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 FD, StringRef NewName, StringRef NewRealPathName)
 180       : FD(FD), 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 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 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 class OverlayFSDirIterImpl : public llvm::vfs::detail::DirIterImpl {
 456   OverlayFileSystem &Overlays;
 457   std::string Path;
 458   OverlayFileSystem::iterator CurrentFS;
 459   directory_iterator CurrentDirIter;
 460   llvm::StringSet<> SeenNames;
 461
 462   std::error_code incrementFS() {
 463     assert(CurrentFS != Overlays.overlays_end() && "incrementing past end");
 464     ++CurrentFS;
 465     for (auto E = Overlays.overlays_end(); CurrentFS != E; ++CurrentFS) {
 466       std::error_code EC;
 467       CurrentDirIter = (*CurrentFS)->dir_begin(Path, EC);
 468       if (EC && EC != errc::no_such_file_or_directory)
 469         return EC;
 470       if (CurrentDirIter != directory_iterator())
 471         break; // found
 472     }
 473     return {};
 474   }
 475
 476   std::error_code incrementDirIter(bool IsFirstTime) {
 477     assert((IsFirstTime || CurrentDirIter != directory_iterator()) &&
 478            "incrementing past end");
 479     std::error_code EC;
 480     if (!IsFirstTime)
 481       CurrentDirIter.increment(EC);
 482     if (!EC && CurrentDirIter == directory_iterator())
 483       EC = incrementFS();
 484     return EC;
 485   }
 486
 487   std::error_code incrementImpl(bool IsFirstTime) {
 488     while (true) {
 489       std::error_code EC = incrementDirIter(IsFirstTime);
 490       if (EC || CurrentDirIter == directory_iterator()) {
 491         CurrentEntry = directory_entry();
 492         return EC;
 493       }
 494       CurrentEntry = *CurrentDirIter;
 495       StringRef Name = llvm::sys::path::filename(CurrentEntry.path());
 496       if (SeenNames.insert(Name).second)
 497         return EC; // name not seen before
 498     }
 499     llvm_unreachable("returned above");
 500   }
 501
 502 public:
 503   OverlayFSDirIterImpl(const Twine &Path, OverlayFileSystem &FS,
 504                        std::error_code &EC)
 505       : Overlays(FS), Path(Path.str()), CurrentFS(Overlays.overlays_begin()) {
 506     CurrentDirIter = (*CurrentFS)->dir_begin(Path, EC);
 507     EC = incrementImpl(true);
 508   }
 509
 510   std::error_code increment() override { return incrementImpl(false); }
 511 };
 512
 513 } // namespace
 514
 515 directory_iterator OverlayFileSystem::dir_begin(const Twine &Dir,
 516                                                 std::error_code &EC) {
 517   return directory_iterator(
 518       std::make_shared<OverlayFSDirIterImpl>(Dir, *this, EC));
 519 }
 520
 521 void ProxyFileSystem::anchor() {}
 522
 523 namespace llvm {
 524 namespace vfs {
 525
 526 namespace detail {
 527
 528 enum InMemoryNodeKind { IME_File, IME_Directory, IME_HardLink };
 529
 530 /// The in memory file system is a tree of Nodes. Every node can either be a
 531 /// file , hardlink or a directory.
 532 class InMemoryNode {
 533   InMemoryNodeKind Kind;
 534   std::string FileName;
 535
 536 public:
 537   InMemoryNode(llvm::StringRef FileName, InMemoryNodeKind Kind)
 538       : Kind(Kind), FileName(llvm::sys::path::filename(FileName)) {}
 539   virtual ~InMemoryNode() = default;
 540
 541   /// Get the filename of this node (the name without the directory part).
 542   StringRef getFileName() const { return FileName; }
 543   InMemoryNodeKind getKind() const { return Kind; }
 544   virtual std::string toString(unsigned Indent) const = 0;
 545 };
 546
 547 class InMemoryFile : public InMemoryNode {
 548   Status Stat;
 549   std::unique_ptr<llvm::MemoryBuffer> Buffer;
 550
 551 public:
 552   InMemoryFile(Status Stat, std::unique_ptr<llvm::MemoryBuffer> Buffer)
 553       : InMemoryNode(Stat.getName(), IME_File), Stat(std::move(Stat)),
 554         Buffer(std::move(Buffer)) {}
 555
 556   /// Return the \p Status for this node. \p RequestedName should be the name
 557   /// through which the caller referred to this node. It will override
 558   /// \p Status::Name in the return value, to mimic the behavior of \p RealFile.
 559   Status getStatus(const Twine &RequestedName) const {
 560     return Status::copyWithNewName(Stat, RequestedName);
 561   }
 562   llvm::MemoryBuffer *getBuffer() const { return Buffer.get(); }
 563
 564   std::string toString(unsigned Indent) const override {
 565     return (std::string(Indent, ' ') + Stat.getName() + "\n").str();
 566   }
 567
 568   static bool classof(const InMemoryNode *N) {
 569     return N->getKind() == IME_File;
 570   }
 571 };
 572
 573 namespace {
 574
 575 class InMemoryHardLink : public InMemoryNode {
 576   const InMemoryFile &ResolvedFile;
 577
 578 public:
 579   InMemoryHardLink(StringRef Path, const InMemoryFile &ResolvedFile)
 580       : InMemoryNode(Path, IME_HardLink), ResolvedFile(ResolvedFile) {}
 581   const InMemoryFile &getResolvedFile() const { return ResolvedFile; }
 582
 583   std::string toString(unsigned Indent) const override {
 584     return std::string(Indent, ' ') + "HardLink to -> " +
 585            ResolvedFile.toString(0);
 586   }
 587
 588   static bool classof(const InMemoryNode *N) {
 589     return N->getKind() == IME_HardLink;
 590   }
 591 };
 592
 593 /// Adapt a InMemoryFile for VFS' File interface.  The goal is to make
 594 /// \p InMemoryFileAdaptor mimic as much as possible the behavior of
 595 /// \p RealFile.
 596 class InMemoryFileAdaptor : public File {
 597   const InMemoryFile &Node;
 598   /// The name to use when returning a Status for this file.
 599   std::string RequestedName;
 600
 601 public:
 602   explicit InMemoryFileAdaptor(const InMemoryFile &Node,
 603                                std::string RequestedName)
 604       : Node(Node), RequestedName(std::move(RequestedName)) {}
 605
 606   llvm::ErrorOr<Status> status() override {
 607     return Node.getStatus(RequestedName);
 608   }
 609
 610   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
 611   getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
 612             bool IsVolatile) override {
 613     llvm::MemoryBuffer *Buf = Node.getBuffer();
 614     return llvm::MemoryBuffer::getMemBuffer(
 615         Buf->getBuffer(), Buf->getBufferIdentifier(), RequiresNullTerminator);
 616   }
 617
 618   std::error_code close() override { return {}; }
 619 };
 620 } // namespace
 621
 622 class InMemoryDirectory : public InMemoryNode {
 623   Status Stat;
 624   llvm::StringMap<std::unique_ptr<InMemoryNode>> Entries;
 625
 626 public:
 627   InMemoryDirectory(Status Stat)
 628       : InMemoryNode(Stat.getName(), IME_Directory), Stat(std::move(Stat)) {}
 629
 630   /// Return the \p Status for this node. \p RequestedName should be the name
 631   /// through which the caller referred to this node. It will override
 632   /// \p Status::Name in the return value, to mimic the behavior of \p RealFile.
