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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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