text: //===--- FileManager.cpp - File System Probing and Caching ----------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file implements the FileManager interface.
  //
  //===----------------------------------------------------------------------===//
  //
  // TODO: This should index all interesting directories with dirent calls.
  //  getdirentries ?
  //  opendir/readdir_r/closedir ?
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Basic/FileManager.h"
  #include "clang/Basic/FileSystemStatCache.h"
  #include "clang/Frontend/PCHContainerOperations.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/Config/llvm-config.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/MemoryBuffer.h"
  #include "llvm/Support/Path.h"
  #include "llvm/Support/raw_ostream.h"
  #include <map>
  #include <set>
  #include <string>
  #include <system_error>
  
  using namespace clang;
  
  /// NON_EXISTENT_DIR - A special value distinct from null that is used to
  /// represent a dir name that doesn't exist on the disk.
  #define NON_EXISTENT_DIR reinterpret_cast<DirectoryEntry*>((intptr_t)-1)
  
  /// NON_EXISTENT_FILE - A special value distinct from null that is used to
  /// represent a filename that doesn't exist on the disk.
  #define NON_EXISTENT_FILE reinterpret_cast<FileEntry*>((intptr_t)-1)
  
  //===----------------------------------------------------------------------===//
  // Common logic.
  //===----------------------------------------------------------------------===//
  
  FileManager::FileManager(const FileSystemOptions &FSO,
                           IntrusiveRefCntPtr<vfs::FileSystem> FS)
    : FS(FS), FileSystemOpts(FSO),
      SeenDirEntries(64), SeenFileEntries(64), NextFileUID(0) {
    NumDirLookups = NumFileLookups = 0;
    NumDirCacheMisses = NumFileCacheMisses = 0;
  
    // If the caller doesn't provide a virtual file system, just grab the real
    // file system.
    if (!FS)
      this->FS = vfs::getRealFileSystem();
  }
  
  FileManager::~FileManager() {
    for (unsigned i = 0, e = VirtualFileEntries.size(); i != e; ++i)
      delete VirtualFileEntries[i];
    for (unsigned i = 0, e = VirtualDirectoryEntries.size(); i != e; ++i)
      delete VirtualDirectoryEntries[i];
  }
  
  void FileManager::addStatCache(std::unique_ptr<FileSystemStatCache> statCache,
                                 bool AtBeginning) {
    assert(statCache && "No stat cache provided?");
    if (AtBeginning || !StatCache.get()) {
      statCache->setNextStatCache(std::move(StatCache));
      StatCache = std::move(statCache);
      return;
    }
    
    FileSystemStatCache *LastCache = StatCache.get();
    while (LastCache->getNextStatCache())
      LastCache = LastCache->getNextStatCache();
  
    LastCache->setNextStatCache(std::move(statCache));
  }
  
  void FileManager::removeStatCache(FileSystemStatCache *statCache) {
    if (!statCache)
      return;
    
    if (StatCache.get() == statCache) {
      // This is the first stat cache.
      StatCache = StatCache->takeNextStatCache();
      return;
    }
    
    // Find the stat cache in the list.
    FileSystemStatCache *PrevCache = StatCache.get();
    while (PrevCache && PrevCache->getNextStatCache() != statCache)
      PrevCache = PrevCache->getNextStatCache();
    
    assert(PrevCache && "Stat cache not found for removal");
    PrevCache->setNextStatCache(statCache->takeNextStatCache());
  }
  
  void FileManager::clearStatCaches() {
    StatCache.reset();
  }
  
  /// \brief Retrieve the directory that the given file name resides in.
  /// Filename can point to either a real file or a virtual file.
  static const DirectoryEntry *getDirectoryFromFile(FileManager &FileMgr,
                                                    StringRef Filename,
                                                    bool CacheFailure) {
    if (Filename.empty())
      return nullptr;
  
    if (llvm::sys::path::is_separator(Filename[Filename.size() - 1]))
      return nullptr; // If Filename is a directory.
  