 633   Status getStatus(const Twine &RequestedName) const {
 634     return Status::copyWithNewName(Stat, RequestedName);
 635   }
 636   InMemoryNode *getChild(StringRef Name) {
 637     auto I = Entries.find(Name);
 638     if (I != Entries.end())
 639       return I->second.get();
 640     return nullptr;
 641   }
 642
 643   InMemoryNode *addChild(StringRef Name, std::unique_ptr<InMemoryNode> Child) {
 644     return Entries.insert(make_pair(Name, std::move(Child)))
 645         .first->second.get();
 646   }
 647
 648   using const_iterator = decltype(Entries)::const_iterator;
 649
 650   const_iterator begin() const { return Entries.begin(); }
 651   const_iterator end() const { return Entries.end(); }
 652
 653   std::string toString(unsigned Indent) const override {
 654     std::string Result =
 655         (std::string(Indent, ' ') + Stat.getName() + "\n").str();
 656     for (const auto &Entry : Entries)
 657       Result += Entry.second->toString(Indent + 2);
 658     return Result;
 659   }
 660
 661   static bool classof(const InMemoryNode *N) {
 662     return N->getKind() == IME_Directory;
 663   }
 664 };
 665
 666 namespace {
 667 Status getNodeStatus(const InMemoryNode *Node, const Twine &RequestedName) {
 668   if (auto Dir = dyn_cast<detail::InMemoryDirectory>(Node))
 669     return Dir->getStatus(RequestedName);
 670   if (auto File = dyn_cast<detail::InMemoryFile>(Node))
 671     return File->getStatus(RequestedName);
 672   if (auto Link = dyn_cast<detail::InMemoryHardLink>(Node))
 673     return Link->getResolvedFile().getStatus(RequestedName);
 674   llvm_unreachable("Unknown node type");
 675 }
 676 } // namespace
 677 } // namespace detail
 678
 679 InMemoryFileSystem::InMemoryFileSystem(bool UseNormalizedPaths)
 680     : Root(new detail::InMemoryDirectory(
 681           Status("", getNextVirtualUniqueID(), llvm::sys::TimePoint<>(), 0, 0,
 682                  0, llvm::sys::fs::file_type::directory_file,
 683                  llvm::sys::fs::perms::all_all))),
 684       UseNormalizedPaths(UseNormalizedPaths) {}
 685
 686 InMemoryFileSystem::~InMemoryFileSystem() = default;
 687
 688 std::string InMemoryFileSystem::toString() const {
 689   return Root->toString(/*Indent=*/0);
 690 }
 691
 692 bool InMemoryFileSystem::addFile(const Twine &P, time_t ModificationTime,
 693                                  std::unique_ptr<llvm::MemoryBuffer> Buffer,
 694                                  Optional<uint32_t> User,
 695                                  Optional<uint32_t> Group,
 696                                  Optional<llvm::sys::fs::file_type> Type,
 697                                  Optional<llvm::sys::fs::perms> Perms,
 698                                  const detail::InMemoryFile *HardLinkTarget) {
 699   SmallString<128> Path;
 700   P.toVector(Path);
 701
 702   // Fix up relative paths. This just prepends the current working directory.
 703   std::error_code EC = makeAbsolute(Path);
 704   assert(!EC);
 705   (void)EC;
 706
 707   if (useNormalizedPaths())
 708     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 709
 710   if (Path.empty())
 711     return false;
 712
 713   detail::InMemoryDirectory *Dir = Root.get();
 714   auto I = llvm::sys::path::begin(Path), E = sys::path::end(Path);
 715   const auto ResolvedUser = User.getValueOr(0);
 716   const auto ResolvedGroup = Group.getValueOr(0);
 717   const auto ResolvedType = Type.getValueOr(sys::fs::file_type::regular_file);
 718   const auto ResolvedPerms = Perms.getValueOr(sys::fs::all_all);
 719   assert(!(HardLinkTarget && Buffer) && "HardLink cannot have a buffer");
 720   // Any intermediate directories we create should be accessible by
 721   // the owner, even if Perms says otherwise for the final path.
 722   const auto NewDirectoryPerms = ResolvedPerms | sys::fs::owner_all;
 723   while (true) {
 724     StringRef Name = *I;
 725     detail::InMemoryNode *Node = Dir->getChild(Name);
 726     ++I;
 727     if (!Node) {
 728       if (I == E) {
 729         // End of the path.
 730         std::unique_ptr<detail::InMemoryNode> Child;
 731         if (HardLinkTarget)
 732           Child.reset(new detail::InMemoryHardLink(P.str(), *HardLinkTarget));
 733         else {
 734           // Create a new file or directory.
 735           Status Stat(P.str(), getNextVirtualUniqueID(),
 736                       llvm::sys::toTimePoint(ModificationTime), ResolvedUser,
 737                       ResolvedGroup, Buffer->getBufferSize(), ResolvedType,
 738                       ResolvedPerms);
 739           if (ResolvedType == sys::fs::file_type::directory_file) {
 740             Child.reset(new detail::InMemoryDirectory(std::move(Stat)));
 741           } else {
 742             Child.reset(
 743                 new detail::InMemoryFile(std::move(Stat), std::move(Buffer)));
 744           }
 745         }
 746         Dir->addChild(Name, std::move(Child));
 747         return true;
 748       }
 749
 750       // Create a new directory. Use the path up to here.
 751       Status Stat(
 752           StringRef(Path.str().begin(), Name.end() - Path.str().begin()),
 753           getNextVirtualUniqueID(), llvm::sys::toTimePoint(ModificationTime),
 754           ResolvedUser, ResolvedGroup, 0, sys::fs::file_type::directory_file,
 755           NewDirectoryPerms);
 756       Dir = cast<detail::InMemoryDirectory>(Dir->addChild(
 757           Name, std::make_unique<detail::InMemoryDirectory>(std::move(Stat))));
 758       continue;
 759     }
 760
 761     if (auto *NewDir = dyn_cast<detail::InMemoryDirectory>(Node)) {
 762       Dir = NewDir;
 763     } else {
 764       assert((isa<detail::InMemoryFile>(Node) ||
 765               isa<detail::InMemoryHardLink>(Node)) &&
 766              "Must be either file, hardlink or directory!");
 767
 768       // Trying to insert a directory in place of a file.
 769       if (I != E)
 770         return false;
 771
 772       // Return false only if the new file is different from the existing one.
 773       if (auto Link = dyn_cast<detail::InMemoryHardLink>(Node)) {
 774         return Link->getResolvedFile().getBuffer()->getBuffer() ==
 775                Buffer->getBuffer();
 776       }
 777       return cast<detail::InMemoryFile>(Node)->getBuffer()->getBuffer() ==
 778              Buffer->getBuffer();
 779     }
 780   }
 781 }
 782
 783 bool InMemoryFileSystem::addFile(const Twine &P, time_t ModificationTime,
 784                                  std::unique_ptr<llvm::MemoryBuffer> Buffer,
 785                                  Optional<uint32_t> User,
 786                                  Optional<uint32_t> Group,
 787                                  Optional<llvm::sys::fs::file_type> Type,
 788                                  Optional<llvm::sys::fs::perms> Perms) {
 789   return addFile(P, ModificationTime, std::move(Buffer), User, Group, Type,
 790                  Perms, /*HardLinkTarget=*/nullptr);
 791 }
 792
 793 bool InMemoryFileSystem::addFileNoOwn(const Twine &P, time_t ModificationTime,
 794                                       llvm::MemoryBuffer *Buffer,
 795                                       Optional<uint32_t> User,
 796                                       Optional<uint32_t> Group,
 797                                       Optional<llvm::sys::fs::file_type> Type,
 798                                       Optional<llvm::sys::fs::perms> Perms) {
 799   return addFile(P, ModificationTime,
 800                  llvm::MemoryBuffer::getMemBuffer(
 801                      Buffer->getBuffer(), Buffer->getBufferIdentifier()),
 802                  std::move(User), std::move(Group), std::move(Type),
 803                  std::move(Perms));
 804 }
 805
 806 static ErrorOr<const detail::InMemoryNode *>
 807 lookupInMemoryNode(const InMemoryFileSystem &FS, detail::InMemoryDirectory *Dir,
 808                    const Twine &P) {
 809   SmallString<128> Path;
 810   P.toVector(Path);
 811
 812   // Fix up relative paths. This just prepends the current working directory.
 813   std::error_code EC = FS.makeAbsolute(Path);
 814   assert(!EC);
 815   (void)EC;
 816
 817   if (FS.useNormalizedPaths())
 818     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 819
 820   if (Path.empty())
 821     return Dir;
 822
 823   auto I = llvm::sys::path::begin(Path), E = llvm::sys::path::end(Path);
 824   while (true) {
 825     detail::InMemoryNode *Node = Dir->getChild(*I);
 826     ++I;
 827     if (!Node)
 828       return errc::no_such_file_or_directory;
 829
 830     // Return the file if it's at the end of the path.
 831     if (auto File = dyn_cast<detail::InMemoryFile>(Node)) {
 832       if (I == E)
 833         return File;
 834       return errc::no_such_file_or_directory;
 835     }
 836
 837     // If Node is HardLink then return the resolved file.
 838     if (auto File = dyn_cast<detail::InMemoryHardLink>(Node)) {
 839       if (I == E)
 840         return &File->getResolvedFile();
 841       return errc::no_such_file_or_directory;
 842     }
 843     // Traverse directories.
 844     Dir = cast<detail::InMemoryDirectory>(Node);
 845     if (I == E)
 846       return Dir;
 847   }
 848 }
 849
 850 bool InMemoryFileSystem::addHardLink(const Twine &FromPath,
 851                                      const Twine &ToPath) {
 852   auto FromNode = lookupInMemoryNode(*this, Root.get(), FromPath);
 853   auto ToNode = lookupInMemoryNode(*this, Root.get(), ToPath);
 854   // FromPath must not have been added before. ToPath must have been added
 855   // before. Resolved ToPath must be a File.
