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87 lines
2.6 KiB
87 lines
2.6 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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// Class to model the static dictionary. |
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#ifndef BROTLI_ENC_STATIC_DICT_H_ |
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#define BROTLI_ENC_STATIC_DICT_H_ |
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#include <algorithm> |
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#include <unordered_map> |
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#include <string> |
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#include "./dictionary.h" |
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#include "./transform.h" |
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namespace brotli { |
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class StaticDictionary { |
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public: |
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StaticDictionary() {} |
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void Fill(bool enable_transforms) { |
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const int num_transforms = enable_transforms ? kNumTransforms : 1; |
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for (int t = num_transforms - 1; t >= 0; --t) { |
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for (int i = kMaxDictionaryWordLength; |
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i >= kMinDictionaryWordLength; --i) { |
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const int num_words = 1 << kBrotliDictionarySizeBitsByLength[i]; |
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for (int j = num_words - 1; j >= 0; --j) { |
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int word_id = t * num_words + j; |
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std::string word = GetTransformedDictionaryWord(i, word_id); |
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if (word.size() >= 4) { |
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Insert(word, i, word_id); |
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} |
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} |
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} |
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} |
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} |
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void Insert(const std::string &str, int len, int dist) { |
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int ix = (dist << 6) + len; |
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std::unordered_map<std::string, int>::const_iterator it = map_.find(str); |
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if (it != map_.end() && ix >= it->second) { |
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return; |
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} |
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map_[str] = ix; |
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uint32_t v = 0; |
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for (int i = 0; i < 4 && i < str.size(); ++i) { |
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v += static_cast<uint32_t>(str[i]) << (8 * i); |
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} |
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if (prefix_map_[v] < str.size()) { |
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prefix_map_[v] = str.size(); |
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} |
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} |
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int GetLength(uint32_t v) const { |
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std::unordered_map<uint32_t, int>::const_iterator it = prefix_map_.find(v); |
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if (it == prefix_map_.end()) { |
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return 0; |
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} |
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return it->second; |
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} |
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bool Get(const std::string &str, int *len, int *dist) const { |
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std::unordered_map<std::string, int>::const_iterator it = map_.find(str); |
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if (it == map_.end()) { |
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return false; |
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} |
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int v = it->second; |
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*len = v & 63; |
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*dist = v >> 6; |
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return true; |
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} |
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private: |
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std::unordered_map<std::string, int> map_; |
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std::unordered_map<uint32_t, int> prefix_map_; |
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}; |
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} // namespace brotli |
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#endif // BROTLI_ENC_STATIC_DICT_H_
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