llvm/lib/Support/VirtualFileSystem.cpp

   1 //===- VirtualFileSystem.cpp - Virtual File System Layer ------------------===//
   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 implements the VirtualFileSystem interface.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Support/VirtualFileSystem.h"
  14 #include "llvm/ADT/ArrayRef.h"
  15 #include "llvm/ADT/DenseMap.h"
  16 #include "llvm/ADT/IntrusiveRefCntPtr.h"
  17 #include "llvm/ADT/None.h"
  18 #include "llvm/ADT/Optional.h"
  19 #include "llvm/ADT/STLExtras.h"
  20 #include "llvm/ADT/SmallString.h"
  21 #include "llvm/ADT/SmallVector.h"
  22 #include "llvm/ADT/StringRef.h"
  23 #include "llvm/ADT/StringSet.h"
  24 #include "llvm/ADT/Twine.h"
  25 #include "llvm/ADT/iterator_range.h"
  26 #include "llvm/Config/llvm-config.h"
  27 #include "llvm/Support/Casting.h"
  28 #include "llvm/Support/Chrono.h"
  29 #include "llvm/Support/Compiler.h"
  30 #include "llvm/Support/Debug.h"
  31 #include "llvm/Support/Errc.h"
  32 #include "llvm/Support/ErrorHandling.h"
  33 #include "llvm/Support/ErrorOr.h"
  34 #include "llvm/Support/FileSystem.h"
  35 #include "llvm/Support/MemoryBuffer.h"
  36 #include "llvm/Support/Path.h"
  37 #include "llvm/Support/Process.h"
  38 #include "llvm/Support/SMLoc.h"
  39 #include "llvm/Support/SourceMgr.h"
  40 #include "llvm/Support/YAMLParser.h"
  41 #include "llvm/Support/raw_ostream.h"
  42 #include <algorithm>
  43 #include <atomic>
  44 #include <cassert>
  45 #include <cstdint>
  46 #include <iterator>
  47 #include <limits>
  48 #include <map>
  49 #include <memory>
  50 #include <mutex>
  51 #include <string>
  52 #include <system_error>
  53 #include <utility>
  54 #include <vector>
  55
  56 using namespace llvm;
  57 using namespace llvm::vfs;
  58
  59 using llvm::sys::fs::file_t;
  60 using llvm::sys::fs::file_status;
  61 using llvm::sys::fs::file_type;
  62 using llvm::sys::fs::kInvalidFile;
  63 using llvm::sys::fs::perms;
  64 using llvm::sys::fs::UniqueID;
  65
  66 Status::Status(const file_status &Status)
  67     : UID(Status.getUniqueID()), MTime(Status.getLastModificationTime()),
  68       User(Status.getUser()), Group(Status.getGroup()), Size(Status.getSize()),
  69       Type(Status.type()), Perms(Status.permissions()) {}
  70
  71 Status::Status(const Twine &Name, UniqueID UID, sys::TimePoint<> MTime,
  72                uint32_t User, uint32_t Group, uint64_t Size, file_type Type,
  73                perms Perms)
  74     : Name(Name.str()), UID(UID), MTime(MTime), User(User), Group(Group),
  75       Size(Size), Type(Type), Perms(Perms) {}
  76
  77 Status Status::copyWithNewName(const Status &In, const Twine &NewName) {
  78   return Status(NewName, In.getUniqueID(), In.getLastModificationTime(),
  79                 In.getUser(), In.getGroup(), In.getSize(), In.getType(),
  80                 In.getPermissions());
  81 }
  82
  83 Status Status::copyWithNewName(const file_status &In, const Twine &NewName) {
  84   return Status(NewName, In.getUniqueID(), In.getLastModificationTime(),
  85                 In.getUser(), In.getGroup(), In.getSize(), In.type(),
  86                 In.permissions());
  87 }
  88
  89 bool Status::equivalent(const Status &Other) const {
  90   assert(isStatusKnown() && Other.isStatusKnown());
  91   return getUniqueID() == Other.getUniqueID();
  92 }
  93
  94 bool Status::isDirectory() const { return Type == file_type::directory_file; }
  95
  96 bool Status::isRegularFile() const { return Type == file_type::regular_file; }
  97
  98 bool Status::isOther() const {
  99   return exists() && !isRegularFile() && !isDirectory() && !isSymlink();
 100 }
 101
 102 bool Status::isSymlink() const { return Type == file_type::symlink_file; }
 103
 104 bool Status::isStatusKnown() const { return Type != file_type::status_error; }
 105
 106 bool Status::exists() const {
 107   return isStatusKnown() && Type != file_type::file_not_found;
 108 }
 109
 110 File::~File() = default;
 111
 112 FileSystem::~FileSystem() = default;
 113
 114 ErrorOr<std::unique_ptr<MemoryBuffer>>
 115 FileSystem::getBufferForFile(const llvm::Twine &Name, int64_t FileSize,
 116                              bool RequiresNullTerminator, bool IsVolatile) {
 117   auto F = openFileForRead(Name);
 118   if (!F)
 119     return F.getError();
 120
 121   return (*F)->getBuffer(Name, FileSize, RequiresNullTerminator, IsVolatile);
 122 }
 123
 124 std::error_code FileSystem::makeAbsolute(SmallVectorImpl<char> &Path) const {
 125   if (llvm::sys::path::is_absolute(Path))
 126     return {};
 127
 128   auto WorkingDir = getCurrentWorkingDirectory();
 129   if (!WorkingDir)
 130     return WorkingDir.getError();
 131
 132   llvm::sys::fs::make_absolute(WorkingDir.get(), Path);
 133   return {};
 134 }
 135
 136 std::error_code FileSystem::getRealPath(const Twine &Path,
 137                                         SmallVectorImpl<char> &Output) const {
 138   return errc::operation_not_permitted;
 139 }
 140
 141 std::error_code FileSystem::isLocal(const Twine &Path, bool &Result) {
 142   return errc::operation_not_permitted;
 143 }
 144
 145 bool FileSystem::exists(const Twine &Path) {
 146   auto Status = status(Path);
 147   return Status && Status->exists();
 148 }
 149
 150 #ifndef NDEBUG
 151 static bool isTraversalComponent(StringRef Component) {
 152   return Component.equals("..") || Component.equals(".");
 153 }
 154
 155 static bool pathHasTraversal(StringRef Path) {
 156   using namespace llvm::sys;
 157
 158   for (StringRef Comp : llvm::make_range(path::begin(Path), path::end(Path)))
 159     if (isTraversalComponent(Comp))
 160       return true;
 161   return false;
 162 }
 163 #endif
 164
 165 //===-----------------------------------------------------------------------===/
 166 // RealFileSystem implementation
 167 //===-----------------------------------------------------------------------===/
 168
 169 namespace {
 170
 171 /// Wrapper around a raw file descriptor.
 172 class RealFile : public File {
 173   friend class RealFileSystem;
 174
 175   file_t FD;
 176   Status S;
 177   std::string RealName;
 178
 179   RealFile(file_t RawFD, StringRef NewName, StringRef NewRealPathName)
 180       : FD(RawFD), S(NewName, {}, {}, {}, {}, {},
 181                      llvm::sys::fs::file_type::status_error, {}),
 182         RealName(NewRealPathName.str()) {
 183     assert(FD != kInvalidFile && "Invalid or inactive file descriptor");
 184   }
 185
 186 public:
 187   ~RealFile() override;
 188
 189   ErrorOr<Status> status() override;
 190   ErrorOr<std::string> getName() override;
 191   ErrorOr<std::unique_ptr<MemoryBuffer>> getBuffer(const Twine &Name,
 192                                                    int64_t FileSize,
 193                                                    bool RequiresNullTerminator,
 194                                                    bool IsVolatile) override;
 195   std::error_code close() override;
 196 };
 197
 198 } // namespace
 199
 200 RealFile::~RealFile() { close(); }
 201
 202 ErrorOr<Status> RealFile::status() {
 203   assert(FD != kInvalidFile && "cannot stat closed file");
 204   if (!S.isStatusKnown()) {
 205     file_status RealStatus;
 206     if (std::error_code EC = sys::fs::status(FD, RealStatus))
 207       return EC;
 208     S = Status::copyWithNewName(RealStatus, S.getName());
 209   }
 210   return S;
 211 }
 212
 213 ErrorOr<std::string> RealFile::getName() {
 214   return RealName.empty() ? S.getName().str() : RealName;
 215 }
 216
 217 ErrorOr<std::unique_ptr<MemoryBuffer>>
 218 RealFile::getBuffer(const Twine &Name, int64_t FileSize,
 219                     bool RequiresNullTerminator, bool IsVolatile) {
 220   assert(FD != kInvalidFile && "cannot get buffer for closed file");
 221   return MemoryBuffer::getOpenFile(FD, Name, FileSize, RequiresNullTerminator,
 222                                    IsVolatile);
 223 }
 224
 225 std::error_code RealFile::close() {
 226   std::error_code EC = sys::fs::closeFile(FD);
 227   FD = kInvalidFile;
 228   return EC;
 229 }
 230
 231 namespace {
 232
 233 /// A file system according to your operating system.
 234 /// This may be linked to the process's working directory, or maintain its own.
 235 ///
 236 /// Currently, its own working directory is emulated by storing the path and
 237 /// sending absolute paths to llvm::sys::fs:: functions.
 238 /// A more principled approach would be to push this down a level, modelling
 239 /// the working dir as an llvm::sys::fs::WorkingDir or similar.
 240 /// This would enable the use of openat()-style functions on some platforms.
 241 class RealFileSystem : public FileSystem {
 242 public:
 243   explicit RealFileSystem(bool LinkCWDToProcess) {
 244     if (!LinkCWDToProcess) {
 245       SmallString<128> PWD, RealPWD;
 246       if (llvm::sys::fs::current_path(PWD))
 247         return; // Awful, but nothing to do here.
 248       if (llvm::sys::fs::real_path(PWD, RealPWD))
 249         WD = {PWD, PWD};
 250       else
 251         WD = {PWD, RealPWD};
 252     }
 253   }
 254
 255   ErrorOr<Status> status(const Twine &Path) override;
 256   ErrorOr<std::unique_ptr<File>> openFileForRead(const Twine &Path) override;
 257   directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
 258
 259   llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override;
 260   std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
 261   std::error_code isLocal(const Twine &Path, bool &Result) override;
 262   std::error_code getRealPath(const Twine &Path,
 263                               SmallVectorImpl<char> &Output) const override;
 264
 265 private:
 266   // If this FS has its own working dir, use it to make Path absolute.
 267   // The returned twine is safe to use as long as both Storage and Path live.
 268   Twine adjustPath(const Twine &Path, SmallVectorImpl<char> &Storage) const {
 269     if (!WD)
 270       return Path;
 271     Path.toVector(Storage);
 272     sys::fs::make_absolute(WD->Resolved, Storage);
 273     return Storage;
 274   }
 275
 276   struct WorkingDirectory {
 277     // The current working directory, without symlinks resolved. (echo $PWD).
 278     SmallString<128> Specified;
 279     // The current working directory, with links resolved. (readlink .).