 856   if (!ToNode || FromNode || !isa<detail::InMemoryFile>(*ToNode))
 857     return false;
 858   return this->addFile(FromPath, 0, nullptr, None, None, None, None,
 859                        cast<detail::InMemoryFile>(*ToNode));
 860 }
 861
 862 llvm::ErrorOr<Status> InMemoryFileSystem::status(const Twine &Path) {
 863   auto Node = lookupInMemoryNode(*this, Root.get(), Path);
 864   if (Node)
 865     return detail::getNodeStatus(*Node, Path);
 866   return Node.getError();
 867 }
 868
 869 llvm::ErrorOr<std::unique_ptr<File>>
 870 InMemoryFileSystem::openFileForRead(const Twine &Path) {
 871   auto Node = lookupInMemoryNode(*this, Root.get(), Path);
 872   if (!Node)
 873     return Node.getError();
 874
 875   // When we have a file provide a heap-allocated wrapper for the memory buffer
 876   // to match the ownership semantics for File.
 877   if (auto *F = dyn_cast<detail::InMemoryFile>(*Node))
 878     return std::unique_ptr<File>(
 879         new detail::InMemoryFileAdaptor(*F, Path.str()));
 880
 881   // FIXME: errc::not_a_file?
 882   return make_error_code(llvm::errc::invalid_argument);
 883 }
 884
 885 namespace {
 886
 887 /// Adaptor from InMemoryDir::iterator to directory_iterator.
 888 class InMemoryDirIterator : public llvm::vfs::detail::DirIterImpl {
 889   detail::InMemoryDirectory::const_iterator I;
 890   detail::InMemoryDirectory::const_iterator E;
 891   std::string RequestedDirName;
 892
 893   void setCurrentEntry() {
 894     if (I != E) {
 895       SmallString<256> Path(RequestedDirName);
 896       llvm::sys::path::append(Path, I->second->getFileName());
 897       sys::fs::file_type Type;
 898       switch (I->second->getKind()) {
 899       case detail::IME_File:
 900       case detail::IME_HardLink:
 901         Type = sys::fs::file_type::regular_file;
 902         break;
 903       case detail::IME_Directory:
 904         Type = sys::fs::file_type::directory_file;
 905         break;
 906       }
 907       CurrentEntry = directory_entry(Path.str(), Type);
 908     } else {
 909       // When we're at the end, make CurrentEntry invalid and DirIterImpl will
 910       // do the rest.
 911       CurrentEntry = directory_entry();
 912     }
 913   }
 914
 915 public:
 916   InMemoryDirIterator() = default;
 917
 918   explicit InMemoryDirIterator(const detail::InMemoryDirectory &Dir,
 919                                std::string RequestedDirName)
 920       : I(Dir.begin()), E(Dir.end()),
 921         RequestedDirName(std::move(RequestedDirName)) {
 922     setCurrentEntry();
 923   }
 924
 925   std::error_code increment() override {
 926     ++I;
 927     setCurrentEntry();
 928     return {};
 929   }
 930 };
 931
 932 } // namespace
 933
 934 directory_iterator InMemoryFileSystem::dir_begin(const Twine &Dir,
 935                                                  std::error_code &EC) {
 936   auto Node = lookupInMemoryNode(*this, Root.get(), Dir);
 937   if (!Node) {
 938     EC = Node.getError();
 939     return directory_iterator(std::make_shared<InMemoryDirIterator>());
 940   }
 941
 942   if (auto *DirNode = dyn_cast<detail::InMemoryDirectory>(*Node))
 943     return directory_iterator(
 944         std::make_shared<InMemoryDirIterator>(*DirNode, Dir.str()));
 945
 946   EC = make_error_code(llvm::errc::not_a_directory);
 947   return directory_iterator(std::make_shared<InMemoryDirIterator>());
 948 }
 949
 950 std::error_code InMemoryFileSystem::setCurrentWorkingDirectory(const Twine &P) {
 951   SmallString<128> Path;
 952   P.toVector(Path);
 953
 954   // Fix up relative paths. This just prepends the current working directory.
 955   std::error_code EC = makeAbsolute(Path);
 956   assert(!EC);
 957   (void)EC;
 958
 959   if (useNormalizedPaths())
 960     llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
 961
 962   if (!Path.empty())
 963     WorkingDirectory = Path.str();
 964   return {};
 965 }
 966
 967 std::error_code
 968 InMemoryFileSystem::getRealPath(const Twine &Path,
 969                                 SmallVectorImpl<char> &Output) const {
 970   auto CWD = getCurrentWorkingDirectory();
 971   if (!CWD || CWD->empty())
 972     return errc::operation_not_permitted;
 973   Path.toVector(Output);
 974   if (auto EC = makeAbsolute(Output))
 975     return EC;
 976   llvm::sys::path::remove_dots(Output, /*remove_dot_dot=*/true);
 977   return {};
 978 }
 979
 980 std::error_code InMemoryFileSystem::isLocal(const Twine &Path, bool &Result) {
 981   Result = false;
 982   return {};
 983 }
 984
 985 } // namespace vfs
 986 } // namespace llvm
 987
 988 //===-----------------------------------------------------------------------===/
 989 // RedirectingFileSystem implementation
 990 //===-----------------------------------------------------------------------===/
 991
 992 // FIXME: reuse implementation common with OverlayFSDirIterImpl as these
 993 // iterators are conceptually similar.
 994 class llvm::vfs::VFSFromYamlDirIterImpl
 995     : public llvm::vfs::detail::DirIterImpl {
 996   std::string Dir;
 997   RedirectingFileSystem::RedirectingDirectoryEntry::iterator Current, End;
 998
 999   // To handle 'fallthrough' mode we need to iterate at first through
1000   // RedirectingDirectoryEntry and then through ExternalFS. These operations are
1001   // done sequentially, we just need to keep a track of what kind of iteration
1002   // we are currently performing.
1003
1004   /// Flag telling if we should iterate through ExternalFS or stop at the last
1005   /// RedirectingDirectoryEntry::iterator.
1006   bool IterateExternalFS;
1007   /// Flag telling if we have switched to iterating through ExternalFS.
1008   bool IsExternalFSCurrent = false;
1009   FileSystem &ExternalFS;
1010   directory_iterator ExternalDirIter;
1011   llvm::StringSet<> SeenNames;
1012
1013   /// To combine multiple iterations, different methods are responsible for
1014   /// different iteration steps.
1015   /// @{
1016
1017   /// Responsible for dispatching between RedirectingDirectoryEntry iteration
1018   /// and ExternalFS iteration.
1019   std::error_code incrementImpl(bool IsFirstTime);
1020   /// Responsible for RedirectingDirectoryEntry iteration.
1021   std::error_code incrementContent(bool IsFirstTime);
1022   /// Responsible for ExternalFS iteration.
