[12657] | 1 | #region License Information
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| 2 | /* SimSharp - A .NET port of SimPy, discrete event simulation framework
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[14185] | 3 | Copyright (C) 2002-2016 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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[12657] | 4 |
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| 5 | This program is free software: you can redistribute it and/or modify
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| 6 | it under the terms of the GNU General Public License as published by
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| 7 | the Free Software Foundation, either version 3 of the License, or
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| 8 | (at your option) any later version.
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| 9 |
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| 10 | This program is distributed in the hope that it will be useful,
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | GNU General Public License for more details.
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| 14 |
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| 15 | You should have received a copy of the GNU General Public License
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| 16 | along with this program. If not, see <http://www.gnu.org/licenses/>.*/
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| 17 | #endregion
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| 18 |
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| 19 | using System;
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| 20 | using System.Collections.Generic;
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| 21 |
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| 22 | namespace SimSharp {
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| 23 | /// <summary>
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| 24 | /// A Process handles the iteration of events. Processes may define steps that
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| 25 | /// a certain entity in the simulation has to perform. Each time the process
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| 26 | /// should wait it yields an event and will be resumed when that event is processed.
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| 27 | /// </summary>
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| 28 | /// <remarks>
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| 29 | /// Since an iterator method does not have access to its process, the method can
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| 30 | /// retrieve the associated Process through the ActiveProcess property of the
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| 31 | /// environment. Each Process sets and resets that property during Resume.
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| 32 | /// </remarks>
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| 33 | public class Process : Event {
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| 34 | private readonly IEnumerator<Event> generator;
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| 35 | private Event target;
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| 36 | /// <summary>
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| 37 | /// Target is the event that is expected to be executed next in the process.
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| 38 | /// </summary>
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| 39 | public Event Target {
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| 40 | get { return target; }
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| 41 | protected set { target = value; }
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| 42 | }
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| 43 |
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| 44 | public Process(Environment environment, IEnumerable<Event> generator)
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| 45 | : base(environment) {
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| 46 | this.generator = generator.GetEnumerator();
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| 47 | IsOk = true;
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| 48 | target = new Initialize(environment, this);
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| 49 | }
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| 50 |
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| 51 | /// <summary>
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| 52 | /// This interrupts a process and causes the IsOk flag to be set to false.
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| 53 | /// If a process is interrupted the iterator method needs to call HandleFault()
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| 54 | /// before continuing to yield further events.
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| 55 | /// </summary>
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| 56 | /// <exception cref="InvalidOperationException">This is thrown in three conditions:
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| 57 | /// - If the process has already been triggered.
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| 58 | /// - If the process attempts to interrupt itself.
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| 59 | /// - If the process continues to yield events despite being faulted.</exception>
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| 60 | /// <param name="cause">The cause of the interrupt.</param>
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| 61 | public virtual void Interrupt(object cause = null) {
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| 62 | if (IsTriggered) throw new InvalidOperationException("The process has terminated and cannot be interrupted.");
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| 63 | if (Environment.ActiveProcess == this) throw new InvalidOperationException("A process is not allowed to interrupt itself.");
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| 64 |
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| 65 | var interruptEvent = new Event(Environment);
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| 66 | interruptEvent.AddCallback(Resume);
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| 67 | interruptEvent.Fail(cause);
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| 68 |
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| 69 | if (Target != null)
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| 70 | Target.RemoveCallback(Resume);
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| 71 | }
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| 72 |
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| 73 | protected virtual void Resume(Event @event) {
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| 74 | Environment.ActiveProcess = this;
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| 75 | while (true) {
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| 76 | if (@event.IsOk) {
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| 77 | if (generator.MoveNext()) {
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| 78 | if (IsTriggered) {
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| 79 | // the generator called e.g. Environment.ActiveProcess.Fail
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| 80 | Environment.ActiveProcess = null;
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| 81 | return;
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| 82 | }
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| 83 | if (ProceedToEvent()) break;
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| 84 | } else if (!IsTriggered) {
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| 85 | Succeed(@event.Value);
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| 86 | break;
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| 87 | } else break;
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| 88 | } else {
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| 89 | /* Fault handling differs from SimPy as in .NET it is not possible to inject an
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| 90 | * exception into an enumerator and it is impossible to put a yield return inside
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| 91 | * a try-catch block. In SimSharp the Process will set IsOk and will then move to
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| 92 | * the next yield in the generator. However, if after this move IsOk is still false
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| 93 | * we know that the error was not handled. It is assumed the error is handled if
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| 94 | * HandleFault() is called on the environment's ActiveProcess which will reset the
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| 95 | * flag. */
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| 96 | IsOk = false;
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| 97 | Value = @event.Value;
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| 98 |
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| 99 | if (generator.MoveNext()) {
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| 100 | if (IsTriggered) {
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| 101 | // the generator called e.g. Environment.ActiveProcess.Fail
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| 102 | Environment.ActiveProcess = null;
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| 103 | return;
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| 104 | }
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| 105 | // if we move next, but IsOk is still false
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| 106 | if (!IsOk) throw new InvalidOperationException("The process did not react to being faulted.");
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| 107 | // otherwise HandleFault was called and the fault was handled
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| 108 | if (ProceedToEvent()) break;
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| 109 | } else if (!IsTriggered) {
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| 110 | if (!IsOk) Fail(@event.Value);
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| 111 | else Succeed(@event.Value);
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| 112 | break;
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| 113 | } else break;
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| 114 | }
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| 115 | }
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| 116 | Environment.ActiveProcess = null;
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| 117 | }
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| 118 |
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| 119 | protected virtual bool ProceedToEvent() {
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| 120 | target = generator.Current;
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| 121 | Value = target.Value;
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| 122 | if (target.IsProcessed) return false;
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| 123 | target.AddCallback(Resume);
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| 124 | return true;
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| 125 | }
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| 126 |
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| 127 | /// <summary>
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| 128 | /// This method must be called to reset the IsOk flag of the process back to true.
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| 129 | /// The IsOk flag may be set to false if the process waited on an event that failed.
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| 130 | /// </summary>
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| 131 | /// <remarks>
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| 132 | /// In SimPy a faulting process would throw an exception which is then catched and
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| 133 | /// chained. In SimSharp catching exceptions from a yield is not possible as a yield
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| 134 | /// return statement may not throw an exception.
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| 135 | /// If a processes faulted the Value property may indicate a cause for the fault.
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| 136 | /// </remarks>
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| 137 | /// <returns>True if a faulting situation needs to be handled, false if the process
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| 138 | /// is okay and the last yielded event succeeded.</returns>
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| 139 | public virtual bool HandleFault() {
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| 140 | if (IsOk) return false;
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| 141 | IsOk = true;
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| 142 | return true;
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| 143 | }
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| 144 |
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| 145 | private class Initialize : Event {
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| 146 | public Initialize(Environment environment, Process process)
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| 147 | : base(environment) {
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| 148 | CallbackList.Add(process.Resume);
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| 149 | IsOk = true;
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| 150 | IsTriggered = true;
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| 151 | environment.Schedule(this);
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| 152 | }
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| 153 | }
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| 154 | }
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| 155 | }
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