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 
31 void FileSystemStatCache::anchor() { }
32 
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 }
43 
44 /// FileSystemStatCache::get - Get the 'stat' information for the specified
45 /// path, using the cache to accelerate it if possible.  This returns true if
46 /// the path does not exist or false if it exists.
47 ///
48 /// If isFile is true, then this lookup should only return success for files
49 /// (not directories).  If it is false this lookup should only return
50 /// success for directories (not files).  On a successful file lookup, the
51 /// implementation can optionally fill in FileDescriptor with a valid
52 /// descriptor and the client guarantees that it will close it.
53 bool FileSystemStatCache::get(const char *Path, FileData &Data, bool isFile,
54                               vfs::File **F, FileSystemStatCache *Cache,
55                               vfs::FileSystem &FS) {
56   LookupResult R;
57   bool isForDir = !isFile;
58 
59   // If we have a cache, use it to resolve the stat query.
60   if (Cache)
61     R = Cache->getStat(Path, Data, isFile, F, FS);
62   else if (isForDir || !F) {
63     // If this is a directory or a file descriptor is not needed and we have
64     // no cache, just go to the file system.
65     llvm::ErrorOr<vfs::Status> Status = FS.status(Path);
66     if (!Status) {
67       R = CacheMissing;
68     } else {
69       R = CacheExists;
70       copyStatusToFileData(*Status, Data);
71     }
72   } else {
73     // Otherwise, we have to go to the filesystem.  We can always just use
74     // 'stat' here, but (for files) the client is asking whether the file exists
75     // because it wants to turn around and *open* it.  It is more efficient to
76     // do "open+fstat" on success than it is to do "stat+open".
77     //
78     // Because of this, check to see if the file exists with 'open'.  If the
79     // open succeeds, use fstat to get the stat info.
80     llvm::OwningPtr<vfs::File> OwnedFile;
81     llvm::error_code EC = FS.openFileForRead(Path, OwnedFile);
82 
83     if (EC) {
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 = OwnedFile.take();
95       } else {
96         // fstat rarely fails.  If it does, claim the initial open didn't
97         // succeed.
98         R = CacheMissing;
99         *F = 0;
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 && *F) {
112       (*F)->close();
113       *F = 0;
114     }
115 
116     return true;
117   }
118 
119   return false;
120 }
121 
122 MemorizeStatCalls::LookupResult
123 MemorizeStatCalls::getStat(const char *Path, FileData &Data, bool isFile,
124                            vfs::File **F, vfs::FileSystem &FS) {
125   LookupResult Result = statChained(Path, Data, isFile, F, FS);
126 
127   // Do not cache failed stats, it is easy to construct common inconsistent
128   // situations if we do, and they are not important for PCH performance (which
129   // currently only needs the stats to construct the initial FileManager
130   // entries).
131   if (Result == CacheMissing)
132     return Result;
133 
134   // Cache file 'stat' results and directories with absolutely paths.
135   if (!Data.IsDirectory || llvm::sys::path::is_absolute(Path))
136     StatCalls[Path] = Data;
137 
138   return Result;
139 }
140