Lift VFS from clang to llvm (NFC)

This patch moves the virtual file system form clang to llvm so it can be
used by more projects.

Concretely the patch:
 - Moves VirtualFileSystem.{h|cpp} from clang/Basic to llvm/Support.
 - Moves the corresponding unit test from clang to llvm.
 - Moves the vfs namespace from clang::vfs to llvm::vfs.
 - Formats the lines affected by this change, mostly this is the result of
   the added llvm namespace.

RFC on the mailing list:
http://lists.llvm.org/pipermail/llvm-dev/2018-October/126657.html

Differential revision: https://reviews.llvm.org/D52783

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@344140 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/VirtualFileSystem.h

+//===- VirtualFileSystem.h - Virtual File System Layer ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Defines the virtual file system interface vfs::FileSystem.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_VIRTUALFILESYSTEM_H
+#define LLVM_SUPPORT_VIRTUALFILESYSTEM_H
+
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/ADT/None.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Support/Chrono.h"
+#include "llvm/Support/ErrorOr.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/SourceMgr.h"
+#include <cassert>
+#include <cstdint>
+#include <ctime>
+#include <memory>
+#include <stack>
+#include <string>
+#include <system_error>
+#include <utility>
+#include <vector>
+
+namespace llvm {
+
+class MemoryBuffer;
+
+namespace vfs {
+
+/// The result of a \p status operation.
+class Status {
+  std::string Name;
+  llvm::sys::fs::UniqueID UID;
+  llvm::sys::TimePoint<> MTime;
+  uint32_t User;
+  uint32_t Group;
+  uint64_t Size;
+  llvm::sys::fs::file_type Type = llvm::sys::fs::file_type::status_error;
+  llvm::sys::fs::perms Perms;
+
+public:
+  // FIXME: remove when files support multiple names
+  bool IsVFSMapped = false;
+
+  Status() = default;
+  Status(const llvm::sys::fs::file_status &Status);
+  Status(StringRef Name, llvm::sys::fs::UniqueID UID,
+         llvm::sys::TimePoint<> MTime, uint32_t User, uint32_t Group,
+         uint64_t Size, llvm::sys::fs::file_type Type,
+         llvm::sys::fs::perms Perms);
+
+  /// Get a copy of a Status with a different name.
+  static Status copyWithNewName(const Status &In, StringRef NewName);
+  static Status copyWithNewName(const llvm::sys::fs::file_status &In,
+                                StringRef NewName);
+
+  /// Returns the name that should be used for this file or directory.
+  StringRef getName() const { return Name; }
+
+  /// @name Status interface from llvm::sys::fs
+  /// @{
+  llvm::sys::fs::file_type getType() const { return Type; }
+  llvm::sys::fs::perms getPermissions() const { return Perms; }
+  llvm::sys::TimePoint<> getLastModificationTime() const { return MTime; }
+  llvm::sys::fs::UniqueID getUniqueID() const { return UID; }
+  uint32_t getUser() const { return User; }
+  uint32_t getGroup() const { return Group; }
+  uint64_t getSize() const { return Size; }
+  /// @}
+  /// @name Status queries
+  /// These are static queries in llvm::sys::fs.
+  /// @{
+  bool equivalent(const Status &Other) const;
+  bool isDirectory() const;
+  bool isRegularFile() const;
+  bool isOther() const;
+  bool isSymlink() const;
+  bool isStatusKnown() const;
+  bool exists() const;
+  /// @}
+};
+
+/// Represents an open file.
+class File {
+public:
+  /// Destroy the file after closing it (if open).
+  /// Sub-classes should generally call close() inside their destructors.  We
+  /// cannot do that from the base class, since close is virtual.
+  virtual ~File();
+
+  /// Get the status of the file.
+  virtual llvm::ErrorOr<Status> status() = 0;
+
+  /// Get the name of the file
+  virtual llvm::ErrorOr<std::string> getName() {
+    if (auto Status = status())
+      return Status->getName().str();
+    else
+      return Status.getError();
+  }
+
+  /// Get the contents of the file as a \p MemoryBuffer.
+  virtual llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+  getBuffer(const Twine &Name, int64_t FileSize = -1,
