141 lines
3.6 KiB
C#
141 lines
3.6 KiB
C#
//------------------------------------------------------------
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//------------------------------------------------------------
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namespace System.IdentityModel
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{
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using System.Collections.Generic;
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// Embed this struct in a class to represent a field of that class
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// that is logically a list, but contains just one item in all but
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// the rarest of scenarios. When this class must be passed around
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// in internal APIs, use it as a ref parameter.
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struct MostlySingletonList<T> where T : class
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{
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int count;
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T singleton;
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List<T> list;
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public T this[int index]
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{
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get
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{
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if (this.list == null)
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{
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EnsureValidSingletonIndex(index);
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return this.singleton;
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}
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else
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{
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return this.list[index];
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}
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}
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}
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public int Count
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{
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get { return this.count; }
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}
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public void Add(T item)
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{
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if (this.list == null)
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{
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if (this.count == 0)
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{
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this.singleton = item;
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this.count = 1;
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return;
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}
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this.list = new List<T>();
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this.list.Add(this.singleton);
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this.singleton = null;
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}
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this.list.Add(item);
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this.count++;
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}
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static bool Compare(T x, T y)
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{
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return x == null ? y == null : x.Equals(y);
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}
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public bool Contains(T item)
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{
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return IndexOf(item) >= 0;
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}
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void EnsureValidSingletonIndex(int index)
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{
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if (this.count != 1 )
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{
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throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentOutOfRangeException("count", SR.GetString(SR.ValueMustBeOne)));
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}
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if (index != 0)
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{
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throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentOutOfRangeException("index", SR.GetString(SR.ValueMustBeZero)));
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}
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}
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bool MatchesSingleton(T item)
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{
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return this.count == 1 && Compare(this.singleton, item);
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}
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public int IndexOf(T item)
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{
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if (this.list == null)
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{
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return MatchesSingleton(item) ? 0 : -1;
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}
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else
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{
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return this.list.IndexOf(item);
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}
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}
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public bool Remove(T item)
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{
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if (this.list == null)
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{
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if (MatchesSingleton(item))
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{
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this.singleton = null;
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this.count = 0;
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return true;
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}
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else
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{
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return false;
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}
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}
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else
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{
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bool result = this.list.Remove(item);
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if (result)
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{
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this.count--;
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}
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return result;
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}
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}
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public void RemoveAt(int index)
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{
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if (this.list == null)
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{
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EnsureValidSingletonIndex(index);
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this.singleton = null;
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this.count = 0;
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}
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else
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{
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this.list.RemoveAt(index);
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this.count--;
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}
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}
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}
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}
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