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 "llvm/System/Path.h"
16 
17 // FIXME: This is terrible, we need this for ::close.
18 #if !defined(_MSC_VER) && !defined(__MINGW32__)
19 #include <unistd.h>
20 #include <sys/uio.h>
21 #else
22 #include <io.h>
23 #endif
24 using namespace clang;
25 
26 #if defined(_MSC_VER)
27 #define S_ISDIR(s) (_S_IFDIR & s)
28 #endif
29 
30 /// FileSystemStatCache::get - Get the 'stat' information for the specified
31 /// path, using the cache to accellerate it if possible.  This returns true if
32 /// the path does not exist or false if it exists.
33 ///
34 /// If FileDescriptor is non-null, then this lookup should only return success
35 /// for files (not directories).  If it is null this lookup should only return
36 /// success for directories (not files).  On a successful file lookup, the
37 /// implementation can optionally fill in FileDescriptor with a valid
38 /// descriptor and the client guarantees that it will close it.
39 bool FileSystemStatCache::get(const char *Path, struct stat &StatBuf,
40                               int *FileDescriptor, FileSystemStatCache *Cache) {
41   LookupResult R;
42 
43   if (Cache)
44     R = Cache->getStat(Path, StatBuf, FileDescriptor);
45   else
46     R = ::stat(Path, &StatBuf) != 0 ? CacheMissing : CacheExists;
47 
48   // If the path doesn't exist, return failure.
49   if (R == CacheMissing) return true;
50 
51   // If the path exists, make sure that its "directoryness" matches the clients
52   // demands.
53   bool isForDir = FileDescriptor == 0;
54   if (S_ISDIR(StatBuf.st_mode) != isForDir) {
55     // If not, close the file if opened.
56     if (FileDescriptor && *FileDescriptor != -1) {
57       ::close(*FileDescriptor);
58       *FileDescriptor = -1;
59     }
60 
61     return true;
62   }
63 
64   return false;
65 }
66 
67 
68 MemorizeStatCalls::LookupResult
69 MemorizeStatCalls::getStat(const char *Path, struct stat &StatBuf,
70                            int *FileDescriptor) {
71   LookupResult Result = statChained(Path, StatBuf, FileDescriptor);
72 
73   // Do not cache failed stats, it is easy to construct common inconsistent
74   // situations if we do, and they are not important for PCH performance (which
75   // currently only needs the stats to construct the initial FileManager
76   // entries).
77   if (Result == CacheMissing)
78     return Result;
79 
80   // Cache file 'stat' results and directories with absolutely paths.
81   if (!S_ISDIR(StatBuf.st_mode) || llvm::sys::Path(Path).isAbsolute())
82     StatCalls[Path] = StatBuf;
83 
84   return Result;
85 }
86