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_status;
  60 using llvm::sys::fs::file_type;
  61 using llvm::sys::fs::perms;
  62 using llvm::sys::fs::UniqueID;
  63
  64 Status::Status(const file_status &Status)
  65     : UID(Status.getUniqueID()), MTime(Status.getLastModificationTime()),
  66       User(Status.getUser()), Group(Status.getGroup()), Size(Status.getSize()),
  67       Type(Status.type()), Perms(Status.permissions()) {}
  68
  69 Status::Status(StringRef Name, UniqueID UID, sys::TimePoint<> MTime,
  70                uint32_t User, uint32_t Group, uint64_t Size, file_type Type,
  71                perms Perms)
  72     : Name(Name), UID(UID), MTime(MTime), User(User), Group(Group), Size(Size),
  73       Type(Type), Perms(Perms) {}
  74
  75 Status Status::copyWithNewName(const Status &In, StringRef NewName) {
  76   return Status(NewName, In.getUniqueID(), In.getLastModificationTime(),
  77                 In.getUser(), In.getGroup(), In.getSize(), In.getType(),
  78                 In.getPermissions());
  79 }
  80
  81 Status Status::copyWithNewName(const file_status &In, StringRef NewName) {
  82   return Status(NewName, In.getUniqueID(), In.getLastModificationTime(),
  83                 In.getUser(), In.getGroup(), In.getSize(), In.type(),
  84                 In.permissions());
  85 }
  86
  87 bool Status::equivalent(const Status &Other) const {
  88   assert(isStatusKnown() && Other.isStatusKnown());
  89   return getUniqueID() == Other.getUniqueID();
  90 }
  91
  92 bool Status::isDirectory() const { return Type == file_type::directory_file; }
  93
  94 bool Status::isRegularFile() const { return Type == file_type::regular_file; }
  95
  96 bool Status::isOther() const {
  97   return exists() && !isRegularFile() && !isDirectory() && !isSymlink();
  98 }
  99
 100 bool Status::isSymlink() const { return Type == file_type::symlink_file; }
 101
 102 bool Status::isStatusKnown() const { return Type != file_type::status_error; }
 103
 104 bool Status::exists() const {
 105   return isStatusKnown() && Type != file_type::file_not_found;
 106 }
 107
 108 File::~File() = default;
 109
 110 FileSystem::~FileSystem() = default;
 111
 112 ErrorOr<std::unique_ptr<MemoryBuffer>>
 113 FileSystem::getBufferForFile(const llvm::Twine &Name, int64_t FileSize,
 114                              bool RequiresNullTerminator, bool IsVolatile) {
 115   auto F = openFileForRead(Name);
 116   if (!F)
 117     return F.getError();
 118
 119   return (*F)->getBuffer(Name, FileSize, RequiresNullTerminator, IsVolatile);
 120 }
 121
 122 std::error_code FileSystem::makeAbsolute(SmallVectorImpl<char> &Path) const {
 123   if (llvm::sys::path::is_absolute(Path))
 124     return {};
 125
 126   auto WorkingDir = getCurrentWorkingDirectory();
 127   if (!WorkingDir)
 128     return WorkingDir.getError();
 129
 130   llvm::sys::fs::make_absolute(WorkingDir.get(), Path);
 131   return {};
 132 }
 133
 134 std::error_code FileSystem::getRealPath(const Twine &Path,
 135                                         SmallVectorImpl<char> &Output) const {
 136   return errc::operation_not_permitted;
 137 }
 138
 139 std::error_code FileSystem::isLocal(const Twine &Path, bool &Result) {
 140   return errc::operation_not_permitted;
 141 }
 142
 143 bool FileSystem::exists(const Twine &Path) {
 144   auto Status = status(Path);
 145   return Status && Status->exists();
 146 }
 147
 148 #ifndef NDEBUG
 149 static bool isTraversalComponent(StringRef Component) {
 150   return Component.equals("..") || Component.equals(".");
 151 }
 152
 153 static bool pathHasTraversal(StringRef Path) {
 154   using namespace llvm::sys;
 155
 156   for (StringRef Comp : llvm::make_range(path::begin(Path), path::end(Path)))
 157     if (isTraversalComponent(Comp))
 158       return true;
 159   return false;
 160 }
 161 #endif
 162
 163 //===-----------------------------------------------------------------------===/
 164 // RealFileSystem implementation
 165 //===-----------------------------------------------------------------------===/
 166
 167 namespace {
 168
 169 /// Wrapper around a raw file descriptor.
 170 class RealFile : public File {
 171   friend class RealFileSystem;
 172
 173   int FD;
 174   Status S;
 175   std::string RealName;
 176
 177   RealFile(int FD, StringRef NewName, StringRef NewRealPathName)
 178       : FD(FD), S(NewName, {}, {}, {}, {}, {},
 179                   llvm::sys::fs::file_type::status_error, {}),
 180         RealName(NewRealPathName.str()) {
 181     assert(FD >= 0 && "Invalid or inactive file descriptor");
 182   }
 183
 184 public:
 185   ~RealFile() override;
 186
 187   ErrorOr<Status> status() override;
 188   ErrorOr<std::string> getName() override;
 189   ErrorOr<std::unique_ptr<MemoryBuffer>> getBuffer(const Twine &Name,
 190                                                    int64_t FileSize,
 191                                                    bool RequiresNullTerminator,
 192                                                    bool IsVolatile) override;
 193   std::error_code close() override;
 194 };
 195
 196 } // namespace
 197
 198 RealFile::~RealFile() { close(); }
 199
 200 ErrorOr<Status> RealFile::status() {
 201   assert(FD != -1 && "cannot stat closed file");
 202   if (!S.isStatusKnown()) {
 203     file_status RealStatus;
 204     if (std::error_code EC = sys::fs::status(FD, RealStatus))
 205       return EC;
 206     S = Status::copyWithNewName(RealStatus, S.getName());
 207   }
 208   return S;
 209 }
 210
 211 ErrorOr<std::string> RealFile::getName() {
 212   return RealName.empty() ? S.getName().str() : RealName;
 213 }
 214
 215 ErrorOr<std::unique_ptr<MemoryBuffer>>
 216 RealFile::getBuffer(const Twine &Name, int64_t FileSize,
 217                     bool RequiresNullTerminator, bool IsVolatile) {
 218   assert(FD != -1 && "cannot get buffer for closed file");
 219   return MemoryBuffer::getOpenFile(FD, Name, FileSize, RequiresNullTerminator,
 220                                    IsVolatile);
 221 }
 222
 223 std::error_code RealFile::close() {
 224   std::error_code EC = sys::Process::SafelyCloseFileDescriptor(FD);
 225   FD = -1;
 226   return EC;
 227 }
 228
 229 namespace {
 230
 231 /// A file system according to your operating system.
 232 /// This may be linked to the process's working directory, or maintain its own.
 233 ///
 234 /// Currently, its own working directory is emulated by storing the path and
 235 /// sending absolute paths to llvm::sys::fs:: functions.
 236 /// A more principled approach would be to push this down a level, modelling
 237 /// the working dir as an llvm::sys::fs::WorkingDir or similar.
 238 /// This would enable the use of openat()-style functions on some platforms.
 239 class RealFileSystem : public FileSystem {
 240 public:
 241   explicit RealFileSystem(bool LinkCWDToProcess) {
 242     if (!LinkCWDToProcess) {
 243       SmallString<128> PWD, RealPWD;
 244       if (llvm::sys::fs::current_path(PWD))
 245         return; // Awful, but nothing to do here.
 246       if (llvm::sys::fs::real_path(PWD, RealPWD))
 247         WD = {PWD, PWD};
 248       else
 249         WD = {PWD, RealPWD};
 250     }
 251   }
 252
 253   ErrorOr<Status> status(const Twine &Path) override;
 254   ErrorOr<std::unique_ptr<File>> openFileForRead(const Twine &Path) override;
 255   directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
 256
 257   llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override;
 258   std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
 259   std::error_code isLocal(const Twine &Path, bool &Result) override;
 260   std::error_code getRealPath(const Twine &Path,
 261                               SmallVectorImpl<char> &Output) const override;
 262
 263 private:
 264   // If this FS has its own working dir, use it to make Path absolute.
 265   // The returned twine is safe to use as long as both Storage and Path live.
 266   Twine adjustPath(const Twine &Path, SmallVectorImpl<char> &Storage) const {
 267     if (!WD)
 268       return Path;
 269     Path.toVector(Storage);
 270     sys::fs::make_absolute(WD->Resolved, Storage);
 271     return Storage;
 272   }
 273
 274   struct WorkingDirectory {
 275     // The current working directory, without symlinks resolved. (echo $PWD).
 276     SmallString<128> Specified;
 277     // The current working directory, with links resolved. (readlink .).
