FileSystemStatCache.cpp revision 898a061f69e1145bf89a987c08203132b9922a3c 
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"
16using namespace clang;
17
18#if defined(_MSC_VER)
19#define S_ISDIR(s) (_S_IFDIR & s)
20#endif
21
22/// FileSystemStatCache::get - Get the 'stat' information for the specified
23/// path, using the cache to accellerate it if possible.  This returns true if
24/// the path does not exist or false if it exists.
25///
26/// If FileDescriptor is non-null, then this lookup should only return success
27/// for files (not directories).  If it is null this lookup should only return
28/// success for directories (not files).  On a successful file lookup, the
29/// implementation can optionally fill in FileDescriptor with a valid
30/// descriptor and the client guarantees that it will close it.
31bool FileSystemStatCache::get(const char *Path, struct stat &StatBuf,
32                              int *FileDescriptor, FileSystemStatCache *Cache) {
33  LookupResult R;
34
35  if (Cache)
36    R = Cache->getStat(Path, StatBuf, FileDescriptor);
37  else
38    R = ::stat(Path, &StatBuf) != 0 ? CacheMissing : CacheExists;
39
40  if (R == CacheMissing) return true;
41
42  bool isForDir = FileDescriptor == 0;
43  return S_ISDIR(StatBuf.st_mode) != isForDir;
44}
45
46
47MemorizeStatCalls::LookupResult
48MemorizeStatCalls::getStat(const char *Path, struct stat &StatBuf,
49                           int *FileDescriptor) {
50  LookupResult Result = statChained(Path, StatBuf, FileDescriptor);
51
52  // Do not cache failed stats, it is easy to construct common inconsistent
53  // situations if we do, and they are not important for PCH performance (which
54  // currently only needs the stats to construct the initial FileManager
55  // entries).
56  if (Result == CacheMissing)
57    return Result;
58
59  // Cache file 'stat' results and directories with absolutely paths.
60  if (!S_ISDIR(StatBuf.st_mode) || llvm::sys::Path(Path).isAbsolute())
61    StatCalls[Path] = StatBuf;
62
63  return Result;
64}
65