1 //===- FileSystemStatCache.h - Caching for 'stat' calls ---------*- 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 /// \file
10 /// Defines the FileSystemStatCache interface.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H
15 #define LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H
16 
17 #include "clang/Basic/LLVM.h"
18 #include "llvm/ADT/StringMap.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/Support/Allocator.h"
21 #include "llvm/Support/FileSystem.h"
22 #include "llvm/Support/VirtualFileSystem.h"
23 #include <cstdint>
24 #include <ctime>
25 #include <memory>
26 #include <optional>
27 #include <string>
28 #include <utility>
29 
30 namespace clang {
31 
32 /// Abstract interface for introducing a FileManager cache for 'stat'
33 /// system calls, which is used by precompiled and pretokenized headers to
34 /// improve performance.
35 class FileSystemStatCache {
36   virtual void anchor();
37 
38 public:
39   virtual ~FileSystemStatCache() = default;
40 
41   /// Get the 'stat' information for the specified path, using the cache
42   /// to accelerate it if possible.
43   ///
44   /// \returns \c true if the path does not exist or \c false if it exists.
45   ///
46   /// If isFile is true, then this lookup should only return success for files
47   /// (not directories).  If it is false this lookup should only return
48   /// success for directories (not files).  On a successful file lookup, the
49   /// implementation can optionally fill in \p F with a valid \p File object and
50   /// the client guarantees that it will close it.
51   static std::error_code
52   get(StringRef Path, llvm::vfs::Status &Status, bool isFile,
53       std::unique_ptr<llvm::vfs::File> *F,
54       FileSystemStatCache *Cache, llvm::vfs::FileSystem &FS);
55 
56 protected:
57   // FIXME: The pointer here is a non-owning/optional reference to the
58   // unique_ptr. std::optional<unique_ptr<vfs::File>&> might be nicer, but
59   // Optional needs some work to support references so this isn't possible yet.
60   virtual std::error_code getStat(StringRef Path, llvm::vfs::Status &Status,
61                                   bool isFile,
62                                   std::unique_ptr<llvm::vfs::File> *F,
63                                   llvm::vfs::FileSystem &FS) = 0;
64 };
65 
66 /// A stat "cache" that can be used by FileManager to keep
67 /// track of the results of stat() calls that occur throughout the
68 /// execution of the front end.
69 class MemorizeStatCalls : public FileSystemStatCache {
70 public:
71   /// The set of stat() calls that have been seen.
72   llvm::StringMap<llvm::vfs::Status, llvm::BumpPtrAllocator> StatCalls;
73 
74   using iterator =
75       llvm::StringMap<llvm::vfs::Status,
76                       llvm::BumpPtrAllocator>::const_iterator;
77 
78   iterator begin() const { return StatCalls.begin(); }
79   iterator end() const { return StatCalls.end(); }
80 
81   std::error_code getStat(StringRef Path, llvm::vfs::Status &Status,
82                           bool isFile,
83                           std::unique_ptr<llvm::vfs::File> *F,
84                           llvm::vfs::FileSystem &FS) override;
85 };
86 
87 } // namespace clang
88 
89 #endif // LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H
90