 278     SmallString<128> Resolved;
 279   };
 280   Optional<WorkingDirectory> WD;
 281 };
 282
 283 } // namespace
 284
 285 ErrorOr<Status> RealFileSystem::status(const Twine &Path) {
 286   SmallString<256> Storage;
 287   sys::fs::file_status RealStatus;
 288   if (std::error_code EC =
 289           sys::fs::status(adjustPath(Path, Storage), RealStatus))
 290     return EC;
 291   return Status::copyWithNewName(RealStatus, Path.str());
 292 }
 293
 294 ErrorOr<std::unique_ptr<File>>
 295 RealFileSystem::openFileForRead(const Twine &Name) {
 296   int FD;
 297   SmallString<256> RealName, Storage;
 298   if (std::error_code EC = sys::fs::openFileForRead(
 299           adjustPath(Name, Storage), FD, sys::fs::OF_None, &RealName))
 300     return EC;
 301   return std::unique_ptr<File>(new RealFile(FD, Name.str(), RealName.str()));
 302 }
 303
 304 llvm::ErrorOr<std::string> RealFileSystem::getCurrentWorkingDirectory() const {
 305   if (WD)
 306     return WD->Specified.str();
 307
 308   SmallString<128> Dir;
 309   if (std::error_code EC = llvm::sys::fs::current_path(Dir))
 310     return EC;
 311   return Dir.str();
 312 }
 313
 314 std::error_code RealFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
 315   if (!WD)
 316     return llvm::sys::fs::set_current_path(Path);
 317
 318   SmallString<128> Absolute, Resolved, Storage;
 319   adjustPath(Path, Storage).toVector(Absolute);
 320   bool IsDir;
 321   if (auto Err = llvm::sys::fs::is_directory(Absolute, IsDir))
 322     return Err;
 323   if (!IsDir)
 324     return std::make_error_code(std::errc::not_a_directory);
 325   if (auto Err = llvm::sys::fs::real_path(Absolute, Resolved))
 326     return Err;
 327   WD = {Absolute, Resolved};
 328   return std::error_code();
 329 }
 330
 331 std::error_code RealFileSystem::isLocal(const Twine &Path, bool &Result) {
 332   SmallString<256> Storage;
 333   return llvm::sys::fs::is_local(adjustPath(Path, Storage), Result);
 334 }
 335
 336 std::error_code
 337 RealFileSystem::getRealPath(const Twine &Path,
 338                             SmallVectorImpl<char> &Output) const {
 339   SmallString<256> Storage;
 340   return llvm::sys::fs::real_path(adjustPath(Path, Storage), Output);
 341 }
 342
 343 IntrusiveRefCntPtr<FileSystem> vfs::getRealFileSystem() {
 344   static IntrusiveRefCntPtr<FileSystem> FS(new RealFileSystem(true));
 345   return FS;
 346 }
 347
 348 std::unique_ptr<FileSystem> vfs::createPhysicalFileSystem() {
 349   return llvm::make_unique<RealFileSystem>(false);
 350 }
 351
 352 namespace {
 353
 354 class RealFSDirIter : public llvm::vfs::detail::DirIterImpl {
 355   llvm::sys::fs::directory_iterator Iter;
 356
 357 public:
 358   RealFSDirIter(const Twine &Path, std::error_code &EC) : Iter(Path, EC) {
 359     if (Iter != llvm::sys::fs::directory_iterator())
 360       CurrentEntry = directory_entry(Iter->path(), Iter->type());
 361   }
 362
 363   std::error_code increment() override {
 364     std::error_code EC;
 365     Iter.increment(EC);
 366     CurrentEntry = (Iter == llvm::sys::fs::directory_iterator())
 367                        ? directory_entry()
 368                        : directory_entry(Iter->path(), Iter->type());
 369     return EC;
 370   }
 371 };
 372
 373 } // namespace
 374
 375 directory_iterator RealFileSystem::dir_begin(const Twine &Dir,
 376                                              std::error_code &EC) {
 377   SmallString<128> Storage;
 378   return directory_iterator(
 379       std::make_shared<RealFSDirIter>(adjustPath(Dir, Storage), EC));
 380 }
 381
 382 //===-----------------------------------------------------------------------===/
 383 // OverlayFileSystem implementation
 384 //===-----------------------------------------------------------------------===/
 385
 386 OverlayFileSystem::OverlayFileSystem(IntrusiveRefCntPtr<FileSystem> BaseFS) {
 387   FSList.push_back(std::move(BaseFS));
 388 }
 389
 390 void OverlayFileSystem::pushOverlay(IntrusiveRefCntPtr<FileSystem> FS) {
 391   FSList.push_back(FS);
 392   // Synchronize added file systems by duplicating the working directory from
 393   // the first one in the list.
 394   FS->setCurrentWorkingDirectory(getCurrentWorkingDirectory().get());
 395 }
 396
 397 ErrorOr<Status> OverlayFileSystem::status(const Twine &Path) {
 398   // FIXME: handle symlinks that cross file systems
 399   for (iterator I = overlays_begin(), E = overlays_end(); I != E; ++I) {
 400     ErrorOr<Status> Status = (*I)->status(Path);
 401     if (Status || Status.getError() != llvm::errc::no_such_file_or_directory)
 402       return Status;
 403   }
 404   return make_error_code(llvm::errc::no_such_file_or_directory);
 405 }
 406
 407 ErrorOr<std::unique_ptr<File>>
 408 OverlayFileSystem::openFileForRead(const llvm::Twine &Path) {
 409   // FIXME: handle symlinks that cross file systems
 410   for (iterator I = overlays_begin(), E = overlays_end(); I != E; ++I) {
 411     auto Result = (*I)->openFileForRead(Path);
 412     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
 413       return Result;
 414   }
 415   return make_error_code(llvm::errc::no_such_file_or_directory);
 416 }
 417
 418 llvm::ErrorOr<std::string>
 419 OverlayFileSystem::getCurrentWorkingDirectory() const {
 420   // All file systems are synchronized, just take the first working directory.
 421   return FSList.front()->getCurrentWorkingDirectory();
 422 }
 423
 424 std::error_code
 425 OverlayFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
 426   for (auto &FS : FSList)
 427     if (std::error_code EC = FS->setCurrentWorkingDirectory(Path))
 428       return EC;
 429   return {};
 430 }
 431
 432 std::error_code OverlayFileSystem::isLocal(const Twine &Path, bool &Result) {
 433   for (auto &FS : FSList)
 434     if (FS->exists(Path))
 435       return FS->isLocal(Path, Result);
 436   return errc::no_such_file_or_directory;
 437 }
 438
 439 std::error_code
 440 OverlayFileSystem::getRealPath(const Twine &Path,
 441                                SmallVectorImpl<char> &Output) const {
 442   for (auto &FS : FSList)
 443     if (FS->exists(Path))
 444       return FS->getRealPath(Path, Output);
 445   return errc::no_such_file_or_directory;
 446 }
 447
 448 llvm::vfs::detail::DirIterImpl::~DirIterImpl() = default;
 449
 450 namespace {
 451
 452 class OverlayFSDirIterImpl : public llvm::vfs::detail::DirIterImpl {
 453   OverlayFileSystem &Overlays;
 454   std::string Path;
 455   OverlayFileSystem::iterator CurrentFS;
 456   directory_iterator CurrentDirIter;
 457   llvm::StringSet<> SeenNames;
 458
 459   std::error_code incrementFS() {
 460     assert(CurrentFS != Overlays.overlays_end() && "incrementing past end");
 461     ++CurrentFS;
 462     for (auto E = Overlays.overlays_end(); CurrentFS != E; ++CurrentFS) {
 463       std::error_code EC;
 464       CurrentDirIter = (*CurrentFS)->dir_begin(Path, EC);
 465       if (EC && EC != errc::no_such_file_or_directory)
 466         return EC;
 467       if (CurrentDirIter != directory_iterator())
 468         break; // found
 469     }
 470     return {};
 471   }
 472
 473   std::error_code incrementDirIter(bool IsFirstTime) {
 474     assert((IsFirstTime || CurrentDirIter != directory_iterator()) &&
 475            "incrementing past end");
 476     std::error_code EC;
 477     if (!IsFirstTime)
 478       CurrentDirIter.increment(EC);
 479     if (!EC && CurrentDirIter == directory_iterator())
 480       EC = incrementFS();
 481     return EC;
 482   }
 483
 484   std::error_code incrementImpl(bool IsFirstTime) {
 485     while (true) {
 486       std::error_code EC = incrementDirIter(IsFirstTime);
 487       if (EC || CurrentDirIter == directory_iterator()) {
 488         CurrentEntry = directory_entry();
 489         return EC;
 490       }
 491       CurrentEntry = *CurrentDirIter;
 492       StringRef Name = llvm::sys::path::filename(CurrentEntry.path());
 493       if (SeenNames.insert(Name).second)
 494         return EC; // name not seen before
 495     }
 496     llvm_unreachable("returned above");
 497   }
 498
 499 public:
 500   OverlayFSDirIterImpl(const Twine &Path, OverlayFileSystem &FS,
 501                        std::error_code &EC)
 502       : Overlays(FS), Path(Path.str()), CurrentFS(Overlays.overlays_begin()) {
 503     CurrentDirIter = (*CurrentFS)->dir_begin(Path, EC);
 504     EC = incrementImpl(true);
 505   }
 506
 507   std::error_code increment() override { return incrementImpl(false); }
 508 };
 509
 510 } // namespace
 511
 512 directory_iterator OverlayFileSystem::dir_begin(const Twine &Dir,
 513                                                 std::error_code &EC) {
 514   return directory_iterator(
 515       std::make_shared<OverlayFSDirIterImpl>(Dir, *this, EC));
 516 }
 517
 518 void ProxyFileSystem::anchor() {}
 519
 520 namespace llvm {
 521 namespace vfs {
 522
 523 namespace detail {
 524
 525 enum InMemoryNodeKind { IME_File, IME_Directory, IME_HardLink };
 526
 527 /// The in memory file system is a tree of Nodes. Every node can either be a
 528 /// file , hardlink or a directory.
 529 class InMemoryNode {
 530   InMemoryNodeKind Kind;
 531   std::string FileName;
 532
 533 public:
 534   InMemoryNode(llvm::StringRef FileName, InMemoryNodeKind Kind)
 535       : Kind(Kind), FileName(llvm::sys::path::filename(FileName)) {}
 536   virtual ~InMemoryNode() = default;
 537
 538   /// Get the filename of this node (the name without the directory part).
 539   StringRef getFileName() const { return FileName; }
 540   InMemoryNodeKind getKind() const { return Kind; }
 541   virtual std::string toString(unsigned Indent) const = 0;
 542 };
 543
 544 class InMemoryFile : public InMemoryNode {
 545   Status Stat;
 546   std::unique_ptr<llvm::MemoryBuffer> Buffer;
 547
 548 public:
 549   InMemoryFile(Status Stat, std::unique_ptr<llvm::MemoryBuffer> Buffer)
 550       : InMemoryNode(Stat.getName(), IME_File), Stat(std::move(Stat)),
 551         Buffer(std::move(Buffer)) {}
 552
 553   /// Return the \p Status for this node. \p RequestedName should be the name
 554   /// through which the caller referred to this node. It will override
 555   /// \p Status::Name in the return value, to mimic the behavior of \p RealFile.
 556   Status getStatus(StringRef RequestedName) const {
 557     return Status::copyWithNewName(Stat, RequestedName);
 558   }
 559   llvm::MemoryBuffer *getBuffer() const { return Buffer.get(); }
 560
 561   std::string toString(unsigned Indent) const override {
 562     return (std::string(Indent, ' ') + Stat.getName() + "\n").str();
 563   }
 564
 565   static bool classof(const InMemoryNode *N) {
 566     return N->getKind() == IME_File;
 567   }
 568 };
 569
 570 namespace {
 571
 572 class InMemoryHardLink : public InMemoryNode {
 573   const InMemoryFile &ResolvedFile;
 574
 575 public:
 576   InMemoryHardLink(StringRef Path, const InMemoryFile &ResolvedFile)
 577       : InMemoryNode(Path, IME_HardLink), ResolvedFile(ResolvedFile) {}
 578   const InMemoryFile &getResolvedFile() const { return ResolvedFile; }
 579
 580   std::string toString(unsigned Indent) const override {
 581     return std::string(Indent, ' ') + "HardLink to -> " +
 582            ResolvedFile.toString(0);
 583   }
 584
 585   static bool classof(const InMemoryNode *N) {
 586     return N->getKind() == IME_HardLink;
 587   }
 588 };
 589
 590 /// Adapt a InMemoryFile for VFS' File interface.  The goal is to make
 591 /// \p InMemoryFileAdaptor mimic as much as possible the behavior of
 592 /// \p RealFile.
