forked from OSchip/llvm-project
68 lines
2.7 KiB
C++
68 lines
2.7 KiB
C++
//===--- Trigram.h - Trigram generation for Fuzzy Matching ------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// Trigrams are attributes of the symbol unqualified name used to effectively
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/// extract symbols which can be fuzzy-matched given user query from the
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/// inverted index. To match query with the extracted set of trigrams Q, the set
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/// of generated trigrams T for identifier (unqualified symbol name) should
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/// contain all items of Q, i.e. Q ⊆ T.
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///
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/// Trigram sets extracted from unqualified name and from query are different:
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/// the set of query trigrams only contains consecutive sequences of three
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/// characters (which is only a subset of all trigrams generated for an
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/// identifier).
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_DEX_TRIGRAM_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_DEX_TRIGRAM_H
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#include "Token.h"
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#include <string>
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namespace clang {
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namespace clangd {
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namespace dex {
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/// Returns list of unique fuzzy-search trigrams from unqualified symbol.
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/// The trigrams give the 3-character query substrings this symbol can match.
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///
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/// The symbol's name is broken into segments, e.g. "FooBar" has two segments.
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/// Trigrams can start at any character in the input. Then we can choose to move
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/// to the next character or to the start of the next segment.
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///
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/// Short trigrams (length 1-2) are used for short queries. These are:
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/// - prefixes of the identifier, of length 1 and 2
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/// - the first character + next head character
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///
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/// For "FooBar" we get the following trigrams:
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/// {f, fo, fb, foo, fob, fba, oob, oba, bar}.
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///
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/// Trigrams are lowercase, as trigram matching is case-insensitive.
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/// Trigrams in the returned list are deduplicated.
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std::vector<Token> generateIdentifierTrigrams(llvm::StringRef Identifier);
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/// Returns list of unique fuzzy-search trigrams given a query.
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///
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/// Query is segmented using FuzzyMatch API and downcasted to lowercase. Then,
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/// the simplest trigrams - sequences of three consecutive letters and digits
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/// are extracted and returned after deduplication.
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///
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/// For short queries (less than 3 characters with Head or Tail roles in Fuzzy
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/// Matching segmentation) this returns a single trigram with the first
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/// characters (up to 3) to perform prefix match.
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std::vector<Token> generateQueryTrigrams(llvm::StringRef Query);
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} // namespace dex
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} // namespace clangd
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} // namespace clang
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#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_DEX_TRIGRAM_H
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