A Discrete-Event Network Simulator
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scheduler.h
Go to the documentation of this file.
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/*
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* Copyright (c) 2005 INRIA
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*
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* SPDX-License-Identifier: GPL-2.0-only
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*
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* Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
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*/
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#ifndef SCHEDULER_H
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#define SCHEDULER_H
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#include "
object.h
"
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#include <stdint.h>
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/**
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* \file
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* \ingroup scheduler
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* \ingroup events
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* ns3::Scheduler abstract base class, ns3::Scheduler::Event and
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* ns3::Scheduler::EventKey declarations.
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*/
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namespace
ns3
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{
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class
EventImpl;
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/**
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* \ingroup core
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* \defgroup scheduler Scheduler and Events
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* \brief Manage the event list by creating and scheduling events.
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*/
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/**
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* \ingroup scheduler
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* \defgroup events Events
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*/
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/**
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* \ingroup scheduler
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* \brief Maintain the event list
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*
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*
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* In ns-3 the Scheduler manages the future event list. There are several
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* different Scheduler implementations with different time and space tradeoffs.
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* Which one is "best" depends in part on the characteristics
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* of the model being executed. For optimized production work common
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* practice is to benchmark each Scheduler on the model of interest.
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* The utility program utils/bench-scheduler.cc can do simple benchmarking
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* of each SchedulerImpl against an exponential or user-provided
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* event time distribution.
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*
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* The most important Scheduler functions for time performance are (usually)
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* Scheduler::Insert (for new events) and Scheduler::RemoveNext (for pulling
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* off the next event to execute). Simulator::Cancel is usually
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* implemented by simply setting a bit on the Event, but leaving it in the
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* Scheduler; the Simulator just skips those events as they are encountered.
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*
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* For models which need a large event list the Scheduler overhead
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* and per-event memory cost could also be important. Some models
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* rely heavily on Scheduler::Cancel, however, and these might benefit
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* from using Scheduler::Remove instead, to reduce the size of the event
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* list, at the time cost of actually removing events from the list.
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*
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* A summary of the main characteristics
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* of each SchedulerImpl is provided below. See the individual
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* Scheduler pages for details on the complexity of the other API calls.
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* (Memory overheads assume pointers and `std::size_t` are both 8 bytes.)
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*
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* <table class="markdownTable">
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* <tr class="markdownTableHead">
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* <th class="markdownTableHeadCenter" colspan="2"> %Scheduler Type </th>
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* <th class="markdownTableHeadCenter" colspan="4">Complexity</th>
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* </tr>
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* <tr class="markdownTableHead">
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* <th class="markdownTableHeadLeft" rowspan="2"> %SchedulerImpl </th>
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* <th class="markdownTableHeadLeft" rowspan="2"> Method </th>
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* <th class="markdownTableHeadCenter" colspan="2"> %Time </th>
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* <th class="markdownTableHeadCenter" colspan="2"> Space</th>
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* </tr>
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* <tr class="markdownTableHead">
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* <th class="markdownTableHeadLeft"> %Insert()</th>
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* <th class="markdownTableHeadLeft"> %RemoveNext()</th>
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* <th class="markdownTableHeadLeft"> Overhead</th>
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* <th class="markdownTableHeadLeft"> Per %Event</th>
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* </tr>
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* <tr class="markdownTableBody">
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* <td class="markdownTableBodyLeft"> CalendarScheduler </td>
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* <td class="markdownTableBodyLeft"> `<std::list> []` </td>
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* <td class="markdownTableBodyLeft"> Constant </td>
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* <td class="markdownTableBodyLeft"> Constant </td>
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* <td class="markdownTableBodyLeft"> 24 bytes </td>
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* <td class="markdownTableBodyLeft"> 16 bytes </td>
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* </tr>
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* <tr class="markdownTableBody">
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* <td class="markdownTableBodyLeft"> HeapScheduler </td>
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* <td class="markdownTableBodyLeft"> Heap on `std::vector` </td>
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* <td class="markdownTableBodyLeft"> Logarithmic </td>
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* <td class="markdownTableBodyLeft"> Logarithmic </td>
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* <td class="markdownTableBodyLeft"> 24 bytes </td>
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* <td class="markdownTableBodyLeft"> 0 </td>
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* </tr>
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* <tr class="markdownTableBody">
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* <td class="markdownTableBodyLeft"> ListScheduler </td>
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* <td class="markdownTableBodyLeft"> `std::list` </td>
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* <td class="markdownTableBodyLeft"> Linear </td>
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* <td class="markdownTableBodyLeft"> Constant </td>
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* <td class="markdownTableBodyLeft"> 24 bytes </td>
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* <td class="markdownTableBodyLeft"> 16 bytes </td>
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* </tr>
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* <tr class="markdownTableBody">
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* <td class="markdownTableBodyLeft"> MapScheduler </td>
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* <td class="markdownTableBodyLeft"> `std::map` </td>
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* <td class="markdownTableBodyLeft"> Logarithmic </td>
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* <td class="markdownTableBodyLeft"> Constant </td>
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* <td class="markdownTableBodyLeft"> 40 bytes </td>
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* <td class="markdownTableBodyLeft"> 32 bytes </td>
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* </tr>
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* <tr class="markdownTableBody">
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* <td class="markdownTableBodyLeft"> PriorityQueueScheduler </td>
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* <td class="markdownTableBodyLeft"> `std::priority_queue<,std::vector>` </td>
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* <td class="markdownTableBodyLeft"> Logarithmic </td>
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* <td class="markdownTableBodyLeft"> Logarithmic </td>
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* <td class="markdownTableBodyLeft"> 24 bytes </td>
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* <td class="markdownTableBodyLeft"> 0 </td>
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* </tr>
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* </table>
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*
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* It is possible to change the Scheduler choice during a simulation,
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* via Simulator::SetScheduler.
