clang-tools 17.0.0git
FuzzyMatch.h
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1//===--- FuzzyMatch.h - Approximate identifier matching ---------*- C++-*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements fuzzy-matching of strings against identifiers.
10// It indicates both the existence and quality of a match:
11// 'eb' matches both 'emplace_back' and 'embed', the former has a better score.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FUZZYMATCH_H
16#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FUZZYMATCH_H
17
18#include "llvm/ADT/ArrayRef.h"
19#include "llvm/ADT/SmallString.h"
20#include "llvm/ADT/StringRef.h"
21#include "llvm/Support/raw_ostream.h"
22#include <optional>
23
24namespace clang {
25namespace clangd {
26
27// Utilities for word segmentation.
28// FuzzyMatcher already incorporates this logic, so most users don't need this.
29//
30// A name like "fooBar_baz" consists of several parts foo, bar, baz.
31// Aligning segmentation of word and pattern improves the fuzzy-match.
32// For example: [lol] matches "LaughingOutLoud" better than "LionPopulation"
33//
34// First we classify each character into types (uppercase, lowercase, etc).
35// Then we look at the sequence: e.g. [upper, lower] is the start of a segment.
36
37// We distinguish the types of characters that affect segmentation.
38// It's not obvious how to segment digits, we treat them as lowercase letters.
39// As we don't decode UTF-8, we treat bytes over 127 as lowercase too.
40// This means we require exact (case-sensitive) match for those characters.
41enum CharType : unsigned char {
42 Empty = 0, // Before-the-start and after-the-end (and control chars).
43 Lower = 1, // Lowercase letters, digits, and non-ASCII bytes.
44 Upper = 2, // Uppercase letters.
45 Punctuation = 3, // ASCII punctuation (including Space)
46};
47// A CharTypeSet is a bitfield representing all the character types in a word.
48// Its bits are 1<<Empty, 1<<Lower, etc.
49using CharTypeSet = unsigned char;
50
51// Each character's Role is the Head or Tail of a segment, or a Separator.
52// e.g. XMLHttpRequest_Async
53// +--+---+------ +----
54// ^Head ^Tail ^Separator
55enum CharRole : unsigned char {
56 Unknown = 0, // Stray control characters or impossible states.
57 Tail = 1, // Part of a word segment, but not the first character.
58 Head = 2, // The first character of a word segment.
59 Separator = 3, // Punctuation characters that separate word segments.
60};
61
62// Compute segmentation of Text.
63// Character roles are stored in Roles (Roles.size() must equal Text.size()).
64// The set of character types encountered is returned, this may inform
65// heuristics for dealing with poorly-segmented identifiers like "strndup".
66CharTypeSet calculateRoles(llvm::StringRef Text,
67 llvm::MutableArrayRef<CharRole> Roles);
68
69// A matcher capable of matching and scoring strings against a single pattern.
70// It's optimized for matching against many strings - match() does not allocate.
72public:
73 // Characters beyond MaxPat are ignored.
74 FuzzyMatcher(llvm::StringRef Pattern);
75
76 // If Word matches the pattern, return a score indicating the quality match.
77 // Scores usually fall in a [0,1] range, with 1 being a very good score.
78 // "Super" scores in (1,2] are possible if the pattern is the full word.
79 // Characters beyond MaxWord are ignored.
80 std::optional<float> match(llvm::StringRef Word);
81
82 llvm::StringRef pattern() const { return llvm::StringRef(Pat, PatN); }
83 bool empty() const { return PatN == 0; }
84
85 // Dump internal state from the last match() to the stream, for debugging.
86 // Returns the pattern with [] around matched characters, e.g.
87 // [u_p] + "unique_ptr" --> "[u]nique[_p]tr"
88 llvm::SmallString<256> dumpLast(llvm::raw_ostream &) const;
89
90private:
91 // We truncate the pattern and the word to bound the cost of matching.
92 constexpr static int MaxPat = 63, MaxWord = 127;
93 // Action describes how a word character was matched to the pattern.
94 // It should be an enum, but this causes bitfield problems:
95 // - for MSVC the enum type must be explicitly unsigned for correctness
96 // - GCC 4.8 complains not all values fit if the type is unsigned
97 using Action = bool;
98 constexpr static Action Miss = false; // Word character was skipped.
99 constexpr static Action Match = true; // Matched against a pattern character.
100
101 bool init(llvm::StringRef Word);
102 void buildGraph();
103 bool allowMatch(int P, int W, Action Last) const;
104 int skipPenalty(int W, Action Last) const;
105 int matchBonus(int P, int W, Action Last) const;
106
107 // Pattern data is initialized by the constructor, then constant.
108 char Pat[MaxPat]; // Pattern data
109 int PatN; // Length
110 char LowPat[MaxPat]; // Pattern in lowercase
111 CharRole PatRole[MaxPat]; // Pattern segmentation info
112 CharTypeSet PatTypeSet; // Bitmask of 1<<CharType for all Pattern characters
113 float ScoreScale; // Normalizes scores for the pattern length.
114
115 // Word data is initialized on each call to match(), mostly by init().
116 char Word[MaxWord]; // Word data
117 int WordN; // Length
118 char LowWord[MaxWord]; // Word in lowercase
119 CharRole WordRole[MaxWord]; // Word segmentation info
120 CharTypeSet WordTypeSet; // Bitmask of 1<<CharType for all Word characters
121 bool WordContainsPattern; // Simple substring check
122
123 // Cumulative best-match score table.
124 // Boundary conditions are filled in by the constructor.
125 // The rest is repopulated for each match(), by buildGraph().
126 struct ScoreInfo {
127 signed int Score : 15;
128 Action Prev : 1;
129 };
130 ScoreInfo Scores[MaxPat + 1][MaxWord + 1][/* Last Action */ 2];
131};
132
133} // namespace clangd
134} // namespace clang
135
136#endif
std::string Word
std::optional< float > Score
FieldAction Action
llvm::SmallString< 256 > dumpLast(llvm::raw_ostream &) const
Definition: FuzzyMatch.cpp:308
std::optional< float > match(llvm::StringRef Word)
Definition: FuzzyMatch.cpp:92
llvm::StringRef pattern() const
Definition: FuzzyMatch.h:82
unsigned char CharTypeSet
Definition: FuzzyMatch.h:49
CharTypeSet calculateRoles(llvm::StringRef Text, llvm::MutableArrayRef< CharRole > Roles)
Definition: FuzzyMatch.cpp:154
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//