spell check, mostly in comments.
/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
* Copyright (c) 2008 University of Washington
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation;
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef SYNCHRONIZER_H
#define SYNCHRONIZER_H
#include <stdint.h>
#include "nstime.h"
#include "ns3/object.h"
namespace ns3 {
/**
* @brief Base class used for synchronizing the simulation events to some
* real time "wall clock."
*
* The simulation clock is maintained as a 64-bit integer in a unit specified
* by the user through the TimeStepPrecision::Set function. This means that
* it is not possible to specify event expiration times with anything better
* than this user-specified accuracy. We use this clock for the simulation
* time.
*
* The real-time clock is maintained as a 64-bit integer count of nanoseconds.
*
* The synchronization between the simulation clock and the real-time clock
* is maintained using a combination of sleep-waiting, busy-waiting and a
* feedback loop.
*/
class Synchronizer : public Object
{
public:
static TypeId GetTypeId (void);
Synchronizer ();
virtual ~Synchronizer ();
/**
* @brief Return true if this synchronizer is actually synchronizing to a
* realtime clock. The simulator sometimes needs to know this.
* @returns True if locked with realtime, false if not.
*/
bool Realtime (void);
/**
* @brief Retrieve the value of the origin of the underlying normalized wall
* clock time in simulator timestep units.
*
* @returns The normalized wall clock time (in simulator timestep units).
* @see TimeStepPrecision::Get
* @see Synchronizer::SetOrigin
*/
uint64_t GetCurrentRealtime (void);
/**
* @brief Establish a correspondence between a simulation time and the
* synchronizer real time.
*
* This method is expected to be called at the "instant" before simulation
* begins. At this point, simulation time = 0, and a
* set = 0 in this method. We then associate this time with the current
* value of the real time clock that will be used to actually perform the
* synchronization.
*
* Subclasses are expected to implement the corresponding DoSetOrigin pure
* virtual method to do the actual real-time-clock-specific work of making the
* correspondence mentioned above.
*
* @param ts The simulation time we should use as the origin (in simulator
* timestep units).
* @see TimeStepPrecision::Get
* @see TimeStepPrecision::DoSetOrigin
*/
void SetOrigin (uint64_t ts);
/**
* @brief Retrieve the value of the origin of the simulation time in
* simulator timestep units.
*
* @returns The simulation time used as the origin (in simulator timestep
* units).
* @see TimeStepPrecision::Get
* @see Synchronizer::SetOrigin
*/
uint64_t GetOrigin (void);
/**
* @brief Retrieve the difference between the real time clock used to
* synchronize the simulation and the simulation time (in simulator timestep
* units).
*
* @param ts Simulation timestep from the simulator interpreted as current time
* in the simulator.
* @returns Simulation timestep (in simulator timestep units) minus origin
* time (stored internally in nanosecond units).
* @see TimeStepPrecision::Get
* @see Synchronizer::SetOrigin
* @see Synchronizer::DoGetDrift
*/
int64_t GetDrift (uint64_t ts);
/**
* @brief Wait until the real time is in sync with the specified simulation
* time or until the synchronizer is Sigalled.
*
* This is where the real work of synchronization is done. The Time passed
* in as a parameter is the simulation time. The job of Synchronize is to
* translate from simulation time to synchronizer time (in a perfect world
* this is the same time) and then figure out how long in real-time it needs
* to wait until that synchronizer / simulation time comes around.
*
* Subclasses are expected to implement the corresponding DoSynchronize pure
* virtual method to do the actual real-time-clock-specific work of waiting
* (either busy-waiting or sleeping, or some combination thereof) until the
* requested simulation time.
*
* @param tsCurrent The current simulation time (in simulator timestep units).
* @param tsDelay The simulation time we need to wait for (in simulator
* timestep units).
* @returns True if the function ran to completion, false if it was interrupted
* by a Signal.
* @see TimeStepPrecision::Get
* @see Synchronizer::DoSynchronize
* @see Synchronizer::Signal
*/
bool Synchronize (uint64_t tsCurrent, uint64_t tsDelay);
/**
* @brief Tell a possible simulator thread waiting in the Synchronize method
* that an event has happened which demands a reevaluation of the wait time.
* This will cause the thread to wake and return to the simulator proper
* where it can get its bearings.
*
* @see Synchronizer::Synchronize
* @see Synchronizer::DoSignal
*/
void Signal (void);
/**
* @brief Set the condition variable that tells a possible simulator thread
* waiting in the Synchronize method that an event has happened which demands
* a reevaluation of the wait time.
*
* @see Synchronizer::Signal
*/
void SetCondition (bool);
/**
* @brief Ask the synchronizer to remember what time it is. Typically used
* with EventEnd to determine the real execution time of a simulation event.
*
* @see Synchronizer::EventEnd
* @see TimeStepPrecision::Get
*/
void EventStart (void);
/**
* @brief Ask the synchronizer to return the time step between the instant
* remembered during EventStart and now. Used in conjunction with EventStart
* to determine the real execution time of a simulation event.
