Circular Iterator : IEnumerator « Data Structure « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. Data Structure
3. IEnumerator

/*
Quote from
Accelerated C# 2005
# By Trey Nash
# ISBN: 1-59059-717-6
# 432 pp.
# Published: Aug 2006
*/

using System;
using System.Collections;
using System.Collections.Generic;

public class MainClass
{
    static void Main() {
        LinkedList<int> intList = new LinkedList<int>();
        for( int i = 1; i < 6; ++i ) {
            intList.AddLast( i );
        }

        CircularIterator<int> iter = new CircularIterator<int>(intList, intList.First);

        int counter = 0;
        foreach( int n in iter ) {
            Console.WriteLine( n );

            if( counter++ == 100 ) {
                iter.Stop();
            }
        }
    }
}

public class CircularIterator<T> : IEnumerable<T>
{
    public CircularIterator( LinkedList<T> list, LinkedListNode<T> start ) {
        enumerator = CreateEnumerator( list, start, false ).GetEnumerator();
        enumType = enumerator.GetType();
    }

    public void Stop() {
        enumType.GetField("stop").SetValue( enumerator, true );
    }

    private IEnumerator<T> enumerator;
    private Type enumType;

    private IEnumerable<T> CreateEnumerator( LinkedList<T> list, LinkedListNode<T> start, bool stop ) {
        LinkedListNode<T> current = null;
        do {
            if( current == null ) {
                current = start;
            } else {
                current = current.Next;
                if( current == null ) {
                    current = start;
                }
            }

            yield return current.Value;
        } while( !stop );
    }

    public IEnumerator<T> GetEnumerator() {
        return enumerator;
    }

    IEnumerator IEnumerable.GetEnumerator() {
        return GetEnumerator();
    }
}

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