1023   std::error_code incrementExternal();
1024   /// @}
1025
1026 public:
1027   VFSFromYamlDirIterImpl(
1028       const Twine &Path,
1029       RedirectingFileSystem::RedirectingDirectoryEntry::iterator Begin,
1030       RedirectingFileSystem::RedirectingDirectoryEntry::iterator End,
1031       bool IterateExternalFS, FileSystem &ExternalFS, std::error_code &EC);
1032
1033   std::error_code increment() override;
1034 };
1035
1036 llvm::ErrorOr<std::string>
1037 RedirectingFileSystem::getCurrentWorkingDirectory() const {
1038   return ExternalFS->getCurrentWorkingDirectory();
1039 }
1040
1041 std::error_code
1042 RedirectingFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
1043   return ExternalFS->setCurrentWorkingDirectory(Path);
1044 }
1045
1046 std::error_code RedirectingFileSystem::isLocal(const Twine &Path,
1047                                                bool &Result) {
1048   return ExternalFS->isLocal(Path, Result);
1049 }
1050
1051 directory_iterator RedirectingFileSystem::dir_begin(const Twine &Dir,
1052                                                     std::error_code &EC) {
1053   ErrorOr<RedirectingFileSystem::Entry *> E = lookupPath(Dir);
1054   if (!E) {
1055     EC = E.getError();
1056     if (IsFallthrough && EC == errc::no_such_file_or_directory)
1057       return ExternalFS->dir_begin(Dir, EC);
1058     return {};
1059   }
1060   ErrorOr<Status> S = status(Dir, *E);
1061   if (!S) {
1062     EC = S.getError();
1063     return {};
1064   }
1065   if (!S->isDirectory()) {
1066     EC = std::error_code(static_cast<int>(errc::not_a_directory),
1067                          std::system_category());
1068     return {};
1069   }
1070
1071   auto *D = cast<RedirectingFileSystem::RedirectingDirectoryEntry>(*E);
1072   return directory_iterator(std::make_shared<VFSFromYamlDirIterImpl>(
1073       Dir, D->contents_begin(), D->contents_end(),
1074       /*IterateExternalFS=*/IsFallthrough, *ExternalFS, EC));
1075 }
1076
1077 void RedirectingFileSystem::setExternalContentsPrefixDir(StringRef PrefixDir) {
1078   ExternalContentsPrefixDir = PrefixDir.str();
1079 }
1080
1081 StringRef RedirectingFileSystem::getExternalContentsPrefixDir() const {
1082   return ExternalContentsPrefixDir;
1083 }
1084
1085 void RedirectingFileSystem::dump(raw_ostream &OS) const {
1086   for (const auto &Root : Roots)
1087     dumpEntry(OS, Root.get());
1088 }
1089
1090 void RedirectingFileSystem::dumpEntry(raw_ostream &OS,
1091                                       RedirectingFileSystem::Entry *E,
1092                                       int NumSpaces) const {
1093   StringRef Name = E->getName();
1094   for (int i = 0, e = NumSpaces; i < e; ++i)
1095     OS << " ";
1096   OS << "'" << Name.str().c_str() << "'"
1097      << "\n";
1098
1099   if (E->getKind() == RedirectingFileSystem::EK_Directory) {
1100     auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(E);
1101     assert(DE && "Should be a directory");
1102
1103     for (std::unique_ptr<Entry> &SubEntry :
1104          llvm::make_range(DE->contents_begin(), DE->contents_end()))
1105       dumpEntry(OS, SubEntry.get(), NumSpaces + 2);
1106   }
1107 }
1108
1109 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1110 LLVM_DUMP_METHOD void RedirectingFileSystem::dump() const { dump(dbgs()); }
1111 #endif
1112
1113 /// A helper class to hold the common YAML parsing state.
1114 class llvm::vfs::RedirectingFileSystemParser {
1115   yaml::Stream &Stream;
1116
1117   void error(yaml::Node *N, const Twine &Msg) { Stream.printError(N, Msg); }
1118
1119   // false on error
1120   bool parseScalarString(yaml::Node *N, StringRef &Result,
1121                          SmallVectorImpl<char> &Storage) {
1122     const auto *S = dyn_cast<yaml::ScalarNode>(N);
1123
1124     if (!S) {
1125       error(N, "expected string");
1126       return false;
1127     }
1128     Result = S->getValue(Storage);
1129     return true;
1130   }
1131
1132   // false on error
1133   bool parseScalarBool(yaml::Node *N, bool &Result) {
1134     SmallString<5> Storage;
1135     StringRef Value;
1136     if (!parseScalarString(N, Value, Storage))
1137       return false;
1138
1139     if (Value.equals_lower("true") || Value.equals_lower("on") ||
1140         Value.equals_lower("yes") || Value == "1") {
1141       Result = true;
1142       return true;
1143     } else if (Value.equals_lower("false") || Value.equals_lower("off") ||
1144                Value.equals_lower("no") || Value == "0") {
1145       Result = false;
1146       return true;
1147     }
1148
1149     error(N, "expected boolean value");
1150     return false;
1151   }
1152
1153   struct KeyStatus {
1154     bool Required;
1155     bool Seen = false;
1156
1157     KeyStatus(bool Required = false) : Required(Required) {}
1158   };
1159
1160   using KeyStatusPair = std::pair<StringRef, KeyStatus>;
1161
1162   // false on error
1163   bool checkDuplicateOrUnknownKey(yaml::Node *KeyNode, StringRef Key,
1164                                   DenseMap<StringRef, KeyStatus> &Keys) {
1165     if (!Keys.count(Key)) {
1166       error(KeyNode, "unknown key");
1167       return false;
1168     }
1169     KeyStatus &S = Keys[Key];
1170     if (S.Seen) {
1171       error(KeyNode, Twine("duplicate key '") + Key + "'");
1172       return false;
1173     }
1174     S.Seen = true;
1175     return true;
1176   }
1177
1178   // false on error
1179   bool checkMissingKeys(yaml::Node *Obj, DenseMap<StringRef, KeyStatus> &Keys) {
1180     for (const auto &I : Keys) {
1181       if (I.second.Required && !I.second.Seen) {
1182         error(Obj, Twine("missing key '") + I.first + "'");
1183         return false;
1184       }
1185     }
1186     return true;
1187   }
1188
1189   RedirectingFileSystem::Entry *
1190   lookupOrCreateEntry(RedirectingFileSystem *FS, StringRef Name,
1191                       RedirectingFileSystem::Entry *ParentEntry = nullptr) {
1192     if (!ParentEntry) { // Look for a existent root
1193       for (const auto &Root : FS->Roots) {
1194         if (Name.equals(Root->getName())) {
1195           ParentEntry = Root.get();
1196           return ParentEntry;
1197         }
1198       }
1199     } else { // Advance to the next component
1200       auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(
1201           ParentEntry);
1202       for (std::unique_ptr<RedirectingFileSystem::Entry> &Content :
1203            llvm::make_range(DE->contents_begin(), DE->contents_end())) {
1204         auto *DirContent =
1205             dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(
1206                 Content.get());
1207         if (DirContent && Name.equals(Content->getName()))
1208           return DirContent;
1209       }
1210     }
1211
1212     // ... or create a new one
1213     std::unique_ptr<RedirectingFileSystem::Entry> E =
1214         std::make_unique<RedirectingFileSystem::RedirectingDirectoryEntry>(
1215             Name, Status("", getNextVirtualUniqueID(),
1216                          std::chrono::system_clock::now(), 0, 0, 0,
1217                          file_type::directory_file, sys::fs::all_all));
1218
1219     if (!ParentEntry) { // Add a new root to the overlay
1220       FS->Roots.push_back(std::move(E));
1221       ParentEntry = FS->Roots.back().get();
1222       return ParentEntry;
1223     }
1224
1225     auto *DE =
1226         dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(ParentEntry);
1227     DE->addContent(std::move(E));
1228     return DE->getLastContent();
1229   }
1230
1231   void uniqueOverlayTree(RedirectingFileSystem *FS,
1232                          RedirectingFileSystem::Entry *SrcE,
1233                          RedirectingFileSystem::Entry *NewParentE = nullptr) {
1234     StringRef Name = SrcE->getName();
1235     switch (SrcE->getKind()) {
1236     case RedirectingFileSystem::EK_Directory: {
1237       auto *DE =
1238           dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(SrcE);
1239       assert(DE && "Must be a directory");
1240       // Empty directories could be present in the YAML as a way to
1241       // describe a file for a current directory after some of its subdir
1242       // is parsed. This only leads to redundant walks, ignore it.
1243       if (!Name.empty())
1244         NewParentE = lookupOrCreateEntry(FS, Name, NewParentE);
1245       for (std::unique_ptr<RedirectingFileSystem::Entry> &SubEntry :
1246            llvm::make_range(DE->contents_begin(), DE->contents_end()))
1247         uniqueOverlayTree(FS, SubEntry.get(), NewParentE);
1248       break;
1249     }
1250     case RedirectingFileSystem::EK_File: {
1251       auto *FE = dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(SrcE);
1252       assert(FE && "Must be a file");
1253       assert(NewParentE && "Parent entry must exist");
1254       auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(
1255           NewParentE);
1256       DE->addContent(
1257           std::make_unique<RedirectingFileSystem::RedirectingFileEntry>(
1258               Name, FE->getExternalContentsPath(), FE->getUseName()));
1259       break;
1260     }
1261     }
1262   }
1263
1264   std::unique_ptr<RedirectingFileSystem::Entry>
1265   parseEntry(yaml::Node *N, RedirectingFileSystem *FS, bool IsRootEntry) {
1266     auto *M = dyn_cast<yaml::MappingNode>(N);
1267     if (!M) {
1268       error(N, "expected mapping node for file or directory entry");
1269       return nullptr;
1270     }
1271
1272     KeyStatusPair Fields[] = {
1273         KeyStatusPair("name", true),
1274         KeyStatusPair("type", true),
1275         KeyStatusPair("contents", false),
1276         KeyStatusPair("external-contents", false),
1277         KeyStatusPair("use-external-name", false),
1278     };
1279
1280     DenseMap<StringRef, KeyStatus> Keys(std::begin(Fields), std::end(Fields));
1281
1282     bool HasContents = false; // external or otherwise
1283     std::vector<std::unique_ptr<RedirectingFileSystem::Entry>>
1284         EntryArrayContents;
1285     std::string ExternalContentsPath;
1286     std::string Name;
1287     yaml::Node *NameValueNode = nullptr;
1288     auto UseExternalName =
1289         RedirectingFileSystem::RedirectingFileEntry::NK_NotSet;
1290     RedirectingFileSystem::EntryKind Kind;
1291
1292     for (auto &I : *M) {
1293       StringRef Key;
1294       // Reuse the buffer for key and value, since we don't look at key after
1295       // parsing value.
