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// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
namespace WixToolset.Dtf.Compression.Cab
{
using System;
using System.Collections.Generic;
/// <summary>
/// Generic class for managing allocations of integer handles
/// for objects of a certain type.
/// </summary>
/// <typeparam name="T">The type of objects the handles refer to.</typeparam>
internal sealed class HandleManager<T> where T : class
{
/// <summary>
/// Auto-resizing list of objects for which handles have been allocated.
/// Each handle is just an index into this list. When a handle is freed,
/// the list item at that index is set to null.
/// </summary>
private List<T> handles;
/// <summary>
/// Creates a new HandleManager instance.
/// </summary>
public HandleManager()
{
this.handles = new List<T>();
}
/// <summary>
/// Gets the object of a handle, or null if the handle is invalid.
/// </summary>
/// <param name="handle">The integer handle previously allocated
/// for the desired object.</param>
/// <returns>The object for which the handle was allocated.</returns>
public T this[int handle]
{
get
{
if (handle > 0 && handle <= this.handles.Count)
{
return this.handles[handle - 1];
}
else
{
return null;
}
}
}
/// <summary>
/// Allocates a new handle for an object.
/// </summary>
/// <param name="obj">Object that the handle will refer to.</param>
/// <returns>New handle that can be later used to retrieve the object.</returns>
public int AllocHandle(T obj)
{
this.handles.Add(obj);
int handle = this.handles.Count;
return handle;
}
/// <summary>
/// Frees a handle that was previously allocated. Afterward the handle
/// will be invalid and the object it referred to can no longer retrieved.
/// </summary>
/// <param name="handle">Handle to be freed.</param>
public void FreeHandle(int handle)
{
if (handle > 0 && handle <= this.handles.Count)
{
this.handles[handle - 1] = null;
}
}
}
}
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