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88 lines
2.6 KiB
C++
88 lines
2.6 KiB
C++
// 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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