Recommit virtual file system

Previously reverted in r201755 due to causing an assertion failure.

I've removed the offending assertion, and taught the CompilerInstance to
create a default virtual file system inside createFileManager. In the
future, we should be able to reach into the CompilerInvocation to
customize this behaviour without breaking clients that don't care.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201818 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 162 insertions, 0 deletions

diff --git a/include/clang/Basic/VirtualFileSystem.h b/include/clang/Basic/VirtualFileSystem.h
new file mode 100644
index 0000000000..694c6ddec8
--- /dev/null
+++ b/include/clang/Basic/VirtualFileSystem.h
@@ -0,0 +1,162 @@
+//===- 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
+/// \brief Defines the virtual file system interface vfs::FileSystem.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_BASIC_VIRTUAL_FILE_SYSTEM_H
+#define LLVM_CLANG_BASIC_VIRTUAL_FILE_SYSTEM_H
+
+#include "clang/Basic/LLVM.h"
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/ErrorOr.h"
+
+namespace llvm {
+class MemoryBuffer;
+}
+
+namespace clang {
+namespace vfs {
+
+/// \brief The result of a \p status operation.
+class Status {
+  std::string Name;
+  std::string ExternalName;
+  llvm::sys::fs::UniqueID UID;
+  llvm::sys::TimeValue MTime;
+  uint32_t User;
+  uint32_t Group;
+  uint64_t Size;
+  llvm::sys::fs::file_type Type;
+  llvm::sys::fs::perms Perms;
+
+public:
+  Status() : Type(llvm::sys::fs::file_type::status_error) {}
+  Status(const llvm::sys::fs::file_status &Status);
+  Status(StringRef Name, StringRef RealName, llvm::sys::fs::UniqueID UID,
+         llvm::sys::TimeValue MTime, uint32_t User, uint32_t Group,
+         uint64_t Size, llvm::sys::fs::file_type Type,
+         llvm::sys::fs::perms Perms);
+
+  /// \brief Returns the name this status was looked up by.
+  StringRef getName() const { return Name; }
+
+  /// \brief Returns the name to use outside the compiler.
+  ///
+  /// For example, in diagnostics or debug info we should use this name.
+  StringRef getExternalName() const { return ExternalName; }
+
+  void setName(StringRef N) { Name = N; }
+  void setExternalName(StringRef N) { ExternalName = N; }
+
+  /// @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::TimeValue 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; }
+  void setType(llvm::sys::fs::file_type v) { Type = v; }
+  void setPermissions(llvm::sys::fs::perms p) { Perms = p; }
+  /// @}
+  /// @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;
+  /// @}
+};
+
+/// \brief Represents an open file.
+class File {
+public:
+  /// \brief 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();
+  /// \brief Get the status of the file.
+  virtual llvm::ErrorOr<Status> status() = 0;
+  /// \brief Get the contents of the file as a \p MemoryBuffer.
+  virtual llvm::error_code getBuffer(const Twine &Name,
+                                     OwningPtr<llvm::MemoryBuffer> &Result,
+                                     int64_t FileSize = -1,
+                                     bool RequiresNullTerminator = true) = 0;
+  /// \brief Closes the file.
+  virtual llvm::error_code close() = 0;
+};
+
+/// \brief The virtual file system interface.
+class FileSystem : public RefCountedBase<FileSystem> {
+public:
+  virtual ~FileSystem();
+
+  /// \brief Get the status of the entry at \p Path, if one exists.
+  virtual llvm::ErrorOr<Status> status(const Twine &Path) = 0;
+  /// \brief Get a \p File object for the file at \p Path, if one exists.
+  virtual llvm::error_code openFileForRead(const Twine &Path,
+                                           OwningPtr<File> &Result) = 0;
+
+  /// This is a convenience method that opens a file, gets its content and then
+  /// closes the file.
+  llvm::error_code getBufferForFile(const Twine &Name,
+                                    OwningPtr<llvm::MemoryBuffer> &Result,
+                                    int64_t FileSize = -1,
+                                    bool RequiresNullTerminator = true);
+};
+
+/// \brief Gets an \p vfs::FileSystem for the 'real' file system, as seen by
+/// the operating system.
+IntrusiveRefCntPtr<FileSystem> getRealFileSystem();
+
+/// \brief A file system that allows overlaying one \p AbstractFileSystem on top
+/// of another.
+///
+/// Consists of a stack of >=1 \p FileSytem 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 {
+  typedef SmallVector<IntrusiveRefCntPtr<FileSystem>, 1> FileSystemList;
+  typedef FileSystemList::reverse_iterator iterator;
+
+  /// \brief The stack of file systems, implemented as a list in order of
+  /// their addition.
+  FileSystemList FSList;
+
+  /// \brief Get an iterator pointing to the most recently added file system.
+  iterator overlays_begin() { return FSList.rbegin(); }
+
+  /// \brief Get an iterator pointing one-past the least recently added file
+  /// system.
+  iterator overlays_end() { return FSList.rend(); }
+
+public:
+  OverlayFileSystem(IntrusiveRefCntPtr<FileSystem> Base);
+  /// \brief Pushes a file system on top of the stack.
+  void pushOverlay(IntrusiveRefCntPtr<FileSystem> FS);
+
+  llvm::ErrorOr<Status> status(const Twine &Path) LLVM_OVERRIDE;
+  llvm::error_code openFileForRead(const Twine &Path,
+                                   OwningPtr<File> &Result) LLVM_OVERRIDE;
+};
+
+} // end namespace vfs
+} // end namespace clang
+#endif // LLVM_CLANG_BASIC_VIRTUAL_FILE_SYSTEM_H