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rocksdb/include/rocksdb/system_clock.h

116 lines
4.2 KiB

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include <stdint.h>
#include <memory>
#include "rocksdb/customizable.h"
#include "rocksdb/rocksdb_namespace.h"
#include "rocksdb/status.h"
#ifdef _WIN32
// Windows API macro interference
#undef GetCurrentTime
#endif
namespace ROCKSDB_NAMESPACE {
struct ConfigOptions;
// A SystemClock is an interface used by the rocksdb implementation to access
// operating system time-related functionality.
class SystemClock : public Customizable {
public:
virtual ~SystemClock() {}
static const char* Type() { return "SystemClock"; }
static Status CreateFromString(const ConfigOptions& options,
const std::string& value,
std::shared_ptr<SystemClock>* result);
// The name of this system clock
virtual const char* Name() const override = 0;
// The name/nickname for the Default SystemClock. This name can be used
// to determine if the clock is the default one.
static const char* kDefaultName() { return "DefaultClock"; }
// Return a default SystemClock suitable for the current operating
// system.
static const std::shared_ptr<SystemClock>& Default();
// Returns the number of micro-seconds since some fixed point in time.
// It is often used as system time such as in GenericRateLimiter
// and other places so a port needs to return system time in order to work.
virtual uint64_t NowMicros() = 0;
// Returns the number of nano-seconds since some fixed point in time. Only
// useful for computing deltas of time in one run.
// Default implementation simply relies on NowMicros.
// In platform-specific implementations, NowNanos() should return time points
// that are MONOTONIC.
virtual uint64_t NowNanos() { return NowMicros() * 1000; }
// Returns the number of micro-seconds of CPU time used by the current thread.
// 0 indicates not supported.
virtual uint64_t CPUMicros() { return 0; }
// Returns the number of nano-seconds of CPU time used by the current thread.
// Default implementation simply relies on CPUMicros.
// 0 indicates not supported.
virtual uint64_t CPUNanos() { return CPUMicros() * 1000; }
// Sleep/delay the thread for the prescribed number of micro-seconds.
virtual void SleepForMicroseconds(int micros) = 0;
// Get the number of seconds since the Epoch, 1970-01-01 00:00:00 (UTC).
// Only overwrites *unix_time on success.
virtual Status GetCurrentTime(int64_t* unix_time) = 0;
// Converts seconds-since-Jan-01-1970 to a printable string
virtual std::string TimeToString(uint64_t time) = 0;
};
// Wrapper class for a SystemClock. Redirects all methods (except Name)
// of the SystemClock interface to the target/wrapped class.
class SystemClockWrapper : public SystemClock {
public:
explicit SystemClockWrapper(const std::shared_ptr<SystemClock>& t);
uint64_t NowMicros() override { return target_->NowMicros(); }
uint64_t NowNanos() override { return target_->NowNanos(); }
uint64_t CPUMicros() override { return target_->CPUMicros(); }
uint64_t CPUNanos() override { return target_->CPUNanos(); }
virtual void SleepForMicroseconds(int micros) override {
return target_->SleepForMicroseconds(micros);
}
Status GetCurrentTime(int64_t* unix_time) override {
return target_->GetCurrentTime(unix_time);
}
std::string TimeToString(uint64_t time) override {
return target_->TimeToString(time);
}
Status PrepareOptions(const ConfigOptions& options) override;
#ifndef ROCKSDB_LITE
std::string SerializeOptions(const ConfigOptions& config_options,
const std::string& header) const override;
#endif // ROCKSDB_LITE
const Customizable* Inner() const override { return target_.get(); }
protected:
std::shared_ptr<SystemClock> target_;
};
} // end namespace ROCKSDB_NAMESPACE