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1 //===--- FileManager.h - File System Probing and Caching --------*- 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 /// \file
11 /// \brief Defines the clang::FileManager interface and associated types.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_CLANG_BASIC_FILEMANAGER_H
16 #define LLVM_CLANG_BASIC_FILEMANAGER_H
17 
18 #include "clang/Basic/FileSystemOptions.h"
19 #include "clang/Basic/LLVM.h"
20 #include "clang/Basic/VirtualFileSystem.h"
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/IntrusiveRefCntPtr.h"
23 #include "llvm/ADT/SmallVector.h"
24 #include "llvm/ADT/StringMap.h"
25 #include "llvm/ADT/StringRef.h"
26 #include "llvm/Support/Allocator.h"
27 #include <memory>
28 #include <map>
29 
30 namespace llvm {
31 class MemoryBuffer;
32 }
33 
34 namespace clang {
35 class FileManager;
36 class FileSystemStatCache;
37 
38 /// \brief Cached information about one directory (either on disk or in
39 /// the virtual file system).
40 class DirectoryEntry {
41   const char *Name;   // Name of the directory.
42   friend class FileManager;
43 public:
DirectoryEntry()44   DirectoryEntry() : Name(nullptr) {}
getName()45   const char *getName() const { return Name; }
46 };
47 
48 /// \brief Cached information about one file (either on disk
49 /// or in the virtual file system).
50 ///
51 /// If the 'File' member is valid, then this FileEntry has an open file
52 /// descriptor for the file.
53 class FileEntry {
54   const char *Name;           // Name of the file.
55   std::string RealPathName;   // Real path to the file; could be empty.
56   off_t Size;                 // File size in bytes.
57   time_t ModTime;             // Modification time of file.
58   const DirectoryEntry *Dir;  // Directory file lives in.
59   unsigned UID;               // A unique (small) ID for the file.
60   llvm::sys::fs::UniqueID UniqueID;
61   bool IsNamedPipe;
62   bool InPCH;
63   bool IsValid;               // Is this \c FileEntry initialized and valid?
64 
65   /// \brief The open file, if it is owned by the \p FileEntry.
66   mutable std::unique_ptr<vfs::File> File;
67   friend class FileManager;
68 
69   void operator=(const FileEntry &) = delete;
70 
71 public:
FileEntry()72   FileEntry()
73       : UniqueID(0, 0), IsNamedPipe(false), InPCH(false), IsValid(false)
74   {}
75 
76   // FIXME: this is here to allow putting FileEntry in std::map.  Once we have
77   // emplace, we shouldn't need a copy constructor anymore.
78   /// Intentionally does not copy fields that are not set in an uninitialized
79   /// \c FileEntry.
FileEntry(const FileEntry & FE)80   FileEntry(const FileEntry &FE) : UniqueID(FE.UniqueID),
81       IsNamedPipe(FE.IsNamedPipe), InPCH(FE.InPCH), IsValid(FE.IsValid) {
82     assert(!isValid() && "Cannot copy an initialized FileEntry");
83   }
84 
getName()85   const char *getName() const { return Name; }
tryGetRealPathName()86   StringRef tryGetRealPathName() const { return RealPathName; }
isValid()87   bool isValid() const { return IsValid; }
getSize()88   off_t getSize() const { return Size; }
getUID()89   unsigned getUID() const { return UID; }
getUniqueID()90   const llvm::sys::fs::UniqueID &getUniqueID() const { return UniqueID; }
isInPCH()91   bool isInPCH() const { return InPCH; }
getModificationTime()92   time_t getModificationTime() const { return ModTime; }
93 
94   /// \brief Return the directory the file lives in.
getDir()95   const DirectoryEntry *getDir() const { return Dir; }
96 
97   bool operator<(const FileEntry &RHS) const { return UniqueID < RHS.UniqueID; }
98 
99   /// \brief Check whether the file is a named pipe (and thus can't be opened by
100   /// the native FileManager methods).
isNamedPipe()101   bool isNamedPipe() const { return IsNamedPipe; }
102 
closeFile()103   void closeFile() const {
104     File.reset(); // rely on destructor to close File
105   }
106 };
107 
108 struct FileData;
109 
110 /// \brief Implements support for file system lookup, file system caching,
111 /// and directory search management.