 280     SmallString<128> Resolved;
 281   };
 282   Optional<WorkingDirectory> WD;
 283 };
 284
 285 } // namespace
 286
 287 ErrorOr<Status> RealFileSystem::status(const Twine &Path) {
 288   SmallString<256> Storage;
 289   sys::fs::file_status RealStatus;
 290   if (std::error_code EC =
 291           sys::fs::status(adjustPath(Path, Storage), RealStatus))
 292     return EC;
 293   return Status::copyWithNewName(RealStatus, Path);
 294 }
 295
 296 ErrorOr<std::unique_ptr<File>>
 297 RealFileSystem::openFileForRead(const Twine &Name) {
 298   SmallString<256> RealName, Storage;
 299   Expected<file_t> FDOrErr = sys::fs::openNativeFileForRead(
 300       adjustPath(Name, Storage), sys::fs::OF_None, &RealName);
 301   if (!FDOrErr)
 302     return errorToErrorCode(FDOrErr.takeError());
 303   return std::unique_ptr<File>(
 304       new RealFile(*FDOrErr, Name.str(), RealName.str()));
 305 }
 306
 307 llvm::ErrorOr<std::string> RealFileSystem::getCurrentWorkingDirectory() const {
 308   if (WD)
 309     return std::string(WD->Specified.str());
 310
 311   SmallString<128> Dir;
 312   if (std::error_code EC = llvm::sys::fs::current_path(Dir))
 313     return EC;
 314   return std::string(Dir.str());
 315 }
 316
 317 std::error_code RealFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
 318   if (!WD)
 319     return llvm::sys::fs::set_current_path(Path);
 320
 321   SmallString<128> Absolute, Resolved, Storage;
 322   adjustPath(Path, Storage).toVector(Absolute);
 323   bool IsDir;
 324   if (auto Err = llvm::sys::fs::is_directory(Absolute, IsDir))
 325     return Err;
 326   if (!IsDir)
 327     return std::make_error_code(std::errc::not_a_directory);
 328   if (auto Err = llvm::sys::fs::real_path(Absolute, Resolved))
 329     return Err;
 330   WD = {Absolute, Resolved};
 331   return std::error_code();
 332 }
 333
 334 std::error_code RealFileSystem::isLocal(const Twine &Path, bool &Result) {
 335   SmallString<256> Storage;
 336   return llvm::sys::fs::is_local(adjustPath(Path, Storage), Result);
 337 }
 338
 339 std::error_code
 340 RealFileSystem::getRealPath(const Twine &Path,
 341                             SmallVectorImpl<char> &Output) const {
 342   SmallString<256> Storage;
 343   return llvm::sys::fs::real_path(adjustPath(Path, Storage), Output);
 344 }
 345
 346 IntrusiveRefCntPtr<FileSystem> vfs::getRealFileSystem() {
 347   static IntrusiveRefCntPtr<FileSystem> FS(new RealFileSystem(true));
 348   return FS;
 349 }
 350
 351 std::unique_ptr<FileSystem> vfs::createPhysicalFileSystem() {
 352   return std::make_unique<RealFileSystem>(false);
 353 }
 354
 355 namespace {
 356
 357 class RealFSDirIter : public llvm::vfs::detail::DirIterImpl {
 358   llvm::sys::fs::directory_iterator Iter;
 359
 360 public:
 361   RealFSDirIter(const Twine &Path, std::error_code &EC) : Iter(Path, EC) {
 362     if (Iter != llvm::sys::fs::directory_iterator())
 363       CurrentEntry = directory_entry(Iter->path(), Iter->type());
 364   }
 365
 366   std::error_code increment() override {
 367     std::error_code EC;
 368     Iter.increment(EC);
 369     CurrentEntry = (Iter == llvm::sys::fs::directory_iterator())
 370                        ? directory_entry()
 371                        : directory_entry(Iter->path(), Iter->type());
 372     return EC;
 373   }
 374 };
 375
 376 } // namespace
 377
 378 directory_iterator RealFileSystem::dir_begin(const Twine &Dir,
 379                                              std::error_code &EC) {
 380   SmallString<128> Storage;
 381   return directory_iterator(
 382       std::make_shared<RealFSDirIter>(adjustPath(Dir, Storage), EC));
 383 }
 384
 385 //===-----------------------------------------------------------------------===/
 386 // OverlayFileSystem implementation
 387 //===-----------------------------------------------------------------------===/
 388
 389 OverlayFileSystem::OverlayFileSystem(IntrusiveRefCntPtr<FileSystem> BaseFS) {
 390   FSList.push_back(std::move(BaseFS));
 391 }
 392
 393 void OverlayFileSystem::pushOverlay(IntrusiveRefCntPtr<FileSystem> FS) {
 394   FSList.push_back(FS);
 395   // Synchronize added file systems by duplicating the working directory from
 396   // the first one in the list.
 397   FS->setCurrentWorkingDirectory(getCurrentWorkingDirectory().get());
 398 }
 399
 400 ErrorOr<Status> OverlayFileSystem::status(const Twine &Path) {
 401   // FIXME: handle symlinks that cross file systems
 402   for (iterator I = overlays_begin(), E = overlays_end(); I != E; ++I) {
 403     ErrorOr<Status> Status = (*I)->status(Path);
 404     if (Status || Status.getError() != llvm::errc::no_such_file_or_directory)
 405       return Status;
 406   }
 407   return make_error_code(llvm::errc::no_such_file_or_directory);
 408 }
 409
 410 ErrorOr<std::unique_ptr<File>>
 411 OverlayFileSystem::openFileForRead(const llvm::Twine &Path) {
 412   // FIXME: handle symlinks that cross file systems
 413   for (iterator I = overlays_begin(), E = overlays_end(); I != E; ++I) {
 414     auto Result = (*I)->openFileForRead(Path);
 415     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
 416       return Result;
 417   }
 418   return make_error_code(llvm::errc::no_such_file_or_directory);
 419 }
 420
 421 llvm::ErrorOr<std::string>
 422 OverlayFileSystem::getCurrentWorkingDirectory() const {
 423   // All file systems are synchronized, just take the first working directory.
 424   return FSList.front()->getCurrentWorkingDirectory();
 425 }
 426
 427 std::error_code
 428 OverlayFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
 429   for (auto &FS : FSList)
 430     if (std::error_code EC = FS->setCurrentWorkingDirectory(Path))
 431       return EC;
 432   return {};
 433 }
 434
 435 std::error_code OverlayFileSystem::isLocal(const Twine &Path, bool &Result) {
 436   for (auto &FS : FSList)
 437     if (FS->exists(Path))
 438       return FS->isLocal(Path, Result);
 439   return errc::no_such_file_or_directory;
 440 }
 441
 442 std::error_code
 443 OverlayFileSystem::getRealPath(const Twine &Path,
 444                                SmallVectorImpl<char> &Output) const {
 445   for (auto &FS : FSList)
 446     if (FS->exists(Path))
 447       return FS->getRealPath(Path, Output);
 448   return errc::no_such_file_or_directory;
 449 }
 450
 451 llvm::vfs::detail::DirIterImpl::~DirIterImpl() = default;
 452
 453 namespace {
 454
 455 /// Combines and deduplicates directory entries across multiple file systems.
 456 class CombiningDirIterImpl : public llvm::vfs::detail::DirIterImpl {
 457   using FileSystemPtr = llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>;
 458
 459   /// File systems to check for entries in. Processed in reverse order.
 460   SmallVector<FileSystemPtr, 8> FSList;
 461   /// The directory iterator for the current filesystem.
 462   directory_iterator CurrentDirIter;
 463   /// The path of the directory to iterate the entries of.
 464   std::string DirPath;
 465   /// The set of names already returned as entries.
 466   llvm::StringSet<> SeenNames;
 467
 468   /// Sets \c CurrentDirIter to an iterator of \c DirPath in the next file
 469   /// system in the list, or leaves it as is (at its end position) if we've
 470   /// already gone through them all.
 471   std::error_code incrementFS() {
 472     while (!FSList.empty()) {
 473       std::error_code EC;
 474       CurrentDirIter = FSList.back()->dir_begin(DirPath, EC);
 475       FSList.pop_back();
 476       if (EC && EC != errc::no_such_file_or_directory)
 477         return EC;
 478       if (CurrentDirIter != directory_iterator())
 479         break; // found
 480     }
 481     return {};
 482   }
 483
 484   std::error_code incrementDirIter(bool IsFirstTime) {
 485     assert((IsFirstTime || CurrentDirIter != directory_iterator()) &&
 486            "incrementing past end");
 487     std::error_code EC;
 488     if (!IsFirstTime)
 489       CurrentDirIter.increment(EC);
 490     if (!EC && CurrentDirIter == directory_iterator())
 491       EC = incrementFS();
 492     return EC;
 493   }
 494
 495   std::error_code incrementImpl(bool IsFirstTime) {
 496     while (true) {
 497       std::error_code EC = incrementDirIter(IsFirstTime);
 498       if (EC || CurrentDirIter == directory_iterator()) {
 499         CurrentEntry = directory_entry();
 500         return EC;
 501       }
 502       CurrentEntry = *CurrentDirIter;
 503       StringRef Name = llvm::sys::path::filename(CurrentEntry.path());
 504       if (SeenNames.insert(Name).second)
 505         return EC; // name not seen before
 506     }
 507     llvm_unreachable("returned above");
 508   }
 509
 510 public:
 511   CombiningDirIterImpl(ArrayRef<FileSystemPtr> FileSystems, std::string Dir,
 512                        std::error_code &EC)
 513       : FSList(FileSystems.begin(), FileSystems.end()),
 514         DirPath(std::move(Dir)) {
 515     if (!FSList.empty()) {
 516       CurrentDirIter = FSList.back()->dir_begin(DirPath, EC);
 517       FSList.pop_back();
 518       if (!EC || EC == errc::no_such_file_or_directory)
 519         EC = incrementImpl(true);
 520     }
 521   }
 522
 523   CombiningDirIterImpl(directory_iterator FirstIter, FileSystemPtr Fallback,
 524                        std::string FallbackDir, std::error_code &EC)
 525       : FSList({Fallback}), CurrentDirIter(FirstIter),
 526         DirPath(std::move(FallbackDir)) {
 527     if (!EC || EC == errc::no_such_file_or_directory)
 528       EC = incrementImpl(true);
 529   }
 530
 531   std::error_code increment() override { return incrementImpl(false); }
 532 };
 533
 534 } // namespace
 535
 536 directory_iterator OverlayFileSystem::dir_begin(const Twine &Dir,
 537                                                 std::error_code &EC) {
 538   return directory_iterator(
 539       std::make_shared<CombiningDirIterImpl>(FSList, Dir.str(), EC));
 540 }
 541
 542 void ProxyFileSystem::anchor() {}
 543
 544 namespace llvm {
 545 namespace vfs {
 546
 547 namespace detail {
 548
 549 enum InMemoryNodeKind { IME_File, IME_Directory, IME_HardLink };
 550
 551 /// The in memory file system is a tree of Nodes. Every node can either be a
 552 /// file , hardlink or a directory.
 553 class InMemoryNode {
 554   InMemoryNodeKind Kind;
 555   std::string FileName;
 556
 557 public:
 558   InMemoryNode(llvm::StringRef FileName, InMemoryNodeKind Kind)
 559       : Kind(Kind), FileName(std::string(llvm::sys::path::filename(FileName))) {
 560   }
 561   virtual ~InMemoryNode() = default;
 562
 563   /// Get the filename of this node (the name without the directory part).
 564   StringRef getFileName() const { return FileName; }
 565   InMemoryNodeKind getKind() const { return Kind; }
 566   virtual std::string toString(unsigned Indent) const = 0;
 567 };
 568
 569 class InMemoryFile : public InMemoryNode {
 570   Status Stat;
 571   std::unique_ptr<llvm::MemoryBuffer> Buffer;
 572
 573 public:
 574   InMemoryFile(Status Stat, std::unique_ptr<llvm::MemoryBuffer> Buffer)
 575       : InMemoryNode(Stat.getName(), IME_File), Stat(std::move(Stat)),
 576         Buffer(std::move(Buffer)) {}
 577
 578   /// Return the \p Status for this node. \p RequestedName should be the name
 579   /// through which the caller referred to this node. It will override
 580   /// \p Status::Name in the return value, to mimic the behavior of \p RealFile.
 581   Status getStatus(const Twine &RequestedName) const {
 582     return Status::copyWithNewName(Stat, RequestedName);
 583   }
 584   llvm::MemoryBuffer *getBuffer() const { return Buffer.get(); }
 585
 586   std::string toString(unsigned Indent) const override {
 587     return (std::string(Indent, ' ') + Stat.getName() + "\n").str();
 588   }
 589
 590   static bool classof(const InMemoryNode *N) {
 591     return N->getKind() == IME_File;
 592   }
 593 };
 594
 595 namespace {
 596
 597 class InMemoryHardLink : public InMemoryNode {
 598   const InMemoryFile &ResolvedFile;
 599
 600 public:
 601   InMemoryHardLink(StringRef Path, const InMemoryFile &ResolvedFile)
 602       : InMemoryNode(Path, IME_HardLink), ResolvedFile(ResolvedFile) {}
 603   const InMemoryFile &getResolvedFile() const { return ResolvedFile; }
 604
 605   std::string toString(unsigned Indent) const override {
 606     return std::string(Indent, ' ') + "HardLink to -> " +
 607            ResolvedFile.toString(0);
 608   }
 609
 610   static bool classof(const InMemoryNode *N) {
 611     return N->getKind() == IME_HardLink;
 612   }
 613 };
 614
 615 /// Adapt a InMemoryFile for VFS' File interface.  The goal is to make
 616 /// \p InMemoryFileAdaptor mimic as much as possible the behavior of
 617 /// \p RealFile.
