src/stat_cache.h

// Copyright 2023 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef NINJA_STAT_CACHE_H_
#define NINJA_STAT_CACHE_H_

#include <memory>
#include <string>

#include "timestamp.h"

/// Implement a cache for file path timestamps.
class StatCache {
 public:
  /// Constructor
  StatCache();

  /// Destructor
  ~StatCache();

  /// Enable caching of timestamps. If false (the default), the Stat() performs
  /// a single stat() operation per file and no caching is performed.
  void Enable(bool enabled);

  /// Mark a path as invalid.
  void Invalidate(const std::string& path);

  /// Return the timestamp of a given file path. On error, set |*err| then
  /// return -1. Otherwise, return 0 if the file is missing, or a strictly
  /// positive value if it exists.
  TimeStamp Stat(const std::string& path, std::string* err) const;

  /// Synchronize the cache state with recent filesystem events.
  /// Call this before one or more Stat() calls.
  void Sync();

  /// Remove all entries from the cache.
  void Flush();

 private:
  class Impl;
  std::unique_ptr<Impl> impl_;
};

#endif  // NINJA_STAT_CACHE_H_