112 ///
113 /// This also handles more advanced properties, such as uniquing files based
114 /// on "inode", so that a file with two names (e.g. symlinked) will be treated
115 /// as a single file.
116 ///
117 class FileManager : public RefCountedBase<FileManager> {
118   IntrusiveRefCntPtr<vfs::FileSystem> FS;
119   FileSystemOptions FileSystemOpts;
120 
121   /// \brief Cache for existing real directories.
122   std::map<llvm::sys::fs::UniqueID, DirectoryEntry> UniqueRealDirs;
123 
124   /// \brief Cache for existing real files.
125   std::map<llvm::sys::fs::UniqueID, FileEntry> UniqueRealFiles;
126 
127   /// \brief The virtual directories that we have allocated.
128   ///
129   /// For each virtual file (e.g. foo/bar/baz.cpp), we add all of its parent
130   /// directories (foo/ and foo/bar/) here.
131   SmallVector<std::unique_ptr<DirectoryEntry>, 4> VirtualDirectoryEntries;
132   /// \brief The virtual files that we have allocated.
133   SmallVector<std::unique_ptr<FileEntry>, 4> VirtualFileEntries;
134 
135   /// \brief A cache that maps paths to directory entries (either real or
136   /// virtual) we have looked up
137   ///
138   /// The actual Entries for real directories/files are
139   /// owned by UniqueRealDirs/UniqueRealFiles above, while the Entries
140   /// for virtual directories/files are owned by
141   /// VirtualDirectoryEntries/VirtualFileEntries above.
142   ///
143   llvm::StringMap<DirectoryEntry*, llvm::BumpPtrAllocator> SeenDirEntries;
144 
145   /// \brief A cache that maps paths to file entries (either real or
146   /// virtual) we have looked up.
147   ///
148   /// \see SeenDirEntries
149   llvm::StringMap<FileEntry*, llvm::BumpPtrAllocator> SeenFileEntries;
150 
151   /// \brief The canonical names of directories.
152   llvm::DenseMap<const DirectoryEntry *, llvm::StringRef> CanonicalDirNames;
153 
154   /// \brief Storage for canonical names that we have computed.
155   llvm::BumpPtrAllocator CanonicalNameStorage;
156 
157   /// \brief Each FileEntry we create is assigned a unique ID #.
158   ///
159   unsigned NextFileUID;
160 
161   // Statistics.
162   unsigned NumDirLookups, NumFileLookups;
163   unsigned NumDirCacheMisses, NumFileCacheMisses;
164 
165   // Caching.
166   std::unique_ptr<FileSystemStatCache> StatCache;
167 
168   bool getStatValue(const char *Path, FileData &Data, bool isFile,
169                     std::unique_ptr<vfs::File> *F);
170 
171   /// Add all ancestors of the given path (pointing to either a file
172   /// or a directory) as virtual directories.
173   void addAncestorsAsVirtualDirs(StringRef Path);
174 
175 public:
176   FileManager(const FileSystemOptions &FileSystemOpts,
177               IntrusiveRefCntPtr<vfs::FileSystem> FS = nullptr);
178   ~FileManager();
179 
180   /// \brief Installs the provided FileSystemStatCache object within
181   /// the FileManager.
182   ///
183   /// Ownership of this object is transferred to the FileManager.
184   ///
185   /// \param statCache the new stat cache to install. Ownership of this
186   /// object is transferred to the FileManager.
187   ///
188   /// \param AtBeginning whether this new stat cache must be installed at the
189   /// beginning of the chain of stat caches. Otherwise, it will be added to
190   /// the end of the chain.
191   void addStatCache(std::unique_ptr<FileSystemStatCache> statCache,
192                     bool AtBeginning = false);
193 
194   /// \brief Removes the specified FileSystemStatCache object from the manager.
