289 lines
11 KiB
C#
289 lines
11 KiB
C#
#region Apache License 2.0
|
|
/*
|
|
Nuclex .NET Framework
|
|
Copyright (C) 2002-2024 Markus Ewald / Nuclex Development Labs
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
|
you may not use this file except in compliance with the License.
|
|
You may obtain a copy of the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
See the License for the specific language governing permissions and
|
|
limitations under the License.
|
|
*/
|
|
#endregion // Apache License 2.0
|
|
|
|
using System;
|
|
using System.Collections;
|
|
using System.Collections.Generic;
|
|
|
|
namespace Nuclex.Support.Collections {
|
|
|
|
/// <summary>Collection that transforms the contents of another collection.</summary>
|
|
/// <typeparam name="TContainedItem">
|
|
/// Type of the items contained in the wrapped collection.
|
|
/// </typeparam>
|
|
/// <typeparam name="TExposedItem">
|
|
/// Type this collection exposes its items as.
|
|
/// </typeparam>
|
|
/// <remarks>
|
|
/// <para>
|
|
/// This collection is useful if you want to expose the objects of an arbitrary
|
|
/// collection under a different type. It can be used, for example, to construct
|
|
/// wrappers for the items in a collection on-the-fly, eliminating the need to
|
|
/// manage the wrappers in parallel to the real items and improving performance
|
|
/// by only constructing a wrapper when an item is actually requested.
|
|
/// </para>
|
|
/// <para>
|
|
/// Another common use would be if you have a private collection of a non-public
|
|
/// type that's derived from some publicly visible type. By using this collection,
|
|
/// you can return the items under the publicly visible type while still having
|
|
/// your private collection under the non-public type, eliminating the need to
|
|
/// downcast each time you need to access elements of the non-public type.
|
|
/// </para>
|
|
/// </remarks>
|
|
public abstract partial class TransformingReadOnlyCollection<
|
|
TContainedItem, TExposedItem
|
|
> : IList<TExposedItem>, IList {
|
|
|
|
#region class TransformingEnumerator
|
|
|
|
/// <summary>
|
|
/// An enumerator that transforms the items returned by an enumerator of the
|
|
/// wrapped collection into the exposed type on-the-fly.
|
|
/// </summary>
|
|
private class TransformingEnumerator : IEnumerator<TExposedItem> {
|
|
|
|
/// <summary>Initializes a new transforming enumerator</summary>
|
|
/// <param name="transformer">Owner; used to invoke the Transform() method</param>
|
|
/// <param name="containedTypeEnumerator">Enumerator of the wrapped collection</param>
|
|
public TransformingEnumerator(
|
|
TransformingReadOnlyCollection<TContainedItem, TExposedItem> transformer,
|
|
IEnumerator<TContainedItem> containedTypeEnumerator
|
|
) {
|
|
this.transformer = transformer;
|
|
this.containedTypeEnumerator = containedTypeEnumerator;
|
|
}
|
|
|
|
/// <summary>Immediately releases all resources used by the instance</summary>
|
|
public void Dispose() {
|
|
this.containedTypeEnumerator.Dispose();
|
|
}
|
|
|
|
/// <summary>
|
|
/// The element in the collection at the current position of the enumerator.
|
|
/// </summary>
|
|
public TExposedItem Current {
|
|
get {
|
|
return this.transformer.Transform(this.containedTypeEnumerator.Current);
|
|
}
|
|
}
|
|
|
|
/// <summary>Gets the current element in the collection.</summary>
|
|
/// <returns>The current element in the collection.</returns>
|
|
/// <exception cref="System.InvalidOperationException">
|
|
/// The enumerator is positioned before the first element of the collection
|
|
/// or after the last element.
|
|
/// </exception>
|
|
public bool MoveNext() {
|
|
return this.containedTypeEnumerator.MoveNext();
|
|
}
|
|
|
|
/// <summary>
|
|
/// Sets the enumerator to its initial position, which is before the first element
|
|
/// in the collection.
|
|
/// </summary>
|
|
/// <exception cref="System.InvalidOperationException">
|
|
/// The collection was modified after the enumerator was created.
|
|
/// </exception>
|
|
public void Reset() {
|
|
this.containedTypeEnumerator.Reset();
|
|
}
|
|
|
|
/// <summary>The current element in the collection.</summary>
|
|
/// <exception cref="System.InvalidOperationException">
|
|
/// The enumerator is positioned before the first element of the collection
|
|
/// or after the last element.
|
|
/// </exception>
|
|
object IEnumerator.Current {
|
|
get { return Current; }
|
|
}
|
|
|
|
/// <summary>
|
|
/// Collection that owns this enumerator; required to invoke the item
|
|
/// transformation method.
|
|
/// </summary>
|
|
private TransformingReadOnlyCollection<TContainedItem, TExposedItem> transformer;
|
|
/// <summary>An enumerator from the wrapped collection</summary>
|
|
private IEnumerator<TContainedItem> containedTypeEnumerator;
|
|
|
|
}
|
|
|
|
#endregion // class TransformingEnumerator
|
|
|
|
/// <summary>Initializes a new transforming collection wrapper</summary>
|
|
/// <param name="items">
|
|
/// Internal list of items that are transformed into the exposed type when
|
|
/// accessed through the TransformingReadOnlyCollection.
|
|
/// </param>
|
|
public TransformingReadOnlyCollection(IList<TContainedItem> items) {
|
|
this.items = items;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Determines whether an element is in the TransformingReadOnlyCollection
|
|
/// </summary>
|
|
/// <param name="item">
|
|
/// The object to locate in the TransformingReadOnlyCollection.
|
|
/// The value can be null for reference types.
|
|
/// </param>
|
|
/// <returns>
|
|
/// True if value is found in the TransformingReadOnlyCollection; otherwise, false.