    StringRef DirName = llvm::sys::path::parent_path(Filename);
    // Use the current directory if file has no path component.
    if (DirName.empty())
      DirName = ".";
  
    return FileMgr.getDirectory(DirName, CacheFailure);
  }
  
  /// Add all ancestors of the given path (pointing to either a file or
  /// a directory) as virtual directories.
  void FileManager::addAncestorsAsVirtualDirs(StringRef Path) {
    StringRef DirName = llvm::sys::path::parent_path(Path);
    if (DirName.empty())
      return;
  
    auto &NamedDirEnt =
        *SeenDirEntries.insert(std::make_pair(DirName, nullptr)).first;
  
    // When caching a virtual directory, we always cache its ancestors
    // at the same time.  Therefore, if DirName is already in the cache,
    // we don't need to recurse as its ancestors must also already be in
    // the cache.
    if (NamedDirEnt.second)
      return;
  
    // Add the virtual directory to the cache.
    DirectoryEntry *UDE = new DirectoryEntry;
    UDE->Name = NamedDirEnt.first().data();
    NamedDirEnt.second = UDE;
    VirtualDirectoryEntries.push_back(UDE);
  
    // Recursively add the other ancestors.
    addAncestorsAsVirtualDirs(DirName);
  }
  
  const DirectoryEntry *FileManager::getDirectory(StringRef DirName,
                                                  bool CacheFailure) {
    // stat doesn't like trailing separators except for root directory.
    // At least, on Win32 MSVCRT, stat() cannot strip trailing '/'.
    // (though it can strip '\\')
    if (DirName.size() > 1 &&
        DirName != llvm::sys::path::root_path(DirName) &&
        llvm::sys::path::is_separator(DirName.back()))
      DirName = DirName.substr(0, DirName.size()-1);
  #ifdef LLVM_ON_WIN32
    // Fixing a problem with "clang C:test.c" on Windows.
    // Stat("C:") does not recognize "C:" as a valid directory
    std::string DirNameStr;
    if (DirName.size() > 1 && DirName.back() == ':' &&
        DirName.equals_lower(llvm::sys::path::root_name(DirName))) {
      DirNameStr = DirName.str() + '.';
      DirName = DirNameStr;
    }
  #endif
  
    ++NumDirLookups;
    auto &NamedDirEnt =
        *SeenDirEntries.insert(std::make_pair(DirName, nullptr)).first;
  
    // See if there was already an entry in the map.  Note that the map
    // contains both virtual and real directories.
    if (NamedDirEnt.second)
      return NamedDirEnt.second == NON_EXISTENT_DIR ? nullptr
                                                    : NamedDirEnt.second;
  
    ++NumDirCacheMisses;
  
    // By default, initialize it to invalid.
    NamedDirEnt.second = NON_EXISTENT_DIR;
  
    // Get the null-terminated directory name as stored as the key of the
    // SeenDirEntries map.
    const char *InterndDirName = NamedDirEnt.first().data();
  
    // Check to see if the directory exists.
    FileData Data;
    if (getStatValue(InterndDirName, Data, false, nullptr /*directory lookup*/)) {
      // There's no real directory at the given path.
      if (!CacheFailure)
        SeenDirEntries.erase(DirName);
      return nullptr;
    }
  
    // It exists.  See if we have already opened a directory with the
    // same inode (this occurs on Unix-like systems when one dir is
    // symlinked to another, for example) or the same path (on
    // Windows).
    DirectoryEntry &UDE = UniqueRealDirs[Data.UniqueID];
  
    NamedDirEnt.second = &UDE;
    if (!UDE.getName()) {
      // We don't have this directory yet, add it.  We use the string
      // key from the SeenDirEntries map as the string.
      UDE.Name  = InterndDirName;
    }
  
    return &UDE;
  }
  
  const FileEntry *FileManager::getFile(StringRef Filename, bool openFile,
                                        bool CacheFailure) {
    ++NumFileLookups;
  
    // See if there is already an entry in the map.
    auto &NamedFileEnt =
        *SeenFileEntries.insert(std::make_pair(Filename, nullptr)).first;
  
    // See if there is already an entry in the map.
    if (NamedFileEnt.second)
      return NamedFileEnt.second == NON_EXISTENT_FILE ? nullptr
                                                      : NamedFileEnt.second;
  
    ++NumFileCacheMisses;
  
    // By default, initialize it to invalid.
    NamedFileEnt.second = NON_EXISTENT_FILE;
  
    // Get the null-terminated file name as stored as the key of the
    // SeenFileEntries map.
    const char *InterndFileName = NamedFileEnt.first().data();
  
    // Look up the directory for the file.  When looking up something like
    // sys/foo.h we'll discover all of the search directories that have a 'sys'
    // subdirectory.  This will let us avoid having to waste time on known-to-fail
    // searches when we go to find sys/bar.h, because all the search directories
    // without a 'sys' subdir will get a cached failure result.
    const DirectoryEntry *DirInfo = getDirectoryFromFile(*this, Filename,
                                                         CacheFailure);
    if (DirInfo == nullptr) { // Directory doesn't exist, file can't exist.
      if (!CacheFailure)
        SeenFileEntries.erase(Filename);
  
      return nullptr;
    }
    
    // FIXME: Use the directory info to prune this, before doing the stat syscall.
    // FIXME: This will reduce the # syscalls.
  