 593 class InMemoryFileAdaptor : public File {
 594   const InMemoryFile &Node;
 595   /// The name to use when returning a Status for this file.
 596   std::string RequestedName;
 597
 598 public:
 599   explicit InMemoryFileAdaptor(const InMemoryFile &Node,
 600                                std::string RequestedName)
 601       : Node(Node), RequestedName(std::move(RequestedName)) {}
 602
 603   llvm::ErrorOr<Status> status() override {
 604     return Node.getStatus(RequestedName);
 605   }
 606
 607   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
 608   getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
 609             bool IsVolatile) override {
 610     llvm::MemoryBuffer *Buf = Node.getBuffer();
 611     return llvm::MemoryBuffer::getMemBuffer(
 612         Buf->getBuffer(), Buf->getBufferIdentifier(), RequiresNullTerminator);
 613   }
 614
 615   std::error_code close() override { return {}; }
 616 };
 617 } // namespace
 618
 619 class InMemoryDirectory : public InMemoryNode {
 620   Status Stat;
 621   llvm::StringMap<std::unique_ptr<InMemoryNode>> Entries;
 622
 623 public:
 624   InMemoryDirectory(Status Stat)
 625       : InMemoryNode(Stat.getName(), IME_Directory), Stat(std::move(Stat)) {}
 626
 627   /// Return the \p Status for this node. \p RequestedName should be the name
 628   /// through which the caller referred to this node. It will override
 629   /// \p Status::Name in the return value, to mimic the behavior of \p RealFile.
 630   Status getStatus(StringRef RequestedName) const {
 631     return Status::copyWithNewName(Stat, RequestedName);
 632   }
 633   InMemoryNode *getChild(StringRef Name) {
 634     auto I = Entries.find(Name);
 635     if (I != Entries.end())
 636       return I->second.get();
 637     return nullptr;
 638   }
 639
 640   InMemoryNode *addChild(StringRef Name, std::unique_ptr<InMemoryNode> Child) {
 641     return Entries.insert(make_pair(Name, std::move(Child)))
 642         .first->second.get();
 643   }
 644
 645   using const_iterator = decltype(Entries)::const_iterator;
 646
 647   const_iterator begin() const { return Entries.begin(); }
 648   const_iterator end() const { return Entries.end(); }
 649
 650   std::string toString(unsigned Indent) const override {
 651     std::string Result =
 652         (std::string(Indent, ' ') + Stat.getName() + "\n").str();
 653     for (const auto &Entry : Entries)
 654       Result += Entry.second->toString(Indent + 2);
 655     return Result;
 656   }
 657
 658   static bool classof(const InMemoryNode *N) {
 659     return N->getKind() == IME_Directory;
 660   }
 661 };
 662
 663 namespace {
 664 Status getNodeStatus(const InMemoryNode *Node, StringRef RequestedName) {
 665   if (auto Dir = dyn_cast<detail::InMemoryDirectory>(Node))
 666     return Dir->getStatus(RequestedName);
 667   if (auto File = dyn_cast<detail::InMemoryFile>(Node))
 668     return File->getStatus(RequestedName);
 669   if (auto Link = dyn_cast<detail::InMemoryHardLink>(Node))
 670     return Link->getResolvedFile().getStatus(RequestedName);
 671   llvm_unreachable("Unknown node type");
 672 }
 673 } // namespace
 674 } // namespace detail
 675
 676 InMemoryFileSystem::InMemoryFileSystem(bool UseNormalizedPaths)
 677     : Root(new detail::InMemoryDirectory(
 678           Status("", getNextVirtualUniqueID(), llvm::sys::TimePoint<>(), 0, 0,
 679                  0, llvm::sys::fs::file_type::directory_file,
 680                  llvm::sys::fs::perms::all_all))),
 681       UseNormalizedPaths(UseNormalizedPaths) {}
 682
 683 InMemoryFileSystem::~InMemoryFileSystem() = default;
 684
 685 std::string InMemoryFileSystem::toString() const {
 686   return Root->toString(/*Indent=*/0);
 687 }
 688
 689 bool InMemoryFileSystem::addFile(const Twine &P, time_t ModificationTime,
 690                                  std::unique_ptr<llvm::MemoryBuffer> Buffer,
 691                                  Optional<uint32_t> User,
 692                                  Optional<uint32_t> Group,
 693                                  Optional<llvm::sys::fs::file_type> Type,
 694                                  Optional<llvm::sys::fs::perms> Perms,
 695                                  const detail::InMemoryFile *HardLinkTarget) {
 696   SmallString<128> Path;
 697   P.toVector(Path);
 698
 699   // Fix up relative paths. This just prepends the current working directory.
 700   std::error_code EC = makeAbsolute(Path);
 701   assert(!EC);
 702   (void)EC;
 703
 704   if (useNormalizedPaths())
 705     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 706
 707   if (Path.empty())
 708     return false;
 709
 710   detail::InMemoryDirectory *Dir = Root.get();
 711   auto I = llvm::sys::path::begin(Path), E = sys::path::end(Path);
 712   const auto ResolvedUser = User.getValueOr(0);
 713   const auto ResolvedGroup = Group.getValueOr(0);
 714   const auto ResolvedType = Type.getValueOr(sys::fs::file_type::regular_file);
 715   const auto ResolvedPerms = Perms.getValueOr(sys::fs::all_all);
 716   assert(!(HardLinkTarget && Buffer) && "HardLink cannot have a buffer");
 717   // Any intermediate directories we create should be accessible by
 718   // the owner, even if Perms says otherwise for the final path.
 719   const auto NewDirectoryPerms = ResolvedPerms | sys::fs::owner_all;
 720   while (true) {
 721     StringRef Name = *I;
 722     detail::InMemoryNode *Node = Dir->getChild(Name);
 723     ++I;
 724     if (!Node) {
 725       if (I == E) {
 726         // End of the path.
 727         std::unique_ptr<detail::InMemoryNode> Child;
 728         if (HardLinkTarget)
 729           Child.reset(new detail::InMemoryHardLink(P.str(), *HardLinkTarget));
 730         else {
 731           // Create a new file or directory.
 732           Status Stat(P.str(), getNextVirtualUniqueID(),
 733                       llvm::sys::toTimePoint(ModificationTime), ResolvedUser,
 734                       ResolvedGroup, Buffer->getBufferSize(), ResolvedType,
 735                       ResolvedPerms);
 736           if (ResolvedType == sys::fs::file_type::directory_file) {
 737             Child.reset(new detail::InMemoryDirectory(std::move(Stat)));
 738           } else {
 739             Child.reset(
 740                 new detail::InMemoryFile(std::move(Stat), std::move(Buffer)));
 741           }
 742         }
 743         Dir->addChild(Name, std::move(Child));
 744         return true;
 745       }
 746
 747       // Create a new directory. Use the path up to here.
 748       Status Stat(
 749           StringRef(Path.str().begin(), Name.end() - Path.str().begin()),
 750           getNextVirtualUniqueID(), llvm::sys::toTimePoint(ModificationTime),
 751           ResolvedUser, ResolvedGroup, 0, sys::fs::file_type::directory_file,
 752           NewDirectoryPerms);
 753       Dir = cast<detail::InMemoryDirectory>(Dir->addChild(
 754           Name, llvm::make_unique<detail::InMemoryDirectory>(std::move(Stat))));
 755       continue;
 756     }
 757
 758     if (auto *NewDir = dyn_cast<detail::InMemoryDirectory>(Node)) {
 759       Dir = NewDir;
 760     } else {
 761       assert((isa<detail::InMemoryFile>(Node) ||
 762               isa<detail::InMemoryHardLink>(Node)) &&
 763              "Must be either file, hardlink or directory!");
 764
 765       // Trying to insert a directory in place of a file.
 766       if (I != E)
 767         return false;
 768
 769       // Return false only if the new file is different from the existing one.
 770       if (auto Link = dyn_cast<detail::InMemoryHardLink>(Node)) {
 771         return Link->getResolvedFile().getBuffer()->getBuffer() ==
 772                Buffer->getBuffer();
 773       }
 774       return cast<detail::InMemoryFile>(Node)->getBuffer()->getBuffer() ==
 775              Buffer->getBuffer();
 776     }
 777   }
 778 }
 779
 780 bool InMemoryFileSystem::addFile(const Twine &P, time_t ModificationTime,
 781                                  std::unique_ptr<llvm::MemoryBuffer> Buffer,
 782                                  Optional<uint32_t> User,
 783                                  Optional<uint32_t> Group,
 784                                  Optional<llvm::sys::fs::file_type> Type,
 785                                  Optional<llvm::sys::fs::perms> Perms) {
 786   return addFile(P, ModificationTime, std::move(Buffer), User, Group, Type,
 787                  Perms, /*HardLinkTarget=*/nullptr);
 788 }
 789
 790 bool InMemoryFileSystem::addFileNoOwn(const Twine &P, time_t ModificationTime,
 791                                       llvm::MemoryBuffer *Buffer,
 792                                       Optional<uint32_t> User,
 793                                       Optional<uint32_t> Group,
 794                                       Optional<llvm::sys::fs::file_type> Type,
 795                                       Optional<llvm::sys::fs::perms> Perms) {
 796   return addFile(P, ModificationTime,
 797                  llvm::MemoryBuffer::getMemBuffer(
 798                      Buffer->getBuffer(), Buffer->getBufferIdentifier()),
 799                  std::move(User), std::move(Group), std::move(Type),
 800                  std::move(Perms));
 801 }
 802
 803 static ErrorOr<const detail::InMemoryNode *>
 804 lookupInMemoryNode(const InMemoryFileSystem &FS, detail::InMemoryDirectory *Dir,
 805                    const Twine &P) {
 806   SmallString<128> Path;
 807   P.toVector(Path);
 808
 809   // Fix up relative paths. This just prepends the current working directory.
 810   std::error_code EC = FS.makeAbsolute(Path);
 811   assert(!EC);
 812   (void)EC;
 813
 814   if (FS.useNormalizedPaths())
 815     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 816
 817   if (Path.empty())
 818     return Dir;
 819
 820   auto I = llvm::sys::path::begin(Path), E = llvm::sys::path::end(Path);
 821   while (true) {
 822     detail::InMemoryNode *Node = Dir->getChild(*I);
 823     ++I;
 824     if (!Node)
 825       return errc::no_such_file_or_directory;
 826
 827     // Return the file if it's at the end of the path.
