text: //===--- FileManager.h - File System Probing and Caching --------*- C++ -*-===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  ///
  /// \file
  /// Defines the clang::FileManager interface and associated types.
  ///
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CLANG_BASIC_FILEMANAGER_H
  #define LLVM_CLANG_BASIC_FILEMANAGER_H
  
  #include "clang/Basic/DirectoryEntry.h"
  #include "clang/Basic/FileEntry.h"
  #include "clang/Basic/FileSystemOptions.h"
  #include "clang/Basic/LLVM.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/IntrusiveRefCntPtr.h"
  #include "llvm/ADT/PointerUnion.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringMap.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Support/Allocator.h"
  #include "llvm/Support/ErrorOr.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/VirtualFileSystem.h"
  #include <ctime>
  #include <map>
  #include <memory>
  #include <string>
  
  namespace llvm {
  
  class MemoryBuffer;
  
  } // end namespace llvm
  
  namespace clang {
  
  class FileSystemStatCache;
  
  /// Implements support for file system lookup, file system caching,
  /// and directory search management.
  ///
  /// This also handles more advanced properties, such as uniquing files based
  /// on "inode", so that a file with two names (e.g. symlinked) will be treated
  /// as a single file.
  ///
  class FileManager : public RefCountedBase<FileManager> {
    IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS;
    FileSystemOptions FileSystemOpts;
  
    /// Cache for existing real directories.
    std::map<llvm::sys::fs::UniqueID, DirectoryEntry> UniqueRealDirs;
  
    /// Cache for existing real files.
    std::map<llvm::sys::fs::UniqueID, FileEntry> UniqueRealFiles;
  
    /// The virtual directories that we have allocated.
    ///
    /// For each virtual file (e.g. foo/bar/baz.cpp), we add all of its parent
    /// directories (foo/ and foo/bar/) here.
    SmallVector<std::unique_ptr<DirectoryEntry>, 4> VirtualDirectoryEntries;
    /// The virtual files that we have allocated.
    SmallVector<std::unique_ptr<FileEntry>, 4> VirtualFileEntries;
  
    /// A set of files that bypass the maps and uniquing.  They can have
    /// conflicting filenames.
    SmallVector<std::unique_ptr<FileEntry>, 0> BypassFileEntries;
  
    /// A cache that maps paths to directory entries (either real or
    /// virtual) we have looked up, or an error that occurred when we looked up
    /// the directory.
    ///
    /// The actual Entries for real directories/files are
    /// owned by UniqueRealDirs/UniqueRealFiles above, while the Entries
    /// for virtual directories/files are owned by
    /// VirtualDirectoryEntries/VirtualFileEntries above.
    ///
    llvm::StringMap<llvm::ErrorOr<DirectoryEntry &>, llvm::BumpPtrAllocator>
    SeenDirEntries;
  
    /// A cache that maps paths to file entries (either real or
    /// virtual) we have looked up, or an error that occurred when we looked up
    /// the file.
    ///
    /// \see SeenDirEntries
    llvm::StringMap<llvm::ErrorOr<FileEntryRef::MapValue>, llvm::BumpPtrAllocator>
        SeenFileEntries;
  
    /// A mirror of SeenFileEntries to give fake answers for getBypassFile().
    ///
    /// Don't bother hooking up a BumpPtrAllocator. This should be rarely used,
    /// and only on error paths.
    std::unique_ptr<llvm::StringMap<llvm::ErrorOr<FileEntryRef::MapValue>>>
        SeenBypassFileEntries;
  
    /// The canonical names of files and directories .
    llvm::DenseMap<const void *, llvm::StringRef> CanonicalNames;
  
    /// Storage for canonical names that we have computed.
    llvm::BumpPtrAllocator CanonicalNameStorage;
  
    /// Each FileEntry we create is assigned a unique ID #.
    ///
    unsigned NextFileUID;
  
    // Caching.
    std::unique_ptr<FileSystemStatCache> StatCache;
  
    std::error_code getStatValue(StringRef Path, llvm::vfs::Status &Status,
                                 bool isFile,
                                 std::unique_ptr<llvm::vfs::File> *F);
  