+            bool RequiresNullTerminator = true, bool IsVolatile = false) = 0;
+
+  /// Closes the file.
+  virtual std::error_code close() = 0;
+};
+
+/// A member of a directory, yielded by a directory_iterator.
+/// Only information available on most platforms is included.
+class directory_entry {
+  std::string Path;
+  llvm::sys::fs::file_type Type;
+
+public:
+  directory_entry() = default;
+  directory_entry(std::string Path, llvm::sys::fs::file_type Type)
+      : Path(std::move(Path)), Type(Type) {}
+
+  llvm::StringRef path() const { return Path; }
+  llvm::sys::fs::file_type type() const { return Type; }
+};
+
+namespace detail {
+
+/// An interface for virtual file systems to provide an iterator over the
+/// (non-recursive) contents of a directory.
+struct DirIterImpl {
+  virtual ~DirIterImpl();
+
+  /// Sets \c CurrentEntry to the next entry in the directory on success,
+  /// to directory_entry() at end,  or returns a system-defined \c error_code.
+  virtual std::error_code increment() = 0;
+
+  directory_entry CurrentEntry;
+};
+
+} // namespace detail
+
+/// An input iterator over the entries in a virtual path, similar to
+/// llvm::sys::fs::directory_iterator.
+class directory_iterator {
+  std::shared_ptr<detail::DirIterImpl> Impl; // Input iterator semantics on copy
+
+public:
+  directory_iterator(std::shared_ptr<detail::DirIterImpl> I)
+      : Impl(std::move(I)) {
+    assert(Impl.get() != nullptr && "requires non-null implementation");
+    if (Impl->CurrentEntry.path().empty())
+      Impl.reset(); // Normalize the end iterator to Impl == nullptr.
+  }
+
+  /// Construct an 'end' iterator.
+  directory_iterator() = default;
+
+  /// Equivalent to operator++, with an error code.
+  directory_iterator &increment(std::error_code &EC) {
+    assert(Impl && "attempting to increment past end");
+    EC = Impl->increment();
+    if (Impl->CurrentEntry.path().empty())
+      Impl.reset(); // Normalize the end iterator to Impl == nullptr.
+    return *this;
+  }
+
+  const directory_entry &operator*() const { return Impl->CurrentEntry; }
+  const directory_entry *operator->() const { return &Impl->CurrentEntry; }
+
+  bool operator==(const directory_iterator &RHS) const {
+    if (Impl && RHS.Impl)
+      return Impl->CurrentEntry.path() == RHS.Impl->CurrentEntry.path();
+    return !Impl && !RHS.Impl;
+  }
+  bool operator!=(const directory_iterator &RHS) const {
+    return !(*this == RHS);
+  }
+};
+
+class FileSystem;
+
+/// An input iterator over the recursive contents of a virtual path,
+/// similar to llvm::sys::fs::recursive_directory_iterator.
+class recursive_directory_iterator {
+  using IterState =
+      std::stack<directory_iterator, std::vector<directory_iterator>>;
+
+  FileSystem *FS;
+  std::shared_ptr<IterState> State; // Input iterator semantics on copy.
+
+public:
+  recursive_directory_iterator(FileSystem &FS, const Twine &Path,
+                               std::error_code &EC);
+
+  /// Construct an 'end' iterator.
+  recursive_directory_iterator() = default;
+
+  /// Equivalent to operator++, with an error code.
+  recursive_directory_iterator &increment(std::error_code &EC);
+
+  const directory_entry &operator*() const { return *State->top(); }
+  const directory_entry *operator->() const { return &*State->top(); }
+
+  bool operator==(const recursive_directory_iterator &Other) const {
+    return State == Other.State; // identity
+  }
+  bool operator!=(const recursive_directory_iterator &RHS) const {
+    return !(*this == RHS);
+  }
+
+  /// Gets the current level. Starting path is at level 0.
+  int level() const {
+    assert(!State->empty() && "Cannot get level without any iteration state");
+    return State->size() - 1;
+  }
+};
+
+/// The virtual file system interface.
+class FileSystem : public llvm::ThreadSafeRefCountedBase<FileSystem> {
+public:
+  virtual ~FileSystem();
+
+  /// Get the status of the entry at \p Path, if one exists.
+  virtual llvm::ErrorOr<Status> status(const Twine &Path) = 0;
+
