llvm-project/clang-tools-extra/clangd/index/dex/Trigram.cpp

160 lines
5.0 KiB
C++

//===--- Trigram.cpp - Trigram generation for Fuzzy Matching ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "Trigram.h"
#include "../../FuzzyMatch.h"
#include "Token.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/StringExtras.h"
#include <cctype>
#include <queue>
#include <string>
using namespace llvm;
namespace clang {
namespace clangd {
namespace dex {
/// This is used to mark unigrams and bigrams and distinct them from complete
/// trigrams. Since '$' is not present in valid identifier names, it is safe to
/// use it as the special symbol.
static const char END_MARKER = '$';
std::vector<Token> generateIdentifierTrigrams(llvm::StringRef Identifier) {
// Apply fuzzy matching text segmentation.
std::vector<CharRole> Roles(Identifier.size());
calculateRoles(Identifier,
llvm::makeMutableArrayRef(Roles.data(), Identifier.size()));
std::string LowercaseIdentifier = Identifier.lower();
// For each character, store indices of the characters to which fuzzy matching
// algorithm can jump. There are 3 possible variants:
//
// * Next Tail - next character from the same segment
// * Next Head - front character of the next segment
// * Skip-1-Next Head - front character of the skip-1-next segment
//
// Next stores tuples of three indices in the presented order, if a variant is
// not available then 0 is stored.
std::vector<std::array<unsigned, 3>> Next(LowercaseIdentifier.size());
unsigned NextTail = 0, NextHead = 0, NextNextHead = 0;
// Store two first HEAD characters in the identifier (if present).
std::deque<char> TwoHeads;
for (int I = LowercaseIdentifier.size() - 1; I >= 0; --I) {
Next[I] = {{NextTail, NextHead, NextNextHead}};
NextTail = Roles[I] == Tail ? I : 0;
if (Roles[I] == Head) {
NextNextHead = NextHead;
NextHead = I;
TwoHeads.push_front(LowercaseIdentifier[I]);
if (TwoHeads.size() > 2)
TwoHeads.pop_back();
}
}
DenseSet<Token> UniqueTrigrams;
auto add = [&](std::string Chars) {
UniqueTrigrams.insert(Token(Token::Kind::Trigram, Chars));
};
if (TwoHeads.size() == 2)
add({{TwoHeads.front(), TwoHeads.back(), END_MARKER}});
if (!LowercaseIdentifier.empty())
add({{LowercaseIdentifier.front(), END_MARKER, END_MARKER}});
if (LowercaseIdentifier.size() >= 2)
add({{LowercaseIdentifier[0], LowercaseIdentifier[1], END_MARKER}});
if (LowercaseIdentifier.size() >= 3)
add({{LowercaseIdentifier[0], LowercaseIdentifier[1],
LowercaseIdentifier[2]}});
// Iterate through valid seqneces of three characters Fuzzy Matcher can
// process.
for (size_t I = 0; I < LowercaseIdentifier.size(); ++I) {
// Skip delimiters.
if (Roles[I] != Head && Roles[I] != Tail)
continue;
for (const unsigned J : Next[I]) {
if (!J)
continue;
for (const unsigned K : Next[J]) {
if (!K)
continue;
add({{LowercaseIdentifier[I], LowercaseIdentifier[J],
LowercaseIdentifier[K]}});
}
}
}
std::vector<Token> Result;
for (const auto &Trigram : UniqueTrigrams)
Result.push_back(Trigram);
return Result;
}
std::vector<Token> generateQueryTrigrams(llvm::StringRef Query) {
// Apply fuzzy matching text segmentation.
std::vector<CharRole> Roles(Query.size());
calculateRoles(Query, llvm::makeMutableArrayRef(Roles.data(), Query.size()));
// Additional pass is necessary to count valid identifier characters.
// Depending on that, this function might return incomplete trigram.
unsigned ValidSymbolsCount = 0;
for (size_t I = 0; I < Roles.size(); ++I)
if (Roles[I] == Head || Roles[I] == Tail)
++ValidSymbolsCount;
std::string LowercaseQuery = Query.lower();
DenseSet<Token> UniqueTrigrams;
// If the number of symbols which can form fuzzy matching trigram is not
// sufficient, generate a single incomplete trigram for query.
if (ValidSymbolsCount < 3) {
std::string Chars =
LowercaseQuery.substr(0, std::min<size_t>(3UL, Query.size()));
Chars.append(3 - Chars.size(), END_MARKER);
UniqueTrigrams.insert(Token(Token::Kind::Trigram, Chars));
} else {
std::deque<char> Chars;
for (size_t I = 0; I < LowercaseQuery.size(); ++I) {
// If current symbol is delimiter, just skip it.
if (Roles[I] != Head && Roles[I] != Tail)
continue;
Chars.push_back(LowercaseQuery[I]);
if (Chars.size() > 3)
Chars.pop_front();
if (Chars.size() == 3) {
UniqueTrigrams.insert(
Token(Token::Kind::Trigram, std::string(begin(Chars), end(Chars))));
}
}
}
std::vector<Token> Result;
for (const auto &Trigram : UniqueTrigrams)
Result.push_back(Trigram);
return Result;
}
} // namespace dex
} // namespace clangd
} // namespace clang