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*
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* The Scheduler base class specifies the interface used to maintain the
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* event list. If you want to provide a new event list scheduler,
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* you need to create a subclass of this base class and implement
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* all the pure virtual methods defined here.
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*
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* The only tricky aspect of this API is the memory management of
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* the EventImpl pointer which is a member of the Event data structure.
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* The lifetime of this pointer is assumed to always be longer than
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* the lifetime of the Scheduler class which means that the caller
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* is responsible for ensuring that this invariant holds through
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* calling EventId::Ref and SimpleRefCount::Unref at the right time.
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* Typically, EventId::Ref is called before Insert and SimpleRefCount::Unref is called
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* after a call to one of the Remove methods.
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*/
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class
Scheduler
:
public
Object
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{
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public
:
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/**
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* Register this type.
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* \return The object TypeId.
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*/
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static
TypeId
GetTypeId
();
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/**
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* \ingroup events
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* Structure for sorting and comparing Events.
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*/
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struct
EventKey
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{
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uint64_t
m_ts
;
/**< Event time stamp. */
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uint32_t
m_uid
;
/**< Event unique id. */
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uint32_t
m_context
;
/**< Event context. */
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};
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/**
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* \ingroup events
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* Scheduler event.
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*
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* An Event consists of an EventKey, used for maintaining the schedule,
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* and an EventImpl which is the actual implementation.
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*/
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struct
Event
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{
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EventImpl
*
impl
;
/**< Pointer to the event implementation. */
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EventKey
key
;
/**< Key for sorting and ordering Events. */
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};
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/** Destructor. */
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~Scheduler
()
override
= 0;
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/**
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* Insert a new Event in the schedule.
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*
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* \param [in] ev Event to store in the event list
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*/
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virtual
void
Insert
(
const
Event
& ev) = 0;
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/**
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* Test if the schedule is empty.
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*
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* \returns \c true if the event list is empty and \c false otherwise.
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*/
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virtual
bool
IsEmpty
()
const
= 0;
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/**
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* Get a pointer to the next event.
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*
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* This method cannot be invoked if the list is empty.
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*
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* \returns A pointer to the next earliest event. The caller
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* takes ownership of the returned pointer.
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*/
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virtual
Event
PeekNext
()
const
= 0;
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/**
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* Remove the earliest event from the event list.
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*
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* This method cannot be invoked if the list is empty.
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*
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* \return The Event.
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*/
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virtual
Event
RemoveNext
() = 0;
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/**
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* Remove a specific event from the event list.
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*
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* This method cannot be invoked if the list is empty.
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*
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* \param [in] ev The event to remove
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*/
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virtual
void
Remove
(
const
Event
& ev) = 0;
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};
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/**
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* \ingroup events
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* Compare (equal) two events by EventKey.
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*
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* \param [in] a The first event.
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* \param [in] b The second event.
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* \returns \c true if \c a != \c b
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*/
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inline
bool
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operator==
(
const
Scheduler::EventKey
& a,
const
Scheduler::EventKey
& b)
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{
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return
a.
m_uid
== b.
m_uid
;
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}
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/**
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* \ingroup events
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* Compare (not equal) two events by EventKey.
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*
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* \param [in] a The first event.
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* \param [in] b The second event.
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* \returns \c true if \c a != \c b
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*/
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inline
bool
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operator!=
(
const
Scheduler::EventKey
& a,
const
Scheduler::EventKey
& b)
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{
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return
a.
m_uid
!= b.
m_uid
;
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}
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/**
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* \ingroup events
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* Compare (less than) two events by EventKey.
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*
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* Note the invariants which this function must provide:
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* - irreflexibility: f (x,x) is false
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* - antisymmetry: f(x,y) = !f(y,x)
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* - transitivity: f(x,y) and f(y,z) => f(x,z)
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*
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* \param [in] a The first event.
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* \param [in] b The second event.
