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/*
* Copyright (C) 2015 The Android Open Source Project
*
* 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 METRICS_PERSISTENT_INTEGER_H_
#define METRICS_PERSISTENT_INTEGER_H_
#include <stdint.h>
#include <string>
#include <base/files/file_path.h>
namespace chromeos_metrics {
// PersistentIntegers is a named 64-bit integer value backed by a file.
// The in-memory value acts as a write-through cache of the file value.
// If the backing file doesn't exist or has bad content, the value is 0.
class PersistentInteger {
public:
PersistentInteger(const std::string& name, const base::FilePath& directory);
// Virtual only because of mock.
virtual ~PersistentInteger();
// Sets the value. This writes through to the backing file.
void Set(int64_t v);
// Gets the value. May sync from backing file first.
int64_t Get();
// Returns the name of the object.
std::string Name() { return name_; }
// Convenience function for Get() followed by Set(0).
int64_t GetAndClear();
// Convenience function for v = Get, Set(v + x).
// Virtual only because of mock.
virtual void Add(int64_t x);
private:
static const int kVersion = 1001;
// Writes |value_| to the backing file, creating it if necessary.
void Write();
// Reads the value from the backing file, stores it in |value_|, and returns
// true if the backing file is valid. Returns false otherwise, and creates
// a valid backing file as a side effect.
bool Read();
int64_t value_;
int32_t version_;
std::string name_;
base::FilePath backing_file_path_;
bool synced_;
};
} // namespace chromeos_metrics
#endif // METRICS_PERSISTENT_INTEGER_H_
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