 828     if (auto File = dyn_cast<detail::InMemoryFile>(Node)) {
 829       if (I == E)
 830         return File;
 831       return errc::no_such_file_or_directory;
 832     }
 833
 834     // If Node is HardLink then return the resolved file.
 835     if (auto File = dyn_cast<detail::InMemoryHardLink>(Node)) {
 836       if (I == E)
 837         return &File->getResolvedFile();
 838       return errc::no_such_file_or_directory;
 839     }
 840     // Traverse directories.
 841     Dir = cast<detail::InMemoryDirectory>(Node);
 842     if (I == E)
 843       return Dir;
 844   }
 845 }
 846
 847 bool InMemoryFileSystem::addHardLink(const Twine &FromPath,
 848                                      const Twine &ToPath) {
 849   auto FromNode = lookupInMemoryNode(*this, Root.get(), FromPath);
 850   auto ToNode = lookupInMemoryNode(*this, Root.get(), ToPath);
 851   // FromPath must not have been added before. ToPath must have been added
 852   // before. Resolved ToPath must be a File.
 853   if (!ToNode || FromNode || !isa<detail::InMemoryFile>(*ToNode))
 854     return false;
 855   return this->addFile(FromPath, 0, nullptr, None, None, None, None,
 856                        cast<detail::InMemoryFile>(*ToNode));
 857 }
 858
 859 llvm::ErrorOr<Status> InMemoryFileSystem::status(const Twine &Path) {
 860   auto Node = lookupInMemoryNode(*this, Root.get(), Path);
 861   if (Node)
 862     return detail::getNodeStatus(*Node, Path.str());
 863   return Node.getError();
 864 }
 865
 866 llvm::ErrorOr<std::unique_ptr<File>>
 867 InMemoryFileSystem::openFileForRead(const Twine &Path) {
 868   auto Node = lookupInMemoryNode(*this, Root.get(), Path);
 869   if (!Node)
 870     return Node.getError();
 871
 872   // When we have a file provide a heap-allocated wrapper for the memory buffer
 873   // to match the ownership semantics for File.
 874   if (auto *F = dyn_cast<detail::InMemoryFile>(*Node))
 875     return std::unique_ptr<File>(
 876         new detail::InMemoryFileAdaptor(*F, Path.str()));
 877
 878   // FIXME: errc::not_a_file?
 879   return make_error_code(llvm::errc::invalid_argument);
 880 }
 881
 882 namespace {
 883
 884 /// Adaptor from InMemoryDir::iterator to directory_iterator.
 885 class InMemoryDirIterator : public llvm::vfs::detail::DirIterImpl {
 886   detail::InMemoryDirectory::const_iterator I;
 887   detail::InMemoryDirectory::const_iterator E;
 888   std::string RequestedDirName;
 889
 890   void setCurrentEntry() {
 891     if (I != E) {
 892       SmallString<256> Path(RequestedDirName);
 893       llvm::sys::path::append(Path, I->second->getFileName());
 894       sys::fs::file_type Type;
 895       switch (I->second->getKind()) {
 896       case detail::IME_File:
 897       case detail::IME_HardLink:
 898         Type = sys::fs::file_type::regular_file;
 899         break;
 900       case detail::IME_Directory:
 901         Type = sys::fs::file_type::directory_file;
 902         break;
 903       }
 904       CurrentEntry = directory_entry(Path.str(), Type);
 905     } else {
 906       // When we're at the end, make CurrentEntry invalid and DirIterImpl will
 907       // do the rest.
 908       CurrentEntry = directory_entry();
 909     }
 910   }
 911
 912 public:
 913   InMemoryDirIterator() = default;
 914
 915   explicit InMemoryDirIterator(const detail::InMemoryDirectory &Dir,
 916                                std::string RequestedDirName)
 917       : I(Dir.begin()), E(Dir.end()),
 918         RequestedDirName(std::move(RequestedDirName)) {
 919     setCurrentEntry();
 920   }
 921
 922   std::error_code increment() override {
 923     ++I;
 924     setCurrentEntry();
 925     return {};
 926   }
 927 };
 928
 929 } // namespace
 930
 931 directory_iterator InMemoryFileSystem::dir_begin(const Twine &Dir,
 932                                                  std::error_code &EC) {
 933   auto Node = lookupInMemoryNode(*this, Root.get(), Dir);
 934   if (!Node) {
 935     EC = Node.getError();
 936     return directory_iterator(std::make_shared<InMemoryDirIterator>());
 937   }
 938
 939   if (auto *DirNode = dyn_cast<detail::InMemoryDirectory>(*Node))
 940     return directory_iterator(
 941         std::make_shared<InMemoryDirIterator>(*DirNode, Dir.str()));
 942
 943   EC = make_error_code(llvm::errc::not_a_directory);
 944   return directory_iterator(std::make_shared<InMemoryDirIterator>());
 945 }
 946
 947 std::error_code InMemoryFileSystem::setCurrentWorkingDirectory(const Twine &P) {
 948   SmallString<128> Path;
 949   P.toVector(Path);
 950
 951   // Fix up relative paths. This just prepends the current working directory.
 952   std::error_code EC = makeAbsolute(Path);
 953   assert(!EC);
 954   (void)EC;
 955
 956   if (useNormalizedPaths())
 957     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 958
 959   if (!Path.empty())
 960     WorkingDirectory = Path.str();
 961   return {};
 962 }
 963
 964 std::error_code
 965 InMemoryFileSystem::getRealPath(const Twine &Path,
 966                                 SmallVectorImpl<char> &Output) const {
 967   auto CWD = getCurrentWorkingDirectory();
 968   if (!CWD || CWD->empty())
 969     return errc::operation_not_permitted;
 970   Path.toVector(Output);
 971   if (auto EC = makeAbsolute(Output))
 972     return EC;
 973   llvm::sys::path::remove_dots(Output, /*remove_dot_dot=*/true);
 974   return {};
 975 }
 976
 977 std::error_code InMemoryFileSystem::isLocal(const Twine &Path, bool &Result) {
 978   Result = false;
 979   return {};
 980 }
 981
 982 } // namespace vfs
 983 } // namespace llvm
 984
 985 //===-----------------------------------------------------------------------===/
 986 // RedirectingFileSystem implementation
 987 //===-----------------------------------------------------------------------===/
 988
 989 // FIXME: reuse implementation common with OverlayFSDirIterImpl as these
 990 // iterators are conceptually similar.
 991 class llvm::vfs::VFSFromYamlDirIterImpl
 992     : public llvm::vfs::detail::DirIterImpl {
 993   std::string Dir;
 994   RedirectingFileSystem::RedirectingDirectoryEntry::iterator Current, End;
 995
 996   // To handle 'fallthrough' mode we need to iterate at first through
 997   // RedirectingDirectoryEntry and then through ExternalFS. These operations are
 998   // done sequentially, we just need to keep a track of what kind of iteration
 999   // we are currently performing.
1000
1001   /// Flag telling if we should iterate through ExternalFS or stop at the last
1002   /// RedirectingDirectoryEntry::iterator.
1003   bool IterateExternalFS;
1004   /// Flag telling if we have switched to iterating through ExternalFS.
1005   bool IsExternalFSCurrent = false;
1006   FileSystem &ExternalFS;
1007   directory_iterator ExternalDirIter;
1008   llvm::StringSet<> SeenNames;
1009
1010   /// To combine multiple iterations, different methods are responsible for
1011   /// different iteration steps.
1012   /// @{
1013
1014   /// Responsible for dispatching between RedirectingDirectoryEntry iteration
1015   /// and ExternalFS iteration.
1016   std::error_code incrementImpl(bool IsFirstTime);
1017   /// Responsible for RedirectingDirectoryEntry iteration.
1018   std::error_code incrementContent(bool IsFirstTime);
1019   /// Responsible for ExternalFS iteration.
1020   std::error_code incrementExternal();
1021   /// @}
1022
1023 public:
1024   VFSFromYamlDirIterImpl(
1025       const Twine &Path,
1026       RedirectingFileSystem::RedirectingDirectoryEntry::iterator Begin,
1027       RedirectingFileSystem::RedirectingDirectoryEntry::iterator End,
1028       bool IterateExternalFS, FileSystem &ExternalFS, std::error_code &EC);
1029
1030   std::error_code increment() override;
1031 };
1032
1033 llvm::ErrorOr<std::string>
1034 RedirectingFileSystem::getCurrentWorkingDirectory() const {
1035   return ExternalFS->getCurrentWorkingDirectory();
1036 }
1037
1038 std::error_code
1039 RedirectingFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
1040   return ExternalFS->setCurrentWorkingDirectory(Path);
1041 }
1042
1043 std::error_code RedirectingFileSystem::isLocal(const Twine &Path,
1044                                                bool &Result) {
1045   return ExternalFS->isLocal(Path, Result);
1046 }
1047
1048 directory_iterator RedirectingFileSystem::dir_begin(const Twine &Dir,
1049                                                     std::error_code &EC) {
1050   ErrorOr<RedirectingFileSystem::Entry *> E = lookupPath(Dir);
1051   if (!E) {
1052     EC = E.getError();
1053     if (IsFallthrough && EC == errc::no_such_file_or_directory)
1054       return ExternalFS->dir_begin(Dir, EC);
1055     return {};
1056   }
1057   ErrorOr<Status> S = status(Dir, *E);
1058   if (!S) {
1059     EC = S.getError();
1060     return {};
1061   }
1062   if (!S->isDirectory()) {
1063     EC = std::error_code(static_cast<int>(errc::not_a_directory),
1064                          std::system_category());
1065     return {};
1066   }
1067
1068   auto *D = cast<RedirectingFileSystem::RedirectingDirectoryEntry>(*E);
1069   return directory_iterator(std::make_shared<VFSFromYamlDirIterImpl>(
1070       Dir, D->contents_begin(), D->contents_end(),
1071       /*IterateExternalFS=*/IsFallthrough, *ExternalFS, EC));
1072 }
1073
1074 void RedirectingFileSystem::setExternalContentsPrefixDir(StringRef PrefixDir) {
1075   ExternalContentsPrefixDir = PrefixDir.str();
1076 }
1077
1078 StringRef RedirectingFileSystem::getExternalContentsPrefixDir() const {
1079   return ExternalContentsPrefixDir;
1080 }
1081
1082 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1083 LLVM_DUMP_METHOD void RedirectingFileSystem::dump() const {
1084   for (const auto &Root : Roots)
1085     dumpEntry(Root.get());
1086 }
1087
1088 LLVM_DUMP_METHOD void
1089 RedirectingFileSystem::dumpEntry(RedirectingFileSystem::Entry *E,
1090                                  int NumSpaces) const {
1091   StringRef Name = E->getName();
1092   for (int i = 0, e = NumSpaces; i < e; ++i)
1093     dbgs() << " ";
1094   dbgs() << "'" << Name.str().c_str() << "'"
1095          << "\n";
1096
1097   if (E->getKind() == RedirectingFileSystem::EK_Directory) {
1098     auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(E);
1099     assert(DE && "Should be a directory");
1100
1101     for (std::unique_ptr<Entry> &SubEntry :
1102          llvm::make_range(DE->contents_begin(), DE->contents_end()))
1103       dumpEntry(SubEntry.get(), NumSpaces + 2);
1104   }
1105 }
1106 #endif
1107
1108 /// A helper class to hold the common YAML parsing state.