+  /// Get a \p File object for the file at \p Path, if one exists.
+  virtual llvm::ErrorOr<std::unique_ptr<File>>
+  openFileForRead(const Twine &Path) = 0;
+
+  /// This is a convenience method that opens a file, gets its content and then
+  /// closes the file.
+  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+  getBufferForFile(const Twine &Name, int64_t FileSize = -1,
+                   bool RequiresNullTerminator = true, bool IsVolatile = false);
+
+  /// Get a directory_iterator for \p Dir.
+  /// \note The 'end' iterator is directory_iterator().
+  virtual directory_iterator dir_begin(const Twine &Dir,
+                                       std::error_code &EC) = 0;
+
+  /// Set the working directory. This will affect all following operations on
+  /// this file system and may propagate down for nested file systems.
+  virtual std::error_code setCurrentWorkingDirectory(const Twine &Path) = 0;
+
+  /// Get the working directory of this file system.
+  virtual llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const = 0;
+
+  /// Gets real path of \p Path e.g. collapse all . and .. patterns, resolve
+  /// symlinks. For real file system, this uses `llvm::sys::fs::real_path`.
+  /// This returns errc::operation_not_permitted if not implemented by subclass.
+  virtual std::error_code getRealPath(const Twine &Path,
+                                      SmallVectorImpl<char> &Output) const;
+
+  /// Check whether a file exists. Provided for convenience.
+  bool exists(const Twine &Path);
+
+  /// Make \a Path an absolute path.
+  ///
+  /// Makes \a Path absolute using the current directory if it is not already.
+  /// An empty \a Path will result in the current directory.
+  ///
+  /// /absolute/path   => /absolute/path
+  /// relative/../path => <current-directory>/relative/../path
+  ///
+  /// \param Path A path that is modified to be an absolute path.
+  /// \returns success if \a path has been made absolute, otherwise a
+  ///          platform-specific error_code.
+  std::error_code makeAbsolute(SmallVectorImpl<char> &Path) const;
+};
+
+/// Gets an \p vfs::FileSystem for the 'real' file system, as seen by
+/// the operating system.
+IntrusiveRefCntPtr<FileSystem> getRealFileSystem();
+
+/// A file system that allows overlaying one \p AbstractFileSystem on top
+/// of another.
+///
+/// Consists of a stack of >=1 \p FileSystem objects, which are treated as being
+/// one merged file system. When there is a directory that exists in more than
+/// one file system, the \p OverlayFileSystem contains a directory containing
+/// the union of their contents.  The attributes (permissions, etc.) of the
+/// top-most (most recently added) directory are used.  When there is a file
+/// that exists in more than one file system, the file in the top-most file
+/// system overrides the other(s).
+class OverlayFileSystem : public FileSystem {
+  using FileSystemList = SmallVector<IntrusiveRefCntPtr<FileSystem>, 1>;
+
+  /// The stack of file systems, implemented as a list in order of
+  /// their addition.
+  FileSystemList FSList;
+
+public:
+  OverlayFileSystem(IntrusiveRefCntPtr<FileSystem> Base);
+
+  /// Pushes a file system on top of the stack.
+  void pushOverlay(IntrusiveRefCntPtr<FileSystem> FS);
+
+  llvm::ErrorOr<Status> status(const Twine &Path) override;
+  llvm::ErrorOr<std::unique_ptr<File>>
+  openFileForRead(const Twine &Path) override;
+  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
+  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override;
+  std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
+  std::error_code getRealPath(const Twine &Path,
+                              SmallVectorImpl<char> &Output) const override;
+
+  using iterator = FileSystemList::reverse_iterator;
+  using const_iterator = FileSystemList::const_reverse_iterator;
+
+  /// Get an iterator pointing to the most recently added file system.
+  iterator overlays_begin() { return FSList.rbegin(); }
+  const_iterator overlays_begin() const { return FSList.rbegin(); }
+
