.Next(); |
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(*insert_and_copy_histograms)[insert_and_copy_it.type_].Add( |
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cmd.cmd_prefix_); |
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for (int j = 0; j < cmd.insert_len_; ++j) { |
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literal_it.Next(); |
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int context = (literal_it.type_ << kLiteralContextBits) + |
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Context(prev_byte, prev_byte2, context_modes[literal_it.type_]); |
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(*literal_histograms)[context].Add(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 += cmd.copy_len_; |
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if (cmd.copy_len_ > 0) { |
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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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dist_it.Next(); |
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int context = (dist_it.type_ << kDistanceContextBits) + |
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cmd.DistanceContext(); |
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(*copy_dist_histograms)[context].Add(cmd.dist_prefix_); |
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} |
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} |
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} |
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} |
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} // namespace brotli
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