1296       SmallString<256> Buffer;
1297       if (!parseScalarString(I.getKey(), Key, Buffer))
1298         return nullptr;
1299
1300       if (!checkDuplicateOrUnknownKey(I.getKey(), Key, Keys))
1301         return nullptr;
1302
1303       StringRef Value;
1304       if (Key == "name") {
1305         if (!parseScalarString(I.getValue(), Value, Buffer))
1306           return nullptr;
1307
1308         NameValueNode = I.getValue();
1309         if (FS->UseCanonicalizedPaths) {
1310           SmallString<256> Path(Value);
1311           // Guarantee that old YAML files containing paths with ".." and "."
1312           // are properly canonicalized before read into the VFS.
1313           Path = sys::path::remove_leading_dotslash(Path);
1314           sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
1315           Name = Path.str();
1316         } else {
1317           Name = Value;
1318         }
1319       } else if (Key == "type") {
1320         if (!parseScalarString(I.getValue(), Value, Buffer))
1321           return nullptr;
1322         if (Value == "file")
1323           Kind = RedirectingFileSystem::EK_File;
1324         else if (Value == "directory")
1325           Kind = RedirectingFileSystem::EK_Directory;
1326         else {
1327           error(I.getValue(), "unknown value for 'type'");
1328           return nullptr;
1329         }
1330       } else if (Key == "contents") {
1331         if (HasContents) {
1332           error(I.getKey(),
1333                 "entry already has 'contents' or 'external-contents'");
1334           return nullptr;
1335         }
1336         HasContents = true;
1337         auto *Contents = dyn_cast<yaml::SequenceNode>(I.getValue());
1338         if (!Contents) {
1339           // FIXME: this is only for directories, what about files?
1340           error(I.getValue(), "expected array");
1341           return nullptr;
1342         }
1343
1344         for (auto &I : *Contents) {
1345           if (std::unique_ptr<RedirectingFileSystem::Entry> E =
1346                   parseEntry(&I, FS, /*IsRootEntry*/ false))
1347             EntryArrayContents.push_back(std::move(E));
1348           else
1349             return nullptr;
1350         }
1351       } else if (Key == "external-contents") {
1352         if (HasContents) {
1353           error(I.getKey(),
1354                 "entry already has 'contents' or 'external-contents'");
1355           return nullptr;
1356         }
1357         HasContents = true;
1358         if (!parseScalarString(I.getValue(), Value, Buffer))
1359           return nullptr;
1360
1361         SmallString<256> FullPath;
1362         if (FS->IsRelativeOverlay) {
1363           FullPath = FS->getExternalContentsPrefixDir();
1364           assert(!FullPath.empty() &&
1365                  "External contents prefix directory must exist");
1366           llvm::sys::path::append(FullPath, Value);
1367         } else {
1368           FullPath = Value;
1369         }
1370
1371         if (FS->UseCanonicalizedPaths) {
1372           // Guarantee that old YAML files containing paths with ".." and "."
1373           // are properly canonicalized before read into the VFS.
1374           FullPath = sys::path::remove_leading_dotslash(FullPath);
1375           sys::path::remove_dots(FullPath, /*remove_dot_dot=*/true);
1376         }
1377         ExternalContentsPath = FullPath.str();
1378       } else if (Key == "use-external-name") {
1379         bool Val;
1380         if (!parseScalarBool(I.getValue(), Val))
1381           return nullptr;
1382         UseExternalName =
1383             Val ? RedirectingFileSystem::RedirectingFileEntry::NK_External
1384                 : RedirectingFileSystem::RedirectingFileEntry::NK_Virtual;
1385       } else {
1386         llvm_unreachable("key missing from Keys");
1387       }
1388     }
1389
1390     if (Stream.failed())
1391       return nullptr;
1392
1393     // check for missing keys
1394     if (!HasContents) {
1395       error(N, "missing key 'contents' or 'external-contents'");
1396       return nullptr;
1397     }
1398     if (!checkMissingKeys(N, Keys))
1399       return nullptr;
1400
1401     // check invalid configuration
1402     if (Kind == RedirectingFileSystem::EK_Directory &&
1403         UseExternalName !=
1404             RedirectingFileSystem::RedirectingFileEntry::NK_NotSet) {
1405       error(N, "'use-external-name' is not supported for directories");
1406       return nullptr;
1407     }
1408
1409     if (IsRootEntry && !sys::path::is_absolute(Name)) {
1410       assert(NameValueNode && "Name presence should be checked earlier");
1411       error(NameValueNode,
1412             "entry with relative path at the root level is not discoverable");
1413       return nullptr;
1414     }
1415
1416     // Remove trailing slash(es), being careful not to remove the root path
1417     StringRef Trimmed(Name);
1418     size_t RootPathLen = sys::path::root_path(Trimmed).size();
1419     while (Trimmed.size() > RootPathLen &&
1420            sys::path::is_separator(Trimmed.back()))
1421       Trimmed = Trimmed.slice(0, Trimmed.size() - 1);
1422     // Get the last component
1423     StringRef LastComponent = sys::path::filename(Trimmed);
1424
1425     std::unique_ptr<RedirectingFileSystem::Entry> Result;
1426     switch (Kind) {
1427     case RedirectingFileSystem::EK_File:
1428       Result = std::make_unique<RedirectingFileSystem::RedirectingFileEntry>(
1429           LastComponent, std::move(ExternalContentsPath), UseExternalName);
1430       break;
1431     case RedirectingFileSystem::EK_Directory:
1432       Result =
1433           std::make_unique<RedirectingFileSystem::RedirectingDirectoryEntry>(
1434               LastComponent, std::move(EntryArrayContents),
1435               Status("", getNextVirtualUniqueID(),
1436                      std::chrono::system_clock::now(), 0, 0, 0,
1437                      file_type::directory_file, sys::fs::all_all));
1438       break;
1439     }
1440
1441     StringRef Parent = sys::path::parent_path(Trimmed);
1442     if (Parent.empty())
1443       return Result;
1444
1445     // if 'name' contains multiple components, create implicit directory entries
1446     for (sys::path::reverse_iterator I = sys::path::rbegin(Parent),
1447                                      E = sys::path::rend(Parent);
1448          I != E; ++I) {
1449       std::vector<std::unique_ptr<RedirectingFileSystem::Entry>> Entries;
1450       Entries.push_back(std::move(Result));
1451       Result =
1452           std::make_unique<RedirectingFileSystem::RedirectingDirectoryEntry>(
1453               *I, std::move(Entries),
1454               Status("", getNextVirtualUniqueID(),
1455                      std::chrono::system_clock::now(), 0, 0, 0,
1456                      file_type::directory_file, sys::fs::all_all));
1457     }
1458     return Result;
1459   }
1460
1461 public:
1462   RedirectingFileSystemParser(yaml::Stream &S) : Stream(S) {}
1463
1464   // false on error
1465   bool parse(yaml::Node *Root, RedirectingFileSystem *FS) {
1466     auto *Top = dyn_cast<yaml::MappingNode>(Root);
1467     if (!Top) {
1468       error(Root, "expected mapping node");
1469       return false;
1470     }
1471
1472     KeyStatusPair Fields[] = {
1473         KeyStatusPair("version", true),
1474         KeyStatusPair("case-sensitive", false),
1475         KeyStatusPair("use-external-names", false),
1476         KeyStatusPair("overlay-relative", false),
1477         KeyStatusPair("fallthrough", false),
1478         KeyStatusPair("roots", true),
1479     };
1480
1481     DenseMap<StringRef, KeyStatus> Keys(std::begin(Fields), std::end(Fields));
1482     std::vector<std::unique_ptr<RedirectingFileSystem::Entry>> RootEntries;
1483
1484     // Parse configuration and 'roots'
1485     for (auto &I : *Top) {
1486       SmallString<10> KeyBuffer;
1487       StringRef Key;
1488       if (!parseScalarString(I.getKey(), Key, KeyBuffer))
1489         return false;
1490
1491       if (!checkDuplicateOrUnknownKey(I.getKey(), Key, Keys))
1492         return false;
1493
1494       if (Key == "roots") {
1495         auto *Roots = dyn_cast<yaml::SequenceNode>(I.getValue());
1496         if (!Roots) {
1497           error(I.getValue(), "expected array");
1498           return false;
1499         }
1500
1501         for (auto &I : *Roots) {
1502           if (std::unique_ptr<RedirectingFileSystem::Entry> E =
1503                   parseEntry(&I, FS, /*IsRootEntry*/ true))
1504             RootEntries.push_back(std::move(E));
1505           else
1506             return false;
1507         }
1508       } else if (Key == "version") {
1509         StringRef VersionString;
1510         SmallString<4> Storage;
1511         if (!parseScalarString(I.getValue(), VersionString, Storage))
1512           return false;
1513         int Version;
1514         if (VersionString.getAsInteger<int>(10, Version)) {
1515           error(I.getValue(), "expected integer");
1516           return false;
1517         }
1518         if (Version < 0) {
1519           error(I.getValue(), "invalid version number");
1520           return false;
1521         }
1522         if (Version != 0) {
1523           error(I.getValue(), "version mismatch, expected 0");
1524           return false;
1525         }
1526       } else if (Key == "case-sensitive") {
1527         if (!parseScalarBool(I.getValue(), FS->CaseSensitive))
1528           return false;
1529       } else if (Key == "overlay-relative") {
1530         if (!parseScalarBool(I.getValue(), FS->IsRelativeOverlay))
1531           return false;
1532       } else if (Key == "use-external-names") {
1533         if (!parseScalarBool(I.getValue(), FS->UseExternalNames))
1534           return false;
1535       } else if (Key == "fallthrough") {
1536         if (!parseScalarBool(I.getValue(), FS->IsFallthrough))
1537           return false;
1538       } else {
1539         llvm_unreachable("key missing from Keys");
1540       }
1541     }
1542
1543     if (Stream.failed())
1544       return false;
1545
1546     if (!checkMissingKeys(Top, Keys))
1547       return false;
1548
1549     // Now that we sucessefully parsed the YAML file, canonicalize the internal
1550     // representation to a proper directory tree so that we can search faster
1551     // inside the VFS.