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* \returns \c true if \c a < \c b
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*/
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inline
bool
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operator<
(
const
Scheduler::EventKey
& a,
const
Scheduler::EventKey
& b)
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{
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return
(a.
m_ts
< b.
m_ts
|| (a.
m_ts
== b.
m_ts
&& a.
m_uid
< b.
m_uid
));
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}
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/**
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* Compare (greater than) two events by EventKey.
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*
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* \param [in] a The first event.
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* \param [in] b The second event.
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* \returns \c true if \c a > \c b
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*/
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inline
bool
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operator>
(
const
Scheduler::EventKey
& a,
const
Scheduler::EventKey
& b)
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{
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return
(a.
m_ts
> b.
m_ts
|| (a.
m_ts
== b.
m_ts
&& a.
m_uid
> b.
m_uid
));
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}
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/**
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* Compare (equal) two events by Event.
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*
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* \param [in] a The first event.
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* \param [in] b The second event.
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* \returns \c true if \c a == \c b
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*/
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inline
bool
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operator==
(
const
Scheduler::Event
& a,
const
Scheduler::Event
& b)
289
{
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return
a.
key
== b.
key
;
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}
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/**
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* Compare (not equal) two events by Event.
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*
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* \param [in] a The first event.
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* \param [in] b The second event.
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* \returns \c true if \c a != \c b
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*/
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inline
bool
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operator!=
(
const
Scheduler::Event
& a,
const
Scheduler::Event
& b)
302
{
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return
a.
key
!= b.
key
;
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}
305
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/**
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* Compare (less than) two events by Event.
308
*
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* \param [in] a The first event.
310
* \param [in] b The second event.
311
* \returns \c true if \c a < \c b
312
*/
313
inline
bool
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operator<
(
const
Scheduler::Event
& a,
const
Scheduler::Event
& b)
315
{
316
return
a.
key
< b.
key
;
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}
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/**
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* Compare (greater than) two events by Event.
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*
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* \param [in] a The first event.
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* \param [in] b The second event.
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* \returns \c true if \c a > \c b
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*/
326
inline
bool
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operator>
(
const
Scheduler::Event
& a,
const
Scheduler::Event
& b)
328
{
329
return
a.
key
> b.
key
;
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}
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}
// namespace ns3
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#endif
/* SCHEDULER_H */
ns3::EventImpl
A simulation event.
Definition
event-impl.h:35
ns3::Object
A base class which provides memory management and object aggregation.
Definition
object.h:78
ns3::Scheduler
Maintain the event list.
Definition
scheduler.h:146
ns3::Scheduler::~Scheduler
~Scheduler() override=0
Destructor.
Definition
scheduler.cc:27
ns3::Scheduler::IsEmpty
virtual bool IsEmpty() const =0
Test if the schedule is empty.
ns3::Scheduler::GetTypeId
static TypeId GetTypeId()
Register this type.
Definition
scheduler.cc:33
ns3::Scheduler::Remove
virtual void Remove(const Event &ev)=0
Remove a specific event from the event list.
ns3::Scheduler::PeekNext
virtual Event PeekNext() const =0
Get a pointer to the next event.
ns3::Scheduler::Insert
virtual void Insert(const Event &ev)=0
Insert a new Event in the schedule.
ns3::Scheduler::RemoveNext
virtual Event RemoveNext()=0
Remove the earliest event from the event list.
ns3::TypeId
a unique identifier for an interface.
Definition
type-id.h:48
uint32_t
ns3::operator>
bool operator>(const Length &left, const Length &right)
Check if left has a value greater than right.
Definition
length.cc:410
ns3
Every class exported by the ns3 library is enclosed in the ns3 namespace.
ns3::operator!=
bool operator!=(Callback< R, Args... > a, Callback< R, Args... > b)
Inequality test.
Definition
callback.h:658
ns3::operator==
bool operator==(const EventId &a, const EventId &b)
Definition
event-id.h:155
ns3::operator<
bool operator<(const EventId &a, const EventId &b)
Definition
event-id.h:168
object.h
ns3::Object class declaration, which is the root of the Object hierarchy and Aggregation.
ns3::Scheduler::Event
Scheduler event.
Definition
scheduler.h:173
ns3::Scheduler::Event::key
EventKey key
Key for sorting and ordering Events.
Definition
scheduler.h:175
ns3::Scheduler::Event::impl
EventImpl * impl
Pointer to the event implementation.
Definition
scheduler.h:174
ns3::Scheduler::EventKey
Structure for sorting and comparing Events.
Definition
scheduler.h:159
ns3::Scheduler::EventKey::m_context
uint32_t m_context
Event context.
Definition
scheduler.h:162
ns3::Scheduler::EventKey::m_ts
uint64_t m_ts
Event time stamp.
Definition
scheduler.h:160
ns3::Scheduler::EventKey::m_uid
uint32_t m_uid
Event unique id.
Definition
scheduler.h:161
src
core
model
scheduler.h
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