1109 class llvm::vfs::RedirectingFileSystemParser {
1110   yaml::Stream &Stream;
1111
1112   void error(yaml::Node *N, const Twine &Msg) { Stream.printError(N, Msg); }
1113
1114   // false on error
1115   bool parseScalarString(yaml::Node *N, StringRef &Result,
1116                          SmallVectorImpl<char> &Storage) {
1117     const auto *S = dyn_cast<yaml::ScalarNode>(N);
1118
1119     if (!S) {
1120       error(N, "expected string");
1121       return false;
1122     }
1123     Result = S->getValue(Storage);
1124     return true;
1125   }
1126
1127   // false on error
1128   bool parseScalarBool(yaml::Node *N, bool &Result) {
1129     SmallString<5> Storage;
1130     StringRef Value;
1131     if (!parseScalarString(N, Value, Storage))
1132       return false;
1133
1134     if (Value.equals_lower("true") || Value.equals_lower("on") ||
1135         Value.equals_lower("yes") || Value == "1") {
1136       Result = true;
1137       return true;
1138     } else if (Value.equals_lower("false") || Value.equals_lower("off") ||
1139                Value.equals_lower("no") || Value == "0") {
1140       Result = false;
1141       return true;
1142     }
1143
1144     error(N, "expected boolean value");
1145     return false;
1146   }
1147
1148   struct KeyStatus {
1149     bool Required;
1150     bool Seen = false;
1151
1152     KeyStatus(bool Required = false) : Required(Required) {}
1153   };
1154
1155   using KeyStatusPair = std::pair<StringRef, KeyStatus>;
1156
1157   // false on error
1158   bool checkDuplicateOrUnknownKey(yaml::Node *KeyNode, StringRef Key,
1159                                   DenseMap<StringRef, KeyStatus> &Keys) {
1160     if (!Keys.count(Key)) {
1161       error(KeyNode, "unknown key");
1162       return false;
1163     }
1164     KeyStatus &S = Keys[Key];
1165     if (S.Seen) {
1166       error(KeyNode, Twine("duplicate key '") + Key + "'");
1167       return false;
1168     }
1169     S.Seen = true;
1170     return true;
1171   }
1172
1173   // false on error
1174   bool checkMissingKeys(yaml::Node *Obj, DenseMap<StringRef, KeyStatus> &Keys) {
1175     for (const auto &I : Keys) {
1176       if (I.second.Required && !I.second.Seen) {
1177         error(Obj, Twine("missing key '") + I.first + "'");
1178         return false;
1179       }
1180     }
1181     return true;
1182   }
1183
1184   RedirectingFileSystem::Entry *
1185   lookupOrCreateEntry(RedirectingFileSystem *FS, StringRef Name,
1186                       RedirectingFileSystem::Entry *ParentEntry = nullptr) {
1187     if (!ParentEntry) { // Look for a existent root
1188       for (const auto &Root : FS->Roots) {
1189         if (Name.equals(Root->getName())) {
1190           ParentEntry = Root.get();
1191           return ParentEntry;
1192         }
1193       }
1194     } else { // Advance to the next component
1195       auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(
1196           ParentEntry);
1197       for (std::unique_ptr<RedirectingFileSystem::Entry> &Content :
1198            llvm::make_range(DE->contents_begin(), DE->contents_end())) {
1199         auto *DirContent =
1200             dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(
1201                 Content.get());
1202         if (DirContent && Name.equals(Content->getName()))
1203           return DirContent;
1204       }
1205     }
1206
1207     // ... or create a new one
1208     std::unique_ptr<RedirectingFileSystem::Entry> E =
1209         llvm::make_unique<RedirectingFileSystem::RedirectingDirectoryEntry>(
1210             Name, Status("", getNextVirtualUniqueID(),
1211                          std::chrono::system_clock::now(), 0, 0, 0,
1212                          file_type::directory_file, sys::fs::all_all));
1213
1214     if (!ParentEntry) { // Add a new root to the overlay
1215       FS->Roots.push_back(std::move(E));
1216       ParentEntry = FS->Roots.back().get();
1217       return ParentEntry;
1218     }
1219
1220     auto *DE =
1221         dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(ParentEntry);
1222     DE->addContent(std::move(E));
1223     return DE->getLastContent();
1224   }
1225
1226   void uniqueOverlayTree(RedirectingFileSystem *FS,
1227                          RedirectingFileSystem::Entry *SrcE,
1228                          RedirectingFileSystem::Entry *NewParentE = nullptr) {
1229     StringRef Name = SrcE->getName();
1230     switch (SrcE->getKind()) {
1231     case RedirectingFileSystem::EK_Directory: {
1232       auto *DE =
1233           dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(SrcE);
1234       assert(DE && "Must be a directory");
1235       // Empty directories could be present in the YAML as a way to
1236       // describe a file for a current directory after some of its subdir
1237       // is parsed. This only leads to redundant walks, ignore it.
1238       if (!Name.empty())
1239         NewParentE = lookupOrCreateEntry(FS, Name, NewParentE);
1240       for (std::unique_ptr<RedirectingFileSystem::Entry> &SubEntry :
1241            llvm::make_range(DE->contents_begin(), DE->contents_end()))
1242         uniqueOverlayTree(FS, SubEntry.get(), NewParentE);
1243       break;
1244     }
1245     case RedirectingFileSystem::EK_File: {
1246       auto *FE = dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(SrcE);
1247       assert(FE && "Must be a file");
1248       assert(NewParentE && "Parent entry must exist");
1249       auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(
1250           NewParentE);
1251       DE->addContent(
1252           llvm::make_unique<RedirectingFileSystem::RedirectingFileEntry>(
1253               Name, FE->getExternalContentsPath(), FE->getUseName()));
1254       break;
1255     }
1256     }
1257   }
1258
1259   std::unique_ptr<RedirectingFileSystem::Entry>
1260   parseEntry(yaml::Node *N, RedirectingFileSystem *FS, bool IsRootEntry) {
1261     auto *M = dyn_cast<yaml::MappingNode>(N);
1262     if (!M) {
1263       error(N, "expected mapping node for file or directory entry");
1264       return nullptr;
1265     }
1266
1267     KeyStatusPair Fields[] = {
1268         KeyStatusPair("name", true),
1269         KeyStatusPair("type", true),
1270         KeyStatusPair("contents", false),
1271         KeyStatusPair("external-contents", false),
1272         KeyStatusPair("use-external-name", false),
1273     };
1274
1275     DenseMap<StringRef, KeyStatus> Keys(std::begin(Fields), std::end(Fields));
1276
1277     bool HasContents = false; // external or otherwise
1278     std::vector<std::unique_ptr<RedirectingFileSystem::Entry>>
1279         EntryArrayContents;
1280     std::string ExternalContentsPath;
1281     std::string Name;
1282     yaml::Node *NameValueNode;
1283     auto UseExternalName =
1284         RedirectingFileSystem::RedirectingFileEntry::NK_NotSet;
1285     RedirectingFileSystem::EntryKind Kind;
1286
1287     for (auto &I : *M) {
1288       StringRef Key;
1289       // Reuse the buffer for key and value, since we don't look at key after
1290       // parsing value.
1291       SmallString<256> Buffer;
1292       if (!parseScalarString(I.getKey(), Key, Buffer))
1293         return nullptr;
1294
1295       if (!checkDuplicateOrUnknownKey(I.getKey(), Key, Keys))
1296         return nullptr;
1297
1298       StringRef Value;
1299       if (Key == "name") {
1300         if (!parseScalarString(I.getValue(), Value, Buffer))
1301           return nullptr;
1302
1303         NameValueNode = I.getValue();
1304         if (FS->UseCanonicalizedPaths) {
1305           SmallString<256> Path(Value);
1306           // Guarantee that old YAML files containing paths with ".." and "."
1307           // are properly canonicalized before read into the VFS.
1308           Path = sys::path::remove_leading_dotslash(Path);
1309           sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
1310           Name = Path.str();
1311         } else {
1312           Name = Value;
1313         }
1314       } else if (Key == "type") {
1315         if (!parseScalarString(I.getValue(), Value, Buffer))
1316           return nullptr;
1317         if (Value == "file")
1318           Kind = RedirectingFileSystem::EK_File;
1319         else if (Value == "directory")
1320           Kind = RedirectingFileSystem::EK_Directory;
1321         else {
1322           error(I.getValue(), "unknown value for 'type'");
1323           return nullptr;
1324         }
1325       } else if (Key == "contents") {
1326         if (HasContents) {
1327           error(I.getKey(),
1328                 "entry already has 'contents' or 'external-contents'");
1329           return nullptr;
1330         }
1331         HasContents = true;
1332         auto *Contents = dyn_cast<yaml::SequenceNode>(I.getValue());
1333         if (!Contents) {
1334           // FIXME: this is only for directories, what about files?
1335           error(I.getValue(), "expected array");
1336           return nullptr;
1337         }
1338
1339         for (auto &I : *Contents) {
1340           if (std::unique_ptr<RedirectingFileSystem::Entry> E =
1341                   parseEntry(&I, FS, /*IsRootEntry*/ false))
1342             EntryArrayContents.push_back(std::move(E));
1343           else
1344             return nullptr;
1345         }
1346       } else if (Key == "external-contents") {
1347         if (HasContents) {
1348           error(I.getKey(),
1349                 "entry already has 'contents' or 'external-contents'");
1350           return nullptr;
1351         }
1352         HasContents = true;
1353         if (!parseScalarString(I.getValue(), Value, Buffer))
1354           return nullptr;
1355
1356         SmallString<256> FullPath;
1357         if (FS->IsRelativeOverlay) {
1358           FullPath = FS->getExternalContentsPrefixDir();
1359           assert(!FullPath.empty() &&
1360                  "External contents prefix directory must exist");
1361           llvm::sys::path::append(FullPath, Value);
1362         } else {
1363           FullPath = Value;
1364         }
1365
1366         if (FS->UseCanonicalizedPaths) {
1367           // Guarantee that old YAML files containing paths with ".." and "."
