rocksdb/include/rocksdb/system_clock.h
mrambacher 6924869867 Make SystemClock into a Customizable Class (#8636)
Summary:
Made SystemClock into a Customizable class, complete with CreateFromString.

Cleaned up some of the existing SystemClock implementations that were redundant (NoSleep was the same as the internal one for MockEnv).

Changed MockEnv construction to allow Clock to be passed to the Memory/MockFileSystem.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8636

Reviewed By: zhichao-cao

Differential Revision: D30483360

Pulled By: mrambacher

fbshipit-source-id: cd0e3a876c39f8c98fe13374c06e8edbd5b9f2a1
2021-09-21 09:23:48 -07:00

117 lines
4.2 KiB
C++

// 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 = 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