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
25using namespace clang;
26
27#if defined(_MSC_VER)
28#define S_ISDIR(s) ((_S_IFDIR & s) !=0)
29#endif
30
31void FileSystemStatCache::anchor() { }
32
33static 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.
54bool 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    std::unique_ptr<vfs::File> OwnedFile;
82    std::error_code EC = FS.openFileForRead(Path, OwnedFile);
83
84    if (EC) {
85      // If the open fails, our "stat" fails.
86      R = CacheMissing;
87    } else {
88      // Otherwise, the open succeeded.  Do an fstat to get the information
89      // about the file.  We'll end up returning the open file descriptor to the
90      // client to do what they please with it.
91      llvm::ErrorOr<vfs::Status> Status = OwnedFile->status();
92      if (Status) {
93        R = CacheExists;
94        copyStatusToFileData(*Status, Data);
95        *F = std::move(OwnedFile);
96      } else {
97        // fstat rarely fails.  If it does, claim the initial open didn't
98        // succeed.
99        R = CacheMissing;
100        *F = nullptr;
101      }
102    }
103  }
104
105  // If the path doesn't exist, return failure.
106  if (R == CacheMissing) return true;
107
108  // If the path exists, make sure that its "directoryness" matches the clients
109  // demands.
110  if (Data.IsDirectory != isForDir) {
111    // If not, close the file if opened.
112    if (F)
113      *F = nullptr;
114
115    return true;
116  }
117
118  return false;
119}
120
121MemorizeStatCalls::LookupResult
122MemorizeStatCalls::getStat(const char *Path, FileData &Data, bool isFile,
123                           std::unique_ptr<vfs::File> *F, vfs::FileSystem &FS) {
124  LookupResult Result = statChained(Path, Data, isFile, F, FS);
125
126  // Do not cache failed stats, it is easy to construct common inconsistent
127  // situations if we do, and they are not important for PCH performance (which
128  // currently only needs the stats to construct the initial FileManager
129  // entries).
130  if (Result == CacheMissing)
131    return Result;
132
133  // Cache file 'stat' results and directories with absolutely paths.
134  if (!Data.IsDirectory || llvm::sys::path::is_absolute(Path))
135    StatCalls[Path] = Data;
136
137  return Result;
138}
139