1368           // are properly canonicalized before read into the VFS.
1369           FullPath = sys::path::remove_leading_dotslash(FullPath);
1370           sys::path::remove_dots(FullPath, /*remove_dot_dot=*/true);
1371         }
1372         ExternalContentsPath = FullPath.str();
1373       } else if (Key == "use-external-name") {
1374         bool Val;
1375         if (!parseScalarBool(I.getValue(), Val))
1376           return nullptr;
1377         UseExternalName =
1378             Val ? RedirectingFileSystem::RedirectingFileEntry::NK_External
1379                 : RedirectingFileSystem::RedirectingFileEntry::NK_Virtual;
1380       } else {
1381         llvm_unreachable("key missing from Keys");
1382       }
1383     }
1384
1385     if (Stream.failed())
1386       return nullptr;
1387
1388     // check for missing keys
1389     if (!HasContents) {
1390       error(N, "missing key 'contents' or 'external-contents'");
1391       return nullptr;
1392     }
1393     if (!checkMissingKeys(N, Keys))
1394       return nullptr;
1395
1396     // check invalid configuration
1397     if (Kind == RedirectingFileSystem::EK_Directory &&
1398         UseExternalName !=
1399             RedirectingFileSystem::RedirectingFileEntry::NK_NotSet) {
1400       error(N, "'use-external-name' is not supported for directories");
1401       return nullptr;
1402     }
1403
1404     if (IsRootEntry && !sys::path::is_absolute(Name)) {
1405       assert(NameValueNode && "Name presence should be checked earlier");
1406       error(NameValueNode,
1407             "entry with relative path at the root level is not discoverable");
1408       return nullptr;
1409     }
1410
1411     // Remove trailing slash(es), being careful not to remove the root path
1412     StringRef Trimmed(Name);
1413     size_t RootPathLen = sys::path::root_path(Trimmed).size();
1414     while (Trimmed.size() > RootPathLen &&
1415            sys::path::is_separator(Trimmed.back()))
1416       Trimmed = Trimmed.slice(0, Trimmed.size() - 1);
1417     // Get the last component
1418     StringRef LastComponent = sys::path::filename(Trimmed);
1419
1420     std::unique_ptr<RedirectingFileSystem::Entry> Result;
1421     switch (Kind) {
1422     case RedirectingFileSystem::EK_File:
1423       Result = llvm::make_unique<RedirectingFileSystem::RedirectingFileEntry>(
1424           LastComponent, std::move(ExternalContentsPath), UseExternalName);
1425       break;
1426     case RedirectingFileSystem::EK_Directory:
1427       Result =
1428           llvm::make_unique<RedirectingFileSystem::RedirectingDirectoryEntry>(
1429               LastComponent, std::move(EntryArrayContents),
1430               Status("", getNextVirtualUniqueID(),
1431                      std::chrono::system_clock::now(), 0, 0, 0,
1432                      file_type::directory_file, sys::fs::all_all));
1433       break;
1434     }
1435
1436     StringRef Parent = sys::path::parent_path(Trimmed);
1437     if (Parent.empty())
1438       return Result;
1439
1440     // if 'name' contains multiple components, create implicit directory entries
1441     for (sys::path::reverse_iterator I = sys::path::rbegin(Parent),
1442                                      E = sys::path::rend(Parent);
1443          I != E; ++I) {
1444       std::vector<std::unique_ptr<RedirectingFileSystem::Entry>> Entries;
1445       Entries.push_back(std::move(Result));
1446       Result =
1447           llvm::make_unique<RedirectingFileSystem::RedirectingDirectoryEntry>(
1448               *I, std::move(Entries),
1449               Status("", getNextVirtualUniqueID(),
1450                      std::chrono::system_clock::now(), 0, 0, 0,
1451                      file_type::directory_file, sys::fs::all_all));
1452     }
1453     return Result;
1454   }
1455
1456 public:
1457   RedirectingFileSystemParser(yaml::Stream &S) : Stream(S) {}
1458
1459   // false on error
1460   bool parse(yaml::Node *Root, RedirectingFileSystem *FS) {
1461     auto *Top = dyn_cast<yaml::MappingNode>(Root);
1462     if (!Top) {
1463       error(Root, "expected mapping node");
1464       return false;
1465     }
1466
1467     KeyStatusPair Fields[] = {
1468         KeyStatusPair("version", true),
1469         KeyStatusPair("case-sensitive", false),
1470         KeyStatusPair("use-external-names", false),
1471         KeyStatusPair("overlay-relative", false),
1472         KeyStatusPair("fallthrough", false),
1473         KeyStatusPair("roots", true),
1474     };
1475
1476     DenseMap<StringRef, KeyStatus> Keys(std::begin(Fields), std::end(Fields));
1477     std::vector<std::unique_ptr<RedirectingFileSystem::Entry>> RootEntries;
1478
1479     // Parse configuration and 'roots'
1480     for (auto &I : *Top) {
1481       SmallString<10> KeyBuffer;
1482       StringRef Key;
1483       if (!parseScalarString(I.getKey(), Key, KeyBuffer))
1484         return false;
1485
1486       if (!checkDuplicateOrUnknownKey(I.getKey(), Key, Keys))
1487         return false;
1488
1489       if (Key == "roots") {
1490         auto *Roots = dyn_cast<yaml::SequenceNode>(I.getValue());
1491         if (!Roots) {
1492           error(I.getValue(), "expected array");
1493           return false;
1494         }
1495
1496         for (auto &I : *Roots) {
1497           if (std::unique_ptr<RedirectingFileSystem::Entry> E =
1498                   parseEntry(&I, FS, /*IsRootEntry*/ true))
1499             RootEntries.push_back(std::move(E));
1500           else
1501             return false;
1502         }
1503       } else if (Key == "version") {
1504         StringRef VersionString;
1505         SmallString<4> Storage;
1506         if (!parseScalarString(I.getValue(), VersionString, Storage))
1507           return false;
1508         int Version;
1509         if (VersionString.getAsInteger<int>(10, Version)) {
1510           error(I.getValue(), "expected integer");
1511           return false;
1512         }
1513         if (Version < 0) {
1514           error(I.getValue(), "invalid version number");
1515           return false;
1516         }
1517         if (Version != 0) {
1518           error(I.getValue(), "version mismatch, expected 0");
1519           return false;
1520         }
1521       } else if (Key == "case-sensitive") {
1522         if (!parseScalarBool(I.getValue(), FS->CaseSensitive))
1523           return false;
1524       } else if (Key == "overlay-relative") {
1525         if (!parseScalarBool(I.getValue(), FS->IsRelativeOverlay))
1526           return false;
1527       } else if (Key == "use-external-names") {
1528         if (!parseScalarBool(I.getValue(), FS->UseExternalNames))
1529           return false;
1530       } else if (Key == "fallthrough") {
1531         if (!parseScalarBool(I.getValue(), FS->IsFallthrough))
1532           return false;
1533       } else {
1534         llvm_unreachable("key missing from Keys");
1535       }
1536     }
1537
1538     if (Stream.failed())
1539       return false;
1540
1541     if (!checkMissingKeys(Top, Keys))
1542       return false;
1543
1544     // Now that we sucessefully parsed the YAML file, canonicalize the internal
1545     // representation to a proper directory tree so that we can search faster
1546     // inside the VFS.
1547     for (auto &E : RootEntries)
1548       uniqueOverlayTree(FS, E.get());
1549
1550     return true;
1551   }
1552 };
1553
1554 RedirectingFileSystem *
1555 RedirectingFileSystem::create(std::unique_ptr<MemoryBuffer> Buffer,
1556                               SourceMgr::DiagHandlerTy DiagHandler,
1557                               StringRef YAMLFilePath, void *DiagContext,
1558                               IntrusiveRefCntPtr<FileSystem> ExternalFS) {
1559   SourceMgr SM;
1560   yaml::Stream Stream(Buffer->getMemBufferRef(), SM);
1561
1562   SM.setDiagHandler(DiagHandler, DiagContext);
1563   yaml::document_iterator DI = Stream.begin();
1564   yaml::Node *Root = DI->getRoot();
1565   if (DI == Stream.end() || !Root) {
1566     SM.PrintMessage(SMLoc(), SourceMgr::DK_Error, "expected root node");
1567     return nullptr;
1568   }
1569
1570   RedirectingFileSystemParser P(Stream);
1571
1572   std::unique_ptr<RedirectingFileSystem> FS(
1573       new RedirectingFileSystem(std::move(ExternalFS)));
1574
1575   if (!YAMLFilePath.empty()) {
1576     // Use the YAML path from -ivfsoverlay to compute the dir to be prefixed
1577     // to each 'external-contents' path.
1578     //
1579     // Example:
1580     //    -ivfsoverlay dummy.cache/vfs/vfs.yaml
1581     // yields:
1582     //  FS->ExternalContentsPrefixDir => /<absolute_path_to>/dummy.cache/vfs
1583     //
1584     SmallString<256> OverlayAbsDir = sys::path::parent_path(YAMLFilePath);
1585     std::error_code EC = llvm::sys::fs::make_absolute(OverlayAbsDir);
1586     assert(!EC && "Overlay dir final path must be absolute");
1587     (void)EC;
1588     FS->setExternalContentsPrefixDir(OverlayAbsDir);
1589   }
1590
1591   if (!P.parse(Root, FS.get()))
1592     return nullptr;
1593
1594   return FS.release();
1595 }
1596
1597 ErrorOr<RedirectingFileSystem::Entry *>
1598 RedirectingFileSystem::lookupPath(const Twine &Path_) const {
1599   SmallString<256> Path;
1600   Path_.toVector(Path);
1601
1602   // Handle relative paths
1603   if (std::error_code EC = makeAbsolute(Path))
1604     return EC;
1605
1606   // Canonicalize path by removing ".", "..", "./", etc components. This is
1607   // a VFS request, do bot bother about symlinks in the path components
1608   // but canonicalize in order to perform the correct entry search.