1552     for (auto &E : RootEntries)
1553       uniqueOverlayTree(FS, E.get());
1554
1555     return true;
1556   }
1557 };
1558
1559 RedirectingFileSystem *
1560 RedirectingFileSystem::create(std::unique_ptr<MemoryBuffer> Buffer,
1561                               SourceMgr::DiagHandlerTy DiagHandler,
1562                               StringRef YAMLFilePath, void *DiagContext,
1563                               IntrusiveRefCntPtr<FileSystem> ExternalFS) {
1564   SourceMgr SM;
1565   yaml::Stream Stream(Buffer->getMemBufferRef(), SM);
1566
1567   SM.setDiagHandler(DiagHandler, DiagContext);
1568   yaml::document_iterator DI = Stream.begin();
1569   yaml::Node *Root = DI->getRoot();
1570   if (DI == Stream.end() || !Root) {
1571     SM.PrintMessage(SMLoc(), SourceMgr::DK_Error, "expected root node");
1572     return nullptr;
1573   }
1574
1575   RedirectingFileSystemParser P(Stream);
1576
1577   std::unique_ptr<RedirectingFileSystem> FS(
1578       new RedirectingFileSystem(std::move(ExternalFS)));
1579
1580   if (!YAMLFilePath.empty()) {
1581     // Use the YAML path from -ivfsoverlay to compute the dir to be prefixed
1582     // to each 'external-contents' path.
1583     //
1584     // Example:
1585     //    -ivfsoverlay dummy.cache/vfs/vfs.yaml
1586     // yields:
1587     //  FS->ExternalContentsPrefixDir => /<absolute_path_to>/dummy.cache/vfs
1588     //
1589     SmallString<256> OverlayAbsDir = sys::path::parent_path(YAMLFilePath);
1590     std::error_code EC = llvm::sys::fs::make_absolute(OverlayAbsDir);
1591     assert(!EC && "Overlay dir final path must be absolute");
1592     (void)EC;
1593     FS->setExternalContentsPrefixDir(OverlayAbsDir);
1594   }
1595
1596   if (!P.parse(Root, FS.get()))
1597     return nullptr;
1598
1599   return FS.release();
1600 }
1601
1602 ErrorOr<RedirectingFileSystem::Entry *>
1603 RedirectingFileSystem::lookupPath(const Twine &Path_) const {
1604   SmallString<256> Path;
1605   Path_.toVector(Path);
1606
1607   // Handle relative paths
1608   if (std::error_code EC = makeAbsolute(Path))
1609     return EC;
1610
1611   // Canonicalize path by removing ".", "..", "./", etc components. This is
1612   // a VFS request, do bot bother about symlinks in the path components
1613   // but canonicalize in order to perform the correct entry search.
1614   if (UseCanonicalizedPaths) {
1615     Path = sys::path::remove_leading_dotslash(Path);
1616     sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
1617   }
1618
1619   if (Path.empty())
1620     return make_error_code(llvm::errc::invalid_argument);
1621
1622   sys::path::const_iterator Start = sys::path::begin(Path);
1623   sys::path::const_iterator End = sys::path::end(Path);
1624   for (const auto &Root : Roots) {
1625     ErrorOr<RedirectingFileSystem::Entry *> Result =
1626         lookupPath(Start, End, Root.get());
1627     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
1628       return Result;
1629   }
1630   return make_error_code(llvm::errc::no_such_file_or_directory);
1631 }
1632
1633 ErrorOr<RedirectingFileSystem::Entry *>
1634 RedirectingFileSystem::lookupPath(sys::path::const_iterator Start,
1635                                   sys::path::const_iterator End,
1636                                   RedirectingFileSystem::Entry *From) const {
1637 #ifndef _WIN32
1638   assert(!isTraversalComponent(*Start) &&
1639          !isTraversalComponent(From->getName()) &&
1640          "Paths should not contain traversal components");
1641 #else
1642   // FIXME: this is here to support windows, remove it once canonicalized
1643   // paths become globally default.
1644   if (Start->equals("."))
1645     ++Start;
1646 #endif
1647
1648   StringRef FromName = From->getName();
1649
1650   // Forward the search to the next component in case this is an empty one.
1651   if (!FromName.empty()) {
1652     if (CaseSensitive ? !Start->equals(FromName)
1653                       : !Start->equals_lower(FromName))
1654       // failure to match
1655       return make_error_code(llvm::errc::no_such_file_or_directory);
1656
1657     ++Start;
1658
1659     if (Start == End) {
1660       // Match!
1661       return From;
1662     }
1663   }
1664
1665   auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(From);
1666   if (!DE)
1667     return make_error_code(llvm::errc::not_a_directory);
1668
1669   for (const std::unique_ptr<RedirectingFileSystem::Entry> &DirEntry :
1670        llvm::make_range(DE->contents_begin(), DE->contents_end())) {
1671     ErrorOr<RedirectingFileSystem::Entry *> Result =
1672         lookupPath(Start, End, DirEntry.get());
1673     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
1674       return Result;
1675   }
1676   return make_error_code(llvm::errc::no_such_file_or_directory);
1677 }
1678
1679 static Status getRedirectedFileStatus(const Twine &Path, bool UseExternalNames,
1680                                       Status ExternalStatus) {
1681   Status S = ExternalStatus;
1682   if (!UseExternalNames)
1683     S = Status::copyWithNewName(S, Path);
1684   S.IsVFSMapped = true;
1685   return S;
1686 }
1687
1688 ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path,
1689                                               RedirectingFileSystem::Entry *E) {
1690   assert(E != nullptr);
1691   if (auto *F = dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(E)) {
1692     ErrorOr<Status> S = ExternalFS->status(F->getExternalContentsPath());
1693     assert(!S || S->getName() == F->getExternalContentsPath());
1694     if (S)
1695       return getRedirectedFileStatus(Path, F->useExternalName(UseExternalNames),
1696                                      *S);
1697     return S;
1698   } else { // directory
1699     auto *DE = cast<RedirectingFileSystem::RedirectingDirectoryEntry>(E);
1700     return Status::copyWithNewName(DE->getStatus(), Path);
1701   }
1702 }
1703
1704 ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path) {
1705   ErrorOr<RedirectingFileSystem::Entry *> Result = lookupPath(Path);
1706   if (!Result) {
1707     if (IsFallthrough &&
1708         Result.getError() == llvm::errc::no_such_file_or_directory) {
1709       return ExternalFS->status(Path);
1710     }
1711     return Result.getError();
1712   }
1713   return status(Path, *Result);
1714 }
1715
1716 namespace {
1717
1718 /// Provide a file wrapper with an overriden status.