    /// Add all ancestors of the given path (pointing to either a file
    /// or a directory) as virtual directories.
    void addAncestorsAsVirtualDirs(StringRef Path);
  
    /// Fills the RealPathName in file entry.
    void fillRealPathName(FileEntry *UFE, llvm::StringRef FileName);
  
  public:
    /// Construct a file manager, optionally with a custom VFS.
    ///
    /// \param FS if non-null, the VFS to use.  Otherwise uses
    /// llvm::vfs::getRealFileSystem().
    FileManager(const FileSystemOptions &FileSystemOpts,
                IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS = nullptr);
    ~FileManager();
  
    /// Installs the provided FileSystemStatCache object within
    /// the FileManager.
    ///
    /// Ownership of this object is transferred to the FileManager.
    ///
    /// \param statCache the new stat cache to install. Ownership of this
    /// object is transferred to the FileManager.
    void setStatCache(std::unique_ptr<FileSystemStatCache> statCache);
  
    /// Removes the FileSystemStatCache object from the manager.
    void clearStatCache();
  
    /// Returns the number of unique real file entries cached by the file manager.
    size_t getNumUniqueRealFiles() const { return UniqueRealFiles.size(); }
  
    /// Lookup, cache, and verify the specified directory (real or
    /// virtual).
    ///
    /// This returns a \c std::error_code if there was an error reading the
    /// directory. On success, returns the reference to the directory entry
    /// together with the exact path that was used to access a file by a
    /// particular call to getDirectoryRef.
    ///
    /// \param CacheFailure If true and the file does not exist, we'll cache
    /// the failure to find this file.
    llvm::Expected<DirectoryEntryRef> getDirectoryRef(StringRef DirName,
                                                      bool CacheFailure = true);
  
    /// Get a \c DirectoryEntryRef if it exists, without doing anything on error.
    llvm::Optional<DirectoryEntryRef>
    getOptionalDirectoryRef(StringRef DirName, bool CacheFailure = true) {
      return llvm::expectedToOptional(getDirectoryRef(DirName, CacheFailure));
    }
  
    /// Lookup, cache, and verify the specified directory (real or
    /// virtual).
    ///
    /// This function is deprecated and will be removed at some point in the
    /// future, new clients should use
    ///  \c getDirectoryRef.
    ///
    /// This returns a \c std::error_code if there was an error reading the
    /// directory. If there is no error, the DirectoryEntry is guaranteed to be
    /// non-NULL.
    ///
    /// \param CacheFailure If true and the file does not exist, we'll cache
    /// the failure to find this file.
    llvm::ErrorOr<const DirectoryEntry *>
    getDirectory(StringRef DirName, bool CacheFailure = true);
  
    /// Lookup, cache, and verify the specified file (real or
    /// virtual).
    ///
    /// This function is deprecated and will be removed at some point in the
    /// future, new clients should use
    ///  \c getFileRef.
    ///
    /// This returns a \c std::error_code if there was an error loading the file.
    /// If there is no error, the FileEntry is guaranteed to be non-NULL.
    ///
    /// \param OpenFile if true and the file exists, it will be opened.
    ///
    /// \param CacheFailure If true and the file does not exist, we'll cache
    /// the failure to find this file.
    llvm::ErrorOr<const FileEntry *>
    getFile(StringRef Filename, bool OpenFile = false, bool CacheFailure = true);
  
    /// Lookup, cache, and verify the specified file (real or virtual). Return the
    /// reference to the file entry together with the exact path that was used to
    /// access a file by a particular call to getFileRef. If the underlying VFS is
    /// a redirecting VFS that uses external file names, the returned FileEntryRef
    /// will use the external name instead of the filename that was passed to this
    /// method.
    ///
    /// This returns a \c std::error_code if there was an error loading the file,
    /// or a \c FileEntryRef otherwise.
    ///
    /// \param OpenFile if true and the file exists, it will be opened.
    ///
    /// \param CacheFailure If true and the file does not exist, we'll cache
    /// the failure to find this file.
    llvm::Expected<FileEntryRef> getFileRef(StringRef Filename,
                                            bool OpenFile = false,
                                            bool CacheFailure = true);
  