1609   if (UseCanonicalizedPaths) {
1610     Path = sys::path::remove_leading_dotslash(Path);
1611     sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
1612   }
1613
1614   if (Path.empty())
1615     return make_error_code(llvm::errc::invalid_argument);
1616
1617   sys::path::const_iterator Start = sys::path::begin(Path);
1618   sys::path::const_iterator End = sys::path::end(Path);
1619   for (const auto &Root : Roots) {
1620     ErrorOr<RedirectingFileSystem::Entry *> Result =
1621         lookupPath(Start, End, Root.get());
1622     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
1623       return Result;
1624   }
1625   return make_error_code(llvm::errc::no_such_file_or_directory);
1626 }
1627
1628 ErrorOr<RedirectingFileSystem::Entry *>
1629 RedirectingFileSystem::lookupPath(sys::path::const_iterator Start,
1630                                   sys::path::const_iterator End,
1631                                   RedirectingFileSystem::Entry *From) const {
1632 #ifndef _WIN32
1633   assert(!isTraversalComponent(*Start) &&
1634          !isTraversalComponent(From->getName()) &&
1635          "Paths should not contain traversal components");
1636 #else
1637   // FIXME: this is here to support windows, remove it once canonicalized
1638   // paths become globally default.
1639   if (Start->equals("."))
1640     ++Start;
1641 #endif
1642
1643   StringRef FromName = From->getName();
1644
1645   // Forward the search to the next component in case this is an empty one.
1646   if (!FromName.empty()) {
1647     if (CaseSensitive ? !Start->equals(FromName)
1648                       : !Start->equals_lower(FromName))
1649       // failure to match
1650       return make_error_code(llvm::errc::no_such_file_or_directory);
1651
1652     ++Start;
1653
1654     if (Start == End) {
1655       // Match!
1656       return From;
1657     }
1658   }
1659
1660   auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(From);
1661   if (!DE)
1662     return make_error_code(llvm::errc::not_a_directory);
1663
1664   for (const std::unique_ptr<RedirectingFileSystem::Entry> &DirEntry :
1665        llvm::make_range(DE->contents_begin(), DE->contents_end())) {
1666     ErrorOr<RedirectingFileSystem::Entry *> Result =
1667         lookupPath(Start, End, DirEntry.get());
1668     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
1669       return Result;
1670   }
1671   return make_error_code(llvm::errc::no_such_file_or_directory);
1672 }
1673
1674 static Status getRedirectedFileStatus(const Twine &Path, bool UseExternalNames,
1675                                       Status ExternalStatus) {
1676   Status S = ExternalStatus;
1677   if (!UseExternalNames)
1678     S = Status::copyWithNewName(S, Path.str());
1679   S.IsVFSMapped = true;
1680   return S;
1681 }
1682
1683 ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path,
1684                                               RedirectingFileSystem::Entry *E) {
1685   assert(E != nullptr);
1686   if (auto *F = dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(E)) {
1687     ErrorOr<Status> S = ExternalFS->status(F->getExternalContentsPath());
1688     assert(!S || S->getName() == F->getExternalContentsPath());
1689     if (S)
1690       return getRedirectedFileStatus(Path, F->useExternalName(UseExternalNames),
1691                                      *S);
1692     return S;
1693   } else { // directory
1694     auto *DE = cast<RedirectingFileSystem::RedirectingDirectoryEntry>(E);
1695     return Status::copyWithNewName(DE->getStatus(), Path.str());
1696   }
1697 }
1698
1699 ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path) {
1700   ErrorOr<RedirectingFileSystem::Entry *> Result = lookupPath(Path);
1701   if (!Result) {
1702     if (IsFallthrough &&
1703         Result.getError() == llvm::errc::no_such_file_or_directory) {
1704       return ExternalFS->status(Path);
1705     }
1706     return Result.getError();
1707   }
1708   return status(Path, *Result);
1709 }
1710
1711 namespace {
1712
1713 /// Provide a file wrapper with an overriden status.
1714 class FileWithFixedStatus : public File {
1715   std::unique_ptr<File> InnerFile;
1716   Status S;
1717
1718 public:
1719   FileWithFixedStatus(std::unique_ptr<File> InnerFile, Status S)
1720       : InnerFile(std::move(InnerFile)), S(std::move(S)) {}
1721
1722   ErrorOr<Status> status() override { return S; }
1723   ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
1724
1725   getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
1726             bool IsVolatile) override {
1727     return InnerFile->getBuffer(Name, FileSize, RequiresNullTerminator,
1728                                 IsVolatile);
1729   }
1730
1731   std::error_code close() override { return InnerFile->close(); }
1732 };
1733
1734 } // namespace
1735
1736 ErrorOr<std::unique_ptr<File>>
1737 RedirectingFileSystem::openFileForRead(const Twine &Path) {
1738   ErrorOr<RedirectingFileSystem::Entry *> E = lookupPath(Path);
1739   if (!E) {
1740     if (IsFallthrough &&
1741         E.getError() == llvm::errc::no_such_file_or_directory) {
1742       return ExternalFS->openFileForRead(Path);
1743     }
1744     return E.getError();
1745   }
1746
1747   auto *F = dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(*E);
1748   if (!F) // FIXME: errc::not_a_file?
1749     return make_error_code(llvm::errc::invalid_argument);
1750
1751   auto Result = ExternalFS->openFileForRead(F->getExternalContentsPath());
1752   if (!Result)
1753     return Result;
1754
1755   auto ExternalStatus = (*Result)->status();
1756   if (!ExternalStatus)
1757     return ExternalStatus.getError();
1758
1759   // FIXME: Update the status with the name and VFSMapped.
1760   Status S = getRedirectedFileStatus(Path, F->useExternalName(UseExternalNames),
1761                                      *ExternalStatus);
1762   return std::unique_ptr<File>(
1763       llvm::make_unique<FileWithFixedStatus>(std::move(*Result), S));
1764 }
1765
1766 std::error_code
1767 RedirectingFileSystem::getRealPath(const Twine &Path,
1768                                    SmallVectorImpl<char> &Output) const {
1769   ErrorOr<RedirectingFileSystem::Entry *> Result = lookupPath(Path);
1770   if (!Result) {
1771     if (IsFallthrough &&
1772         Result.getError() == llvm::errc::no_such_file_or_directory) {
1773       return ExternalFS->getRealPath(Path, Output);
1774     }
1775     return Result.getError();
1776   }
1777
1778   if (auto *F =
1779           dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(*Result)) {
1780     return ExternalFS->getRealPath(F->getExternalContentsPath(), Output);
1781   }
1782   // Even if there is a directory entry, fall back to ExternalFS if allowed,
1783   // because directories don't have a single external contents path.
1784   return IsFallthrough ? ExternalFS->getRealPath(Path, Output)
1785                        : llvm::errc::invalid_argument;
1786 }
1787
1788 IntrusiveRefCntPtr<FileSystem>
1789 vfs::getVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
1790                     SourceMgr::DiagHandlerTy DiagHandler,
1791                     StringRef YAMLFilePath, void *DiagContext,
1792                     IntrusiveRefCntPtr<FileSystem> ExternalFS) {
1793   return RedirectingFileSystem::create(std::move(Buffer), DiagHandler,
1794                                        YAMLFilePath, DiagContext,
1795                                        std::move(ExternalFS));
1796 }
1797
1798 static void getVFSEntries(RedirectingFileSystem::Entry *SrcE,
1799                           SmallVectorImpl<StringRef> &Path,
1800                           SmallVectorImpl<YAMLVFSEntry> &Entries) {
1801   auto Kind = SrcE->getKind();
1802   if (Kind == RedirectingFileSystem::EK_Directory) {
1803     auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(SrcE);
1804     assert(DE && "Must be a directory");
1805     for (std::unique_ptr<RedirectingFileSystem::Entry> &SubEntry :
1806          llvm::make_range(DE->contents_begin(), DE->contents_end())) {
1807       Path.push_back(SubEntry->getName());
1808       getVFSEntries(SubEntry.get(), Path, Entries);
1809       Path.pop_back();
1810     }
1811     return;
1812   }
1813
1814   assert(Kind == RedirectingFileSystem::EK_File && "Must be a EK_File");
1815   auto *FE = dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(SrcE);
1816   assert(FE && "Must be a file");
1817   SmallString<128> VPath;
1818   for (auto &Comp : Path)
1819     llvm::sys::path::append(VPath, Comp);
1820   Entries.push_back(YAMLVFSEntry(VPath.c_str(), FE->getExternalContentsPath()));
1821 }
1822
1823 void vfs::collectVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
1824                              SourceMgr::DiagHandlerTy DiagHandler,
1825                              StringRef YAMLFilePath,
1826                              SmallVectorImpl<YAMLVFSEntry> &CollectedEntries,
1827                              void *DiagContext,
1828                              IntrusiveRefCntPtr<FileSystem> ExternalFS) {
1829   RedirectingFileSystem *VFS = RedirectingFileSystem::create(
1830       std::move(Buffer), DiagHandler, YAMLFilePath, DiagContext,
1831       std::move(ExternalFS));
1832   ErrorOr<RedirectingFileSystem::Entry *> RootE = VFS->lookupPath("/");
1833   if (!RootE)
1834     return;
1835   SmallVector<StringRef, 8> Components;
1836   Components.push_back("/");
1837   getVFSEntries(*RootE, Components, CollectedEntries);
1838 }
1839
1840 UniqueID vfs::getNextVirtualUniqueID() {
1841   static std::atomic<unsigned> UID;
1842   unsigned ID = ++UID;
1843   // The following assumes that uint64_t max will never collide with a real
1844   // dev_t value from the OS.
1845   return UniqueID(std::numeric_limits<uint64_t>::max(), ID);
1846 }
1847
1848 void YAMLVFSWriter::addFileMapping(StringRef VirtualPath, StringRef RealPath) {
1849   assert(sys::path::is_absolute(VirtualPath) && "virtual path not absolute");
1850   assert(sys::path::is_absolute(RealPath) && "real path not absolute");
1851   assert(!pathHasTraversal(VirtualPath) && "path traversal is not supported");
1852   Mappings.emplace_back(VirtualPath, RealPath);
1853 }
1854
1855 namespace {
1856
1857 class JSONWriter {
1858   llvm::raw_ostream &OS;
1859   SmallVector<StringRef, 16> DirStack;
1860
1861   unsigned getDirIndent() { return 4 * DirStack.size(); }
1862   unsigned getFileIndent() { return 4 * (DirStack.size() + 1); }
1863   bool containedIn(StringRef Parent, StringRef Path);
1864   StringRef containedPart(StringRef Parent, StringRef Path);
1865   void startDirectory(StringRef Path);
1866   void endDirectory();
1867   void writeEntry(StringRef VPath, StringRef RPath);
1868
1869 public:
1870   JSONWriter(llvm::raw_ostream &OS) : OS(OS) {}
1871
1872   void write(ArrayRef<YAMLVFSEntry> Entries, Optional<bool> UseExternalNames,
1873              Optional<bool> IsCaseSensitive, Optional<bool> IsOverlayRelative,
1874              StringRef OverlayDir);
1875 };
1876
1877 } // namespace
1878
1879 bool JSONWriter::containedIn(StringRef Parent, StringRef Path) {
1880   using namespace llvm::sys;
1881
1882   // Compare each path component.
