76 lines
2.1 KiB
C++
76 lines
2.1 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef METRICS_PERSISTENT_INTEGER_H_
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#define METRICS_PERSISTENT_INTEGER_H_
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#include <stdint.h>
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#include <string>
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#include <base/files/file_path.h>
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namespace chromeos_metrics {
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// PersistentIntegers is a named 64-bit integer value backed by a file.
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// The in-memory value acts as a write-through cache of the file value.
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// If the backing file doesn't exist or has bad content, the value is 0.
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class PersistentInteger {
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public:
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PersistentInteger(const std::string& name, const base::FilePath& directory);
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// Virtual only because of mock.
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virtual ~PersistentInteger();
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// Sets the value. This writes through to the backing file.
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void Set(int64_t v);
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// Gets the value. May sync from backing file first.
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int64_t Get();
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// Returns the name of the object.
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std::string Name() { return name_; }
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// Convenience function for Get() followed by Set(0).
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int64_t GetAndClear();
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// Convenience function for v = Get, Set(v + x).
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// Virtual only because of mock.
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virtual void Add(int64_t x);
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private:
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static const int kVersion = 1001;
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// Writes |value_| to the backing file, creating it if necessary.
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void Write();
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// Reads the value from the backing file, stores it in |value_|, and returns
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// true if the backing file is valid. Returns false otherwise, and creates
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// a valid backing file as a side effect.
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bool Read();
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int64_t value_;
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int32_t version_;
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std::string name_;
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base::FilePath backing_file_path_;
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bool synced_;
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};
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} // namespace chromeos_metrics
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#endif // METRICS_PERSISTENT_INTEGER_H_
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