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 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, 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)) 118 StatCalls[Path] = Status; 119 120 return std::error_code(); 121 } 122