1719 class FileWithFixedStatus : public File {
1720   std::unique_ptr<File> InnerFile;
1721   Status S;
1722
1723 public:
1724   FileWithFixedStatus(std::unique_ptr<File> InnerFile, Status S)
1725       : InnerFile(std::move(InnerFile)), S(std::move(S)) {}
1726
1727   ErrorOr<Status> status() override { return S; }
1728   ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
1729
1730   getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
1731             bool IsVolatile) override {
1732     return InnerFile->getBuffer(Name, FileSize, RequiresNullTerminator,
1733                                 IsVolatile);
1734   }
1735
1736   std::error_code close() override { return InnerFile->close(); }
1737 };
1738
1739 } // namespace
1740
1741 ErrorOr<std::unique_ptr<File>>
1742 RedirectingFileSystem::openFileForRead(const Twine &Path) {
1743   ErrorOr<RedirectingFileSystem::Entry *> E = lookupPath(Path);
1744   if (!E) {
1745     if (IsFallthrough &&
1746         E.getError() == llvm::errc::no_such_file_or_directory) {
1747       return ExternalFS->openFileForRead(Path);
1748     }
1749     return E.getError();
1750   }
1751
1752   auto *F = dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(*E);
1753   if (!F) // FIXME: errc::not_a_file?
1754     return make_error_code(llvm::errc::invalid_argument);
1755
1756   auto Result = ExternalFS->openFileForRead(F->getExternalContentsPath());
1757   if (!Result)
1758     return Result;
1759
1760   auto ExternalStatus = (*Result)->status();
1761   if (!ExternalStatus)
1762     return ExternalStatus.getError();
1763
1764   // FIXME: Update the status with the name and VFSMapped.
1765   Status S = getRedirectedFileStatus(Path, F->useExternalName(UseExternalNames),
1766                                      *ExternalStatus);
1767   return std::unique_ptr<File>(
1768       std::make_unique<FileWithFixedStatus>(std::move(*Result), S));
1769 }
1770
1771 std::error_code
1772 RedirectingFileSystem::getRealPath(const Twine &Path,
1773                                    SmallVectorImpl<char> &Output) const {
1774   ErrorOr<RedirectingFileSystem::Entry *> Result = lookupPath(Path);
1775   if (!Result) {
1776     if (IsFallthrough &&
1777         Result.getError() == llvm::errc::no_such_file_or_directory) {
1778       return ExternalFS->getRealPath(Path, Output);
1779     }
1780     return Result.getError();
1781   }
1782
1783   if (auto *F =
1784           dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(*Result)) {
1785     return ExternalFS->getRealPath(F->getExternalContentsPath(), Output);
1786   }
1787   // Even if there is a directory entry, fall back to ExternalFS if allowed,
1788   // because directories don't have a single external contents path.
1789   return IsFallthrough ? ExternalFS->getRealPath(Path, Output)
1790                        : llvm::errc::invalid_argument;
1791 }
1792
1793 IntrusiveRefCntPtr<FileSystem>
1794 vfs::getVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
1795                     SourceMgr::DiagHandlerTy DiagHandler,
1796                     StringRef YAMLFilePath, void *DiagContext,
1797                     IntrusiveRefCntPtr<FileSystem> ExternalFS) {
1798   return RedirectingFileSystem::create(std::move(Buffer), DiagHandler,
1799                                        YAMLFilePath, DiagContext,
1800                                        std::move(ExternalFS));
1801 }
1802
1803 static void getVFSEntries(RedirectingFileSystem::Entry *SrcE,
1804                           SmallVectorImpl<StringRef> &Path,
1805                           SmallVectorImpl<YAMLVFSEntry> &Entries) {
1806   auto Kind = SrcE->getKind();
1807   if (Kind == RedirectingFileSystem::EK_Directory) {
1808     auto *DE = dyn_cast<RedirectingFileSystem::RedirectingDirectoryEntry>(SrcE);
1809     assert(DE && "Must be a directory");
1810     for (std::unique_ptr<RedirectingFileSystem::Entry> &SubEntry :
1811          llvm::make_range(DE->contents_begin(), DE->contents_end())) {
1812       Path.push_back(SubEntry->getName());
1813       getVFSEntries(SubEntry.get(), Path, Entries);
1814       Path.pop_back();
1815     }
1816     return;
1817   }
1818
1819   assert(Kind == RedirectingFileSystem::EK_File && "Must be a EK_File");
1820   auto *FE = dyn_cast<RedirectingFileSystem::RedirectingFileEntry>(SrcE);
1821   assert(FE && "Must be a file");
1822   SmallString<128> VPath;
1823   for (auto &Comp : Path)
1824     llvm::sys::path::append(VPath, Comp);
1825   Entries.push_back(YAMLVFSEntry(VPath.c_str(), FE->getExternalContentsPath()));
1826 }
1827
1828 void vfs::collectVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
1829                              SourceMgr::DiagHandlerTy DiagHandler,
1830                              StringRef YAMLFilePath,
1831                              SmallVectorImpl<YAMLVFSEntry> &CollectedEntries,
1832                              void *DiagContext,
1833                              IntrusiveRefCntPtr<FileSystem> ExternalFS) {
1834   RedirectingFileSystem *VFS = RedirectingFileSystem::create(
1835       std::move(Buffer), DiagHandler, YAMLFilePath, DiagContext,
1836       std::move(ExternalFS));
1837   ErrorOr<RedirectingFileSystem::Entry *> RootE = VFS->lookupPath("/");
1838   if (!RootE)
1839     return;
1840   SmallVector<StringRef, 8> Components;
1841   Components.push_back("/");
1842   getVFSEntries(*RootE, Components, CollectedEntries);
1843 }
1844
1845 UniqueID vfs::getNextVirtualUniqueID() {
1846   static std::atomic<unsigned> UID;
1847   unsigned ID = ++UID;
1848   // The following assumes that uint64_t max will never collide with a real
1849   // dev_t value from the OS.
1850   return UniqueID(std::numeric_limits<uint64_t>::max(), ID);
1851 }
1852
1853 void YAMLVFSWriter::addFileMapping(StringRef VirtualPath, StringRef RealPath) {
1854   assert(sys::path::is_absolute(VirtualPath) && "virtual path not absolute");
1855   assert(sys::path::is_absolute(RealPath) && "real path not absolute");
1856   assert(!pathHasTraversal(VirtualPath) && "path traversal is not supported");
1857   Mappings.emplace_back(VirtualPath, RealPath);
1858 }
1859
1860 namespace {
1861
1862 class JSONWriter {
1863   llvm::raw_ostream &OS;
1864   SmallVector<StringRef, 16> DirStack;
1865
1866   unsigned getDirIndent() { return 4 * DirStack.size(); }
1867   unsigned getFileIndent() { return 4 * (DirStack.size() + 1); }
1868   bool containedIn(StringRef Parent, StringRef Path);
1869   StringRef containedPart(StringRef Parent, StringRef Path);
1870   void startDirectory(StringRef Path);
1871   void endDirectory();
1872   void writeEntry(StringRef VPath, StringRef RPath);
1873
1874 public:
1875   JSONWriter(llvm::raw_ostream &OS) : OS(OS) {}
1876
1877   void write(ArrayRef<YAMLVFSEntry> Entries, Optional<bool> UseExternalNames,
1878              Optional<bool> IsCaseSensitive, Optional<bool> IsOverlayRelative,
1879              StringRef OverlayDir);
1880 };
1881
1882 } // namespace
1883
1884 bool JSONWriter::containedIn(StringRef Parent, StringRef Path) {
1885   using namespace llvm::sys;
1886
1887   // Compare each path component.
1888   auto IParent = path::begin(Parent), EParent = path::end(Parent);
1889   for (auto IChild = path::begin(Path), EChild = path::end(Path);
1890        IParent != EParent && IChild != EChild; ++IParent, ++IChild) {
1891     if (*IParent != *IChild)
1892       return false;
1893   }
1894   // Have we exhausted the parent path?