    /// Get a FileEntryRef if it exists, without doing anything on error.
    llvm::Optional<FileEntryRef> getOptionalFileRef(StringRef Filename,
                                                    bool OpenFile = false,
                                                    bool CacheFailure = true) {
      return llvm::expectedToOptional(
          getFileRef(Filename, OpenFile, CacheFailure));
    }
  
    /// Returns the current file system options
    FileSystemOptions &getFileSystemOpts() { return FileSystemOpts; }
    const FileSystemOptions &getFileSystemOpts() const { return FileSystemOpts; }
  
    llvm::vfs::FileSystem &getVirtualFileSystem() const { return *FS; }
  
    void setVirtualFileSystem(IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS) {
      this->FS = std::move(FS);
    }
  
    /// Retrieve a file entry for a "virtual" file that acts as
    /// if there were a file with the given name on disk.
    ///
    /// The file itself is not accessed.
    FileEntryRef getVirtualFileRef(StringRef Filename, off_t Size,
                                   time_t ModificationTime);
  
    const FileEntry *getVirtualFile(StringRef Filename, off_t Size,
                                    time_t ModificationTime);
  
    /// Retrieve a FileEntry that bypasses VFE, which is expected to be a virtual
    /// file entry, to access the real file.  The returned FileEntry will have
    /// the same filename as FE but a different identity and its own stat.
    ///
    /// This should be used only for rare error recovery paths because it
    /// bypasses all mapping and uniquing, blindly creating a new FileEntry.
    /// There is no attempt to deduplicate these; if you bypass the same file
    /// twice, you get two new file entries.
    llvm::Optional<FileEntryRef> getBypassFile(FileEntryRef VFE);
  
    /// Open the specified file as a MemoryBuffer, returning a new
    /// MemoryBuffer if successful, otherwise returning null.
    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
    getBufferForFile(const FileEntry *Entry, bool isVolatile = false,
                     bool RequiresNullTerminator = true);
    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
    getBufferForFile(StringRef Filename, bool isVolatile = false,
                     bool RequiresNullTerminator = true) {
      return getBufferForFileImpl(Filename, /*FileSize=*/-1, isVolatile,
                                  RequiresNullTerminator);
    }
  
  private:
    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
    getBufferForFileImpl(StringRef Filename, int64_t FileSize, bool isVolatile,
                         bool RequiresNullTerminator);
  
  public:
    /// Get the 'stat' information for the given \p Path.
    ///
    /// If the path is relative, it will be resolved against the WorkingDir of the
    /// FileManager's FileSystemOptions.
    ///
    /// \returns a \c std::error_code describing an error, if there was one
    std::error_code getNoncachedStatValue(StringRef Path,
                                          llvm::vfs::Status &Result);
  
    /// If path is not absolute and FileSystemOptions set the working
    /// directory, the path is modified to be relative to the given
    /// working directory.
    /// \returns true if \c path changed.
    bool FixupRelativePath(SmallVectorImpl<char> &path) const;
  
    /// Makes \c Path absolute taking into account FileSystemOptions and the
    /// working directory option.
    /// \returns true if \c Path changed to absolute.
    bool makeAbsolutePath(SmallVectorImpl<char> &Path) const;
  
    /// Produce an array mapping from the unique IDs assigned to each
    /// file to the corresponding FileEntry pointer.
    void GetUniqueIDMapping(
                      SmallVectorImpl<const FileEntry *> &UIDToFiles) const;
  
    /// Retrieve the canonical name for a given directory.
    ///
    /// This is a very expensive operation, despite its results being cached,
    /// and should only be used when the physical layout of the file system is
    /// required, which is (almost) never.
    StringRef getCanonicalName(const DirectoryEntry *Dir);
  
    /// Retrieve the canonical name for a given file.
    ///
    /// This is a very expensive operation, despite its results being cached,
    /// and should only be used when the physical layout of the file system is
    /// required, which is (almost) never.
    StringRef getCanonicalName(const FileEntry *File);
  
    void PrintStats() const;
  };
  
  } // end namespace clang
  
  #endif // LLVM_CLANG_BASIC_FILEMANAGER_H
  