1 | //===- FileSystemStatCache.cpp - Caching for 'stat' calls -----------------===// |
2 | // |
3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | // See https://llvm.org/LICENSE.txt for license information. |
5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | // |
7 | //===----------------------------------------------------------------------===// |
8 | // |
9 | // This file defines the FileSystemStatCache interface. |
10 | // |
11 | //===----------------------------------------------------------------------===// |
12 | |
13 | #include "clang/Basic/FileSystemStatCache.h" |
14 | #include "llvm/Support/ErrorOr.h" |
15 | #include "llvm/Support/Path.h" |
16 | #include "llvm/Support/VirtualFileSystem.h" |
17 | #include <utility> |
18 | |
19 | using namespace clang; |
20 | |
21 | void FileSystemStatCache::anchor() {} |
22 | |
23 | /// FileSystemStatCache::get - Get the 'stat' information for the specified |
24 | /// path, using the cache to accelerate it if possible. This returns true if |
25 | /// the path does not exist or false if it exists. |
26 | /// |
27 | /// If isFile is true, then this lookup should only return success for files |
28 | /// (not directories). If it is false this lookup should only return |
29 | /// success for directories (not files). On a successful file lookup, the |
30 | /// implementation can optionally fill in FileDescriptor with a valid |
31 | /// descriptor and the client guarantees that it will close it. |
32 | std::error_code FileSystemStatCache::get(StringRef Path, |
33 | llvm::vfs::Status &Status, bool isFile, |
34 | std::unique_ptr<llvm::vfs::File> *F, |
35 | FileSystemStatCache *Cache, |
36 | llvm::vfs::FileSystem &FS, |
37 | bool IsText) { |
38 | bool isForDir = !isFile; |
39 | std::error_code RetCode; |
40 | |
41 | // If we have a cache, use it to resolve the stat query. |
42 | if (Cache) |
43 | RetCode = Cache->getStat(Path, Status, isFile, F, FS); |
44 | else if (isForDir || !F) { |
45 | // If this is a directory or a file descriptor is not needed and we have |
46 | // no cache, just go to the file system. |
47 | llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = FS.status(Path); |
48 | if (!StatusOrErr) { |
49 | RetCode = StatusOrErr.getError(); |
50 | } else { |
51 | Status = *StatusOrErr; |
52 | } |
53 | } else { |
54 | // Otherwise, we have to go to the filesystem. We can always just use |
55 | // 'stat' here, but (for files) the client is asking whether the file exists |
56 | // because it wants to turn around and *open* it. It is more efficient to |
57 | // do "open+fstat" on success than it is to do "stat+open". |
58 | // |
59 | // Because of this, check to see if the file exists with 'open'. If the |
60 | // open succeeds, use fstat to get the stat info. |
61 | auto OwnedFile = |
62 | IsText ? FS.openFileForRead(Path) : FS.openFileForReadBinary(Path); |
63 | |
64 | if (!OwnedFile) { |
65 | // If the open fails, our "stat" fails. |
66 | RetCode = OwnedFile.getError(); |
67 | } else { |
68 | // Otherwise, the open succeeded. Do an fstat to get the information |
69 | // about the file. We'll end up returning the open file descriptor to the |
70 | // client to do what they please with it. |
71 | llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = (*OwnedFile)->status(); |
72 | if (StatusOrErr) { |
73 | Status = *StatusOrErr; |
74 | *F = std::move(*OwnedFile); |
75 | } else { |
76 | // fstat rarely fails. If it does, claim the initial open didn't |
77 | // succeed. |
78 | *F = nullptr; |
79 | RetCode = StatusOrErr.getError(); |
80 | } |
81 | } |
82 | } |
83 | |
84 | // If the path doesn't exist, return failure. |
85 | if (RetCode) |
86 | return RetCode; |
87 | |
88 | // If the path exists, make sure that its "directoryness" matches the clients |
89 | // demands. |
90 | if (Status.isDirectory() != isForDir) { |
91 | // If not, close the file if opened. |
92 | if (F) |
93 | *F = nullptr; |
94 | return std::make_error_code( |
95 | e: Status.isDirectory() ? |
96 | std::errc::is_a_directory : std::errc::not_a_directory); |
97 | } |
98 | |
99 | return std::error_code(); |
100 | } |
101 | |
102 | std::error_code |
103 | MemorizeStatCalls::getStat(StringRef Path, llvm::vfs::Status &Status, |
104 | bool isFile, |
105 | std::unique_ptr<llvm::vfs::File> *F, |
106 | llvm::vfs::FileSystem &FS) { |
107 | auto err = get(Path, Status, isFile, F, Cache: nullptr, FS); |
108 | if (err) { |
109 | // Do not cache failed stats, it is easy to construct common inconsistent |
110 | // situations if we do, and they are not important for PCH performance |
111 | // (which currently only needs the stats to construct the initial |
112 | // FileManager entries). |
113 | return err; |
114 | } |
115 | |
116 | // Cache file 'stat' results and directories with absolutely paths. |
117 | if (!Status.isDirectory() || llvm::sys::path::is_absolute(path: Path)) |
118 | StatCalls[Path] = Status; |
119 | |
120 | return std::error_code(); |
121 | } |
122 | |