Differential D55455 Diff 179323 cfe/trunk/include/clang/Basic/FileSystemStatCache.h

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cfe/trunk/include/clang/Basic/FileSystemStatCache.h

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};		};

/// Abstract interface for introducing a FileManager cache for 'stat'		/// Abstract interface for introducing a FileManager cache for 'stat'
/// system calls, which is used by precompiled and pretokenized headers to		/// system calls, which is used by precompiled and pretokenized headers to
/// improve performance.		/// improve performance.
class FileSystemStatCache {		class FileSystemStatCache {
virtual void anchor();		virtual void anchor();

protected:
std::unique_ptr<FileSystemStatCache> NextStatCache;

public:		public:
virtual ~FileSystemStatCache() = default;		virtual ~FileSystemStatCache() = default;

enum LookupResult {		enum LookupResult {
/// We know the file exists and its cached stat data.		/// We know the file exists and its cached stat data.
CacheExists,		CacheExists,

/// We know that the file doesn't exist.		/// We know that the file doesn't exist.
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/// (not directories). If it is false this lookup should only return		/// (not directories). If it is false this lookup should only return
/// success for directories (not files). On a successful file lookup, the		/// 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		/// implementation can optionally fill in \p F with a valid \p File object and
/// the client guarantees that it will close it.		/// the client guarantees that it will close it.
static bool get(StringRef Path, FileData &Data, bool isFile,		static bool get(StringRef Path, FileData &Data, bool isFile,
std::unique_ptr<llvm::vfs::File> *F,		std::unique_ptr<llvm::vfs::File> *F,
FileSystemStatCache *Cache, llvm::vfs::FileSystem &FS);		FileSystemStatCache *Cache, llvm::vfs::FileSystem &FS);

/// 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);
}

/// Retrieve the next stat call cache in the chain.
FileSystemStatCache *getNextStatCache() { return NextStatCache.get(); }

/// 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);
}

protected:		protected:
// FIXME: The pointer here is a non-owning/optional reference to the		// FIXME: The pointer here is a non-owning/optional reference to the
// unique_ptr. Optional<unique_ptr<vfs::File>&> might be nicer, but		// unique_ptr. Optional<unique_ptr<vfs::File>&> might be nicer, but
// Optional needs some work to support references so this isn't possible yet.		// Optional needs some work to support references so this isn't possible yet.
virtual LookupResult getStat(StringRef Path, FileData &Data, bool isFile,		virtual LookupResult getStat(StringRef Path, FileData &Data, bool isFile,
std::unique_ptr<llvm::vfs::File> *F,		std::unique_ptr<llvm::vfs::File> *F,
llvm::vfs::FileSystem &FS) = 0;		llvm::vfs::FileSystem &FS) = 0;

LookupResult statChained(StringRef Path, FileData &Data, bool isFile,
std::unique_ptr<llvm::vfs::File> *F,
llvm::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;
}
};		};

/// A stat "cache" that can be used by FileManager to keep		/// A stat "cache" that can be used by FileManager to keep
/// track of the results of stat() calls that occur throughout the		/// track of the results of stat() calls that occur throughout the
/// execution of the front end.		/// execution of the front end.
class MemorizeStatCalls : public FileSystemStatCache {		class MemorizeStatCalls : public FileSystemStatCache {
public:		public:
/// The set of stat() calls that have been seen.		/// The set of stat() calls that have been seen.
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