clang-tools 8.0.0

FileDistance.h
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1 //===--- FileDistance.h - File proximity scoring -----------------*- C++-*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This library measures the distance between file paths.
11 // It's used for ranking symbols, e.g. in code completion.
12 // |foo/bar.h -> foo/bar.h| = 0.
13 // |foo/bar.h -> foo/baz.h| < |foo/bar.h -> baz.h|.
14 // This is an edit-distance, where edits go up or down the directory tree.
15 // It's not symmetrical, the costs of going up and down may not match.
16 //
17 // Dealing with multiple sources:
18 // In practice we care about the distance from a source file, but files near
19 // its main-header and #included files are considered "close".
20 // So we start with a set of (anchor, cost) pairs, and call the distance to a
21 // path the minimum of `cost + |source -> path|`.
22 //
23 // We allow each source to limit the number of up-traversals paths may start
24 // with. Up-traversals may reach things that are not "semantically near".
25 //
26 // Symbol URI schemes:
27 // Symbol locations may be represented by URIs rather than file paths directly.
28 // In this case we want to perform distance computations in URI space rather
29 // than in file-space, without performing redundant conversions.
30 // Therefore we have a lookup structure that accepts URIs, so that intermediate
31 // calculations for the same scheme can be reused.
32 //
33 // Caveats:
34 // Assuming up and down traversals each have uniform costs is simplistic.
35 // Often there are "semantic roots" whose children are almost unrelated.
36 // (e.g. /usr/include/, or / in an umbrella repository). We ignore this.
37 //
38 //===----------------------------------------------------------------------===//
39
40 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FILEDISTANCE_H
41 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FILEDISTANCE_H
42
43 #include "URI.h"
44 #include "llvm/ADT/DenseMap.h"
45 #include "llvm/ADT/DenseMapInfo.h"
46 #include "llvm/ADT/SmallString.h"
47 #include "llvm/ADT/StringRef.h"
48 #include "llvm/Support/Allocator.h"
49 #include "llvm/Support/Path.h"
50 #include "llvm/Support/StringSaver.h"
51 #include <memory>
52
53 namespace clang {
54 namespace clangd {
55
56 struct FileDistanceOptions {
57 unsigned UpCost = 2; // |foo/bar.h -> foo|
58 unsigned DownCost = 1; // |foo -> foo/bar.h|
59 unsigned IncludeCost = 2; // |foo.cc -> included_header.h|
60 bool AllowDownTraversalFromRoot = true; // | / -> /a |
61 };
62
63 struct SourceParams {
64 // Base cost for paths starting at this source.
65 unsigned Cost = 0;
66 // Limits the number of upwards traversals allowed from this source.
67 unsigned MaxUpTraversals = std::numeric_limits<unsigned>::max();
68 };
69
70 // Supports lookups to find the minimum distance to a file from any source.
71 // This object should be reused, it memoizes intermediate computations.
72 class FileDistance {
73 public:
74 static constexpr unsigned Unreachable = std::numeric_limits<unsigned>::max();
75 static const llvm::hash_code RootHash;
76
77 FileDistance(llvm::StringMap<SourceParams> Sources,
78 const FileDistanceOptions &Opts = {});
79
80 // Computes the minimum distance from any source to the file path.
81 unsigned distance(llvm::StringRef Path);
82
83 private:
84 // Costs computed so far. Always contains sources and their ancestors.
85 // We store hash codes only. Collisions are rare and consequences aren't dire.
86 llvm::DenseMap<llvm::hash_code, unsigned> Cache;
87 FileDistanceOptions Opts;
88 };
89
90 // Supports lookups like FileDistance, but the lookup keys are URIs.
91 // We convert each of the sources to the scheme of the URI and do a FileDistance
92 // comparison on the bodies.
93 class URIDistance {
94 public:
95 // \p Sources must contain absolute paths, not URIs.
96 URIDistance(llvm::StringMap<SourceParams> Sources,
97 const FileDistanceOptions &Opts = {})
98 : Sources(Sources), Opts(Opts) {}
99
100 // Computes the minimum distance from any source to the URI.
101 // Only sources that can be mapped into the URI's scheme are considered.
102 unsigned distance(llvm::StringRef URI);
103
104 private:
105 // Returns the FileDistance for a URI scheme, creating it if needed.
106 FileDistance &forScheme(llvm::StringRef Scheme);
107
108 // We cache the results using the original strings so we can skip URI parsing.
109 llvm::DenseMap<llvm::hash_code, unsigned> Cache;
110 llvm::StringMap<SourceParams> Sources;
111 llvm::StringMap<std::unique_ptr<FileDistance>> ByScheme;
112 FileDistanceOptions Opts;
113 };
114
115 /// Support lookups like FileDistance, but the lookup keys are symbol scopes.
116 /// For example, a scope "na::nb::" is converted to "/na/nb".
117 class ScopeDistance {
118 public:
119 /// QueryScopes[0] is the preferred scope.
120 ScopeDistance(llvm::ArrayRef<std::string> QueryScopes);
121
122 unsigned distance(llvm::StringRef SymbolScope);
123
124 private:
125 FileDistance Distance;
126 };
127
128 } // namespace clangd
129 } // namespace clang
130
131 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_FILEDISTANCE_H
clang::clangd::FileDistanceOptions
Definition: FileDistance.h:56
clang::clangd::FileDistanceOptions::IncludeCost
unsigned IncludeCost
Definition: FileDistance.h:59
clang::clangd::SourceParams
Definition: FileDistance.h:63
clang::clangd::URIDistance::URIDistance
URIDistance(llvm::StringMap< SourceParams > Sources, const FileDistanceOptions &Opts={})
Definition: FileDistance.h:96
clang::clangd::FileDistanceOptions::DownCost
unsigned DownCost
Definition: FileDistance.h:58
clang::clangd::FileDistance
Definition: FileDistance.h:72
clang::clangd::Path
std::string Path
A typedef to represent a file path.
Definition: Path.h:21
clang::clangd::FileDistanceOptions::UpCost
unsigned UpCost
Definition: FileDistance.h:57
clang::clangd::URIDistance
Definition: FileDistance.h:93
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ChangeNamespace.cpp:18
clang::clangd::ScopeDistance
Support lookups like FileDistance, but the lookup keys are symbol scopes.
Definition: FileDistance.h:117
clang::clangd::URI
A URI describes the location of a source file.
Definition: URI.h:29
URI.h
clang::clangd::FileDistanceOptions::AllowDownTraversalFromRoot
bool AllowDownTraversalFromRoot
Definition: FileDistance.h:60
clang::clangd::FileDistance::RootHash
static const llvm::hash_code RootHash
Definition: FileDistance.h:75