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/Support/FileSystem.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 llvm::sys::fs::file_status &Status,
34                                 FileData &Data) {
35  Data.Size = Status.getSize();
36  Data.ModTime = Status.getLastModificationTime().toEpochTime();
37  Data.UniqueID = Status.getUniqueID();
38  Data.IsDirectory = is_directory(Status);
39  Data.IsNamedPipe = Status.type() == llvm::sys::fs::file_type::fifo_file;
40  Data.InPCH = false;
41}
42
43/// FileSystemStatCache::get - Get the 'stat' information for the specified
44/// path, using the cache to accelerate it if possible.  This returns true if
45/// the path does not exist or false if it exists.
46///
47/// If isFile is true, then this lookup should only return success for files
48/// (not directories).  If it is false this lookup should only return
49/// success for directories (not files).  On a successful file lookup, the
50/// implementation can optionally fill in FileDescriptor with a valid
51/// descriptor and the client guarantees that it will close it.
52bool FileSystemStatCache::get(const char *Path, FileData &Data, bool isFile,
53                              int *FileDescriptor, FileSystemStatCache *Cache) {
54  LookupResult R;
55  bool isForDir = !isFile;
56
57  // If we have a cache, use it to resolve the stat query.
58  if (Cache)
59    R = Cache->getStat(Path, Data, isFile, FileDescriptor);
60  else if (isForDir || !FileDescriptor) {
61    // If this is a directory or a file descriptor is not needed and we have
62    // no cache, just go to the file system.
63    llvm::sys::fs::file_status Status;
64    if (llvm::sys::fs::status(Path, Status)) {
65      R = CacheMissing;
66    } else {
67      R = CacheExists;
68      copyStatusToFileData(Status, Data);
69    }
70  } else {
71    // Otherwise, we have to go to the filesystem.  We can always just use
72    // 'stat' here, but (for files) the client is asking whether the file exists
73    // because it wants to turn around and *open* it.  It is more efficient to
74    // do "open+fstat" on success than it is to do "stat+open".
75    //
76    // Because of this, check to see if the file exists with 'open'.  If the
77    // open succeeds, use fstat to get the stat info.
78    llvm::error_code EC = llvm::sys::fs::openFileForRead(Path, *FileDescriptor);
79
80    if (EC) {
81      // If the open fails, our "stat" fails.
82      R = CacheMissing;
83    } else {
84      // Otherwise, the open succeeded.  Do an fstat to get the information
85      // about the file.  We'll end up returning the open file descriptor to the
86      // client to do what they please with it.
87      llvm::sys::fs::file_status Status;
88      if (!llvm::sys::fs::status(*FileDescriptor, Status)) {
89        R = CacheExists;
90        copyStatusToFileData(Status, Data);
91      } else {
92        // fstat rarely fails.  If it does, claim the initial open didn't
93        // succeed.
94        R = CacheMissing;
95        ::close(*FileDescriptor);
96        *FileDescriptor = -1;
97      }
98    }
99  }
100
101  // If the path doesn't exist, return failure.
102  if (R == CacheMissing) return true;
103
104  // If the path exists, make sure that its "directoryness" matches the clients
105  // demands.
106  if (Data.IsDirectory != isForDir) {
107    // If not, close the file if opened.
108    if (FileDescriptor && *FileDescriptor != -1) {
109      ::close(*FileDescriptor);
110      *FileDescriptor = -1;
111    }
112
113    return true;
114  }
115
116  return false;
117}
118
119MemorizeStatCalls::LookupResult
120MemorizeStatCalls::getStat(const char *Path, FileData &Data, bool isFile,
121                           int *FileDescriptor) {
122  LookupResult Result = statChained(Path, Data, isFile, FileDescriptor);
123
124  // Do not cache failed stats, it is easy to construct common inconsistent
125  // situations if we do, and they are not important for PCH performance (which
126  // currently only needs the stats to construct the initial FileManager
127  // entries).
128  if (Result == CacheMissing)
129    return Result;
130
131  // Cache file 'stat' results and directories with absolutely paths.
132  if (!Data.IsDirectory || llvm::sys::path::is_absolute(Path))
133    StatCalls[Path] = Data;
134
135  return Result;
136}
137