    // Nope, there isn't.  Check to see if the file exists.
    std::unique_ptr<vfs::File> F;
    FileData Data;
    if (getStatValue(InterndFileName, Data, true, openFile ? &F : nullptr)) {
      // There's no real file at the given path.
      if (!CacheFailure)
        SeenFileEntries.erase(Filename);
  
      return nullptr;
    }
  
    assert((openFile || !F) && "undesired open file");
  
    // It exists.  See if we have already opened a file with the same inode.
    // This occurs when one dir is symlinked to another, for example.
    FileEntry &UFE = UniqueRealFiles[Data.UniqueID];
  
    NamedFileEnt.second = &UFE;
  
    // If the name returned by getStatValue is different than Filename, re-intern
    // the name.
    if (Data.Name != Filename) {
      auto &NamedFileEnt =
          *SeenFileEntries.insert(std::make_pair(Data.Name, nullptr)).first;
      if (!NamedFileEnt.second)
        NamedFileEnt.second = &UFE;
      else
        assert(NamedFileEnt.second == &UFE &&
               "filename from getStatValue() refers to wrong file");
      InterndFileName = NamedFileEnt.first().data();
    }
  
    if (UFE.isValid()) { // Already have an entry with this inode, return it.
  
      // FIXME: this hack ensures that if we look up a file by a virtual path in
      // the VFS that the getDir() will have the virtual path, even if we found
      // the file by a 'real' path first. This is required in order to find a
      // module's structure when its headers/module map are mapped in the VFS.
      // We should remove this as soon as we can properly support a file having
      // multiple names.
      if (DirInfo != UFE.Dir && Data.IsVFSMapped)
        UFE.Dir = DirInfo;
  
      // Always update the name to use the last name by which a file was accessed.
      // FIXME: Neither this nor always using the first name is correct; we want
      // to switch towards a design where we return a FileName object that
      // encapsulates both the name by which the file was accessed and the
      // corresponding FileEntry.
      UFE.Name = InterndFileName;
  
      return &UFE;
    }
  
    // Otherwise, we don't have this file yet, add it.
    UFE.Name    = InterndFileName;
    UFE.Size = Data.Size;
    UFE.ModTime = Data.ModTime;
    UFE.Dir     = DirInfo;
    UFE.UID     = NextFileUID++;
    UFE.UniqueID = Data.UniqueID;
    UFE.IsNamedPipe = Data.IsNamedPipe;
    UFE.InPCH = Data.InPCH;
    UFE.File = std::move(F);
    UFE.IsValid = true;
    return &UFE;
  }
  
  const FileEntry *
  FileManager::getVirtualFile(StringRef Filename, off_t Size,
                              time_t ModificationTime) {
    ++NumFileLookups;
  
    // See if there is already an entry in the map.
    auto &NamedFileEnt =
        *SeenFileEntries.insert(std::make_pair(Filename, nullptr)).first;
  
    // See if there is already an entry in the map.
    if (NamedFileEnt.second && NamedFileEnt.second != NON_EXISTENT_FILE)
      return NamedFileEnt.second;
  
    ++NumFileCacheMisses;
  
    // By default, initialize it to invalid.
    NamedFileEnt.second = NON_EXISTENT_FILE;
  
    addAncestorsAsVirtualDirs(Filename);
    FileEntry *UFE = nullptr;
  
    // Now that all ancestors of Filename are in the cache, the
    // following call is guaranteed to find the DirectoryEntry from the
    // cache.
    const DirectoryEntry *DirInfo = getDirectoryFromFile(*this, Filename,
                                                         /*CacheFailure=*/true);
    assert(DirInfo &&
           "The directory of a virtual file should already be in the cache.");
  
    // Check to see if the file exists. If so, drop the virtual file
    FileData Data;
    const char *InterndFileName = NamedFileEnt.first().data();
    if (getStatValue(InterndFileName, Data, true, nullptr) == 0) {
      Data.Size = Size;
      Data.ModTime = ModificationTime;
      UFE = &UniqueRealFiles[Data.UniqueID];
  
      NamedFileEnt.second = UFE;
  
