clang  10.0.0svn
FileSystemStatCache.cpp
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1 //===- FileSystemStatCache.cpp - Caching for 'stat' calls -----------------===//
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 // This file defines the FileSystemStatCache interface.
10 //
11 //===----------------------------------------------------------------------===//
12 
14 #include "llvm/Support/Chrono.h"
15 #include "llvm/Support/ErrorOr.h"
16 #include "llvm/Support/Path.h"
17 #include "llvm/Support/VirtualFileSystem.h"
18 #include <utility>
19 
20 using namespace clang;
21 
22 void FileSystemStatCache::anchor() {}
23 
24 /// FileSystemStatCache::get - Get the 'stat' information for the specified
25 /// path, using the cache to accelerate it if possible. This returns true if
26 /// the path does not exist or false if it exists.
27 ///
28 /// If isFile is true, then this lookup should only return success for files
29 /// (not directories). If it is false this lookup should only return
30 /// success for directories (not files). On a successful file lookup, the
31 /// implementation can optionally fill in FileDescriptor with a valid
32 /// descriptor and the client guarantees that it will close it.
33 std::error_code
34 FileSystemStatCache::get(StringRef Path, llvm::vfs::Status &Status,
35  bool isFile, std::unique_ptr<llvm::vfs::File> *F,
37  llvm::vfs::FileSystem &FS) {
38  bool isForDir = !isFile;
39  std::error_code RetCode;
40 
41  // If we have a cache, use it to resolve the stat query.
42  if (Cache)
43  RetCode = Cache->getStat(Path, Status, isFile, F, FS);
44  else if (isForDir || !F) {
45  // If this is a directory or a file descriptor is not needed and we have
46  // no cache, just go to the file system.
47  llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = FS.status(Path);
48  if (!StatusOrErr) {
49  RetCode = StatusOrErr.getError();
50  } else {
51  Status = *StatusOrErr;
52  }
53  } else {
54  // Otherwise, we have to go to the filesystem. We can always just use
55  // 'stat' here, but (for files) the client is asking whether the file exists
56  // because it wants to turn around and *open* it. It is more efficient to
57  // do "open+fstat" on success than it is to do "stat+open".
58  //
59  // Because of this, check to see if the file exists with 'open'. If the
60  // open succeeds, use fstat to get the stat info.
61  auto OwnedFile = FS.openFileForRead(Path);
62 
63  if (!OwnedFile) {
64  // If the open fails, our "stat" fails.
65  RetCode = OwnedFile.getError();
66  } else {
67  // Otherwise, the open succeeded. Do an fstat to get the information
68  // about the file. We'll end up returning the open file descriptor to the
69  // client to do what they please with it.
70  llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = (*OwnedFile)->status();
71  if (StatusOrErr) {
72  Status = *StatusOrErr;
73  *F = std::move(*OwnedFile);
74  } else {
75  // fstat rarely fails. If it does, claim the initial open didn't
76  // succeed.
77  *F = nullptr;
78  RetCode = StatusOrErr.getError();
79  }
80  }
81  }
82 
83  // If the path doesn't exist, return failure.
84  if (RetCode)
85  return RetCode;
86 
87  // If the path exists, make sure that its "directoryness" matches the clients
88  // demands.
89  if (Status.isDirectory() != isForDir) {
90  // If not, close the file if opened.
91  if (F)
92  *F = nullptr;
93  return std::make_error_code(
94  Status.isDirectory() ?
95  std::errc::is_a_directory : std::errc::not_a_directory);
96  }
97 
98  return std::error_code();
99 }
100 
101 std::error_code
102 MemorizeStatCalls::getStat(StringRef Path, llvm::vfs::Status &Status,
103  bool isFile,
104  std::unique_ptr<llvm::vfs::File> *F,
105  llvm::vfs::FileSystem &FS) {
106  auto err = get(Path, Status, isFile, F, nullptr, FS);
107  if (err) {
108  // Do not cache failed stats, it is easy to construct common inconsistent
109  // situations if we do, and they are not important for PCH performance
110  // (which currently only needs the stats to construct the initial
111  // FileManager entries).
112  return err;
113  }
114 
115  // Cache file 'stat' results and directories with absolutely paths.
116  if (!Status.isDirectory() || llvm::sys::path::is_absolute(Path))
117  StatCalls[Path] = Status;
118 
119  return std::error_code();
120 }
Defines the FileSystemStatCache interface.
std::error_code make_error_code(ParseError e)
Definition: Format.cpp:617
Abstract interface for introducing a FileManager cache for &#39;stat&#39; system calls, which is used by prec...
Dataflow Directional Tag Classes.
virtual std::error_code getStat(StringRef Path, llvm::vfs::Status &Status, bool isFile, std::unique_ptr< llvm::vfs::File > *F, llvm::vfs::FileSystem &FS)=0
The type-property cache.
Definition: Type.cpp:3576
static std::error_code get(StringRef Path, llvm::vfs::Status &Status, 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...
std::error_code getStat(StringRef Path, llvm::vfs::Status &Status, bool isFile, std::unique_ptr< llvm::vfs::File > *F, llvm::vfs::FileSystem &FS) override