 618 class InMemoryFileAdaptor : public File {
 619   const InMemoryFile &Node;
 620   /// The name to use when returning a Status for this file.
 621   std::string RequestedName;
 622
 623 public:
 624   explicit InMemoryFileAdaptor(const InMemoryFile &Node,
 625                                std::string RequestedName)
 626       : Node(Node), RequestedName(std::move(RequestedName)) {}
 627
 628   llvm::ErrorOr<Status> status() override {
 629     return Node.getStatus(RequestedName);
 630   }
 631
 632   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
 633   getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
 634             bool IsVolatile) override {
 635     llvm::MemoryBuffer *Buf = Node.getBuffer();
 636     return llvm::MemoryBuffer::getMemBuffer(
 637         Buf->getBuffer(), Buf->getBufferIdentifier(), RequiresNullTerminator);
 638   }
 639
 640   std::error_code close() override { return {}; }
 641 };
 642 } // namespace
 643
 644 class InMemoryDirectory : public InMemoryNode {
 645   Status Stat;
 646   llvm::StringMap<std::unique_ptr<InMemoryNode>> Entries;
 647
 648 public:
 649   InMemoryDirectory(Status Stat)
 650       : InMemoryNode(Stat.getName(), IME_Directory), Stat(std::move(Stat)) {}
 651
 652   /// Return the \p Status for this node. \p RequestedName should be the name
 653   /// through which the caller referred to this node. It will override
 654   /// \p Status::Name in the return value, to mimic the behavior of \p RealFile.
 655   Status getStatus(const Twine &RequestedName) const {
 656     return Status::copyWithNewName(Stat, RequestedName);
 657   }
 658   InMemoryNode *getChild(StringRef Name) {
 659     auto I = Entries.find(Name);
 660     if (I != Entries.end())
 661       return I->second.get();
 662     return nullptr;
 663   }
 664
 665   InMemoryNode *addChild(StringRef Name, std::unique_ptr<InMemoryNode> Child) {
 666     return Entries.insert(make_pair(Name, std::move(Child)))
 667         .first->second.get();
 668   }
 669
 670   using const_iterator = decltype(Entries)::const_iterator;
 671
 672   const_iterator begin() const { return Entries.begin(); }
 673   const_iterator end() const { return Entries.end(); }
 674
 675   std::string toString(unsigned Indent) const override {
 676     std::string Result =
 677         (std::string(Indent, ' ') + Stat.getName() + "\n").str();
 678     for (const auto &Entry : Entries)
 679       Result += Entry.second->toString(Indent + 2);
 680     return Result;
 681   }
 682
 683   static bool classof(const InMemoryNode *N) {
 684     return N->getKind() == IME_Directory;
 685   }
 686 };
 687
 688 namespace {
 689 Status getNodeStatus(const InMemoryNode *Node, const Twine &RequestedName) {
 690   if (auto Dir = dyn_cast<detail::InMemoryDirectory>(Node))
 691     return Dir->getStatus(RequestedName);
 692   if (auto File = dyn_cast<detail::InMemoryFile>(Node))
 693     return File->getStatus(RequestedName);
 694   if (auto Link = dyn_cast<detail::InMemoryHardLink>(Node))
 695     return Link->getResolvedFile().getStatus(RequestedName);
 696   llvm_unreachable("Unknown node type");
 697 }
 698 } // namespace
 699 } // namespace detail
 700
 701 InMemoryFileSystem::InMemoryFileSystem(bool UseNormalizedPaths)
 702     : Root(new detail::InMemoryDirectory(
 703           Status("", getNextVirtualUniqueID(), llvm::sys::TimePoint<>(), 0, 0,
 704                  0, llvm::sys::fs::file_type::directory_file,
 705                  llvm::sys::fs::perms::all_all))),
 706       UseNormalizedPaths(UseNormalizedPaths) {}
 707
 708 InMemoryFileSystem::~InMemoryFileSystem() = default;
 709
 710 std::string InMemoryFileSystem::toString() const {
 711   return Root->toString(/*Indent=*/0);
 712 }
 713
 714 bool InMemoryFileSystem::addFile(const Twine &P, time_t ModificationTime,
 715                                  std::unique_ptr<llvm::MemoryBuffer> Buffer,
 716                                  Optional<uint32_t> User,
 717                                  Optional<uint32_t> Group,
 718                                  Optional<llvm::sys::fs::file_type> Type,
 719                                  Optional<llvm::sys::fs::perms> Perms,
 720                                  const detail::InMemoryFile *HardLinkTarget) {
 721   SmallString<128> Path;
 722   P.toVector(Path);
 723
 724   // Fix up relative paths. This just prepends the current working directory.
 725   std::error_code EC = makeAbsolute(Path);
 726   assert(!EC);
 727   (void)EC;
 728
 729   if (useNormalizedPaths())
 730     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 731
 732   if (Path.empty())
 733     return false;
 734
 735   detail::InMemoryDirectory *Dir = Root.get();
 736   auto I = llvm::sys::path::begin(Path), E = sys::path::end(Path);
 737   const auto ResolvedUser = User.getValueOr(0);
 738   const auto ResolvedGroup = Group.getValueOr(0);
 739   const auto ResolvedType = Type.getValueOr(sys::fs::file_type::regular_file);
 740   const auto ResolvedPerms = Perms.getValueOr(sys::fs::all_all);
 741   assert(!(HardLinkTarget && Buffer) && "HardLink cannot have a buffer");
 742   // Any intermediate directories we create should be accessible by
 743   // the owner, even if Perms says otherwise for the final path.
 744   const auto NewDirectoryPerms = ResolvedPerms | sys::fs::owner_all;
 745   while (true) {
 746     StringRef Name = *I;
 747     detail::InMemoryNode *Node = Dir->getChild(Name);
 748     ++I;
 749     if (!Node) {
 750       if (I == E) {
 751         // End of the path.
 752         std::unique_ptr<detail::InMemoryNode> Child;
 753         if (HardLinkTarget)
 754           Child.reset(new detail::InMemoryHardLink(P.str(), *HardLinkTarget));
 755         else {
 756           // Create a new file or directory.
 757           Status Stat(P.str(), getNextVirtualUniqueID(),
 758                       llvm::sys::toTimePoint(ModificationTime), ResolvedUser,
 759                       ResolvedGroup, Buffer->getBufferSize(), ResolvedType,
 760                       ResolvedPerms);
 761           if (ResolvedType == sys::fs::file_type::directory_file) {
 762             Child.reset(new detail::InMemoryDirectory(std::move(Stat)));
 763           } else {
 764             Child.reset(
 765                 new detail::InMemoryFile(std::move(Stat), std::move(Buffer)));
 766           }
 767         }
 768         Dir->addChild(Name, std::move(Child));
 769         return true;
 770       }
 771
 772       // Create a new directory. Use the path up to here.
 773       Status Stat(
 774           StringRef(Path.str().begin(), Name.end() - Path.str().begin()),
 775           getNextVirtualUniqueID(), llvm::sys::toTimePoint(ModificationTime),
 776           ResolvedUser, ResolvedGroup, 0, sys::fs::file_type::directory_file,
 777           NewDirectoryPerms);
 778       Dir = cast<detail::InMemoryDirectory>(Dir->addChild(
 779           Name, std::make_unique<detail::InMemoryDirectory>(std::move(Stat))));
 780       continue;
 781     }
 782
 783     if (auto *NewDir = dyn_cast<detail::InMemoryDirectory>(Node)) {
 784       Dir = NewDir;
 785     } else {
 786       assert((isa<detail::InMemoryFile>(Node) ||
 787               isa<detail::InMemoryHardLink>(Node)) &&
 788              "Must be either file, hardlink or directory!");
 789
 790       // Trying to insert a directory in place of a file.
 791       if (I != E)
 792         return false;
 793
 794       // Return false only if the new file is different from the existing one.
 795       if (auto Link = dyn_cast<detail::InMemoryHardLink>(Node)) {
 796         return Link->getResolvedFile().getBuffer()->getBuffer() ==
 797                Buffer->getBuffer();
 798       }
 799       return cast<detail::InMemoryFile>(Node)->getBuffer()->getBuffer() ==
 800              Buffer->getBuffer();
 801     }
 802   }
 803 }
 804
 805 bool InMemoryFileSystem::addFile(const Twine &P, time_t ModificationTime,
 806                                  std::unique_ptr<llvm::MemoryBuffer> Buffer,
 807                                  Optional<uint32_t> User,
 808                                  Optional<uint32_t> Group,
 809                                  Optional<llvm::sys::fs::file_type> Type,
 810                                  Optional<llvm::sys::fs::perms> Perms) {
 811   return addFile(P, ModificationTime, std::move(Buffer), User, Group, Type,
 812                  Perms, /*HardLinkTarget=*/nullptr);
 813 }
 814
 815 bool InMemoryFileSystem::addFileNoOwn(const Twine &P, time_t ModificationTime,
 816                                       const llvm::MemoryBufferRef &Buffer,
 817                                       Optional<uint32_t> User,
 818                                       Optional<uint32_t> Group,
 819                                       Optional<llvm::sys::fs::file_type> Type,
 820                                       Optional<llvm::sys::fs::perms> Perms) {
 821   return addFile(P, ModificationTime, llvm::MemoryBuffer::getMemBuffer(Buffer),
 822                  std::move(User), std::move(Group), std::move(Type),
 823                  std::move(Perms));
 824 }
 825
 826 static ErrorOr<const detail::InMemoryNode *>
 827 lookupInMemoryNode(const InMemoryFileSystem &FS, detail::InMemoryDirectory *Dir,
 828                    const Twine &P) {
 829   SmallString<128> Path;
 830   P.toVector(Path);
 831
 832   // Fix up relative paths. This just prepends the current working directory.
 833   std::error_code EC = FS.makeAbsolute(Path);
 834   assert(!EC);
 835   (void)EC;
 836
 837   if (FS.useNormalizedPaths())
 838     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 839
 840   if (Path.empty())
 841     return Dir;
 842
 843   auto I = llvm::sys::path::begin(Path), E = llvm::sys::path::end(Path);
 844   while (true) {
 845     detail::InMemoryNode *Node = Dir->getChild(*I);
 846     ++I;
 847     if (!Node)
 848       return errc::no_such_file_or_directory;
 849
 850     // Return the file if it's at the end of the path.
 851     if (auto File = dyn_cast<detail::InMemoryFile>(Node)) {
 852       if (I == E)
 853         return File;
 854       return errc::no_such_file_or_directory;
 855     }
 856
 857     // If Node is HardLink then return the resolved file.
 858     if (auto File = dyn_cast<detail::InMemoryHardLink>(Node)) {
 859       if (I == E)
 860         return &File->getResolvedFile();
 861       return errc::no_such_file_or_directory;
 862     }
 863     // Traverse directories.
 864     Dir = cast<detail::InMemoryDirectory>(Node);
 865     if (I == E)
 866       return Dir;
 867   }
 868 }
 869
 870 bool InMemoryFileSystem::addHardLink(const Twine &FromPath,
 871                                      const Twine &ToPath) {
 872   auto FromNode = lookupInMemoryNode(*this, Root.get(), FromPath);
 873   auto ToNode = lookupInMemoryNode(*this, Root.get(), ToPath);
 874   // FromPath must not have been added before. ToPath must have been added
 875   // before. Resolved ToPath must be a File.
 876   if (!ToNode || FromNode || !isa<detail::InMemoryFile>(*ToNode))
 877     return false;
 878   return this->addFile(FromPath, 0, nullptr, None, None, None, None,
 879                        cast<detail::InMemoryFile>(*ToNode));
 880 }
 881
 882 llvm::ErrorOr<Status> InMemoryFileSystem::status(const Twine &Path) {
 883   auto Node = lookupInMemoryNode(*this, Root.get(), Path);
 884   if (Node)
 885     return detail::getNodeStatus(*Node, Path);
 886   return Node.getError();
 887 }
 888
 889 llvm::ErrorOr<std::unique_ptr<File>>
 890 InMemoryFileSystem::openFileForRead(const Twine &Path) {
 891   auto Node = lookupInMemoryNode(*this, Root.get(), Path);
 892   if (!Node)
 893     return Node.getError();
 894
 895   // When we have a file provide a heap-allocated wrapper for the memory buffer
 896   // to match the ownership semantics for File.