      // If we had already opened this file, close it now so we don't
      // leak the descriptor. We're not going to use the file
      // descriptor anyway, since this is a virtual file.
      if (UFE->File)
        UFE->closeFile();
  
      // If we already have an entry with this inode, return it.
      if (UFE->isValid())
        return UFE;
  
      UFE->UniqueID = Data.UniqueID;
      UFE->IsNamedPipe = Data.IsNamedPipe;
      UFE->InPCH = Data.InPCH;
    }
  
    if (!UFE) {
      UFE = new FileEntry();
      VirtualFileEntries.push_back(UFE);
      NamedFileEnt.second = UFE;
    }
  
    UFE->Name    = InterndFileName;
    UFE->Size    = Size;
    UFE->ModTime = ModificationTime;
    UFE->Dir     = DirInfo;
    UFE->UID     = NextFileUID++;
    UFE->File.reset();
    return UFE;
  }
  
  void FileManager::FixupRelativePath(SmallVectorImpl<char> &path) const {
    StringRef pathRef(path.data(), path.size());
  
    if (FileSystemOpts.WorkingDir.empty() 
        || llvm::sys::path::is_absolute(pathRef))
      return;
  
    SmallString<128> NewPath(FileSystemOpts.WorkingDir);
    llvm::sys::path::append(NewPath, pathRef);
    path = NewPath;
  }
  
  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
  FileManager::getBufferForFile(const FileEntry *Entry, bool isVolatile,
                                bool ShouldCloseOpenFile) {
    uint64_t FileSize = Entry->getSize();
    // If there's a high enough chance that the file have changed since we
    // got its size, force a stat before opening it.
    if (isVolatile)
      FileSize = -1;
  
    const char *Filename = Entry->getName();
    // If the file is already open, use the open file descriptor.
    if (Entry->File) {
      auto Result =
          Entry->File->getBuffer(Filename, FileSize,
                                 /*RequiresNullTerminator=*/true, isVolatile);
      // FIXME: we need a set of APIs that can make guarantees about whether a
      // FileEntry is open or not.
      if (ShouldCloseOpenFile)
        Entry->closeFile();
      return Result;
    }
  
    // Otherwise, open the file.
  
    if (FileSystemOpts.WorkingDir.empty())
      return FS->getBufferForFile(Filename, FileSize,
                                  /*RequiresNullTerminator=*/true, isVolatile);
  
    SmallString<128> FilePath(Entry->getName());
    FixupRelativePath(FilePath);
    return FS->getBufferForFile(FilePath, FileSize,
                                /*RequiresNullTerminator=*/true, isVolatile);
  }
  
  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
  FileManager::getBufferForFile(StringRef Filename) {
    if (FileSystemOpts.WorkingDir.empty())
      return FS->getBufferForFile(Filename);
  
    SmallString<128> FilePath(Filename);
    FixupRelativePath(FilePath);
    return FS->getBufferForFile(FilePath.c_str());
  }
  
  /// getStatValue - Get the 'stat' information for the specified path,
  /// using the cache to accelerate it if possible.  This returns true
  /// if the path points to a virtual file or does not exist, or returns
  /// false if it's an existent real file.  If FileDescriptor is NULL,
  /// do directory look-up instead of file look-up.
  bool FileManager::getStatValue(const char *Path, FileData &Data, bool isFile,
                                 std::unique_ptr<vfs::File> *F) {
    // FIXME: FileSystemOpts shouldn't be passed in here, all paths should be
    // absolute!
    if (FileSystemOpts.WorkingDir.empty())
      return FileSystemStatCache::get(Path, Data, isFile, F,StatCache.get(), *FS);
  
    SmallString<128> FilePath(Path);
    FixupRelativePath(FilePath);
  
    return FileSystemStatCache::get(FilePath.c_str(), Data, isFile, F,
                                    StatCache.get(), *FS);
  }
  
  bool FileManager::getNoncachedStatValue(StringRef Path,
                                          vfs::Status &Result) {
    SmallString<128> FilePath(Path);
    FixupRelativePath(FilePath);
  
    llvm::ErrorOr<vfs::Status> S = FS->status(FilePath.c_str());
    if (!S)
      return true;
    Result = *S;
    return false;
  }
  
  void FileManager::invalidateCache(const FileEntry *Entry) {
    assert(Entry && "Cannot invalidate a NULL FileEntry");
  
    SeenFileEntries.erase(Entry->getName());
  