195   void removeStatCache(FileSystemStatCache *statCache);
196 
197   /// \brief Removes all FileSystemStatCache objects from the manager.
198   void clearStatCaches();
199 
200   /// \brief Lookup, cache, and verify the specified directory (real or
201   /// virtual).
202   ///
203   /// This returns NULL if the directory doesn't exist.
204   ///
205   /// \param CacheFailure If true and the file does not exist, we'll cache
206   /// the failure to find this file.
207   const DirectoryEntry *getDirectory(StringRef DirName,
208                                      bool CacheFailure = true);
209 
210   /// \brief Lookup, cache, and verify the specified file (real or
211   /// virtual).
212   ///
213   /// This returns NULL if the file doesn't exist.
214   ///
215   /// \param OpenFile if true and the file exists, it will be opened.
216   ///
217   /// \param CacheFailure If true and the file does not exist, we'll cache
218   /// the failure to find this file.
219   const FileEntry *getFile(StringRef Filename, bool OpenFile = false,
220                            bool CacheFailure = true);
221 
222   /// \brief Returns the current file system options
getFileSystemOpts()223   FileSystemOptions &getFileSystemOpts() { return FileSystemOpts; }
getFileSystemOpts()224   const FileSystemOptions &getFileSystemOpts() const { return FileSystemOpts; }
225 
getVirtualFileSystem()226   IntrusiveRefCntPtr<vfs::FileSystem> getVirtualFileSystem() const {
227     return FS;
228   }
229 
230   /// \brief Retrieve a file entry for a "virtual" file that acts as
231   /// if there were a file with the given name on disk.
232   ///
233   /// The file itself is not accessed.
234   const FileEntry *getVirtualFile(StringRef Filename, off_t Size,
235                                   time_t ModificationTime);
236 
237   /// \brief Open the specified file as a MemoryBuffer, returning a new
238   /// MemoryBuffer if successful, otherwise returning null.
239   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
240   getBufferForFile(const FileEntry *Entry, bool isVolatile = false,
241                    bool ShouldCloseOpenFile = true);
242   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
243   getBufferForFile(StringRef Filename);
244 
245   /// \brief Get the 'stat' information for the given \p Path.
246   ///
247   /// If the path is relative, it will be resolved against the WorkingDir of the
248   /// FileManager's FileSystemOptions.
249   ///
250   /// \returns false on success, true on error.
251   bool getNoncachedStatValue(StringRef Path,
252                              vfs::Status &Result);
253 
254   /// \brief Remove the real file \p Entry from the cache.
255   void invalidateCache(const FileEntry *Entry);
256 
257   /// \brief If path is not absolute and FileSystemOptions set the working
258   /// directory, the path is modified to be relative to the given
259   /// working directory.
260   /// \returns true if \c path changed.
261   bool FixupRelativePath(SmallVectorImpl<char> &path) const;
262 
263   /// Makes \c Path absolute taking into account FileSystemOptions and the
264   /// working directory option.
265   /// \returns true if \c Path changed to absolute.
266   bool makeAbsolutePath(SmallVectorImpl<char> &Path) const;
267 
268   /// \brief Produce an array mapping from the unique IDs assigned to each
269   /// file to the corresponding FileEntry pointer.
270   void GetUniqueIDMapping(
271                     SmallVectorImpl<const FileEntry *> &UIDToFiles) const;
272 
273   /// \brief Modifies the size and modification time of a previously created
274   /// FileEntry. Use with caution.
275   static void modifyFileEntry(FileEntry *File, off_t Size,
276                               time_t ModificationTime);
277 
278   /// \brief Retrieve the canonical name for a given directory.
279   ///
280   /// This is a very expensive operation, despite its results being cached,
281   /// and should only be used when the physical layout of the file system is
282   /// required, which is (almost) never.
283   StringRef getCanonicalName(const DirectoryEntry *Dir);
284 
285   void PrintStats() const;
286 };
287 
288 }  // end namespace clang
289 
290 #endif
291