clang  9.0.0svn
FileMatchTrie.cpp
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1 //===- FileMatchTrie.cpp --------------------------------------------------===//
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 contains the implementation of a FileMatchTrie.
10 //
11 //===----------------------------------------------------------------------===//
12 
14 #include "llvm/ADT/StringMap.h"
15 #include "llvm/ADT/StringRef.h"
16 #include "llvm/Support/FileSystem.h"
17 #include "llvm/Support/Path.h"
18 #include "llvm/Support/raw_ostream.h"
19 #include <string>
20 #include <vector>
21 
22 using namespace clang;
23 using namespace tooling;
24 
25 namespace {
26 
27 /// Default \c PathComparator using \c llvm::sys::fs::equivalent().
28 struct DefaultPathComparator : public PathComparator {
29  bool equivalent(StringRef FileA, StringRef FileB) const override {
30  return FileA == FileB || llvm::sys::fs::equivalent(FileA, FileB);
31  }
32 };
33 
34 } // namespace
35 
36 namespace clang {
37 namespace tooling {
38 
39 /// A node of the \c FileMatchTrie.
40 ///
41 /// Each node has storage for up to one path and a map mapping a path segment to
42 /// child nodes. The trie starts with an empty root node.
44 public:
45  /// Inserts 'NewPath' into this trie. \c ConsumedLength denotes
46  /// the number of \c NewPath's trailing characters already consumed during
47  /// recursion.
48  ///
49  /// An insert of a path
50  /// 'p'starts at the root node and does the following:
51  /// - If the node is empty, insert 'p' into its storage and abort.
52  /// - If the node has a path 'p2' but no children, take the last path segment
53  /// 's' of 'p2', put a new child into the map at 's' an insert the rest of
54  /// 'p2' there.
55  /// - Insert a new child for the last segment of 'p' and insert the rest of
56  /// 'p' there.
57  ///
58  /// An insert operation is linear in the number of a path's segments.
59  void insert(StringRef NewPath, unsigned ConsumedLength = 0) {
60  // We cannot put relative paths into the FileMatchTrie as then a path can be
61  // a postfix of another path, violating a core assumption of the trie.
62  if (llvm::sys::path::is_relative(NewPath))
63  return;
64  if (Path.empty()) {
65  // This is an empty leaf. Store NewPath and return.
66  Path = NewPath;
67  return;
68  }
69  if (Children.empty()) {
70  // This is a leaf, ignore duplicate entry if 'Path' equals 'NewPath'.
71  if (NewPath == Path)
72  return;
73  // Make this a node and create a child-leaf with 'Path'.
74  StringRef Element(llvm::sys::path::filename(
75  StringRef(Path).drop_back(ConsumedLength)));
76  Children[Element].Path = Path;
77  }
78  StringRef Element(llvm::sys::path::filename(
79  StringRef(NewPath).drop_back(ConsumedLength)));
80  Children[Element].insert(NewPath, ConsumedLength + Element.size() + 1);
81  }
82 
83  /// Tries to find the node under this \c FileMatchTrieNode that best
84  /// matches 'FileName'.
85  ///
86  /// If multiple paths fit 'FileName' equally well, \c IsAmbiguous is set to
87  /// \c true and an empty string is returned. If no path fits 'FileName', an
88  /// empty string is returned. \c ConsumedLength denotes the number of
89  /// \c Filename's trailing characters already consumed during recursion.
90  ///
91  /// To find the best matching node for a given path 'p', the
92  /// \c findEquivalent() function is called recursively for each path segment
93  /// (back to front) of 'p' until a node 'n' is reached that does not ..
94  /// - .. have children. In this case it is checked
95  /// whether the stored path is equivalent to 'p'. If yes, the best match is
96  /// found. Otherwise continue with the parent node as if this node did not
97  /// exist.
98  /// - .. a child matching the next path segment. In this case, all children of
99  /// 'n' are an equally good match for 'p'. All children are of 'n' are found
100  /// recursively and their equivalence to 'p' is determined. If none are
101  /// equivalent, continue with the parent node as if 'n' didn't exist. If one
102  /// is equivalent, the best match is found. Otherwise, report and ambigiuity
103  /// error.