    // FileEntry invalidation should not block future optimizations in the file
    // caches. Possible alternatives are cache truncation (invalidate last N) or
    // invalidation of the whole cache.
    UniqueRealFiles.erase(Entry->getUniqueID());
  }
  
  
  void FileManager::GetUniqueIDMapping(
                     SmallVectorImpl<const FileEntry *> &UIDToFiles) const {
    UIDToFiles.clear();
    UIDToFiles.resize(NextFileUID);
    
    // Map file entries
    for (llvm::StringMap<FileEntry*, llvm::BumpPtrAllocator>::const_iterator
           FE = SeenFileEntries.begin(), FEEnd = SeenFileEntries.end();
         FE != FEEnd; ++FE)
      if (FE->getValue() && FE->getValue() != NON_EXISTENT_FILE)
        UIDToFiles[FE->getValue()->getUID()] = FE->getValue();
    
    // Map virtual file entries
    for (SmallVectorImpl<FileEntry *>::const_iterator
           VFE = VirtualFileEntries.begin(), VFEEnd = VirtualFileEntries.end();
         VFE != VFEEnd; ++VFE)
      if (*VFE && *VFE != NON_EXISTENT_FILE)
        UIDToFiles[(*VFE)->getUID()] = *VFE;
  }
  
  void FileManager::modifyFileEntry(FileEntry *File,
                                    off_t Size, time_t ModificationTime) {
    File->Size = Size;
    File->ModTime = ModificationTime;
  }
  
  /// Remove '.' path components from the given absolute path.
  /// \return \c true if any changes were made.
  // FIXME: Move this to llvm::sys::path.
  bool FileManager::removeDotPaths(SmallVectorImpl<char> &Path) {
    using namespace llvm::sys;
  
    SmallVector<StringRef, 16> ComponentStack;
    StringRef P(Path.data(), Path.size());
  
    // Skip the root path, then look for traversal in the components.
    StringRef Rel = path::relative_path(P);
    bool AnyDots = false;
    for (StringRef C : llvm::make_range(path::begin(Rel), path::end(Rel))) {
      if (C == ".") {
        AnyDots = true;
        continue;
      }
      ComponentStack.push_back(C);
    }
  
    if (!AnyDots)
      return false;
  
    SmallString<256> Buffer = path::root_path(P);
    for (StringRef C : ComponentStack)
      path::append(Buffer, C);
  
    Path.swap(Buffer);
    return true;
  }
  
  StringRef FileManager::getCanonicalName(const DirectoryEntry *Dir) {
    // FIXME: use llvm::sys::fs::canonical() when it gets implemented
    llvm::DenseMap<const DirectoryEntry *, llvm::StringRef>::iterator Known
      = CanonicalDirNames.find(Dir);
    if (Known != CanonicalDirNames.end())
      return Known->second;
  
    StringRef CanonicalName(Dir->getName());
  
  #ifdef LLVM_ON_UNIX
    char CanonicalNameBuf[PATH_MAX];
    if (realpath(Dir->getName(), CanonicalNameBuf)) {
      unsigned Len = strlen(CanonicalNameBuf);
      char *Mem = static_cast<char *>(CanonicalNameStorage.Allocate(Len, 1));
      memcpy(Mem, CanonicalNameBuf, Len);
      CanonicalName = StringRef(Mem, Len);
    }
  #else
    SmallString<256> CanonicalNameBuf(CanonicalName);
    llvm::sys::fs::make_absolute(CanonicalNameBuf);
    llvm::sys::path::native(CanonicalNameBuf);
    removeDotPaths(CanonicalNameBuf);
  #endif
  
    CanonicalDirNames.insert(std::make_pair(Dir, CanonicalName));
    return CanonicalName;
  }
  
  void FileManager::PrintStats() const {
    llvm::errs() << "\n*** File Manager Stats:\n";
    llvm::errs() << UniqueRealFiles.size() << " real files found, "
                 << UniqueRealDirs.size() << " real dirs found.\n";
    llvm::errs() << VirtualFileEntries.size() << " virtual files found, "
                 << VirtualDirectoryEntries.size() << " virtual dirs found.\n";
    llvm::errs() << NumDirLookups << " dir lookups, "
                 << NumDirCacheMisses << " dir cache misses.\n";
    llvm::errs() << NumFileLookups << " file lookups, "
                 << NumFileCacheMisses << " file cache misses.\n";
  
    //llvm::errs() << PagesMapped << BytesOfPagesMapped << FSLookups;
  }
  
  // Virtual destructors for abstract base classes that need live in Basic.
  PCHContainerWriter::~PCHContainerWriter() {}
  PCHContainerReader::~PCHContainerReader() {}
  