+  /// Get an iterator pointing one-past the least recently added file
+  /// system.
+  iterator overlays_end() { return FSList.rend(); }
+  const_iterator overlays_end() const { return FSList.rend(); }
+};
+
+/// By default, this delegates all calls to the underlying file system. This
+/// is useful when derived file systems want to override some calls and still
+/// proxy other calls.
+class ProxyFileSystem : public FileSystem {
+public:
+  explicit ProxyFileSystem(IntrusiveRefCntPtr<FileSystem> FS)
+      : FS(std::move(FS)) {}
+
+  llvm::ErrorOr<Status> status(const Twine &Path) override {
+    return FS->status(Path);
+  }
+  llvm::ErrorOr<std::unique_ptr<File>>
+  openFileForRead(const Twine &Path) override {
+    return FS->openFileForRead(Path);
+  }
+  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override {
+    return FS->dir_begin(Dir, EC);
+  }
+  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
+    return FS->getCurrentWorkingDirectory();
+  }
+  std::error_code setCurrentWorkingDirectory(const Twine &Path) override {
+    return FS->setCurrentWorkingDirectory(Path);
+  }
+  std::error_code getRealPath(const Twine &Path,
+                              SmallVectorImpl<char> &Output) const override {
+    return FS->getRealPath(Path, Output);
+  }
+
+protected:
+  FileSystem &getUnderlyingFS() { return *FS; }
+
+private:
+  IntrusiveRefCntPtr<FileSystem> FS;
+};
+
+namespace detail {
+
+class InMemoryDirectory;
+class InMemoryFile;
+
+} // namespace detail
+
+/// An in-memory file system.
+class InMemoryFileSystem : public FileSystem {
+  std::unique_ptr<detail::InMemoryDirectory> Root;
+  std::string WorkingDirectory;
+  bool UseNormalizedPaths = true;
+
+  /// If HardLinkTarget is non-null, a hardlink is created to the To path which
+  /// must be a file. If it is null then it adds the file as the public addFile.
+  bool addFile(const Twine &Path, time_t ModificationTime,
+               std::unique_ptr<llvm::MemoryBuffer> Buffer,
+               Optional<uint32_t> User, Optional<uint32_t> Group,
+               Optional<llvm::sys::fs::file_type> Type,
+               Optional<llvm::sys::fs::perms> Perms,
+               const detail::InMemoryFile *HardLinkTarget);
+
+public:
+  explicit InMemoryFileSystem(bool UseNormalizedPaths = true);
+  ~InMemoryFileSystem() override;
+
+  /// Add a file containing a buffer or a directory to the VFS with a
+  /// path. The VFS owns the buffer.  If present, User, Group, Type
+  /// and Perms apply to the newly-created file or directory.
+  /// \return true if the file or directory was successfully added,
+  /// false if the file or directory already exists in the file system with
+  /// different contents.
+  bool addFile(const Twine &Path, time_t ModificationTime,
+               std::unique_ptr<llvm::MemoryBuffer> Buffer,
+               Optional<uint32_t> User = None, Optional<uint32_t> Group = None,
+               Optional<llvm::sys::fs::file_type> Type = None,
+               Optional<llvm::sys::fs::perms> Perms = None);
+
+  /// Add a hard link to a file.
+  /// Here hard links are not intended to be fully equivalent to the classical
+  /// filesystem. Both the hard link and the file share the same buffer and
+  /// status (and thus have the same UniqueID). Because of this there is no way
+  /// to distinguish between the link and the file after the link has been
+  /// added.
+  ///
+  /// The To path must be an existing file or a hardlink. The From file must not
+  /// have been added before. The To Path must not be a directory. The From Node
+  /// is added as a hard link which points to the resolved file of To Node.
+  /// \return true if the above condition is satisfied and hardlink was
+  /// successfully created, false otherwise.
+  bool addHardLink(const Twine &From, const Twine &To);
+
+  /// Add a buffer to the VFS with a path. The VFS does not own the buffer.
+  /// If present, User, Group, Type and Perms apply to the newly-created file
+  /// or directory.
+  /// \return true if the file or directory was successfully added,