 897   if (auto *F = dyn_cast<detail::InMemoryFile>(*Node))
 898     return std::unique_ptr<File>(
 899         new detail::InMemoryFileAdaptor(*F, Path.str()));
 900
 901   // FIXME: errc::not_a_file?
 902   return make_error_code(llvm::errc::invalid_argument);
 903 }
 904
 905 namespace {
 906
 907 /// Adaptor from InMemoryDir::iterator to directory_iterator.
 908 class InMemoryDirIterator : public llvm::vfs::detail::DirIterImpl {
 909   detail::InMemoryDirectory::const_iterator I;
 910   detail::InMemoryDirectory::const_iterator E;
 911   std::string RequestedDirName;
 912
 913   void setCurrentEntry() {
 914     if (I != E) {
 915       SmallString<256> Path(RequestedDirName);
 916       llvm::sys::path::append(Path, I->second->getFileName());
 917       sys::fs::file_type Type = sys::fs::file_type::type_unknown;
 918       switch (I->second->getKind()) {
 919       case detail::IME_File:
 920       case detail::IME_HardLink:
 921         Type = sys::fs::file_type::regular_file;
 922         break;
 923       case detail::IME_Directory:
 924         Type = sys::fs::file_type::directory_file;
 925         break;
 926       }
 927       CurrentEntry = directory_entry(std::string(Path.str()), Type);
 928     } else {
 929       // When we're at the end, make CurrentEntry invalid and DirIterImpl will
 930       // do the rest.
 931       CurrentEntry = directory_entry();
 932     }
 933   }
 934
 935 public:
 936   InMemoryDirIterator() = default;
 937
 938   explicit InMemoryDirIterator(const detail::InMemoryDirectory &Dir,
 939                                std::string RequestedDirName)
 940       : I(Dir.begin()), E(Dir.end()),
 941         RequestedDirName(std::move(RequestedDirName)) {
 942     setCurrentEntry();
 943   }
 944
 945   std::error_code increment() override {
 946     ++I;
 947     setCurrentEntry();
 948     return {};
 949   }
 950 };
 951
 952 } // namespace
 953
 954 directory_iterator InMemoryFileSystem::dir_begin(const Twine &Dir,
 955                                                  std::error_code &EC) {
 956   auto Node = lookupInMemoryNode(*this, Root.get(), Dir);
 957   if (!Node) {
 958     EC = Node.getError();
 959     return directory_iterator(std::make_shared<InMemoryDirIterator>());
 960   }
 961
 962   if (auto *DirNode = dyn_cast<detail::InMemoryDirectory>(*Node))
 963     return directory_iterator(
 964         std::make_shared<InMemoryDirIterator>(*DirNode, Dir.str()));
 965
 966   EC = make_error_code(llvm::errc::not_a_directory);
 967   return directory_iterator(std::make_shared<InMemoryDirIterator>());
 968 }
 969
 970 std::error_code InMemoryFileSystem::setCurrentWorkingDirectory(const Twine &P) {
 971   SmallString<128> Path;
 972   P.toVector(Path);
 973
 974   // Fix up relative paths. This just prepends the current working directory.
 975   std::error_code EC = makeAbsolute(Path);
 976   assert(!EC);
 977   (void)EC;
 978
 979   if (useNormalizedPaths())
 980     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 981
 982   if (!Path.empty())
 983     WorkingDirectory = std::string(Path.str());
 984   return {};
 985 }
 986
 987 std::error_code
 988 InMemoryFileSystem::getRealPath(const Twine &Path,
 989                                 SmallVectorImpl<char> &Output) const {
 990   auto CWD = getCurrentWorkingDirectory();
 991   if (!CWD || CWD->empty())
 992     return errc::operation_not_permitted;
 993   Path.toVector(Output);
 994   if (auto EC = makeAbsolute(Output))
 995     return EC;
 996   llvm::sys::path::remove_dots(Output, /*remove_dot_dot=*/true);
 997   return {};
 998 }
 999
1000 std::error_code InMemoryFileSystem::isLocal(const Twine &Path, bool &Result) {
1001   Result = false;
1002   return {};
1003 }
1004
1005 } // namespace vfs
1006 } // namespace llvm
1007
1008 //===-----------------------------------------------------------------------===/
1009 // RedirectingFileSystem implementation
1010 //===-----------------------------------------------------------------------===/
1011
1012 namespace {
1013
1014 static llvm::sys::path::Style getExistingStyle(llvm::StringRef Path) {
1015   // Detect the path style in use by checking the first separator.
1016   llvm::sys::path::Style style = llvm::sys::path::Style::native;
1017   const size_t n = Path.find_first_of("/\\");
1018   if (n != static_cast<size_t>(-1))
1019     style = (Path[n] == '/') ? llvm::sys::path::Style::posix
1020                              : llvm::sys::path::Style::windows;
1021   return style;
1022 }
1023
1024 /// Removes leading "./" as well as path components like ".." and ".".
1025 static llvm::SmallString<256> canonicalize(llvm::StringRef Path) {
1026   // First detect the path style in use by checking the first separator.
1027   llvm::sys::path::Style style = getExistingStyle(Path);
1028
1029   // Now remove the dots.  Explicitly specifying the path style prevents the
1030   // direction of the slashes from changing.
1031   llvm::SmallString<256> result =
1032       llvm::sys::path::remove_leading_dotslash(Path, style);
1033   llvm::sys::path::remove_dots(result, /*remove_dot_dot=*/true, style);
1034   return result;
1035 }
1036
1037 } // anonymous namespace
1038
1039
1040 RedirectingFileSystem::RedirectingFileSystem(IntrusiveRefCntPtr<FileSystem> FS)
1041     : ExternalFS(std::move(FS)) {
1042   if (ExternalFS)
1043     if (auto ExternalWorkingDirectory =
1044             ExternalFS->getCurrentWorkingDirectory()) {
1045       WorkingDirectory = *ExternalWorkingDirectory;
1046     }
1047 }
1048
1049 /// Directory iterator implementation for \c RedirectingFileSystem's
1050 /// directory entries.
1051 class llvm::vfs::RedirectingFSDirIterImpl
1052     : public llvm::vfs::detail::DirIterImpl {
1053   std::string Dir;
1054   RedirectingFileSystem::DirectoryEntry::iterator Current, End;
1055
1056   std::error_code incrementImpl(bool IsFirstTime) {
1057     assert((IsFirstTime || Current != End) && "cannot iterate past end");
1058     if (!IsFirstTime)
1059       ++Current;
1060     if (Current != End) {
1061       SmallString<128> PathStr(Dir);
1062       llvm::sys::path::append(PathStr, (*Current)->getName());
1063       sys::fs::file_type Type = sys::fs::file_type::type_unknown;
1064       switch ((*Current)->getKind()) {
1065       case RedirectingFileSystem::EK_Directory:
1066         LLVM_FALLTHROUGH;
1067       case RedirectingFileSystem::EK_DirectoryRemap:
1068         Type = sys::fs::file_type::directory_file;
1069         break;
1070       case RedirectingFileSystem::EK_File:
1071         Type = sys::fs::file_type::regular_file;
1072         break;
1073       }
1074       CurrentEntry = directory_entry(std::string(PathStr.str()), Type);
1075     } else {
1076       CurrentEntry = directory_entry();
1077     }
1078     return {};
1079   };
1080
1081 public:
1082   RedirectingFSDirIterImpl(
1083       const Twine &Path, RedirectingFileSystem::DirectoryEntry::iterator Begin,
1084       RedirectingFileSystem::DirectoryEntry::iterator End, std::error_code &EC)
1085       : Dir(Path.str()), Current(Begin), End(End) {
1086     EC = incrementImpl(/*IsFirstTime=*/true);
1087   }
1088
1089   std::error_code increment() override {
1090     return incrementImpl(/*IsFirstTime=*/false);
1091   }
1092 };
1093
1094 /// Directory iterator implementation for \c RedirectingFileSystem's
1095 /// directory remap entries that maps the paths reported by the external
1096 /// file system's directory iterator back to the virtual directory's path.
1097 class RedirectingFSDirRemapIterImpl : public llvm::vfs::detail::DirIterImpl {
1098   std::string Dir;
1099   llvm::sys::path::Style DirStyle;
1100   llvm::vfs::directory_iterator ExternalIter;
1101
1102 public:
1103   RedirectingFSDirRemapIterImpl(std::string DirPath,
1104                                 llvm::vfs::directory_iterator ExtIter)
1105       : Dir(std::move(DirPath)), DirStyle(getExistingStyle(Dir)),
1106         ExternalIter(ExtIter) {
1107     if (ExternalIter != llvm::vfs::directory_iterator())
1108       setCurrentEntry();
1109   }
1110
1111   void setCurrentEntry() {
1112     StringRef ExternalPath = ExternalIter->path();
1113     llvm::sys::path::Style ExternalStyle = getExistingStyle(ExternalPath);
1114     StringRef File = llvm::sys::path::filename(ExternalPath, ExternalStyle);
1115
1116     SmallString<128> NewPath(Dir);
1117     llvm::sys::path::append(NewPath, DirStyle, File);
1118
1119     CurrentEntry = directory_entry(std::string(NewPath), ExternalIter->type());
1120   }
1121
1122   std::error_code increment() override {
1123     std::error_code EC;
1124     ExternalIter.increment(EC);
1125     if (!EC && ExternalIter != llvm::vfs::directory_iterator())
1126       setCurrentEntry();
1127     else
1128       CurrentEntry = directory_entry();
1129     return EC;
1130   }
1131 };
1132
1133 llvm::ErrorOr<std::string>
1134 RedirectingFileSystem::getCurrentWorkingDirectory() const {
1135   return WorkingDirectory;
1136 }
1137
1138 std::error_code
1139 RedirectingFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
1140   // Don't change the working directory if the path doesn't exist.
1141   if (!exists(Path))
1142     return errc::no_such_file_or_directory;
1143
1144   SmallString<128> AbsolutePath;
1145   Path.toVector(AbsolutePath);
1146   if (std::error_code EC = makeAbsolute(AbsolutePath))
1147     return EC;
1148   WorkingDirectory = std::string(AbsolutePath.str());
1149   return {};
1150 }
1151
1152 std::error_code RedirectingFileSystem::isLocal(const Twine &Path_,
1153                                                bool &Result) {
1154   SmallString<256> Path;
1155   Path_.toVector(Path);
1156
1157   if (std::error_code EC = makeCanonical(Path))
1158     return {};
1159
1160   return ExternalFS->isLocal(Path, Result);
1161 }
1162
1163 std::error_code RedirectingFileSystem::makeAbsolute(SmallVectorImpl<char> &Path) const {
1164   if (llvm::sys::path::is_absolute(Path, llvm::sys::path::Style::posix) ||
1165       llvm::sys::path::is_absolute(Path, llvm::sys::path::Style::windows))
1166     return {};
1167
1168   auto WorkingDir = getCurrentWorkingDirectory();
1169   if (!WorkingDir)
1170     return WorkingDir.getError();
1171
1172   // We can't use sys::fs::make_absolute because that assumes the path style
1173   // is native and there is no way to override that.  Since we know WorkingDir
1174   // is absolute, we can use it to determine which style we actually have and
1175   // append Path ourselves.
1176   sys::path::Style style = sys::path::Style::windows;
1177   if (sys::path::is_absolute(WorkingDir.get(), sys::path::Style::posix)) {
1178     style = sys::path::Style::posix;
1179   }
1180
1181   std::string Result = WorkingDir.get();
1182   StringRef Dir(Result);
1183   if (!Dir.endswith(sys::path::get_separator(style))) {
1184     Result += sys::path::get_separator(style);
1185   }
1186   Result.append(Path.data(), Path.size());
1187   Path.assign(Result.begin(), Result.end());
1188
1189   return {};
1190 }
1191
1192 directory_iterator RedirectingFileSystem::dir_begin(const Twine &Dir,
1193                                                     std::error_code &EC) {
1194   SmallString<256> Path;
1195   Dir.toVector(Path);
1196
1197   EC = makeCanonical(Path);
1198   if (EC)
1199     return {};
1200
1201   ErrorOr<RedirectingFileSystem::LookupResult> Result = lookupPath(Path);
1202   if (!Result) {
1203     EC = Result.getError();
1204     if (shouldFallBackToExternalFS(EC))
1205       return ExternalFS->dir_begin(Path, EC);
1206     return {};
1207   }
1208
1209   // Use status to make sure the path exists and refers to a directory.
