| 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/Chrono.h" |
| 15 | #include "llvm/Support/ErrorOr.h" |
| 16 | #include "llvm/Support/Path.h" |
| 17 | #include "llvm/Support/VirtualFileSystem.h" |
| 18 | #include <utility> |
| 19 | |
| 20 | using namespace clang; |
| 21 | |
| 22 | void FileSystemStatCache::anchor() {} |
| 23 | |
| 24 | /// FileSystemStatCache::get - Get the 'stat' information for the specified |
| 25 | /// path, using the cache to accelerate it if possible. This returns true if |
| 26 | /// the path does not exist or false if it exists. |
| 27 | /// |
| 28 | /// If isFile is true, then this lookup should only return success for files |
| 29 | /// (not directories). If it is false this lookup should only return |
| 30 | /// success for directories (not files). On a successful file lookup, the |
| 31 | /// implementation can optionally fill in FileDescriptor with a valid |
| 32 | /// descriptor and the client guarantees that it will close it. |
| 33 | bool FileSystemStatCache::get(StringRef Path, llvm::vfs::Status &Status, |
| 34 | bool isFile, |
| 35 | std::unique_ptr<llvm::vfs::File> *F, |
| 36 | FileSystemStatCache *Cache, |
| 37 | llvm::vfs::FileSystem &FS) { |
| 38 | LookupResult R; |
| 39 | bool isForDir = !isFile; |
| 40 | |
| 41 | // If we have a cache, use it to resolve the stat query. |
| 42 | if (Cache) |
| 43 | R = 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 | R = CacheMissing; |
| 50 | } else { |
| 51 | R = CacheExists; |
| 52 | Status = *StatusOrErr; |
| 53 | } |
| 54 | } else { |
| 55 | // Otherwise, we have to go to the filesystem. We can always just use |
| 56 | // 'stat' here, but (for files) the client is asking whether the file exists |
| 57 | // because it wants to turn around and *open* it. It is more efficient to |
| 58 | // do "open+fstat" on success than it is to do "stat+open". |
| 59 | // |
| 60 | // Because of this, check to see if the file exists with 'open'. If the |
| 61 | // open succeeds, use fstat to get the stat info. |
| 62 | auto OwnedFile = FS.openFileForRead(Path); |
| 63 | |
| 64 | if (!OwnedFile) { |
| 65 | // If the open fails, our "stat" fails. |
| 66 | R = CacheMissing; |
| 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 | R = CacheExists; |
| 74 | Status = *StatusOrErr; |
| 75 | *F = std::move(*OwnedFile); |
| 76 | } else { |
| 77 | // fstat rarely fails. If it does, claim the initial open didn't |
| 78 | // succeed. |
| 79 | R = CacheMissing; |
| 80 | *F = nullptr; |
| 81 | } |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | // If the path doesn't exist, return failure. |
| 86 | if (R == CacheMissing) return true; |
| 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 | |
| 95 | return true; |
| 96 | } |
| 97 | |
| 98 | return false; |
| 99 | } |
| 100 | |
| 101 | MemorizeStatCalls::LookupResult |
| 102 | MemorizeStatCalls::getStat(StringRef Path, llvm::vfs::Status &Status, |
| 103 | bool isFile, |
| 104 | std::unique_ptr<llvm::vfs::File> *F, |
| 105 | llvm::vfs::FileSystem &FS) { |
| 106 | if (get(Path, Status, isFile, F, nullptr, FS)) { |
| 107 | // Do not cache failed stats, it is easy to construct common inconsistent |
| 108 | // situations if we do, and they are not important for PCH performance |
| 109 | // (which currently only needs the stats to construct the initial |
| 110 | // FileManager entries). |
| 111 | return CacheMissing; |
| 112 | } |
| 113 | |
| 114 | // Cache file 'stat' results and directories with absolutely paths. |
| 115 | if (!Status.isDirectory() || llvm::sys::path::is_absolute(Path)) |
| 116 | StatCalls[Path] = Status; |
| 117 | |
| 118 | return CacheExists; |
| 119 | } |
| 120 |