Initial implementation of virtual file system

This adds the minimum virtual file system support to start migrating
FileManager onto the VFS.

Originally discussed here:
http://lists.cs.uiuc.edu/pipermail/cfe-dev/2014-February/035188.html

Differential Revision: http://llvm-reviews.chandlerc.com/D2745

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201618 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 127 insertions, 0 deletions

diff --git a/include/clang/Basic/VirtualFileSystem.h b/include/clang/Basic/VirtualFileSystem.h
new file mode 100644
index 0000000000..9bd6b2bc63
--- /dev/null
+++ b/include/clang/Basic/VirtualFileSystem.h
@@ -0,0 +1,127 @@
+//===- 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 "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/ErrorOr.h"
+
+namespace llvm {
+template <typename T> class OwningPtr;
+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(llvm::StringRef Name, llvm::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.
+  llvm::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.
+  llvm::StringRef getExternalName() const { return ExternalName; }
+
+  void setName(llvm::StringRef N) { Name = N; }
+  void setExternalName(llvm::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 llvm::Twine &Name,
+            llvm::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 llvm::RefCountedBase<FileSystem> {
+public:
+  virtual ~FileSystem();
+
+  /// \brief Get the status of the entry at \p Path, if one exists.
+  virtual llvm::ErrorOr<Status> status(const llvm::Twine &Path) = 0;
+  /// \brief Get a \p File object for the file at \p Path, if one exists.
+  virtual llvm::error_code openFileForRead(const llvm::Twine &Path,
+                                           llvm::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 llvm::Twine &Name,
+                                    llvm::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.
+llvm::IntrusiveRefCntPtr<FileSystem> getRealFileSystem();
+
+} // end namespace vfs
+} // end namespace clang
+#endif // LLVM_CLANG_BASIC_VIRTUAL_FILE_SYSTEM_H