1210   ErrorOr<Status> S = status(Path, *Result);
1211   if (!S) {
1212     if (shouldFallBackToExternalFS(S.getError(), Result->E))
1213       return ExternalFS->dir_begin(Dir, EC);
1214     EC = S.getError();
1215     return {};
1216   }
1217   if (!S->isDirectory()) {
1218     EC = std::error_code(static_cast<int>(errc::not_a_directory),
1219                          std::system_category());
1220     return {};
1221   }
1222
1223   // Create the appropriate directory iterator based on whether we found a
1224   // DirectoryRemapEntry or DirectoryEntry.
1225   directory_iterator DirIter;
1226   if (auto ExtRedirect = Result->getExternalRedirect()) {
1227     auto RE = cast<RedirectingFileSystem::RemapEntry>(Result->E);
1228     DirIter = ExternalFS->dir_begin(*ExtRedirect, EC);
1229
1230     if (!RE->useExternalName(UseExternalNames)) {
1231       // Update the paths in the results to use the virtual directory's path.
1232       DirIter =
1233           directory_iterator(std::make_shared<RedirectingFSDirRemapIterImpl>(
1234               std::string(Path), DirIter));
1235     }
1236   } else {
1237     auto DE = cast<DirectoryEntry>(Result->E);
1238     DirIter = directory_iterator(std::make_shared<RedirectingFSDirIterImpl>(
1239         Path, DE->contents_begin(), DE->contents_end(), EC));
1240   }
1241
1242   if (!shouldUseExternalFS())
1243     return DirIter;
1244   return directory_iterator(std::make_shared<CombiningDirIterImpl>(
1245       DirIter, ExternalFS, std::string(Path), EC));
1246 }
1247
1248 void RedirectingFileSystem::setExternalContentsPrefixDir(StringRef PrefixDir) {
1249   ExternalContentsPrefixDir = PrefixDir.str();
1250 }
1251
1252 StringRef RedirectingFileSystem::getExternalContentsPrefixDir() const {
1253   return ExternalContentsPrefixDir;
1254 }
1255
1256 void RedirectingFileSystem::setFallthrough(bool Fallthrough) {
1257   IsFallthrough = Fallthrough;
1258 }
1259
1260 std::vector<StringRef> RedirectingFileSystem::getRoots() const {
1261   std::vector<StringRef> R;
1262   for (const auto &Root : Roots)
1263     R.push_back(Root->getName());
1264   return R;
1265 }
1266
1267 void RedirectingFileSystem::dump(raw_ostream &OS) const {
1268   for (const auto &Root : Roots)
1269     dumpEntry(OS, Root.get());
1270 }
1271
1272 void RedirectingFileSystem::dumpEntry(raw_ostream &OS,
1273                                       RedirectingFileSystem::Entry *E,
1274                                       int NumSpaces) const {
1275   StringRef Name = E->getName();
1276   for (int i = 0, e = NumSpaces; i < e; ++i)
1277     OS << " ";
1278   OS << "'" << Name.str().c_str() << "'"
1279      << "\n";
1280
1281   if (E->getKind() == RedirectingFileSystem::EK_Directory) {
1282     auto *DE = dyn_cast<RedirectingFileSystem::DirectoryEntry>(E);
1283     assert(DE && "Should be a directory");
1284
1285     for (std::unique_ptr<Entry> &SubEntry :
1286          llvm::make_range(DE->contents_begin(), DE->contents_end()))
1287       dumpEntry(OS, SubEntry.get(), NumSpaces + 2);
1288   }
1289 }
1290
1291 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1292 LLVM_DUMP_METHOD void RedirectingFileSystem::dump() const { dump(dbgs()); }
1293 #endif
1294
1295 /// A helper class to hold the common YAML parsing state.
1296 class llvm::vfs::RedirectingFileSystemParser {
1297   yaml::Stream &Stream;
1298
1299   void error(yaml::Node *N, const Twine &Msg) { Stream.printError(N, Msg); }
1300
1301   // false on error
1302   bool parseScalarString(yaml::Node *N, StringRef &Result,
1303                          SmallVectorImpl<char> &Storage) {
1304     const auto *S = dyn_cast<yaml::ScalarNode>(N);
1305
1306     if (!S) {
1307       error(N, "expected string");
1308       return false;
1309     }
1310     Result = S->getValue(Storage);
1311     return true;
1312   }
1313
1314   // false on error
1315   bool parseScalarBool(yaml::Node *N, bool &Result) {
1316     SmallString<5> Storage;
1317     StringRef Value;
1318     if (!parseScalarString(N, Value, Storage))
1319       return false;
1320
1321     if (Value.equals_insensitive("true") || Value.equals_insensitive("on") ||
1322         Value.equals_insensitive("yes") || Value == "1") {
1323       Result = true;
1324       return true;
1325     } else if (Value.equals_insensitive("false") ||
1326                Value.equals_insensitive("off") ||
1327                Value.equals_insensitive("no") || Value == "0") {
1328       Result = false;
1329       return true;
1330     }
1331
1332     error(N, "expected boolean value");
1333     return false;
1334   }
1335
1336   struct KeyStatus {
1337     bool Required;
1338     bool Seen = false;
1339
1340     KeyStatus(bool Required = false) : Required(Required) {}
1341   };
1342
1343   using KeyStatusPair = std::pair<StringRef, KeyStatus>;
1344
1345   // false on error
1346   bool checkDuplicateOrUnknownKey(yaml::Node *KeyNode, StringRef Key,
1347                                   DenseMap<StringRef, KeyStatus> &Keys) {
1348     if (!Keys.count(Key)) {
1349       error(KeyNode, "unknown key");
1350       return false;
1351     }
1352     KeyStatus &S = Keys[Key];
1353     if (S.Seen) {
1354       error(KeyNode, Twine("duplicate key '") + Key + "'");
1355       return false;
1356     }
1357     S.Seen = true;
1358     return true;
1359   }
1360
1361   // false on error
1362   bool checkMissingKeys(yaml::Node *Obj, DenseMap<StringRef, KeyStatus> &Keys) {
1363     for (const auto &I : Keys) {
1364       if (I.second.Required && !I.second.Seen) {
1365         error(Obj, Twine("missing key '") + I.first + "'");
1366         return false;
1367       }
1368     }
1369     return true;
1370   }
1371
1372 public:
1373   static RedirectingFileSystem::Entry *
1374   lookupOrCreateEntry(RedirectingFileSystem *FS, StringRef Name,
1375                       RedirectingFileSystem::Entry *ParentEntry = nullptr) {
1376     if (!ParentEntry) { // Look for a existent root
1377       for (const auto &Root : FS->Roots) {
1378         if (Name.equals(Root->getName())) {
1379           ParentEntry = Root.get();
1380           return ParentEntry;
1381         }
1382       }
1383     } else { // Advance to the next component
1384       auto *DE = dyn_cast<RedirectingFileSystem::DirectoryEntry>(ParentEntry);
1385       for (std::unique_ptr<RedirectingFileSystem::Entry> &Content :
1386            llvm::make_range(DE->contents_begin(), DE->contents_end())) {
1387         auto *DirContent =
1388             dyn_cast<RedirectingFileSystem::DirectoryEntry>(Content.get());
1389         if (DirContent && Name.equals(Content->getName()))
1390           return DirContent;
1391       }
1392     }
1393
1394     // ... or create a new one
1395     std::unique_ptr<RedirectingFileSystem::Entry> E =
1396         std::make_unique<RedirectingFileSystem::DirectoryEntry>(
1397             Name, Status("", getNextVirtualUniqueID(),
1398                          std::chrono::system_clock::now(), 0, 0, 0,
1399                          file_type::directory_file, sys::fs::all_all));
1400
1401     if (!ParentEntry) { // Add a new root to the overlay
1402       FS->Roots.push_back(std::move(E));
1403       ParentEntry = FS->Roots.back().get();
1404       return ParentEntry;
1405     }
1406
1407     auto *DE = cast<RedirectingFileSystem::DirectoryEntry>(ParentEntry);
1408     DE->addContent(std::move(E));
1409     return DE->getLastContent();
1410   }
1411
1412 private:
1413   void uniqueOverlayTree(RedirectingFileSystem *FS,
1414                          RedirectingFileSystem::Entry *SrcE,
1415                          RedirectingFileSystem::Entry *NewParentE = nullptr) {
1416     StringRef Name = SrcE->getName();
1417     switch (SrcE->getKind()) {
1418     case RedirectingFileSystem::EK_Directory: {
1419       auto *DE = cast<RedirectingFileSystem::DirectoryEntry>(SrcE);
1420       // Empty directories could be present in the YAML as a way to
1421       // describe a file for a current directory after some of its subdir
1422       // is parsed. This only leads to redundant walks, ignore it.
1423       if (!Name.empty())
1424         NewParentE = lookupOrCreateEntry(FS, Name, NewParentE);
1425       for (std::unique_ptr<RedirectingFileSystem::Entry> &SubEntry :
1426            llvm::make_range(DE->contents_begin(), DE->contents_end()))
1427         uniqueOverlayTree(FS, SubEntry.get(), NewParentE);
1428       break;
1429     }
1430     case RedirectingFileSystem::EK_DirectoryRemap: {
1431       assert(NewParentE && "Parent entry must exist");
1432       auto *DR = cast<RedirectingFileSystem::DirectoryRemapEntry>(SrcE);
1433       auto *DE = cast<RedirectingFileSystem::DirectoryEntry>(NewParentE);
1434       DE->addContent(
1435           std::make_unique<RedirectingFileSystem::DirectoryRemapEntry>(
1436               Name, DR->getExternalContentsPath(), DR->getUseName()));
1437       break;
1438     }
1439     case RedirectingFileSystem::EK_File: {
1440       assert(NewParentE && "Parent entry must exist");
1441       auto *FE = cast<RedirectingFileSystem::FileEntry>(SrcE);
1442       auto *DE = cast<RedirectingFileSystem::DirectoryEntry>(NewParentE);
1443       DE->addContent(std::make_unique<RedirectingFileSystem::FileEntry>(
1444           Name, FE->getExternalContentsPath(), FE->getUseName()));
1445       break;
1446     }
1447     }
1448   }
1449
1450   std::unique_ptr<RedirectingFileSystem::Entry>
1451   parseEntry(yaml::Node *N, RedirectingFileSystem *FS, bool IsRootEntry) {
1452     auto *M = dyn_cast<yaml::MappingNode>(N);
1453     if (!M) {
1454       error(N, "expected mapping node for file or directory entry");
1455       return nullptr;
1456     }
1457
1458     KeyStatusPair Fields[] = {
1459         KeyStatusPair("name", true),
1460         KeyStatusPair("type", true),
1461         KeyStatusPair("contents", false),
1462         KeyStatusPair("external-contents", false),
1463         KeyStatusPair("use-external-name", false),
1464     };
1465
1466     DenseMap<StringRef, KeyStatus> Keys(std::begin(Fields), std::end(Fields));
1467
1468     enum { CF_NotSet, CF_List, CF_External } ContentsField = CF_NotSet;
1469     std::vector<std::unique_ptr<RedirectingFileSystem::Entry>>
1470         EntryArrayContents;
1471     SmallString<256> ExternalContentsPath;
1472     SmallString<256> Name;
1473     yaml::Node *NameValueNode = nullptr;
1474     auto UseExternalName = RedirectingFileSystem::NK_NotSet;
1475     RedirectingFileSystem::EntryKind Kind;
1476
1477     for (auto &I : *M) {
1478       StringRef Key;
1479       // Reuse the buffer for key and value, since we don't look at key after
1480       // parsing value.
1481       SmallString<256> Buffer;
1482       if (!parseScalarString(I.getKey(), Key, Buffer))
1483         return nullptr;
1484
1485       if (!checkDuplicateOrUnknownKey(I.getKey(), Key, Keys))
1486         return nullptr;
1487
1488       StringRef Value;
1489       if (Key == "name") {
1490         if (!parseScalarString(I.getValue(), Value, Buffer))
1491           return nullptr;
1492
1493         NameValueNode = I.getValue();
1494         // Guarantee that old YAML files containing paths with ".." and "."
1495         // are properly canonicalized before read into the VFS.
