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diff --git a/include/clang/Basic/FileManager.h b/include/clang/Basic/FileManager.h
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+//===--- FileManager.h - File System Probing and Caching --------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the FileManager interface.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_FILEMANAGER_H
+#define LLVM_CLANG_FILEMANAGER_H
+
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Config/config.h" // for mode_t
+#include <map>
+#include <set>
+#include <string>
+// FIXME: Enhance libsystem to support inode and other fields in stat.
+#include <sys/types.h>
+#include <sys/stat.h>
+
+namespace clang {
+class FileManager;
+  
+/// DirectoryEntry - Cached information about one directory on the disk.
+///
+class DirectoryEntry {
+  const char *Name;   // Name of the directory.
+  friend class FileManager;
+public:
+  DirectoryEntry() : Name(0) {}
+  const char *getName() const { return Name; } 
+};
+
+/// FileEntry - Cached information about one file on the disk.
+///
+class FileEntry {
+  const char *Name;           // Name of the file.
+  off_t Size;                 // File size in bytes.
+  time_t ModTime;             // Modification time of file.
+  const DirectoryEntry *Dir;  // Directory file lives in.
+  unsigned UID;               // A unique (small) ID for the file.
+  dev_t Device;               // ID for the device containing the file.
+  ino_t Inode;                // Inode number for the file.
+  mode_t FileMode;            // The file mode as returned by 'stat'.
+  friend class FileManager;
+public:
+  FileEntry(dev_t device, ino_t inode, mode_t m)
+    : Name(0), Device(device), Inode(inode), FileMode(m) {}
+  // Add a default constructor for use with llvm::StringMap
+  FileEntry() : Name(0), Device(0), Inode(0), FileMode(0) {}
+  
+  const char *getName() const { return Name; }
+  off_t getSize() const { return Size; }
+  unsigned getUID() const { return UID; }
+  ino_t getInode() const { return Inode; }
+  dev_t getDevice() const { return Device; }
+  time_t getModificationTime() const { return ModTime; }
+  mode_t getFileMode() const { return FileMode; }
+  
+  /// getDir - Return the directory the file lives in.
+  ///
+  const DirectoryEntry *getDir() const { return Dir; }
+  
+  bool operator<(const FileEntry& RHS) const {
+    return Device < RHS.Device || (Device == RHS.Device && Inode < RHS.Inode);
+  }
+};
+
+// FIXME: This is a lightweight shim that is used by FileManager to cache
+//  'stat' system calls.  We will use it with PTH to identify if caching
+//  stat calls in PTH files is a performance win.
+class StatSysCallCache {
+public:
+  virtual ~StatSysCallCache() {}
+  virtual int stat(const char *path, struct stat *buf) = 0;
+};
+
+/// \brief A stat listener that can be used by FileManager to keep
+/// track of the results of stat() calls that occur throughout the
+/// execution of the front end.
+class MemorizeStatCalls : public StatSysCallCache {
+public:
+  /// \brief The result of a stat() call. 
+  ///
+  /// The first member is the result of calling stat(). If stat()
+  /// found something, the second member is a copy of the stat
+  /// structure.
+  typedef std::pair<int, struct stat> StatResult;
+
+  /// \brief The set of stat() calls that have been 
+  llvm::StringMap<StatResult, llvm::BumpPtrAllocator> StatCalls;
+
+  typedef llvm::StringMap<StatResult, llvm::BumpPtrAllocator>::const_iterator
+    iterator;
+  
+  iterator begin() const { return StatCalls.begin(); }
+  iterator end() const { return StatCalls.end(); }
+
+  virtual int stat(const char *path, struct stat *buf);
+};
+
+/// FileManager - 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 {
+
+  class UniqueDirContainer;
+  class UniqueFileContainer;
+
+  /// UniqueDirs/UniqueFiles - Cache for existing directories/files.
+  ///
+  UniqueDirContainer &UniqueDirs;
+  UniqueFileContainer &UniqueFiles;
+
+  /// DirEntries/FileEntries - This is a cache of directory/file entries we have
+  /// looked up.  The actual Entry is owned by UniqueFiles/UniqueDirs above.
+  ///
+  llvm::StringMap<DirectoryEntry*, llvm::BumpPtrAllocator> DirEntries;
+  llvm::StringMap<FileEntry*, llvm::BumpPtrAllocator> FileEntries;
+  
+  /// NextFileUID - Each FileEntry we create is assigned a unique ID #.
+  ///
+  unsigned NextFileUID;
+  
+  // Statistics.
+  unsigned NumDirLookups, NumFileLookups;
+  unsigned NumDirCacheMisses, NumFileCacheMisses;
+  
+  // Caching.
+  llvm::OwningPtr<StatSysCallCache> StatCache;
+
+  int stat_cached(const char* path, struct stat* buf) {
+    return StatCache.get() ? StatCache->stat(path, buf) : stat(path, buf);
+  }
+  
+public:
+  FileManager();
+  ~FileManager();
+
+  /// setStatCache - Installs the provided StatSysCallCache object within
+  ///  the FileManager.  Ownership of this object is transferred to the
+  ///  FileManager.
+  void setStatCache(StatSysCallCache *statCache) {
+    StatCache.reset(statCache);
+  }
+  
+  /// getDirectory - Lookup, cache, and verify the specified directory.  This
+  /// returns null if the directory doesn't exist.
+  /// 
+  const DirectoryEntry *getDirectory(const std::string &Filename) {
+    return getDirectory(&Filename[0], &Filename[0] + Filename.size());
+  }
+  const DirectoryEntry *getDirectory(const char *FileStart,const char *FileEnd);
+  
+  /// getFile - Lookup, cache, and verify the specified file.  This returns null
+  /// if the file doesn't exist.
+  /// 
+  const FileEntry *getFile(const std::string &Filename) {
+    return getFile(&Filename[0], &Filename[0] + Filename.size());
+  }
+  const FileEntry *getFile(const char *FilenameStart,
+                           const char *FilenameEnd);
+  
+  void PrintStats() const;
+};
+
+}  // end namespace clang
+
+#endif