1895   return IParent == EParent;
1896 }
1897
1898 StringRef JSONWriter::containedPart(StringRef Parent, StringRef Path) {
1899   assert(!Parent.empty());
1900   assert(containedIn(Parent, Path));
1901   return Path.slice(Parent.size() + 1, StringRef::npos);
1902 }
1903
1904 void JSONWriter::startDirectory(StringRef Path) {
1905   StringRef Name =
1906       DirStack.empty() ? Path : containedPart(DirStack.back(), Path);
1907   DirStack.push_back(Path);
1908   unsigned Indent = getDirIndent();
1909   OS.indent(Indent) << "{\n";
1910   OS.indent(Indent + 2) << "'type': 'directory',\n";
1911   OS.indent(Indent + 2) << "'name': \"" << llvm::yaml::escape(Name) << "\",\n";
1912   OS.indent(Indent + 2) << "'contents': [\n";
1913 }
1914
1915 void JSONWriter::endDirectory() {
1916   unsigned Indent = getDirIndent();
1917   OS.indent(Indent + 2) << "]\n";
1918   OS.indent(Indent) << "}";
1919
1920   DirStack.pop_back();
1921 }
1922
1923 void JSONWriter::writeEntry(StringRef VPath, StringRef RPath) {
1924   unsigned Indent = getFileIndent();
1925   OS.indent(Indent) << "{\n";
1926   OS.indent(Indent + 2) << "'type': 'file',\n";
1927   OS.indent(Indent + 2) << "'name': \"" << llvm::yaml::escape(VPath) << "\",\n";
1928   OS.indent(Indent + 2) << "'external-contents': \""
1929                         << llvm::yaml::escape(RPath) << "\"\n";
1930   OS.indent(Indent) << "}";
1931 }
1932
1933 void JSONWriter::write(ArrayRef<YAMLVFSEntry> Entries,
1934                        Optional<bool> UseExternalNames,
1935                        Optional<bool> IsCaseSensitive,
1936                        Optional<bool> IsOverlayRelative,
1937                        StringRef OverlayDir) {
1938   using namespace llvm::sys;
1939
1940   OS << "{\n"
1941         "  'version': 0,\n";
1942   if (IsCaseSensitive.hasValue())
1943     OS << "  'case-sensitive': '"
1944        << (IsCaseSensitive.getValue() ? "true" : "false") << "',\n";
1945   if (UseExternalNames.hasValue())
1946     OS << "  'use-external-names': '"
1947        << (UseExternalNames.getValue() ? "true" : "false") << "',\n";
1948   bool UseOverlayRelative = false;
1949   if (IsOverlayRelative.hasValue()) {
1950     UseOverlayRelative = IsOverlayRelative.getValue();
1951     OS << "  'overlay-relative': '" << (UseOverlayRelative ? "true" : "false")
1952        << "',\n";
1953   }
1954   OS << "  'roots': [\n";
1955
1956   if (!Entries.empty()) {
1957     const YAMLVFSEntry &Entry = Entries.front();
1958     startDirectory(path::parent_path(Entry.VPath));
1959
1960     StringRef RPath = Entry.RPath;
1961     if (UseOverlayRelative) {
1962       unsigned OverlayDirLen = OverlayDir.size();
1963       assert(RPath.substr(0, OverlayDirLen) == OverlayDir &&
1964              "Overlay dir must be contained in RPath");
1965       RPath = RPath.slice(OverlayDirLen, RPath.size());
1966     }
1967
1968     writeEntry(path::filename(Entry.VPath), RPath);
1969
1970     for (const auto &Entry : Entries.slice(1)) {
1971       StringRef Dir = path::parent_path(Entry.VPath);
1972       if (Dir == DirStack.back())
1973         OS << ",\n";
1974       else {
1975         while (!DirStack.empty() && !containedIn(DirStack.back(), Dir)) {
1976           OS << "\n";
1977           endDirectory();
1978         }
1979         OS << ",\n";
1980         startDirectory(Dir);
1981       }
1982       StringRef RPath = Entry.RPath;
1983       if (UseOverlayRelative) {
1984         unsigned OverlayDirLen = OverlayDir.size();
1985         assert(RPath.substr(0, OverlayDirLen) == OverlayDir &&
1986                "Overlay dir must be contained in RPath");
1987         RPath = RPath.slice(OverlayDirLen, RPath.size());
1988       }
1989       writeEntry(path::filename(Entry.VPath), RPath);
1990     }
1991
1992     while (!DirStack.empty()) {
1993       OS << "\n";
1994       endDirectory();
1995     }
1996     OS << "\n";
1997   }
1998
1999   OS << "  ]\n"
2000      << "}\n";
2001 }
2002
2003 void YAMLVFSWriter::write(llvm::raw_ostream &OS) {
2004   llvm::sort(Mappings, [](const YAMLVFSEntry &LHS, const YAMLVFSEntry &RHS) {
2005     return LHS.VPath < RHS.VPath;
2006   });
2007
2008   JSONWriter(OS).write(Mappings, UseExternalNames, IsCaseSensitive,
2009                        IsOverlayRelative, OverlayDir);
2010 }
2011
2012 VFSFromYamlDirIterImpl::VFSFromYamlDirIterImpl(
2013     const Twine &_Path,
2014     RedirectingFileSystem::RedirectingDirectoryEntry::iterator Begin,
2015     RedirectingFileSystem::RedirectingDirectoryEntry::iterator End,
2016     bool IterateExternalFS, FileSystem &ExternalFS, std::error_code &EC)
2017     : Dir(_Path.str()), Current(Begin), End(End),
2018       IterateExternalFS(IterateExternalFS), ExternalFS(ExternalFS) {
2019   EC = incrementImpl(/*IsFirstTime=*/true);
2020 }
2021
2022 std::error_code VFSFromYamlDirIterImpl::increment() {
2023   return incrementImpl(/*IsFirstTime=*/false);
2024 }
2025
2026 std::error_code VFSFromYamlDirIterImpl::incrementExternal() {
2027   assert(!(IsExternalFSCurrent && ExternalDirIter == directory_iterator()) &&
2028          "incrementing past end");
2029   std::error_code EC;
2030   if (IsExternalFSCurrent) {
2031     ExternalDirIter.increment(EC);
2032   } else if (IterateExternalFS) {
2033     ExternalDirIter = ExternalFS.dir_begin(Dir, EC);
2034     IsExternalFSCurrent = true;
2035     if (EC && EC != errc::no_such_file_or_directory)
2036       return EC;
2037     EC = {};
2038   }
2039   if (EC || ExternalDirIter == directory_iterator()) {
2040     CurrentEntry = directory_entry();
2041   } else {
2042     CurrentEntry = *ExternalDirIter;
2043   }
2044   return EC;
2045 }
2046
2047 std::error_code VFSFromYamlDirIterImpl::incrementContent(bool IsFirstTime) {
2048   assert((IsFirstTime || Current != End) && "cannot iterate past end");
2049   if (!IsFirstTime)
2050     ++Current;
2051   while (Current != End) {
2052     SmallString<128> PathStr(Dir);
2053     llvm::sys::path::append(PathStr, (*Current)->getName());
2054     sys::fs::file_type Type;
2055     switch ((*Current)->getKind()) {
2056     case RedirectingFileSystem::EK_Directory:
2057       Type = sys::fs::file_type::directory_file;
2058       break;
2059     case RedirectingFileSystem::EK_File:
2060       Type = sys::fs::file_type::regular_file;
2061       break;
2062     }
2063     CurrentEntry = directory_entry(PathStr.str(), Type);
2064     return {};
2065   }
2066   return incrementExternal();
2067 }
2068
2069 std::error_code VFSFromYamlDirIterImpl::incrementImpl(bool IsFirstTime) {
2070   while (true) {
2071     std::error_code EC = IsExternalFSCurrent ? incrementExternal()
2072                                              : incrementContent(IsFirstTime);
2073     if (EC || CurrentEntry.path().empty())
2074       return EC;
2075     StringRef Name = llvm::sys::path::filename(CurrentEntry.path());
2076     if (SeenNames.insert(Name).second)
2077       return EC; // name not seen before
2078   }
2079   llvm_unreachable("returned above");
2080 }
2081
2082 vfs::recursive_directory_iterator::recursive_directory_iterator(
2083     FileSystem &FS_, const Twine &Path, std::error_code &EC)
2084     : FS(&FS_) {
2085   directory_iterator I = FS->dir_begin(Path, EC);
2086   if (I != directory_iterator()) {
2087     State = std::make_shared<detail::RecDirIterState>();
2088     State->Stack.push(I);
2089   }
2090 }
2091
2092 vfs::recursive_directory_iterator &
2093 recursive_directory_iterator::increment(std::error_code &EC) {
2094   assert(FS && State && !State->Stack.empty() && "incrementing past end");
2095   assert(!State->Stack.top()->path().empty() && "non-canonical end iterator");
2096   vfs::directory_iterator End;
2097
2098   if (State->HasNoPushRequest)
2099     State->HasNoPushRequest = false;
2100   else {
2101     if (State->Stack.top()->type() == sys::fs::file_type::directory_file) {
2102       vfs::directory_iterator I = FS->dir_begin(State->Stack.top()->path(), EC);
2103       if (I != End) {
2104         State->Stack.push(I);
2105         return *this;
2106       }
2107     }
2108   }
2109
2110   while (!State->Stack.empty() && State->Stack.top().increment(EC) == End)
2111     State->Stack.pop();
2112
2113   if (State->Stack.empty())
2114     State.reset(); // end iterator
2115
2116   return *this;
2117 }