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//===--- FileSystemStatCache.h - Caching for 'stat' calls -------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
/// \file
/// \brief Defines the FileSystemStatCache interface.
#include "clang/Basic/LLVM.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/Support/FileSystem.h"
#include <memory>
namespace clang {
namespace vfs {
class File;
class FileSystem;
// FIXME: should probably replace this with vfs::Status
struct FileData {
std::string Name;
uint64_t Size;
time_t ModTime;
llvm::sys::fs::UniqueID UniqueID;
bool IsDirectory;
bool IsNamedPipe;
bool InPCH;
bool IsVFSMapped; // FIXME: remove this when files support multiple names
: Size(0), ModTime(0), IsDirectory(false), IsNamedPipe(false),
InPCH(false), IsVFSMapped(false) {}
/// \brief Abstract interface for introducing a FileManager cache for 'stat'
/// system calls, which is used by precompiled and pretokenized headers to
/// improve performance.
class FileSystemStatCache {
virtual void anchor();
std::unique_ptr<FileSystemStatCache> NextStatCache;
virtual ~FileSystemStatCache() {}
enum LookupResult {
CacheExists, ///< We know the file exists and its cached stat data.
CacheMissing ///< We know that the file doesn't exist.
/// \brief Get the 'stat' information for the specified path, using the cache
/// to accelerate it if possible.
/// \returns \c true if the path does not exist or \c 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 \p F with a valid \p File object and
/// the client guarantees that it will close it.
static bool get(StringRef Path, FileData &Data, bool isFile,
std::unique_ptr<vfs::File> *F, FileSystemStatCache *Cache,
vfs::FileSystem &FS);
/// \brief Sets the next stat call cache in the chain of stat caches.
/// Takes ownership of the given stat cache.
void setNextStatCache(std::unique_ptr<FileSystemStatCache> Cache) {
NextStatCache = std::move(Cache);
/// \brief Retrieve the next stat call cache in the chain.
FileSystemStatCache *getNextStatCache() { return NextStatCache.get(); }
/// \brief Retrieve the next stat call cache in the chain, transferring
/// ownership of this cache (and, transitively, all of the remaining caches)
/// to the caller.
std::unique_ptr<FileSystemStatCache> takeNextStatCache() {
return std::move(NextStatCache);
// FIXME: The pointer here is a non-owning/optional reference to the
// unique_ptr. Optional<unique_ptr<vfs::File>&> might be nicer, but
// Optional needs some work to support references so this isn't possible yet.
virtual LookupResult getStat(StringRef Path, FileData &Data, bool isFile,
std::unique_ptr<vfs::File> *F,
vfs::FileSystem &FS) = 0;
LookupResult statChained(StringRef Path, FileData &Data, bool isFile,
std::unique_ptr<vfs::File> *F, vfs::FileSystem &FS) {
if (FileSystemStatCache *Next = getNextStatCache())
return Next->getStat(Path, Data, isFile, F, FS);
// If we hit the end of the list of stat caches to try, just compute and
// return it without a cache.
return get(Path, Data, isFile, F, nullptr, FS) ? CacheMissing : CacheExists;
/// \brief A stat "cache" that can be used by FileManager to keep
/// track of the results of stat() calls that occur throughout the
/// execution of the front end.
class MemorizeStatCalls : public FileSystemStatCache {
/// \brief The set of stat() calls that have been seen.
llvm::StringMap<FileData, llvm::BumpPtrAllocator> StatCalls;
typedef llvm::StringMap<FileData, llvm::BumpPtrAllocator>::const_iterator
iterator begin() const { return StatCalls.begin(); }
iterator end() const { return StatCalls.end(); }
LookupResult getStat(StringRef Path, FileData &Data, bool isFile,
std::unique_ptr<vfs::File> *F,
vfs::FileSystem &FS) override;
} // end namespace clang