68 lines
2.5 KiB
C++
68 lines
2.5 KiB
C++
/*
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* Copyright (C) 2018 The Android Open Source Project
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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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#ifndef LIBTEXTCLASSIFIER_UTILS_CONTAINER_SORTED_STRINGS_TABLE_H_
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#define LIBTEXTCLASSIFIER_UTILS_CONTAINER_SORTED_STRINGS_TABLE_H_
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#include <functional>
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#include <vector>
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#include "utils/base/integral_types.h"
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#include "utils/container/string-set.h"
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#include "utils/strings/stringpiece.h"
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namespace libtextclassifier3 {
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// A matcher to find string pieces matching prefixes of an input string.
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// The list of reference strings are kept in sorted order in a zero separated
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// string.
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// binary search is used to find all prefix matches.
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// num_pieces: Number of sentence pieces.
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// offsets: Offsets into `pieces` where a string starts.
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// pieces: String pieces, concatenated in sorted order and zero byte separated.
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// use_linear_scan_threshold: Minimum size of binary search range before
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// switching to a linear sweep for prefix match testing.
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class SortedStringsTable : public StringSet {
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public:
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SortedStringsTable(const int num_pieces, const uint32* offsets,
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StringPiece pieces,
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const int use_linear_scan_threshold = 10)
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: num_pieces_(num_pieces),
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offsets_(offsets),
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pieces_(pieces),
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use_linear_scan_threshold_(use_linear_scan_threshold) {}
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// Find matches that are prefixes of a string.
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bool FindAllPrefixMatches(StringPiece input,
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std::vector<Match>* matches) const override;
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// Find the longest prefix match of a string.
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bool LongestPrefixMatch(StringPiece input,
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Match* longest_match) const override;
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private:
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void GatherPrefixMatches(StringPiece input,
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const std::function<void(Match)>& update_fn) const;
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const int num_pieces_;
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const uint32* offsets_;
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const StringPiece pieces_;
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const int use_linear_scan_threshold_;
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};
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} // namespace libtextclassifier3
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#endif // LIBTEXTCLASSIFIER_UTILS_CONTAINER_SORTED_STRINGS_TABLE_H_
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