|
|
/// </returns>
|
|
/// <remarks>
|
|
/// The default implementation of this method is very unoptimized and will
|
|
/// enumerate all the items in the collection, transforming one after another
|
|
/// to check whether the transformed item matches the item the user was
|
|
/// looking for. It is recommended to provide a custom implementation of
|
|
/// this method, if possible.
|
|
/// </remarks>
|
|
public virtual bool Contains(TExposedItem item) {
|
|
return (IndexOf(item) != -1);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Copies the entire TransformingReadOnlyCollection to a compatible one-dimensional
|
|
/// System.Array, starting at the specified index of the target array.
|
|
/// </summary>
|
|
/// <param name="array">
|
|
/// The one-dimensional System.Array that is the destination of the elements copied
|
|
/// from the TransformingReadOnlyCollection. The System.Array must have
|
|
/// zero-based indexing.
|
|
/// </param>
|
|
/// <param name="index">
|
|
/// The zero-based index in array at which copying begins.
|
|
/// </param>
|
|
/// <exception cref="System.ArgumentException">
|
|
/// Index is equal to or greater than the length of array or the number of elements
|
|
/// in the source TransformingReadOnlyCollection is greater than the available space
|
|
/// from index to the end of the destination array.
|
|
/// </exception>
|
|
/// <exception cref="System.ArgumentOutOfRangeException">
|
|
/// Index is less than zero.
|
|
/// </exception>
|
|
/// <exception cref="System.ArgumentNullException">
|
|
/// Array is null.
|
|
/// </exception>
|
|
public void CopyTo(TExposedItem[] array, int index) {
|
|
if(this.items.Count > (array.Length - index)) {
|
|
throw new ArgumentException(
|
|
"Array too small to fit the collection items starting at the specified index"
|
|
);
|
|
}
|
|
|
|
for(int itemIndex = 0; itemIndex < this.items.Count; ++itemIndex) {
|
|
array[itemIndex + index] = Transform(this.items[itemIndex]);
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Returns an enumerator that iterates through the TransformingReadOnlyCollection.
|
|
/// </summary>
|
|
/// <returns>
|
|
/// An enumerator or the TransformingReadOnlyCollection.
|
|
/// </returns>
|
|
public IEnumerator<TExposedItem> GetEnumerator() {
|
|
return new TransformingEnumerator(this, this.items.GetEnumerator());
|
|
}
|
|
|
|
/// <summary>
|
|
/// Searches for the specified object and returns the zero-based index of the
|
|
/// first occurrence within the entire TransformingReadOnlyCollection.
|
|
/// </summary>
|
|
/// <param name="item">
|
|
/// The object to locate in the TransformingReadOnlyCollection. The value can
|
|
/// be null for reference types.
|
|
/// </param>
|
|
/// <returns>
|
|
/// The zero-based index of the first occurrence of item within the entire
|
|
/// TransformingReadOnlyCollection, if found; otherwise, -1.
|
|
/// </returns>
|
|
/// <remarks>
|
|
/// The default implementation of this method is very unoptimized and will
|
|
/// enumerate all the items in the collection, transforming one after another
|
|
/// to check whether the transformed item matches the item the user was
|
|
/// looking for. It is recommended to provide a custom implementation of
|
|
/// this method, if possible.
|
|
/// </remarks>
|
|
public int IndexOf(TExposedItem item) {
|
|
|
|
if(item == null) {
|
|
|
|
for(int index = 0; index < this.items.Count; ++index) {
|
|
if(Transform(this.items[index]) == null) {
|
|
return index;
|
|
}
|
|
}
|
|
|
|
} else {
|
|
|
|
var comparer = EqualityComparer<TExposedItem>.Default;
|
|
for(int index = 0; index < this.items.Count; ++index) {
|
|
if(comparer.Equals(Transform(this.items[index]), item)) {
|
|
return index;
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
return -1;
|
|
|
|
}
|
|
|
|
/// <summary>
|
|
/// The number of elements contained in the TransformingReadOnlyCollection instance
|
|
/// </summary>
|
|
public int Count {
|
|
get { return this.items.Count; }
|
|
}
|
|
|
|
/// <summary>Gets the element at the specified index.</summary>
|
|
/// <param name="index">The zero-based index of the element to get.</param>
|
|
/// <returns>The element at the specified index.</returns>
|
|
/// <exception cref="System.ArgumentOutOfRangeException">
|
|
/// Index is less than zero or index is equal to or greater than
|
|
/// TransformingReadOnlyCollection.Count.
|
|
/// </exception>
|
|
public TExposedItem this[int index] {
|
|
get { return Transform(this.items[index]); }
|
|
}
|
|
|
|
/// <summary>Whether the List is write-protected</summary>
|
|
public bool IsReadOnly {
|
|
get { return true; }
|
|
}
|
|
|
|
/// <summary>Transforms an item into the exposed type</summary>
|
|
/// <param name="item">Item to be transformed</param>
|
|
/// <returns>The transformed item</returns>
|
|
/// <remarks>
|
|
/// This method is used to transform an item in the wrapped collection into
|
|
/// the exposed item type whenever the user accesses an item. Expect it to
|
|
/// be called frequently, because the TransformingReadOnlyCollection does
|
|
/// not cache or otherwise store the transformed items.
|
|
/// </remarks>
|
|
protected abstract TExposedItem Transform(TContainedItem item);
|
|
|
|
/// <summary>Items being transformed upon exposure by this collection</summary>
|
|
private IList<TContainedItem> items;
|
|
/// <summary>Synchronization root for threaded accesses to this collection</summary>
|
|
private object syncRoot;
|
|
|
|
}
|
|
|
|
} // namespace Nuclex.Support.Collections
|