1 //===- FileSystemStatCache.h - Caching for 'stat' calls ---------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 /// \file
11 /// Defines the FileSystemStatCache interface.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H
16 #define LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H
17 
18 #include "clang/Basic/LLVM.h"
19 #include "llvm/ADT/StringMap.h"
20 #include "llvm/ADT/StringRef.h"
21 #include "llvm/Support/Allocator.h"
22 #include "llvm/Support/FileSystem.h"
23 #include <cstdint>
24 #include <ctime>
25 #include <memory>
26 #include <string>
27 #include <utility>
28 
29 namespace llvm {
30 
31 namespace vfs {
32 
33 class File;
34 class FileSystem;
35 
36 } // namespace vfs
37 } // namespace llvm
38 
39 namespace clang {
40 
41 // FIXME: should probably replace this with vfs::Status
42 struct FileData {
43   std::string Name;
44   uint64_t Size = 0;
45   time_t ModTime = 0;
46   llvm::sys::fs::UniqueID UniqueID;
47   bool IsDirectory = false;
48   bool IsNamedPipe = false;
49   bool InPCH = false;
50 
51   // FIXME: remove this when files support multiple names
52   bool IsVFSMapped = false;
53 
54   FileData() = default;
55 };
56 
57 /// Abstract interface for introducing a FileManager cache for 'stat'
58 /// system calls, which is used by precompiled and pretokenized headers to
59 /// improve performance.
60 class FileSystemStatCache {
61   virtual void anchor();
62 
63 public:
64   virtual ~FileSystemStatCache() = default;
65 
66   enum LookupResult {
67     /// We know the file exists and its cached stat data.
68     CacheExists,
69 
70     /// We know that the file doesn't exist.
71     CacheMissing
72   };
73 
74   /// Get the 'stat' information for the specified path, using the cache
75   /// to accelerate it if possible.
76   ///
77   /// \returns \c true if the path does not exist or \c false if it exists.
78   ///
79   /// If isFile is true, then this lookup should only return success for files
80   /// (not directories).  If it is false this lookup should only return
81   /// success for directories (not files).  On a successful file lookup, the
82   /// implementation can optionally fill in \p F with a valid \p File object and
83   /// the client guarantees that it will close it.
84   static bool get(StringRef Path, FileData &Data, bool isFile,
85                   std::unique_ptr<llvm::vfs::File> *F,
86                   FileSystemStatCache *Cache, llvm::vfs::FileSystem &FS);
87 
88 protected:
89   // FIXME: The pointer here is a non-owning/optional reference to the
90   // unique_ptr. Optional<unique_ptr<vfs::File>&> might be nicer, but
91   // Optional needs some work to support references so this isn't possible yet.
92   virtual LookupResult getStat(StringRef Path, FileData &Data, bool isFile,
93                                std::unique_ptr<llvm::vfs::File> *F,
94                                llvm::vfs::FileSystem &FS) = 0;
95 };
96 
97 /// A stat "cache" that can be used by FileManager to keep
98 /// track of the results of stat() calls that occur throughout the
99 /// execution of the front end.
100 class MemorizeStatCalls : public FileSystemStatCache {
101 public:
102   /// The set of stat() calls that have been seen.
103   llvm::StringMap<FileData, llvm::BumpPtrAllocator> StatCalls;
104 
105   using iterator =
106       llvm::StringMap<FileData, llvm::BumpPtrAllocator>::const_iterator;
107 
begin()108   iterator begin() const { return StatCalls.begin(); }
end()109   iterator end() const { return StatCalls.end(); }
110 
111   LookupResult getStat(StringRef Path, FileData &Data, bool isFile,
112                        std::unique_ptr<llvm::vfs::File> *F,
113                        llvm::vfs::FileSystem &FS) override;
114 };
115 
116 } // namespace clang
117 
118 #endif // LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H
119