122 lines · cpp
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-exception6//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 19using namespace clang;20 21void FileSystemStatCache::anchor() {}22 23/// FileSystemStatCache::get - Get the 'stat' information for the specified24/// path, using the cache to accelerate it if possible. This returns true if25/// the path does not exist or false if it exists.26///27/// If isFile is true, then this lookup should only return success for files28/// (not directories). If it is false this lookup should only return29/// success for directories (not files). On a successful file lookup, the30/// implementation can optionally fill in FileDescriptor with a valid31/// descriptor and the client guarantees that it will close it.32std::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 have46 // 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 use55 // 'stat' here, but (for files) the client is asking whether the file exists56 // because it wants to turn around and *open* it. It is more efficient to57 // 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 the60 // 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 information69 // about the file. We'll end up returning the open file descriptor to the70 // 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't77 // 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 clients89 // 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 102std::error_code103MemorizeStatCalls::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 inconsistent110 // situations if we do, and they are not important for PCH performance111 // (which currently only needs the stats to construct the initial112 // 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