1496         Name = canonicalize(Value).str();
1497       } else if (Key == "type") {
1498         if (!parseScalarString(I.getValue(), Value, Buffer))
1499           return nullptr;
1500         if (Value == "file")
1501           Kind = RedirectingFileSystem::EK_File;
1502         else if (Value == "directory")
1503           Kind = RedirectingFileSystem::EK_Directory;
1504         else if (Value == "directory-remap")
1505           Kind = RedirectingFileSystem::EK_DirectoryRemap;
1506         else {
1507           error(I.getValue(), "unknown value for 'type'");
1508           return nullptr;
1509         }
1510       } else if (Key == "contents") {
1511         if (ContentsField != CF_NotSet) {
1512           error(I.getKey(),
1513                 "entry already has 'contents' or 'external-contents'");
1514           return nullptr;
1515         }
1516         ContentsField = CF_List;
1517         auto *Contents = dyn_cast<yaml::SequenceNode>(I.getValue());
1518         if (!Contents) {
1519           // FIXME: this is only for directories, what about files?
1520           error(I.getValue(), "expected array");
1521           return nullptr;
1522         }
1523
1524         for (auto &I : *Contents) {
1525           if (std::unique_ptr<RedirectingFileSystem::Entry> E =
1526                   parseEntry(&I, FS, /*IsRootEntry*/ false))
1527             EntryArrayContents.push_back(std::move(E));
1528           else
1529             return nullptr;
1530         }
1531       } else if (Key == "external-contents") {
1532         if (ContentsField != CF_NotSet) {
1533           error(I.getKey(),
1534                 "entry already has 'contents' or 'external-contents'");
1535           return nullptr;
1536         }
1537         ContentsField = CF_External;
1538         if (!parseScalarString(I.getValue(), Value, Buffer))
1539           return nullptr;
1540
1541         SmallString<256> FullPath;
1542         if (FS->IsRelativeOverlay) {
1543           FullPath = FS->getExternalContentsPrefixDir();
1544           assert(!FullPath.empty() &&
1545                  "External contents prefix directory must exist");
1546           llvm::sys::path::append(FullPath, Value);
1547         } else {
1548           FullPath = Value;
1549         }
1550
1551         // Guarantee that old YAML files containing paths with ".." and "."
1552         // are properly canonicalized before read into the VFS.
1553         FullPath = canonicalize(FullPath);
1554         ExternalContentsPath = FullPath.str();
1555       } else if (Key == "use-external-name") {
1556         bool Val;
1557         if (!parseScalarBool(I.getValue(), Val))
1558           return nullptr;
1559         UseExternalName = Val ? RedirectingFileSystem::NK_External
1560                               : RedirectingFileSystem::NK_Virtual;
1561       } else {
1562         llvm_unreachable("key missing from Keys");
1563       }
1564     }
1565
1566     if (Stream.failed())
1567       return nullptr;
1568
1569     // check for missing keys
1570     if (ContentsField == CF_NotSet) {
1571       error(N, "missing key 'contents' or 'external-contents'");
1572       return nullptr;
1573     }
1574     if (!checkMissingKeys(N, Keys))
1575       return nullptr;
1576
1577     // check invalid configuration
1578     if (Kind == RedirectingFileSystem::EK_Directory &&
1579         UseExternalName != RedirectingFileSystem::NK_NotSet) {
1580       error(N, "'use-external-name' is not supported for 'directory' entries");
1581       return nullptr;
1582     }
1583
1584     if (Kind == RedirectingFileSystem::EK_DirectoryRemap &&
1585         ContentsField == CF_List) {
1586       error(N, "'contents' is not supported for 'directory-remap' entries");
1587       return nullptr;
1588     }
1589
1590     sys::path::Style path_style = sys::path::Style::native;
1591     if (IsRootEntry) {
1592       // VFS root entries may be in either Posix or Windows style.  Figure out
1593       // which style we have, and use it consistently.
1594       if (sys::path::is_absolute(Name, sys::path::Style::posix)) {
1595         path_style = sys::path::Style::posix;
1596       } else if (sys::path::is_absolute(Name, sys::path::Style::windows)) {
1597         path_style = sys::path::Style::windows;
1598       } else {
1599         assert(NameValueNode && "Name presence should be checked earlier");
1600         error(NameValueNode,
1601               "entry with relative path at the root level is not discoverable");
1602         return nullptr;
1603       }
1604     }
1605
1606     // Remove trailing slash(es), being careful not to remove the root path
1607     StringRef Trimmed = Name;
1608     size_t RootPathLen = sys::path::root_path(Trimmed, path_style).size();
1609     while (Trimmed.size() > RootPathLen &&
1610            sys::path::is_separator(Trimmed.back(), path_style))
1611       Trimmed = Trimmed.slice(0, Trimmed.size() - 1);
1612
1613     // Get the last component
1614     StringRef LastComponent = sys::path::filename(Trimmed, path_style);
1615
1616     std::unique_ptr<RedirectingFileSystem::Entry> Result;
1617     switch (Kind) {
1618     case RedirectingFileSystem::EK_File:
1619       Result = std::make_unique<RedirectingFileSystem::FileEntry>(
1620           LastComponent, std::move(ExternalContentsPath), UseExternalName);
1621       break;
1622     case RedirectingFileSystem::EK_DirectoryRemap:
1623       Result = std::make_unique<RedirectingFileSystem::DirectoryRemapEntry>(
1624           LastComponent, std::move(ExternalContentsPath), UseExternalName);
1625       break;
1626     case RedirectingFileSystem::EK_Directory:
1627       Result = std::make_unique<RedirectingFileSystem::DirectoryEntry>(
1628           LastComponent, std::move(EntryArrayContents),
1629           Status("", getNextVirtualUniqueID(), std::chrono::system_clock::now(),
1630                  0, 0, 0, file_type::directory_file, sys::fs::all_all));
1631       break;
1632     }
1633
1634     StringRef Parent = sys::path::parent_path(Trimmed, path_style);
1635     if (Parent.empty())
1636       return Result;
1637
1638     // if 'name' contains multiple components, create implicit directory entries
1639     for (sys::path::reverse_iterator I = sys::path::rbegin(Parent, path_style),
1640                                      E = sys::path::rend(Parent);
1641          I != E; ++I) {
1642       std::vector<std::unique_ptr<RedirectingFileSystem::Entry>> Entries;
1643       Entries.push_back(std::move(Result));
1644       Result = std::make_unique<RedirectingFileSystem::DirectoryEntry>(
1645           *I, std::move(Entries),
1646           Status("", getNextVirtualUniqueID(), std::chrono::system_clock::now(),
1647                  0, 0, 0, file_type::directory_file, sys::fs::all_all));
1648     }
1649     return Result;
1650   }
1651
1652 public:
1653   RedirectingFileSystemParser(yaml::Stream &S) : Stream(S) {}
1654
1655   // false on error
1656   bool parse(yaml::Node *Root, RedirectingFileSystem *FS) {
1657     auto *Top = dyn_cast<yaml::MappingNode>(Root);
1658     if (!Top) {
1659       error(Root, "expected mapping node");
1660       return false;
1661     }
1662
1663     KeyStatusPair Fields[] = {
1664         KeyStatusPair("version", true),
1665         KeyStatusPair("case-sensitive", false),
1666         KeyStatusPair("use-external-names", false),
1667         KeyStatusPair("overlay-relative", false),
1668         KeyStatusPair("fallthrough", false),
1669         KeyStatusPair("roots", true),
1670     };
1671
1672     DenseMap<StringRef, KeyStatus> Keys(std::begin(Fields), std::end(Fields));
1673     std::vector<std::unique_ptr<RedirectingFileSystem::Entry>> RootEntries;
1674
1675     // Parse configuration and 'roots'
1676     for (auto &I : *Top) {
1677       SmallString<10> KeyBuffer;
1678       StringRef Key;
1679       if (!parseScalarString(I.getKey(), Key, KeyBuffer))
1680         return false;
1681
1682       if (!checkDuplicateOrUnknownKey(I.getKey(), Key, Keys))
1683         return false;
1684
1685       if (Key == "roots") {
1686         auto *Roots = dyn_cast<yaml::SequenceNode>(I.getValue());
1687         if (!Roots) {
1688           error(I.getValue(), "expected array");
1689           return false;
1690         }
1691
1692         for (auto &I : *Roots) {
1693           if (std::unique_ptr<RedirectingFileSystem::Entry> E =
1694                   parseEntry(&I, FS, /*IsRootEntry*/ true))
1695             RootEntries.push_back(std::move(E));
1696           else
1697             return false;
1698         }
1699       } else if (Key == "version") {
1700         StringRef VersionString;
1701         SmallString<4> Storage;
1702         if (!parseScalarString(I.getValue(), VersionString, Storage))
1703           return false;
1704         int Version;
1705         if (VersionString.getAsInteger<int>(10, Version)) {
1706           error(I.getValue(), "expected integer");
1707           return false;
1708         }
1709         if (Version < 0) {
1710           error(I.getValue(), "invalid version number");
1711           return false;
1712         }
1713         if (Version != 0) {
1714           error(I.getValue(), "version mismatch, expected 0");
1715           return false;
1716         }
1717       } else if (Key == "case-sensitive") {
1718         if (!parseScalarBool(I.getValue(), FS->CaseSensitive))
1719           return false;
1720       } else if (Key == "overlay-relative") {
1721         if (!parseScalarBool(I.getValue(), FS->IsRelativeOverlay))
1722           return false;
1723       } else if (Key == "use-external-names") {
1724         if (!parseScalarBool(I.getValue(), FS->UseExternalNames))
1725           return false;
1726       } else if (Key == "fallthrough") {
1727         if (!parseScalarBool(I.getValue(), FS->IsFallthrough))
1728           return false;
1729       } else {
1730         llvm_unreachable("key missing from Keys");
1731       }
1732     }
1733
1734     if (Stream.failed())
1735       return false;
1736
1737     if (!checkMissingKeys(Top, Keys))
1738       return false;
1739
1740     // Now that we sucessefully parsed the YAML file, canonicalize the internal
1741     // representation to a proper directory tree so that we can search faster
1742     // inside the VFS.
1743     for (auto &E : RootEntries)
1744       uniqueOverlayTree(FS, E.get());
1745
1746     return true;
1747   }
1748 };
1749
1750 std::unique_ptr<RedirectingFileSystem>
1751 RedirectingFileSystem::create(std::unique_ptr<MemoryBuffer> Buffer,
1752                               SourceMgr::DiagHandlerTy DiagHandler,
1753                               StringRef YAMLFilePath, void *DiagContext,
1754                               IntrusiveRefCntPtr<FileSystem> ExternalFS) {
1755   SourceMgr SM;
1756   yaml::Stream Stream(Buffer->getMemBufferRef(), SM);
1757
1758   SM.setDiagHandler(DiagHandler, DiagContext);
1759   yaml::document_iterator DI = Stream.begin();
1760   yaml::Node *Root = DI->getRoot();
1761   if (DI == Stream.end() || !Root) {
1762     SM.PrintMessage(SMLoc(), SourceMgr::DK_Error, "expected root node");
1763     return nullptr;
1764   }
1765
1766   RedirectingFileSystemParser P(Stream);
1767
1768   std::unique_ptr<RedirectingFileSystem> FS(
1769       new RedirectingFileSystem(ExternalFS));
1770
1771   if (!YAMLFilePath.empty()) {
1772     // Use the YAML path from -ivfsoverlay to compute the dir to be prefixed
1773     // to each 'external-contents' path.
1774     //
1775     // Example:
1776     //    -ivfsoverlay dummy.cache/vfs/vfs.yaml
1777     // yields:
1778     //  FS->ExternalContentsPrefixDir => /<absolute_path_to>/dummy.cache/vfs
1779     //
1780     SmallString<256> OverlayAbsDir = sys::path::parent_path(YAMLFilePath);
1781     std::error_code EC = llvm::sys::fs::make_absolute(OverlayAbsDir);
1782     assert(!EC && "Overlay dir final path must be absolute");
1783     (void)EC;
1784     FS->setExternalContentsPrefixDir(OverlayAbsDir);
1785   }
1786
1787   if (!P.parse(Root, FS.get()))
1788     return nullptr;
1789
1790   return FS;
1791 }
1792
1793 std::unique_ptr<RedirectingFileSystem> RedirectingFileSystem::create(
1794     ArrayRef<std::pair<std::string, std::string>> RemappedFiles,
1795     bool UseExternalNames, FileSystem &ExternalFS) {
1796   std::unique_ptr<RedirectingFileSystem> FS(
1797       new RedirectingFileSystem(&ExternalFS));
1798   FS->UseExternalNames = UseExternalNames;
1799
1800   StringMap<RedirectingFileSystem::Entry *> Entries;
1801
1802   for (auto &Mapping : llvm::reverse(RemappedFiles)) {
1803     SmallString<128> From = StringRef(Mapping.first);
1804     SmallString<128> To = StringRef(Mapping.second);
1805     {
1806       auto EC = ExternalFS.makeAbsolute(From);
1807       (void)EC;
1808       assert(!EC && "Could not make absolute path");
1809     }
1810
1811     // Check if we've already mapped this file. The first one we see (in the
1812     // reverse iteration) wins.
