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/Support/VirtualFileSystem.h"
  15 #include <memory>
  16
  17 namespace clang {
  18 namespace clangd {
  19
  20 /// Wrapper for vfs::FileSystem for use in multithreaded programs like clangd.
  21 /// As FileSystem is not threadsafe, concurrent threads must each obtain one.
  22 /// Implementations may choose to depend on Context::current() e.g. to implement
  23 /// snapshot semantics. clangd will not create vfs::FileSystems for use in
  24 /// different contexts, so either ThreadsafeFS::view or the returned FS may
  25 /// contain this logic.
  26 class ThreadsafeFS {
  27 public:
  28   virtual ~ThreadsafeFS() = default;
  29
  30   /// Obtain a vfs::FileSystem with an arbitrary initial working directory.
  31   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>
  32   view(std::nullopt_t CWD) const {
  33     return viewImpl();
  34   }
  35
  36   /// Obtain a vfs::FileSystem with a specified working directory.
  37   /// If the working directory can't be set (e.g. doesn't exist), logs and
  38   /// returns the FS anyway.
  39   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> view(PathRef CWD) const;
  40
  41 private:
  42   /// Overridden by implementations to provide a vfs::FileSystem.
  43   /// This is distinct from view(NoneType) to avoid GCC's -Woverloaded-virtual.
  44   virtual llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> viewImpl() const = 0;
  45 };
  46
  47 class RealThreadsafeFS : public ThreadsafeFS {
  48 private:
  49   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> viewImpl() const override;
  50 };
  51
  52 } // namespace clangd
  53 } // namespace clang
  54
  55 #endif