//===- FileSystemStatCache.h - Caching for 'stat' calls ---------*- C++ -*-===//

//

// 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

//

//===----------------------------------------------------------------------===//

//

/// \file

/// Defines the FileSystemStatCache interface.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H

#define LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H

#include "clang/Basic/LLVM.h"

#include "llvm/ADT/StringMap.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/Support/Allocator.h"

#include "llvm/Support/FileSystem.h"

#include "llvm/Support/VirtualFileSystem.h"

#include <cstdint>

#include <ctime>

#include <memory>

#include <string>

#include <utility>

namespace clang {

/// 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();

public:

  virtual ~FileSystemStatCache() = default;

  /// 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 std::error_code

  get(StringRef Path, llvm::vfs::Status &Status, bool isFile,

      std::unique_ptr<llvm::vfs::File> *F,

      FileSystemStatCache *Cache, llvm::vfs::FileSystem &FS);

protected:

  // 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 std::error_code getStat(StringRef Path, llvm::vfs::Status &Status,

                                  bool isFile,

                                  std::unique_ptr<llvm::vfs::File> *F,

                                  llvm::vfs::FileSystem &FS) = 0;

};

/// 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 {

public:

  /// The set of stat() calls that have been seen.

  llvm::StringMap<llvm::vfs::Status, llvm::BumpPtrAllocator> StatCalls;

  using iterator =

      llvm::StringMap<llvm::vfs::Status,

                      llvm::BumpPtrAllocator>::const_iterator;

  iterator begin() const { return StatCalls.begin(); }

  iterator end() const { return StatCalls.end(); }

  std::error_code getStat(StringRef Path, llvm::vfs::Status &Status,

                          bool isFile,

                          std::unique_ptr<llvm::vfs::File> *F,

                          llvm::vfs::FileSystem &FS) override;

};

} // namespace clang

#endif // LLVM_CLANG_BASIC_FILESYSTEMSTATCACHE_H