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- //===- FileSystemStatCache.cpp - Caching for 'stat' calls -----------------===//
- //
- // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
- // See https://llvm.org/LICENSE.txt for license information.
- // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
- //
- //===----------------------------------------------------------------------===//
- //
- // This file defines the FileSystemStatCache interface.
- //
- //===----------------------------------------------------------------------===//
- #include "clang/Basic/FileSystemStatCache.h"
- #include "llvm/Support/Chrono.h"
- #include "llvm/Support/ErrorOr.h"
- #include "llvm/Support/Path.h"
- #include "llvm/Support/VirtualFileSystem.h"
- #include <utility>
- using namespace clang;
- void FileSystemStatCache::anchor() {}
- /// FileSystemStatCache::get - Get the 'stat' information for the specified
- /// path, using the cache to accelerate it if possible. This returns true if
- /// the path does not exist or false if it exists.
- ///
- /// If isFile is true, then this lookup should only return success for files
- /// (not directories). If it is false this lookup should only return
- /// success for directories (not files). On a successful file lookup, the
- /// implementation can optionally fill in FileDescriptor with a valid
- /// descriptor and the client guarantees that it will close it.
- std::error_code
- FileSystemStatCache::get(StringRef Path, llvm::vfs::Status &Status,
- bool isFile, std::unique_ptr<llvm::vfs::File> *F,
- FileSystemStatCache *Cache,
- llvm::vfs::FileSystem &FS) {
- bool isForDir = !isFile;
- std::error_code RetCode;
- // If we have a cache, use it to resolve the stat query.
- if (Cache)
- RetCode = Cache->getStat(Path, Status, isFile, F, FS);
- else if (isForDir || !F) {
- // If this is a directory or a file descriptor is not needed and we have
- // no cache, just go to the file system.
- llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = FS.status(Path);
- if (!StatusOrErr) {
- RetCode = StatusOrErr.getError();
- } else {
- Status = *StatusOrErr;
- }
- } else {
- // Otherwise, we have to go to the filesystem. We can always just use
- // 'stat' here, but (for files) the client is asking whether the file exists
- // because it wants to turn around and *open* it. It is more efficient to
- // do "open+fstat" on success than it is to do "stat+open".
- //
- // Because of this, check to see if the file exists with 'open'. If the
- // open succeeds, use fstat to get the stat info.
- auto OwnedFile = FS.openFileForRead(Path);
- if (!OwnedFile) {
- // If the open fails, our "stat" fails.
- RetCode = OwnedFile.getError();
- } else {
- // Otherwise, the open succeeded. Do an fstat to get the information
- // about the file. We'll end up returning the open file descriptor to the
- // client to do what they please with it.
- llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = (*OwnedFile)->status();
- if (StatusOrErr) {
- Status = *StatusOrErr;
- *F = std::move(*OwnedFile);
- } else {
- // fstat rarely fails. If it does, claim the initial open didn't
- // succeed.
- *F = nullptr;
- RetCode = StatusOrErr.getError();
- }
- }
- }
- // If the path doesn't exist, return failure.
- if (RetCode)
- return RetCode;
- // If the path exists, make sure that its "directoryness" matches the clients
- // demands.
- if (Status.isDirectory() != isForDir) {
- // If not, close the file if opened.
- if (F)
- *F = nullptr;
- return std::make_error_code(
- Status.isDirectory() ?
- std::errc::is_a_directory : std::errc::not_a_directory);
- }
- return std::error_code();
- }
- std::error_code
- MemorizeStatCalls::getStat(StringRef Path, llvm::vfs::Status &Status,
- bool isFile,
- std::unique_ptr<llvm::vfs::File> *F,
- llvm::vfs::FileSystem &FS) {
- auto err = get(Path, Status, isFile, F, nullptr, FS);
- if (err) {
- // Do not cache failed stats, it is easy to construct common inconsistent
- // situations if we do, and they are not important for PCH performance
- // (which currently only needs the stats to construct the initial
- // FileManager entries).
- return err;
- }
- // Cache file 'stat' results and directories with absolutely paths.
- if (!Status.isDirectory() || llvm::sys::path::is_absolute(Path))
- StatCalls[Path] = Status;
- return std::error_code();
- }
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