clang-tools-extra/clangd/FS.h

   1 //===--- FS.h - File system related utils ------------------------*- 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_FS_H
  10 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FS_H
  11
  12 #include "support/Path.h"
  13 #include "clang/Basic/LLVM.h"
  14 #include "llvm/ADT/StringMap.h"
  15 #include "llvm/Support/VirtualFileSystem.h"
  16 #include <optional>
  17
  18 namespace clang {
  19 namespace clangd {
  20
  21 /// Records status information for files open()ed or stat()ed during preamble
  22 /// build (except for the main file), so we can avoid stat()s on the underlying
  23 /// FS when reusing the preamble. For example, code completion can re-stat files
  24 /// when getting FileID for source locations stored in preamble (e.g. checking
  25 /// whether a location is in the main file).
  26 ///
  27 /// The cache is keyed by absolute path of file name in cached status, as this
  28 /// is what preamble stores.
  29 ///
  30 /// The cache is not thread-safe when updates happen, so the use pattern should
  31 /// be:
  32 ///   - One FS writes to the cache from one thread (or several but strictly
  33 ///   sequenced), e.g. when building preamble.
  34 ///   - Sequence point (no writes after this point, no reads before).
  35 ///   - Several FSs can read from the cache, e.g. code completions.
  36 ///
  37 /// Note that the cache is only valid when reusing preamble.
  38 class PreambleFileStatusCache {
  39 public:
  40   /// \p MainFilePath is the absolute path of the main source file this preamble
  41   /// corresponds to. The stat for the main file will not be cached.
  42   PreambleFileStatusCache(llvm::StringRef MainFilePath);
  43
  44   void update(const llvm::vfs::FileSystem &FS, llvm::vfs::Status S,
  45               llvm::StringRef File);
  46
  47   /// \p Path is a path stored in preamble.
  48   std::optional<llvm::vfs::Status> lookup(llvm::StringRef Path) const;
  49
  50   /// Returns a VFS that collects file status.
  51   /// Only cache stats for files that exist because
  52   ///   1) we only care about existing files when reusing preamble, unlike
  53   ///   building preamble.
  54   ///   2) we use the file name in the Status as the cache key.
  55   ///
  56   /// Note that the returned VFS should not outlive the cache.
  57   IntrusiveRefCntPtr<llvm::vfs::FileSystem>
  58   getProducingFS(IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS);
  59
  60   /// Returns a VFS that uses the cache collected.
  61   ///
  62   /// Note that the returned VFS should not outlive the cache.
  63   IntrusiveRefCntPtr<llvm::vfs::FileSystem>
  64   getConsumingFS(IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS) const;
  65
  66 private:
  67   std::string MainFilePath;
  68   llvm::StringMap<llvm::vfs::Status> StatCache;
  69 };
  70
  71 /// Returns a version of \p File that doesn't contain dots and dot dots.
  72 /// e.g /a/b/../c -> /a/c
  73 ///     /a/b/./c -> /a/b/c
  74 /// FIXME: We should avoid encountering such paths in clangd internals by
  75 /// filtering everything we get over LSP, CDB, etc.
  76 Path removeDots(PathRef File);
  77
  78 } // namespace clangd
  79 } // namespace clang
  80
  81 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_FS_H