1813     RedirectingFileSystem::Entry *&ToEntry = Entries[From];
1814     if (ToEntry)
1815       continue;
1816
1817     // Add parent directories.
1818     RedirectingFileSystem::Entry *Parent = nullptr;
1819     StringRef FromDirectory = llvm::sys::path::parent_path(From);
1820     for (auto I = llvm::sys::path::begin(FromDirectory),
1821               E = llvm::sys::path::end(FromDirectory);
1822          I != E; ++I) {
1823       Parent = RedirectingFileSystemParser::lookupOrCreateEntry(FS.get(), *I,
1824                                                                 Parent);
1825     }
1826     assert(Parent && "File without a directory?");
1827     {
1828       auto EC = ExternalFS.makeAbsolute(To);
1829       (void)EC;
1830       assert(!EC && "Could not make absolute path");
1831     }
1832
1833     // Add the file.
1834     auto NewFile = std::make_unique<RedirectingFileSystem::FileEntry>(
1835         llvm::sys::path::filename(From), To,
1836         UseExternalNames ? RedirectingFileSystem::NK_External
1837                          : RedirectingFileSystem::NK_Virtual);
1838     ToEntry = NewFile.get();
1839     cast<RedirectingFileSystem::DirectoryEntry>(Parent)->addContent(
1840         std::move(NewFile));
1841   }
1842
1843   return FS;
1844 }
1845
1846 RedirectingFileSystem::LookupResult::LookupResult(
1847     Entry *E, sys::path::const_iterator Start, sys::path::const_iterator End)
1848     : E(E) {
1849   assert(E != nullptr);
1850   // If the matched entry is a DirectoryRemapEntry, set ExternalRedirect to the
1851   // path of the directory it maps to in the external file system plus any
1852   // remaining path components in the provided iterator.
1853   if (auto *DRE = dyn_cast<RedirectingFileSystem::DirectoryRemapEntry>(E)) {
1854     SmallString<256> Redirect(DRE->getExternalContentsPath());
1855     sys::path::append(Redirect, Start, End,
1856                       getExistingStyle(DRE->getExternalContentsPath()));
1857     ExternalRedirect = std::string(Redirect);
1858   }
1859 }
1860
1861 bool RedirectingFileSystem::shouldFallBackToExternalFS(
1862     std::error_code EC, RedirectingFileSystem::Entry *E) const {
1863   if (E && !isa<RedirectingFileSystem::DirectoryRemapEntry>(E))
1864     return false;
1865   return shouldUseExternalFS() && EC == llvm::errc::no_such_file_or_directory;
1866 }
1867
1868 std::error_code
1869 RedirectingFileSystem::makeCanonical(SmallVectorImpl<char> &Path) const {
1870   if (std::error_code EC = makeAbsolute(Path))
1871     return EC;
1872
1873   llvm::SmallString<256> CanonicalPath =
1874       canonicalize(StringRef(Path.data(), Path.size()));
1875   if (CanonicalPath.empty())
1876     return make_error_code(llvm::errc::invalid_argument);
1877
1878   Path.assign(CanonicalPath.begin(), CanonicalPath.end());
1879   return {};
1880 }
1881
1882 ErrorOr<RedirectingFileSystem::LookupResult>
1883 RedirectingFileSystem::lookupPath(StringRef Path) const {
1884   sys::path::const_iterator Start = sys::path::begin(Path);
1885   sys::path::const_iterator End = sys::path::end(Path);
1886   for (const auto &Root : Roots) {
1887     ErrorOr<RedirectingFileSystem::LookupResult> Result =
1888         lookupPathImpl(Start, End, Root.get());
1889     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
1890       return Result;
1891   }
1892   return make_error_code(llvm::errc::no_such_file_or_directory);
1893 }
1894
1895 ErrorOr<RedirectingFileSystem::LookupResult>
1896 RedirectingFileSystem::lookupPathImpl(
1897     sys::path::const_iterator Start, sys::path::const_iterator End,
1898     RedirectingFileSystem::Entry *From) const {
1899   assert(!isTraversalComponent(*Start) &&
1900          !isTraversalComponent(From->getName()) &&
1901          "Paths should not contain traversal components");
1902
1903   StringRef FromName = From->getName();
1904
1905   // Forward the search to the next component in case this is an empty one.
1906   if (!FromName.empty()) {
1907     if (!pathComponentMatches(*Start, FromName))
1908       return make_error_code(llvm::errc::no_such_file_or_directory);
1909
1910     ++Start;
1911
1912     if (Start == End) {
1913       // Match!
1914       return LookupResult(From, Start, End);
1915     }
1916   }
1917
1918   if (isa<RedirectingFileSystem::FileEntry>(From))
1919     return make_error_code(llvm::errc::not_a_directory);
1920
1921   if (isa<RedirectingFileSystem::DirectoryRemapEntry>(From))
1922     return LookupResult(From, Start, End);
1923
1924   auto *DE = cast<RedirectingFileSystem::DirectoryEntry>(From);
1925   for (const std::unique_ptr<RedirectingFileSystem::Entry> &DirEntry :
1926        llvm::make_range(DE->contents_begin(), DE->contents_end())) {
1927     ErrorOr<RedirectingFileSystem::LookupResult> Result =
1928         lookupPathImpl(Start, End, DirEntry.get());
1929     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
1930       return Result;
1931   }
1932
1933   return make_error_code(llvm::errc::no_such_file_or_directory);
1934 }
1935
1936 static Status getRedirectedFileStatus(const Twine &Path, bool UseExternalNames,
1937                                       Status ExternalStatus) {
1938   Status S = ExternalStatus;
1939   if (!UseExternalNames)
1940     S = Status::copyWithNewName(S, Path);
1941   S.IsVFSMapped = true;
1942   return S;
1943 }
1944
1945 ErrorOr<Status> RedirectingFileSystem::status(
1946     const Twine &Path, const RedirectingFileSystem::LookupResult &Result) {
1947   if (Optional<StringRef> ExtRedirect = Result.getExternalRedirect()) {
1948     ErrorOr<Status> S = ExternalFS->status(*ExtRedirect);
1949     if (!S)
1950       return S;
1951     auto *RE = cast<RedirectingFileSystem::RemapEntry>(Result.E);
1952     return getRedirectedFileStatus(Path, RE->useExternalName(UseExternalNames),
1953                                    *S);
1954   }
1955
1956   auto *DE = cast<RedirectingFileSystem::DirectoryEntry>(Result.E);
1957   return Status::copyWithNewName(DE->getStatus(), Path);
1958 }
1959
1960 ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path_) {
1961   SmallString<256> Path;
1962   Path_.toVector(Path);
1963
1964   if (std::error_code EC = makeCanonical(Path))
1965     return EC;
1966
1967   ErrorOr<RedirectingFileSystem::LookupResult> Result = lookupPath(Path);
1968   if (!Result) {
1969     if (shouldFallBackToExternalFS(Result.getError()))
1970       return ExternalFS->status(Path);
1971     return Result.getError();
1972   }
1973
1974   ErrorOr<Status> S = status(Path, *Result);
1975   if (!S && shouldFallBackToExternalFS(S.getError(), Result->E))
1976     S = ExternalFS->status(Path);
1977   return S;
1978 }
1979
1980 namespace {
1981
1982 /// Provide a file wrapper with an overriden status.
1983 class FileWithFixedStatus : public File {
1984   std::unique_ptr<File> InnerFile;
1985   Status S;
1986
1987 public:
1988   FileWithFixedStatus(std::unique_ptr<File> InnerFile, Status S)
1989       : InnerFile(std::move(InnerFile)), S(std::move(S)) {}
1990
1991   ErrorOr<Status> status() override { return S; }
1992   ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
1993
1994   getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
1995             bool IsVolatile) override {
1996     return InnerFile->getBuffer(Name, FileSize, RequiresNullTerminator,
1997                                 IsVolatile);
1998   }
1999
2000   std::error_code close() override { return InnerFile->close(); }
2001 };
2002
2003 } // namespace
2004
2005 ErrorOr<std::unique_ptr<File>>
2006 RedirectingFileSystem::openFileForRead(const Twine &Path_) {
2007   SmallString<256> Path;
2008   Path_.toVector(Path);
2009
2010   if (std::error_code EC = makeCanonical(Path))
2011     return EC;
2012
2013   ErrorOr<RedirectingFileSystem::LookupResult> Result = lookupPath(Path);
2014   if (!Result) {
2015     if (shouldFallBackToExternalFS(Result.getError()))
2016       return ExternalFS->openFileForRead(Path);
2017     return Result.getError();
2018   }
2019
2020   if (!Result->getExternalRedirect()) // FIXME: errc::not_a_file?
2021     return make_error_code(llvm::errc::invalid_argument);
2022
2023   StringRef ExtRedirect = *Result->getExternalRedirect();
2024   auto *RE = cast<RedirectingFileSystem::RemapEntry>(Result->E);
2025
2026   auto ExternalFile = ExternalFS->openFileForRead(ExtRedirect);
2027   if (!ExternalFile) {
2028     if (shouldFallBackToExternalFS(ExternalFile.getError(), Result->E))
2029       return ExternalFS->openFileForRead(Path);
2030     return ExternalFile;
2031   }
2032
2033   auto ExternalStatus = (*ExternalFile)->status();
2034   if (!ExternalStatus)
2035     return ExternalStatus.getError();
2036
2037   // FIXME: Update the status with the name and VFSMapped.
2038   Status S = getRedirectedFileStatus(
2039       Path, RE->useExternalName(UseExternalNames), *ExternalStatus);
2040   return std::unique_ptr<File>(
2041       std::make_unique<FileWithFixedStatus>(std::move(*ExternalFile), S));
2042 }
2043
2044 std::error_code
2045 RedirectingFileSystem::getRealPath(const Twine &Path_,
2046                                    SmallVectorImpl<char> &Output) const {
2047   SmallString<256> Path;
2048   Path_.toVector(Path);
2049
2050   if (std::error_code EC = makeCanonical(Path))
2051     return EC;
2052
2053   ErrorOr<RedirectingFileSystem::LookupResult> Result = lookupPath(Path);
2054   if (!Result) {
2055     if (shouldFallBackToExternalFS(Result.getError()))
2056       return ExternalFS->getRealPath(Path, Output);
2057     return Result.getError();
2058   }
2059
2060   // If we found FileEntry or DirectoryRemapEntry, look up the mapped
2061   // path in the external file system.
2062   if (auto ExtRedirect = Result->getExternalRedirect()) {
2063     auto P = ExternalFS->getRealPath(*ExtRedirect, Output);
2064     if (!P && shouldFallBackToExternalFS(P, Result->E)) {
2065       return ExternalFS->getRealPath(Path, Output);
2066     }
2067     return P;
2068   }
2069
2070   // If we found a DirectoryEntry, still fall back to ExternalFS if allowed,
2071   // because directories don't have a single external contents path.
