clang  8.0.0svn
FileSystemStatCache.cpp
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1 //===- FileSystemStatCache.cpp - Caching for 'stat' calls -----------------===//
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 // This file defines the FileSystemStatCache interface.
11 //
12 //===----------------------------------------------------------------------===//
13 
15 #include "llvm/Support/Chrono.h"
16 #include "llvm/Support/ErrorOr.h"
17 #include "llvm/Support/Path.h"
18 #include "llvm/Support/VirtualFileSystem.h"
19 #include <utility>
20 
21 using namespace clang;
22 
23 void FileSystemStatCache::anchor() {}
24 
25 static void copyStatusToFileData(const llvm::vfs::Status &Status,
26  FileData &Data) {
27  Data.Name = Status.getName();
28  Data.Size = Status.getSize();
29  Data.ModTime = llvm::sys::toTimeT(Status.getLastModificationTime());
30  Data.UniqueID = Status.getUniqueID();
31  Data.IsDirectory = Status.isDirectory();
32  Data.IsNamedPipe = Status.getType() == llvm::sys::fs::file_type::fifo_file;
33  Data.InPCH = false;
34  Data.IsVFSMapped = Status.IsVFSMapped;
35 }
36 
37 /// FileSystemStatCache::get - Get the 'stat' information for the specified
38 /// path, using the cache to accelerate it if possible. This returns true if
39 /// the path does not exist or false if it exists.
40 ///
41 /// If isFile is true, then this lookup should only return success for files
42 /// (not directories). If it is false this lookup should only return
43 /// success for directories (not files). On a successful file lookup, the
44 /// implementation can optionally fill in FileDescriptor with a valid
45 /// descriptor and the client guarantees that it will close it.
46 bool FileSystemStatCache::get(StringRef Path, FileData &Data, bool isFile,
47  std::unique_ptr<llvm::vfs::File> *F,
49  llvm::vfs::FileSystem &FS) {
50  LookupResult R;
51  bool isForDir = !isFile;
52 
53  // If we have a cache, use it to resolve the stat query.
54  if (Cache)
55  R = Cache->getStat(Path, Data, isFile, F, FS);
56  else if (isForDir || !F) {
57  // If this is a directory or a file descriptor is not needed and we have
58  // no cache, just go to the file system.
59  llvm::ErrorOr<llvm::vfs::Status> Status = FS.status(Path);
60  if (!Status) {
61  R = CacheMissing;
62  } else {
63  R = CacheExists;
64  copyStatusToFileData(*Status, Data);
65  }
66  } else {
67  // Otherwise, we have to go to the filesystem. We can always just use
68  // 'stat' here, but (for files) the client is asking whether the file exists
69  // because it wants to turn around and *open* it. It is more efficient to
70  // do "open+fstat" on success than it is to do "stat+open".
71  //
72  // Because of this, check to see if the file exists with 'open'. If the
73  // open succeeds, use fstat to get the stat info.
74  auto OwnedFile = FS.openFileForRead(Path);
75 
76  if (!OwnedFile) {
77  // If the open fails, our "stat" fails.
78  R = CacheMissing;
79  } else {
80  // Otherwise, the open succeeded. Do an fstat to get the information
81  // about the file. We'll end up returning the open file descriptor to the
82  // client to do what they please with it.
83  llvm::ErrorOr<llvm::vfs::Status> Status = (*OwnedFile)->status();
84  if (Status) {
85  R = CacheExists;
86  copyStatusToFileData(*Status, Data);
87  *F = std::move(*OwnedFile);
88  } else {
89  // fstat rarely fails. If it does, claim the initial open didn't
90  // succeed.
91  R = CacheMissing;
92  *F = nullptr;
93  }
94  }
95  }
96 
97  // If the path doesn't exist, return failure.
98  if (R == CacheMissing) return true;
99 
100  // If the path exists, make sure that its "directoryness" matches the clients
101  // demands.
102  if (Data.IsDirectory != isForDir) {
103  // If not, close the file if opened.
104  if (F)
105  *F = nullptr;
106 
107  return true;
108  }
109 
110  return false;
111 }
112 
114 MemorizeStatCalls::getStat(StringRef Path, FileData &Data, bool isFile,
115  std::unique_ptr<llvm::vfs::File> *F,
116  llvm::vfs::FileSystem &FS) {
117  LookupResult Result = statChained(Path, Data, isFile, F, FS);
118 
119  // Do not cache failed stats, it is easy to construct common inconsistent
120  // situations if we do, and they are not important for PCH performance (which
121  // currently only needs the stats to construct the initial FileManager
122  // entries).
123  if (Result == CacheMissing)
124  return Result;
125 
126  // Cache file 'stat' results and directories with absolutely paths.
127  if (!Data.IsDirectory || llvm::sys::path::is_absolute(Path))
128  StatCalls[Path] = Data;
129 
130  return Result;
131 }
LookupResult statChained(StringRef Path, FileData &Data, bool isFile, std::unique_ptr< llvm::vfs::File > *F, llvm::vfs::FileSystem &FS)
Defines the FileSystemStatCache interface.
We know the file exists and its cached stat data.
We know that the file doesn&#39;t exist.
Abstract interface for introducing a FileManager cache for &#39;stat&#39; system calls, which is used by prec...
The result type of a method or function.
static bool get(StringRef Path, FileData &Data, bool isFile, std::unique_ptr< llvm::vfs::File > *F, FileSystemStatCache *Cache, llvm::vfs::FileSystem &FS)
Get the &#39;stat&#39; information for the specified path, using the cache to accelerate it if possible...
virtual LookupResult getStat(StringRef Path, FileData &Data, bool isFile, std::unique_ptr< llvm::vfs::File > *F, llvm::vfs::FileSystem &FS)=0
llvm::sys::fs::UniqueID UniqueID
LookupResult getStat(StringRef Path, FileData &Data, bool isFile, std::unique_ptr< llvm::vfs::File > *F, llvm::vfs::FileSystem &FS) override
Dataflow Directional Tag Classes.
The type-property cache.
Definition: Type.cpp:3442
static void copyStatusToFileData(const llvm::vfs::Status &Status, FileData &Data)