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
14 #include "clang/Basic/FileSystemStatCache.h"
15 #include "clang/Basic/VirtualFileSystem.h"
16 #include "llvm/Support/Path.h"
17
18 // FIXME: This is terrible, we need this for ::close.
19 #if !defined(_MSC_VER) && !defined(__MINGW32__)
20 #include <unistd.h>
21 #include <sys/uio.h>
22 #else
23 #include <io.h>
24 #endif
25 using namespace clang;
26
27 #if defined(_MSC_VER)
28 #define S_ISDIR(s) ((_S_IFDIR & s) !=0)
29 #endif
30
anchor()31 void FileSystemStatCache::anchor() { }
32
copyStatusToFileData(const vfs::Status & Status,FileData & Data)33 static void copyStatusToFileData(const vfs::Status &Status,
34 FileData &Data) {
35 Data.Name = Status.getName();
36 Data.Size = Status.getSize();
37 Data.ModTime = Status.getLastModificationTime().toEpochTime();
38 Data.UniqueID = Status.getUniqueID();
39 Data.IsDirectory = Status.isDirectory();
40 Data.IsNamedPipe = Status.getType() == llvm::sys::fs::file_type::fifo_file;
41 Data.InPCH = false;
42 Data.IsVFSMapped = Status.IsVFSMapped;
43 }
44
45 /// FileSystemStatCache::get - Get the 'stat' information for the specified
46 /// path, using the cache to accelerate it if possible. This returns true if
47 /// the path does not exist or false if it exists.
48 ///
49 /// If isFile is true, then this lookup should only return success for files
50 /// (not directories). If it is false this lookup should only return
51 /// success for directories (not files). On a successful file lookup, the
52 /// implementation can optionally fill in FileDescriptor with a valid
53 /// descriptor and the client guarantees that it will close it.
get(const char * Path,FileData & Data,bool isFile,std::unique_ptr<vfs::File> * F,FileSystemStatCache * Cache,vfs::FileSystem & FS)54 bool FileSystemStatCache::get(const char *Path, FileData &Data, bool isFile,
55 std::unique_ptr<vfs::File> *F,
56 FileSystemStatCache *Cache, vfs::FileSystem &FS) {
57 LookupResult R;
58 bool isForDir = !isFile;
59
60 // If we have a cache, use it to resolve the stat query.
61 if (Cache)
62 R = Cache->getStat(Path, Data, isFile, F, FS);
63 else if (isForDir || !F) {
64 // If this is a directory or a file descriptor is not needed and we have
65 // no cache, just go to the file system.
66 llvm::ErrorOr<vfs::Status> Status = FS.status(Path);
67 if (!Status) {
68 R = CacheMissing;
69 } else {
70 R = CacheExists;
71 copyStatusToFileData(*Status, Data);
72 }
73 } else {
74 // Otherwise, we have to go to the filesystem. We can always just use
75 // 'stat' here, but (for files) the client is asking whether the file exists
76 // because it wants to turn around and *open* it. It is more efficient to
77 // do "open+fstat" on success than it is to do "stat+open".
78 //
79 // Because of this, check to see if the file exists with 'open'. If the
80 // open succeeds, use fstat to get the stat info.
81 auto OwnedFile = FS.openFileForRead(Path);
82
83 if (!OwnedFile) {
84 // If the open fails, our "stat" fails.
85 R = CacheMissing;
86 } else {
87 // Otherwise, the open succeeded. Do an fstat to get the information
88 // about the file. We'll end up returning the open file descriptor to the
89 // client to do what they please with it.
90 llvm::ErrorOr<vfs::Status> Status = (*OwnedFile)->status();
91 if (Status) {
92 R = CacheExists;
93 copyStatusToFileData(*Status, Data);
94 *F = std::move(*OwnedFile);
95 } else {
96 // fstat rarely fails. If it does, claim the initial open didn't
97 // succeed.
98 R = CacheMissing;
99 *F = nullptr;
100 }
101 }
102 }
103
104 // If the path doesn't exist, return failure.
105 if (R == CacheMissing) return true;
106
107 // If the path exists, make sure that its "directoryness" matches the clients
108 // demands.
109 if (Data.IsDirectory != isForDir) {
110 // If not, close the file if opened.
111 if (F)
112 *F = nullptr;
113
114 return true;
115 }
116
117 return false;
118 }
119
120 MemorizeStatCalls::LookupResult
getStat(const char * Path,FileData & Data,bool isFile,std::unique_ptr<vfs::File> * F,vfs::FileSystem & FS)121 MemorizeStatCalls::getStat(const char *Path, FileData &Data, bool isFile,
122 std::unique_ptr<vfs::File> *F, vfs::FileSystem &FS) {
123 LookupResult Result = statChained(Path, Data, isFile, F, FS);
124
125 // Do not cache failed stats, it is easy to construct common inconsistent
126 // situations if we do, and they are not important for PCH performance (which
127 // currently only needs the stats to construct the initial FileManager
128 // entries).
129 if (Result == CacheMissing)
130 return Result;
131
132 // Cache file 'stat' results and directories with absolutely paths.
133 if (!Data.IsDirectory || llvm::sys::path::is_absolute(Path))
134 StatCalls[Path] = Data;
135
136 return Result;
137 }
138