2072   return shouldUseExternalFS() ? ExternalFS->getRealPath(Path, Output)
2073                                : llvm::errc::invalid_argument;
2074 }
2075
2076 std::unique_ptr<FileSystem>
2077 vfs::getVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
2078                     SourceMgr::DiagHandlerTy DiagHandler,
2079                     StringRef YAMLFilePath, void *DiagContext,
2080                     IntrusiveRefCntPtr<FileSystem> ExternalFS) {
2081   return RedirectingFileSystem::create(std::move(Buffer), DiagHandler,
2082                                        YAMLFilePath, DiagContext,
2083                                        std::move(ExternalFS));
2084 }
2085
2086 static void getVFSEntries(RedirectingFileSystem::Entry *SrcE,
2087                           SmallVectorImpl<StringRef> &Path,
2088                           SmallVectorImpl<YAMLVFSEntry> &Entries) {
2089   auto Kind = SrcE->getKind();
2090   if (Kind == RedirectingFileSystem::EK_Directory) {
2091     auto *DE = dyn_cast<RedirectingFileSystem::DirectoryEntry>(SrcE);
2092     assert(DE && "Must be a directory");
2093     for (std::unique_ptr<RedirectingFileSystem::Entry> &SubEntry :
2094          llvm::make_range(DE->contents_begin(), DE->contents_end())) {
2095       Path.push_back(SubEntry->getName());
2096       getVFSEntries(SubEntry.get(), Path, Entries);
2097       Path.pop_back();
2098     }
2099     return;
2100   }
2101
2102   if (Kind == RedirectingFileSystem::EK_DirectoryRemap) {
2103     auto *DR = dyn_cast<RedirectingFileSystem::DirectoryRemapEntry>(SrcE);
2104     assert(DR && "Must be a directory remap");
2105     SmallString<128> VPath;
2106     for (auto &Comp : Path)
2107       llvm::sys::path::append(VPath, Comp);
2108     Entries.push_back(
2109         YAMLVFSEntry(VPath.c_str(), DR->getExternalContentsPath()));
2110     return;
2111   }
2112
2113   assert(Kind == RedirectingFileSystem::EK_File && "Must be a EK_File");
2114   auto *FE = dyn_cast<RedirectingFileSystem::FileEntry>(SrcE);
2115   assert(FE && "Must be a file");
2116   SmallString<128> VPath;
2117   for (auto &Comp : Path)
2118     llvm::sys::path::append(VPath, Comp);
2119   Entries.push_back(YAMLVFSEntry(VPath.c_str(), FE->getExternalContentsPath()));
2120 }
2121
2122 void vfs::collectVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
2123                              SourceMgr::DiagHandlerTy DiagHandler,
2124                              StringRef YAMLFilePath,
2125                              SmallVectorImpl<YAMLVFSEntry> &CollectedEntries,
2126                              void *DiagContext,
2127                              IntrusiveRefCntPtr<FileSystem> ExternalFS) {
2128   std::unique_ptr<RedirectingFileSystem> VFS = RedirectingFileSystem::create(
2129       std::move(Buffer), DiagHandler, YAMLFilePath, DiagContext,
2130       std::move(ExternalFS));
2131   if (!VFS)
2132     return;
2133   ErrorOr<RedirectingFileSystem::LookupResult> RootResult =
2134       VFS->lookupPath("/");
2135   if (!RootResult)
2136     return;
2137   SmallVector<StringRef, 8> Components;
2138   Components.push_back("/");
2139   getVFSEntries(RootResult->E, Components, CollectedEntries);
2140 }
2141
2142 UniqueID vfs::getNextVirtualUniqueID() {
2143   static std::atomic<unsigned> UID;
2144   unsigned ID = ++UID;
2145   // The following assumes that uint64_t max will never collide with a real
2146   // dev_t value from the OS.
2147   return UniqueID(std::numeric_limits<uint64_t>::max(), ID);
2148 }
2149
2150 void YAMLVFSWriter::addEntry(StringRef VirtualPath, StringRef RealPath,
2151                              bool IsDirectory) {
2152   assert(sys::path::is_absolute(VirtualPath) && "virtual path not absolute");
2153   assert(sys::path::is_absolute(RealPath) && "real path not absolute");
2154   assert(!pathHasTraversal(VirtualPath) && "path traversal is not supported");
2155   Mappings.emplace_back(VirtualPath, RealPath, IsDirectory);
2156 }
2157
2158 void YAMLVFSWriter::addFileMapping(StringRef VirtualPath, StringRef RealPath) {
2159   addEntry(VirtualPath, RealPath, /*IsDirectory=*/false);
2160 }
2161
2162 void YAMLVFSWriter::addDirectoryMapping(StringRef VirtualPath,
2163                                         StringRef RealPath) {
2164   addEntry(VirtualPath, RealPath, /*IsDirectory=*/true);
2165 }
2166
2167 namespace {
2168
2169 class JSONWriter {
2170   llvm::raw_ostream &OS;
2171   SmallVector<StringRef, 16> DirStack;
2172
2173   unsigned getDirIndent() { return 4 * DirStack.size(); }
2174   unsigned getFileIndent() { return 4 * (DirStack.size() + 1); }
2175   bool containedIn(StringRef Parent, StringRef Path);
2176   StringRef containedPart(StringRef Parent, StringRef Path);
2177   void startDirectory(StringRef Path);
2178   void endDirectory();
2179   void writeEntry(StringRef VPath, StringRef RPath);
2180
2181 public:
2182   JSONWriter(llvm::raw_ostream &OS) : OS(OS) {}
2183
2184   void write(ArrayRef<YAMLVFSEntry> Entries, Optional<bool> UseExternalNames,
2185              Optional<bool> IsCaseSensitive, Optional<bool> IsOverlayRelative,
2186              StringRef OverlayDir);
2187 };
2188
2189 } // namespace
2190
2191 bool JSONWriter::containedIn(StringRef Parent, StringRef Path) {
2192   using namespace llvm::sys;
2193
2194   // Compare each path component.
2195   auto IParent = path::begin(Parent), EParent = path::end(Parent);
2196   for (auto IChild = path::begin(Path), EChild = path::end(Path);
2197        IParent != EParent && IChild != EChild; ++IParent, ++IChild) {
2198     if (*IParent != *IChild)
2199       return false;
2200   }
2201   // Have we exhausted the parent path?
2202   return IParent == EParent;
2203 }
2204
2205 StringRef JSONWriter::containedPart(StringRef Parent, StringRef Path) {
2206   assert(!Parent.empty());
2207   assert(containedIn(Parent, Path));
2208   return Path.slice(Parent.size() + 1, StringRef::npos);
2209 }
2210
2211 void JSONWriter::startDirectory(StringRef Path) {
2212   StringRef Name =
2213       DirStack.empty() ? Path : containedPart(DirStack.back(), Path);
2214   DirStack.push_back(Path);
2215   unsigned Indent = getDirIndent();
2216   OS.indent(Indent) << "{\n";
2217   OS.indent(Indent + 2) << "'type': 'directory',\n";
2218   OS.indent(Indent + 2) << "'name': \"" << llvm::yaml::escape(Name) << "\",\n";
2219   OS.indent(Indent + 2) << "'contents': [\n";
2220 }
2221
2222 void JSONWriter::endDirectory() {
2223   unsigned Indent = getDirIndent();
2224   OS.indent(Indent + 2) << "]\n";
2225   OS.indent(Indent) << "}";
2226
2227   DirStack.pop_back();
2228 }
2229
2230 void JSONWriter::writeEntry(StringRef VPath, StringRef RPath) {
2231   unsigned Indent = getFileIndent();
2232   OS.indent(Indent) << "{\n";
2233   OS.indent(Indent + 2) << "'type': 'file',\n";
2234   OS.indent(Indent + 2) << "'name': \"" << llvm::yaml::escape(VPath) << "\",\n";
2235   OS.indent(Indent + 2) << "'external-contents': \""
2236                         << llvm::yaml::escape(RPath) << "\"\n";
2237   OS.indent(Indent) << "}";
2238 }
2239
2240 void JSONWriter::write(ArrayRef<YAMLVFSEntry> Entries,
2241                        Optional<bool> UseExternalNames,
2242                        Optional<bool> IsCaseSensitive,
2243                        Optional<bool> IsOverlayRelative,
2244                        StringRef OverlayDir) {
2245   using namespace llvm::sys;
2246
2247   OS << "{\n"
2248         "  'version': 0,\n";
2249   if (IsCaseSensitive.hasValue())
2250     OS << "  'case-sensitive': '"
2251        << (IsCaseSensitive.getValue() ? "true" : "false") << "',\n";
2252   if (UseExternalNames.hasValue())
2253     OS << "  'use-external-names': '"
2254        << (UseExternalNames.getValue() ? "true" : "false") << "',\n";
2255   bool UseOverlayRelative = false;
2256   if (IsOverlayRelative.hasValue()) {
2257     UseOverlayRelative = IsOverlayRelative.getValue();
2258     OS << "  'overlay-relative': '" << (UseOverlayRelative ? "true" : "false")
2259        << "',\n";
2260   }
2261   OS << "  'roots': [\n";
2262
2263   if (!Entries.empty()) {
2264     const YAMLVFSEntry &Entry = Entries.front();
2265
2266     startDirectory(
2267       Entry.IsDirectory ? Entry.VPath : path::parent_path(Entry.VPath)
2268     );
2269
2270     StringRef RPath = Entry.RPath;
2271     if (UseOverlayRelative) {
2272       unsigned OverlayDirLen = OverlayDir.size();
2273       assert(RPath.substr(0, OverlayDirLen) == OverlayDir &&
2274              "Overlay dir must be contained in RPath");
2275       RPath = RPath.slice(OverlayDirLen, RPath.size());
2276     }
2277
2278     bool IsCurrentDirEmpty = true;
2279     if (!Entry.IsDirectory) {
2280       writeEntry(path::filename(Entry.VPath), RPath);
2281       IsCurrentDirEmpty = false;
2282     }
2283
2284     for (const auto &Entry : Entries.slice(1)) {
2285       StringRef Dir =
2286           Entry.IsDirectory ? Entry.VPath : path::parent_path(Entry.VPath);
2287       if (Dir == DirStack.back()) {
2288         if (!IsCurrentDirEmpty) {
2289           OS << ",\n";
2290         }
2291       } else {
2292         bool IsDirPoppedFromStack = false;
2293         while (!DirStack.empty() && !containedIn(DirStack.back(), Dir)) {
2294           OS << "\n";
2295           endDirectory();
2296           IsDirPoppedFromStack = true;
2297         }
2298         if (IsDirPoppedFromStack || !IsCurrentDirEmpty) {
2299           OS << ",\n";
2300         }
2301         startDirectory(Dir);
2302         IsCurrentDirEmpty = true;
2303       }
2304       StringRef RPath = Entry.RPath;
2305       if (UseOverlayRelative) {
2306         unsigned OverlayDirLen = OverlayDir.size();
2307         assert(RPath.substr(0, OverlayDirLen) == OverlayDir &&
2308                "Overlay dir must be contained in RPath");
2309         RPath = RPath.slice(OverlayDirLen, RPath.size());
2310       }
2311       if (!Entry.IsDirectory) {
2312         writeEntry(path::filename(Entry.VPath), RPath);
2313         IsCurrentDirEmpty = false;
2314       }
2315     }
2316
2317     while (!DirStack.empty()) {
2318       OS << "\n";
2319       endDirectory();
2320     }
2321     OS << "\n";
2322   }
2323
2324   OS << "  ]\n"
2325      << "}\n";
2326 }
2327
2328 void YAMLVFSWriter::write(llvm::raw_ostream &OS) {
2329   llvm::sort(Mappings, [](const YAMLVFSEntry &LHS, const YAMLVFSEntry &RHS) {
2330     return LHS.VPath < RHS.VPath;
2331   });
2332
2333   JSONWriter(OS).write(Mappings, UseExternalNames, IsCaseSensitive,
2334                        IsOverlayRelative, OverlayDir);
2335 }
2336
2337 vfs::recursive_directory_iterator::recursive_directory_iterator(
2338     FileSystem &FS_, const Twine &Path, std::error_code &EC)
2339     : FS(&FS_) {
2340   directory_iterator I = FS->dir_begin(Path, EC);
2341   if (I != directory_iterator()) {
2342     State = std::make_shared<detail::RecDirIterState>();
2343     State->Stack.push(I);
2344   }
2345 }
2346
2347 vfs::recursive_directory_iterator &
2348 recursive_directory_iterator::increment(std::error_code &EC) {
2349   assert(FS && State && !State->Stack.empty() && "incrementing past end");
2350   assert(!State->Stack.top()->path().empty() && "non-canonical end iterator");
2351   vfs::directory_iterator End;
2352
2353   if (State->HasNoPushRequest)
2354     State->HasNoPushRequest = false;
2355   else {
2356     if (State->Stack.top()->type() == sys::fs::file_type::directory_file) {
2357       vfs::directory_iterator I = FS->dir_begin(State->Stack.top()->path(), EC);
2358       if (I != End) {
2359         State->Stack.push(I);
2360         return *this;
2361       }
2362     }
2363   }
2364
2365   while (!State->Stack.empty() && State->Stack.top().increment(EC) == End)
2366     State->Stack.pop();
2367
2368   if (State->Stack.empty())
2369     State.reset(); // end iterator
2370
2371   return *this;
2372 }