+  /// false if the file or directory already exists in the file system with
+  /// different contents.
+  bool addFileNoOwn(const Twine &Path, time_t ModificationTime,
+                    llvm::MemoryBuffer *Buffer, Optional<uint32_t> User = None,
+                    Optional<uint32_t> Group = None,
+                    Optional<llvm::sys::fs::file_type> Type = None,
+                    Optional<llvm::sys::fs::perms> Perms = None);
+
+  std::string toString() const;
+
+  /// Return true if this file system normalizes . and .. in paths.
+  bool useNormalizedPaths() const { return UseNormalizedPaths; }
+
+  llvm::ErrorOr<Status> status(const Twine &Path) override;
+  llvm::ErrorOr<std::unique_ptr<File>>
+  openFileForRead(const Twine &Path) override;
+  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
+
+  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
+    return WorkingDirectory;
+  }
+  /// Canonicalizes \p Path by combining with the current working
+  /// directory and normalizing the path (e.g. remove dots). If the current
+  /// working directory is not set, this returns errc::operation_not_permitted.
+  ///
+  /// This doesn't resolve symlinks as they are not supported in in-memory file
+  /// system.
+  std::error_code getRealPath(const Twine &Path,
+                              SmallVectorImpl<char> &Output) const override;
+
+  std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
+};
+
+/// Get a globally unique ID for a virtual file or directory.
+llvm::sys::fs::UniqueID getNextVirtualUniqueID();
+
+/// Gets a \p FileSystem for a virtual file system described in YAML
+/// format.
+IntrusiveRefCntPtr<FileSystem>
+getVFSFromYAML(std::unique_ptr<llvm::MemoryBuffer> Buffer,
+               llvm::SourceMgr::DiagHandlerTy DiagHandler,
+               StringRef YAMLFilePath, void *DiagContext = nullptr,
+               IntrusiveRefCntPtr<FileSystem> ExternalFS = getRealFileSystem());
+
+struct YAMLVFSEntry {
+  template <typename T1, typename T2>
+  YAMLVFSEntry(T1 &&VPath, T2 &&RPath)
+      : VPath(std::forward<T1>(VPath)), RPath(std::forward<T2>(RPath)) {}
+  std::string VPath;
+  std::string RPath;
+};
+
+/// Collect all pairs of <virtual path, real path> entries from the
+/// \p YAMLFilePath. This is used by the module dependency collector to forward
+/// the entries into the reproducer output VFS YAML file.
+void collectVFSFromYAML(
+    std::unique_ptr<llvm::MemoryBuffer> Buffer,
+    llvm::SourceMgr::DiagHandlerTy DiagHandler, StringRef YAMLFilePath,
+    SmallVectorImpl<YAMLVFSEntry> &CollectedEntries,
+    void *DiagContext = nullptr,
+    IntrusiveRefCntPtr<FileSystem> ExternalFS = getRealFileSystem());
+
+class YAMLVFSWriter {
+  std::vector<YAMLVFSEntry> Mappings;
+  Optional<bool> IsCaseSensitive;
+  Optional<bool> IsOverlayRelative;
+  Optional<bool> UseExternalNames;
+  Optional<bool> IgnoreNonExistentContents;
+  std::string OverlayDir;
+
+public:
+  YAMLVFSWriter() = default;
+
+  void addFileMapping(StringRef VirtualPath, StringRef RealPath);
+
+  void setCaseSensitivity(bool CaseSensitive) {
+    IsCaseSensitive = CaseSensitive;
+  }
+
+  void setUseExternalNames(bool UseExtNames) { UseExternalNames = UseExtNames; }
+
+  void setIgnoreNonExistentContents(bool IgnoreContents) {
+    IgnoreNonExistentContents = IgnoreContents;
+  }
+
+  void setOverlayDir(StringRef OverlayDirectory) {
+    IsOverlayRelative = true;
+    OverlayDir.assign(OverlayDirectory.str());
+  }
+
+  void write(llvm::raw_ostream &OS);
+};
+
+} // namespace vfs
+} // namespace llvm
+
+#endif // LLVM_SUPPORT_VIRTUALFILESYSTEM_H

lib/Support/CMakeLists.txt

@@ -135,6 +135,7 @@ add_llvm_library(LLVMSupport
   Unicode.cpp
   UnicodeCaseFold.cpp
   VersionTuple.cpp
+  VirtualFileSystem.cpp
   WithColor.cpp
   YAMLParser.cpp
   YAMLTraits.cpp

unittests/Support/CMakeLists.txt

@@ -68,6 +68,7 @@ add_llvm_unittest(SupportTests
   TrigramIndexTest.cpp
   UnicodeTest.cpp
   VersionTupleTest.cpp
+  VirtualFileSystemTest.cpp
   YAMLIOTest.cpp
   YAMLParserTest.cpp
   formatted_raw_ostream_test.cpp