clang-tools-extra/clangd/support/ThreadsafeFS.h

   1 //===--- ThreadsafeFS.h ------------------------------------------*- C++-*-===//
   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 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_SUPPORT_THREADSAFEFS_H
  10 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_SUPPORT_THREADSAFEFS_H
  11
  12 #include "Path.h"
  13 #include "llvm/ADT/IntrusiveRefCntPtr.h"
  14 #include "llvm/ADT/None.h"
  15 #include "llvm/Support/VirtualFileSystem.h"
  16 #include <memory>
  17
  18 namespace clang {
  19 namespace clangd {
  20
  21 /// Wrapper for vfs::FileSystem for use in multithreaded programs like clangd.
  22 /// As FileSystem is not threadsafe, concurrent threads must each obtain one.
  23 /// Implementations may choose to depend on Context::current() e.g. to implement
  24 /// snapshot semantics. clangd will not create vfs::FileSystems for use in
  25 /// different contexts, so either ThreadsafeFS::view or the returned FS may
  26 /// contain this logic.
  27 class ThreadsafeFS {
  28 public:
  29   virtual ~ThreadsafeFS() = default;
  30
  31   /// Obtain a vfs::FileSystem with an arbitrary initial working directory.
  32   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>
  33   view(llvm::NoneType CWD) const {
  34     return viewImpl();
  35   }
  36
  37   /// Obtain a vfs::FileSystem with a specified working directory.
  38   /// If the working directory can't be set (e.g. doesn't exist), logs and
  39   /// returns the FS anyway.
  40   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> view(PathRef CWD) const;
  41
  42 private:
  43   /// Overridden by implementations to provide a vfs::FileSystem.
  44   /// This is distinct from view(NoneType) to avoid GCC's -Woverloaded-virtual.
  45   virtual llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> viewImpl() const = 0;
  46 };
  47
  48 class RealThreadsafeFS : public ThreadsafeFS {
  49 private:
  50   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> viewImpl() const override;
  51 };
  52
  53 } // namespace clangd
  54 } // namespace clang
  55
  56 #endif