*
* @see Synchronizer::EventStart
* @see TimeStepPrecision::Get
*/
uint64_t EventEnd (void);
protected:
/**
* @brief Establish a correspondence between a simulation time and a
* wall-clock (real) time.
*
* @internal
*
* There are three timelines involved here: the simulation time, the
* (absolute) wall-clock time and the (relative) synchronizer real time.
* Calling this method makes a correspondence between the origin of the
* synchronizer time and the current wall-clock time.
*
* This method is expected to be called at the "instant" before simulation
* begins. At this point, simulation time = 0, and synchronizer time is
* set = 0 in this method. We then associate this time with the current
* value of the real time clock that will be used to actually perform the
* synchronization.
*
* Subclasses are expected to implement this method to do the actual
* real-time-clock-specific work of making the correspondence mentioned above.
* for example, this is where the differences between Time parameters and
* parameters to clock_nanosleep would be dealt with.
*
* @param ns The simulation time we need to use as the origin (normalized to
* nanosecond units).
* @see Synchronizer::SetOrigin
* @see TimeStepPrecision::Get
*/
virtual void DoSetOrigin (uint64_t ns) = 0;
/**
* @brief Return true if this synchronizer is actually synchronizing to a
* realtime clock. The simulator sometimes needs to know this.
*
* @internal
*
* Subclasses are expected to implement this method to tell the outside world
* whether or not they are synchronizing to a realtime clock.
*
* @returns True if locked with realtime, false if not.
*/
virtual bool DoRealtime (void) = 0;
/**
* @brief Retrieve the value of the origin of the underlying normalized wall
* clock time in simulator timestep units.
*
* @internal
*
* Subclasses are expected to implement this method to do the actual
* real-time-clock-specific work of getting the current time.
*
* @returns The normalized wall clock time (in nanosecond units).
* @see TimeStepPrecision::Get
* @see Synchronizer::SetOrigin
*/
virtual uint64_t DoGetCurrentRealtime (void) = 0;
/**
* @brief Wait until the real time is in sync with the specified simulation
* time.
*
* @internal
*
* This is where the real work of synchronization is done. The Time passed
* in as a parameter is the simulation time. The job of Synchronize is to
* translate from simulation time to synchronizer time (in a perfect world
* this is the same time) and then figure out how long in real-time it needs
* to wait until that synchronizer / simulation time comes around.
*
* Subclasses are expected to implement this method to do the actual
* real-time-clock-specific work of waiting (either busy-waiting or sleeping,
* or some combination) until the requested simulation time.
*
* @param nsCurrent The current simulation time (normalized to nanosecond
* units).
* @param nsDelay The simulation time we need to wait for (normalized to
* nanosecond units).
* @returns True if the function ran to completion, false if it was interrupted
* by a Signal.
* @see Synchronizer::Synchronize
* @see TimeStepPrecision::Get
* @see Synchronizer::Signal
*/
virtual bool DoSynchronize (uint64_t nsCurrent, uint64_t nsDelay) = 0;
/**
* @brief Declaration of the method used to tell a possible simulator thread
* waiting in the DoSynchronize method that an event has happened which
* demands a reevaluation of the wait time.
*
* @see Synchronizer::Signal
*/
virtual void DoSignal (void) = 0;
/**
* @brief Declaration of the method used to set the condition variable that
* tells a possible simulator thread waiting in the Synchronize method that an
* event has happened which demands a reevaluation of the wait time.
*
* @see Synchronizer::SetCondition
*/
virtual void DoSetCondition (bool) = 0;
/**
* @brief Declaration of method used to retrieve drift between the real time
* clock used to synchronize the simulation and the current simulation time.
*
* @internal
*
* @param ns Simulation timestep from the simulator normalized to nanosecond
* steps.
* @returns Drift in nanosecond units.
* @see TimeStepPrecision::Get
* @see Synchronizer::SetOrigin
* @see Synchronizer::GetDrift
*/
virtual int64_t DoGetDrift (uint64_t ns) = 0;
virtual void DoEventStart (void) = 0;
virtual uint64_t DoEventEnd (void) = 0;
uint64_t m_realtimeOriginNano;
uint64_t m_simOriginNano;
private:
/**
* @brief Convert a simulator time step (which can be steps of time in a
* user-specified unit) to a normalized time step in nanosecond units.
*
* @internal
*
* @param ts The simulation time step to be normalized.
* @returns The simulation time step normalized to nanosecond units.
* @see TimeStepPrecision::Get
*/
uint64_t TimeStepToNanosecond (uint64_t ts);
/**
* @brief Convert a normalized nanosecond count into a simulator time step
* (which can be steps of time in a user-specified unit).
*
* @internal
*
* @param ns The nanosecond count step to be converted
* @returns The simulation time step to be interpreted in appropriate units.
* @see TimeStepPrecision::Get
*/
uint64_t NanosecondToTimeStep (uint64_t ns);
};
}; // namespace ns3
#endif /* SYNCHRONIZER_H */