104  StringRef findEquivalent(const PathComparator& Comparator,
105  StringRef FileName,
106  bool &IsAmbiguous,
107  unsigned ConsumedLength = 0) const {
108  if (Children.empty()) {
109  if (Comparator.equivalent(StringRef(Path), FileName))
110  return StringRef(Path);
111  return {};
112  }
113  StringRef Element(llvm::sys::path::filename(FileName.drop_back(
114  ConsumedLength)));
115  llvm::StringMap<FileMatchTrieNode>::const_iterator MatchingChild =
116  Children.find(Element);
117  if (MatchingChild != Children.end()) {
118  StringRef Result = MatchingChild->getValue().findEquivalent(
119  Comparator, FileName, IsAmbiguous,
120  ConsumedLength + Element.size() + 1);
121  if (!Result.empty() || IsAmbiguous)
122  return Result;
123  }
124  std::vector<StringRef> AllChildren;
125  getAll(AllChildren, MatchingChild);
126  StringRef Result;
127  for (const auto &Child : AllChildren) {
128  if (Comparator.equivalent(Child, FileName)) {
129  if (Result.empty()) {
130  Result = Child;
131  } else {
132  IsAmbiguous = true;
133  return {};
134  }
135  }
136  }
137  return Result;
138  }
139 
140 private:
141  /// Gets all paths under this FileMatchTrieNode.
142  void getAll(std::vector<StringRef> &Results,
143  llvm::StringMap<FileMatchTrieNode>::const_iterator Except) const {
144  if (Path.empty())
145  return;
146  if (Children.empty()) {
147  Results.push_back(StringRef(Path));
148  return;
149  }
150  for (llvm::StringMap<FileMatchTrieNode>::const_iterator
151  It = Children.begin(), E = Children.end();
152  It != E; ++It) {
153  if (It == Except)
154  continue;
155  It->getValue().getAll(Results, Children.end());
156  }
157  }
158 
159  // The stored absolute path in this node. Only valid for leaf nodes, i.e.
160  // nodes where Children.empty().
161  std::string Path;
162 
163  // The children of this node stored in a map based on the next path segment.
164  llvm::StringMap<FileMatchTrieNode> Children;
165 };
166 
167 } // namespace tooling
168 } // namespace clang
169 
171  : Root(new FileMatchTrieNode), Comparator(new DefaultPathComparator()) {}
172 
174  : Root(new FileMatchTrieNode), Comparator(Comparator) {}
175 
177  delete Root;
178 }
179 
180 void FileMatchTrie::insert(StringRef NewPath) {
181  Root->insert(NewPath);
182 }
183 
184 StringRef FileMatchTrie::findEquivalent(StringRef FileName,
185  raw_ostream &Error) const {
186  if (llvm::sys::path::is_relative(FileName)) {
187  Error << "Cannot resolve relative paths";
188  return {};
189  }
190  bool IsAmbiguous = false;
191  StringRef Result = Root->findEquivalent(*Comparator, FileName, IsAmbiguous);
192  if (IsAmbiguous)
193  Error << "Path is ambiguous";
194  return Result;
195 }
void insert(StringRef NewPath)
Insert a new absolute path. Relative paths are ignored.
void insert(StringRef NewPath, unsigned ConsumedLength=0)
Inserts &#39;NewPath&#39; into this trie.
virtual bool equivalent(StringRef FileA, StringRef FileB) const =0
Dataflow Directional Tag Classes.
A node of the FileMatchTrie.
StringRef findEquivalent(StringRef FileName, raw_ostream &Error) const
Finds the corresponding file in this trie.
StringRef findEquivalent(const PathComparator &Comparator, StringRef FileName, bool &IsAmbiguous, unsigned ConsumedLength=0) const
Tries to find the node under this FileMatchTrieNode that best matches &#39;FileName&#39;. ...