1883   auto IParent = path::begin(Parent), EParent = path::end(Parent);
1884   for (auto IChild = path::begin(Path), EChild = path::end(Path);
1885        IParent != EParent && IChild != EChild; ++IParent, ++IChild) {
1886     if (*IParent != *IChild)
1887       return false;
1888   }
1889   // Have we exhausted the parent path?
1890   return IParent == EParent;
1891 }
1892
1893 StringRef JSONWriter::containedPart(StringRef Parent, StringRef Path) {
1894   assert(!Parent.empty());
1895   assert(containedIn(Parent, Path));
1896   return Path.slice(Parent.size() + 1, StringRef::npos);
1897 }
1898
1899 void JSONWriter::startDirectory(StringRef Path) {
1900   StringRef Name =
1901       DirStack.empty() ? Path : containedPart(DirStack.back(), Path);
1902   DirStack.push_back(Path);
1903   unsigned Indent = getDirIndent();
1904   OS.indent(Indent) << "{\n";
1905   OS.indent(Indent + 2) << "'type': 'directory',\n";
1906   OS.indent(Indent + 2) << "'name': \"" << llvm::yaml::escape(Name) << "\",\n";
1907   OS.indent(Indent + 2) << "'contents': [\n";
1908 }
1909
1910 void JSONWriter::endDirectory() {
1911   unsigned Indent = getDirIndent();
1912   OS.indent(Indent + 2) << "]\n";
1913   OS.indent(Indent) << "}";
1914
1915   DirStack.pop_back();
1916 }
1917
1918 void JSONWriter::writeEntry(StringRef VPath, StringRef RPath) {
1919   unsigned Indent = getFileIndent();
1920   OS.indent(Indent) << "{\n";
1921   OS.indent(Indent + 2) << "'type': 'file',\n";
1922   OS.indent(Indent + 2) << "'name': \"" << llvm::yaml::escape(VPath) << "\",\n";
1923   OS.indent(Indent + 2) << "'external-contents': \""
1924                         << llvm::yaml::escape(RPath) << "\"\n";
1925   OS.indent(Indent) << "}";
1926 }
1927
1928 void JSONWriter::write(ArrayRef<YAMLVFSEntry> Entries,
1929                        Optional<bool> UseExternalNames,
1930                        Optional<bool> IsCaseSensitive,
1931                        Optional<bool> IsOverlayRelative,
1932                        StringRef OverlayDir) {
1933   using namespace llvm::sys;
1934
1935   OS << "{\n"
1936         "  'version': 0,\n";
1937   if (IsCaseSensitive.hasValue())
1938     OS << "  'case-sensitive': '"
1939        << (IsCaseSensitive.getValue() ? "true" : "false") << "',\n";
1940   if (UseExternalNames.hasValue())
1941     OS << "  'use-external-names': '"
1942        << (UseExternalNames.getValue() ? "true" : "false") << "',\n";
1943   bool UseOverlayRelative = false;
1944   if (IsOverlayRelative.hasValue()) {
1945     UseOverlayRelative = IsOverlayRelative.getValue();
1946     OS << "  'overlay-relative': '" << (UseOverlayRelative ? "true" : "false")
1947        << "',\n";
1948   }
1949   OS << "  'roots': [\n";
1950
1951   if (!Entries.empty()) {
1952     const YAMLVFSEntry &Entry = Entries.front();
1953     startDirectory(path::parent_path(Entry.VPath));
1954
1955     StringRef RPath = Entry.RPath;
1956     if (UseOverlayRelative) {
1957       unsigned OverlayDirLen = OverlayDir.size();
1958       assert(RPath.substr(0, OverlayDirLen) == OverlayDir &&
1959              "Overlay dir must be contained in RPath");
1960       RPath = RPath.slice(OverlayDirLen, RPath.size());
1961     }
1962
1963     writeEntry(path::filename(Entry.VPath), RPath);
1964
1965     for (const auto &Entry : Entries.slice(1)) {
1966       StringRef Dir = path::parent_path(Entry.VPath);
1967       if (Dir == DirStack.back())
1968         OS << ",\n";
1969       else {
1970         while (!DirStack.empty() && !containedIn(DirStack.back(), Dir)) {
1971           OS << "\n";
1972           endDirectory();
1973         }
1974         OS << ",\n";
1975         startDirectory(Dir);
1976       }
1977       StringRef RPath = Entry.RPath;
1978       if (UseOverlayRelative) {
1979         unsigned OverlayDirLen = OverlayDir.size();
1980         assert(RPath.substr(0, OverlayDirLen) == OverlayDir &&
1981                "Overlay dir must be contained in RPath");
1982         RPath = RPath.slice(OverlayDirLen, RPath.size());
1983       }
1984       writeEntry(path::filename(Entry.VPath), RPath);
1985     }
1986
1987     while (!DirStack.empty()) {
1988       OS << "\n";
1989       endDirectory();
1990     }
1991     OS << "\n";
1992   }
1993
1994   OS << "  ]\n"
1995      << "}\n";
1996 }
1997
1998 void YAMLVFSWriter::write(llvm::raw_ostream &OS) {
1999   llvm::sort(Mappings, [](const YAMLVFSEntry &LHS, const YAMLVFSEntry &RHS) {
2000     return LHS.VPath < RHS.VPath;
2001   });
2002
2003   JSONWriter(OS).write(Mappings, UseExternalNames, IsCaseSensitive,
2004                        IsOverlayRelative, OverlayDir);
2005 }
2006
2007 VFSFromYamlDirIterImpl::VFSFromYamlDirIterImpl(
2008     const Twine &_Path,
2009     RedirectingFileSystem::RedirectingDirectoryEntry::iterator Begin,
2010     RedirectingFileSystem::RedirectingDirectoryEntry::iterator End,
2011     bool IterateExternalFS, FileSystem &ExternalFS, std::error_code &EC)
2012     : Dir(_Path.str()), Current(Begin), End(End),
2013       IterateExternalFS(IterateExternalFS), ExternalFS(ExternalFS) {
2014   EC = incrementImpl(/*IsFirstTime=*/true);
2015 }
2016
2017 std::error_code VFSFromYamlDirIterImpl::increment() {
2018   return incrementImpl(/*IsFirstTime=*/false);
2019 }
2020
2021 std::error_code VFSFromYamlDirIterImpl::incrementExternal() {
2022   assert(!(IsExternalFSCurrent && ExternalDirIter == directory_iterator()) &&
2023          "incrementing past end");
2024   std::error_code EC;
2025   if (IsExternalFSCurrent) {
2026     ExternalDirIter.increment(EC);
2027   } else if (IterateExternalFS) {
2028     ExternalDirIter = ExternalFS.dir_begin(Dir, EC);
2029     IsExternalFSCurrent = true;
2030     if (EC && EC != errc::no_such_file_or_directory)
2031       return EC;
2032     EC = {};
2033   }
2034   if (EC || ExternalDirIter == directory_iterator()) {
2035     CurrentEntry = directory_entry();
2036   } else {
2037     CurrentEntry = *ExternalDirIter;
2038   }
2039   return EC;
2040 }
2041
2042 std::error_code VFSFromYamlDirIterImpl::incrementContent(bool IsFirstTime) {
2043   assert((IsFirstTime || Current != End) && "cannot iterate past end");
2044   if (!IsFirstTime)
2045     ++Current;
2046   while (Current != End) {
2047     SmallString<128> PathStr(Dir);
2048     llvm::sys::path::append(PathStr, (*Current)->getName());
2049     sys::fs::file_type Type;
2050     switch ((*Current)->getKind()) {
2051     case RedirectingFileSystem::EK_Directory:
2052       Type = sys::fs::file_type::directory_file;
2053       break;
2054     case RedirectingFileSystem::EK_File:
2055       Type = sys::fs::file_type::regular_file;
2056       break;
2057     }
2058     CurrentEntry = directory_entry(PathStr.str(), Type);
2059     return {};
2060   }
2061   return incrementExternal();
2062 }
2063
2064 std::error_code VFSFromYamlDirIterImpl::incrementImpl(bool IsFirstTime) {
2065   while (true) {
2066     std::error_code EC = IsExternalFSCurrent ? incrementExternal()
2067                                              : incrementContent(IsFirstTime);
2068     if (EC || CurrentEntry.path().empty())
2069       return EC;
2070     StringRef Name = llvm::sys::path::filename(CurrentEntry.path());
2071     if (SeenNames.insert(Name).second)
2072       return EC; // name not seen before
2073   }
2074   llvm_unreachable("returned above");
2075 }
2076
2077 vfs::recursive_directory_iterator::recursive_directory_iterator(
2078     FileSystem &FS_, const Twine &Path, std::error_code &EC)
2079     : FS(&FS_) {
2080   directory_iterator I = FS->dir_begin(Path, EC);
2081   if (I != directory_iterator()) {
2082     State = std::make_shared<detail::RecDirIterState>();
2083     State->Stack.push(I);
2084   }
2085 }
2086
2087 vfs::recursive_directory_iterator &
2088 recursive_directory_iterator::increment(std::error_code &EC) {
2089   assert(FS && State && !State->Stack.empty() && "incrementing past end");
2090   assert(!State->Stack.top()->path().empty() && "non-canonical end iterator");
2091   vfs::directory_iterator End;
2092
2093   if (State->HasNoPushRequest)
2094     State->HasNoPushRequest = false;
2095   else {
2096     if (State->Stack.top()->type() == sys::fs::file_type::directory_file) {
2097       vfs::directory_iterator I = FS->dir_begin(State->Stack.top()->path(), EC);
2098       if (I != End) {
2099         State->Stack.push(I);
2100         return *this;
2101       }
2102     }
2103   }
2104
2105   while (!State->Stack.empty() && State->Stack.top().increment(EC) == End)
2106     State->Stack.pop();
2107
2108   if (State->Stack.empty())
2109     State.reset(); // end iterator
2110
2111   return *this;
2112 }