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//------------------------------------------------------------------------------
// <copyright file="XmlNamedNodeMap.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
// <owner current="true" primary="true">lionelu</owner>
//------------------------------------------------------------------------------
namespace System.Xml {
using System.Collections;
partial class XmlNamedNodeMap {
// Optimized to minimize space in the zero or one element cases.
internal struct SmallXmlNodeList {
// If field is null, that represents an empty list.
// If field is non-null, but not an ArrayList, then the 'list' contains a single
// object.
// Otherwise, field is an ArrayList. Once the field upgrades to an ArrayList, it
// never degrades back, even if all elements are removed.
private object field;
public int Count {
get {
if (field == null)
return 0;
ArrayList list = field as ArrayList;
if (list != null)
return list.Count;
return 1;
}
}
public object this[int index] {
get {
if (field == null)
throw new ArgumentOutOfRangeException("index");
ArrayList list = field as ArrayList;
if (list != null)
return list[index];
if (index != 0)
throw new ArgumentOutOfRangeException("index");
return field;
}
}
public void Add(object value) {
if (field == null) {
if (value == null) {
// If a single null value needs to be stored, then
// upgrade to an ArrayList
ArrayList temp = new ArrayList();
temp.Add(null);
field = temp;
}
else
field = value;
return;
}
ArrayList list = field as ArrayList;
if (list != null) {
list.Add(value);
}
else {
list = new ArrayList();
list.Add(field);
list.Add(value);
field = list;
}
}
public void RemoveAt(int index) {
if (field == null)
throw new ArgumentOutOfRangeException("index");
ArrayList list = field as ArrayList;
if (list != null) {
list.RemoveAt(index);
return;
}
if (index != 0)
throw new ArgumentOutOfRangeException("index");
field = null;
}
public void Insert(int index, object value) {
if (field == null) {
if (index != 0)
throw new ArgumentOutOfRangeException("index");
Add(value);
return;
}
ArrayList list = field as ArrayList;
if (list != null) {
list.Insert(index, value);
return;
}
if (index == 0) {
list = new ArrayList();
list.Add(value);
list.Add(field);
field = list;
}
else if (index == 1) {
list = new ArrayList();
list.Add(field);
list.Add(value);
field = list;
}
else {
throw new ArgumentOutOfRangeException("index");
}
}
class SingleObjectEnumerator : IEnumerator {
object loneValue;
int position = -1;
public SingleObjectEnumerator(object value) {
loneValue = value;
}
public object Current {
get {
if (position != 0) {
throw new InvalidOperationException();
}
return this.loneValue;
}
}
public bool MoveNext() {
if (position < 0) {
position = 0;
return true;
}
position = 1;
return false;
}
public void Reset() {
position = -1;
}
}
public IEnumerator GetEnumerator() {
if (field == null) {
return XmlDocument.EmptyEnumerator;
}
ArrayList list = field as ArrayList;
if (list != null) {
return list.GetEnumerator();
}
return new SingleObjectEnumerator(field);
}
}
}
}
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