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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef LIBTEXTCLASSIFIER_UTILS_SENTENCEPIECE_SORTED_STRINGS_TABLE_H_
#define LIBTEXTCLASSIFIER_UTILS_SENTENCEPIECE_SORTED_STRINGS_TABLE_H_
#include <functional>
#include <vector>
#include "utils/sentencepiece/matcher.h"
#include "utils/strings/stringpiece.h"
namespace libtextclassifier3 {
// A matcher to find string pieces matching prefixes of an input string.
// The list of reference strings are kept in sorted order in a zero separated
// string.
// binary search is used to find all prefix matches.
// num_pieces: Number of sentence pieces.
// offsets: Offsets into `pieces` where a string starts.
// pieces: String pieces, concatenated in sorted order and zero byte separated.
// use_linear_scan_threshold: Minimum size of binary search range before
// switching to a linear sweep for prefix match testing.
class SortedStringsTable : public SentencePieceMatcher {
public:
SortedStringsTable(const int num_pieces, const int* offsets,
StringPiece pieces,
const int use_linear_scan_threshold = 10)
: num_pieces_(num_pieces),
offsets_(offsets),
pieces_(pieces),
use_linear_scan_threshold_(use_linear_scan_threshold) {}
// Find matches that are prefixes of a string.
bool FindAllPrefixMatches(StringPiece input,
std::vector<TrieMatch>* matches) const override;
// Find the longest prefix match of a string.
bool LongestPrefixMatch(StringPiece input,
TrieMatch* longest_match) const override;
private:
void GatherPrefixMatches(
StringPiece input, const std::function<void(TrieMatch)>& update_fn) const;
const int num_pieces_;
const int* offsets_;
const StringPiece pieces_;
const int use_linear_scan_threshold_;
};
} // namespace libtextclassifier3
#endif // LIBTEXTCLASSIFIER_UTILS_SENTENCEPIECE_SORTED_STRINGS_TABLE_H_
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