mirror of
https://github.com/chylex/.NET-Community-Toolkit.git
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155 lines
5.0 KiB
C#
155 lines
5.0 KiB
C#
// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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using System;
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using System.Collections.Generic;
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using System.ComponentModel;
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using System.Runtime.CompilerServices;
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using System.Runtime.InteropServices;
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namespace CommunityToolkit.HighPerformance.Enumerables;
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/// <summary>
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/// A <see langword="ref"/> <see langword="struct"/> that enumerates the items in a given <see cref="ReadOnlySpan{T}"/> instance.
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/// </summary>
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/// <typeparam name="T">The type of items to enumerate.</typeparam>
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[EditorBrowsable(EditorBrowsableState.Never)]
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public ref struct ReadOnlySpanEnumerable<T>
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{
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/// <summary>
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/// The source <see cref="ReadOnlySpan{T}"/> instance.
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/// </summary>
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private readonly ReadOnlySpan<T> span;
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/// <summary>
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/// The current index within <see cref="span"/>.
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/// </summary>
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private int index;
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/// <summary>
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/// Initializes a new instance of the <see cref="ReadOnlySpanEnumerable{T}"/> struct.
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/// </summary>
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/// <param name="span">The source <see cref="ReadOnlySpan{T}"/> instance.</param>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public ReadOnlySpanEnumerable(ReadOnlySpan<T> span)
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{
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this.span = span;
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this.index = -1;
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}
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/// <summary>
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/// Implements the duck-typed <see cref="IEnumerable{T}.GetEnumerator"/> method.
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/// </summary>
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/// <returns>An <see cref="ReadOnlySpanEnumerable{T}"/> instance targeting the current <see cref="ReadOnlySpan{T}"/> value.</returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public readonly ReadOnlySpanEnumerable<T> GetEnumerator() => this;
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/// <summary>
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/// Implements the duck-typed <see cref="System.Collections.IEnumerator.MoveNext"/> method.
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/// </summary>
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/// <returns><see langword="true"/> whether a new element is available, <see langword="false"/> otherwise</returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public bool MoveNext()
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{
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return ++this.index < this.span.Length;
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}
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/// <summary>
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/// Gets the duck-typed <see cref="IEnumerator{T}.Current"/> property.
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/// </summary>
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public readonly Item Current
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{
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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get
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{
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#if NETSTANDARD2_1_OR_GREATER
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ref T r0 = ref MemoryMarshal.GetReference(this.span);
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ref T ri = ref Unsafe.Add(ref r0, (nint)(uint)this.index);
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// See comment in SpanEnumerable<T> about this
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return new(ref ri, this.index);
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#else
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return new(this.span, this.index);
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#endif
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}
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}
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/// <summary>
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/// An item from a source <see cref="Span{T}"/> instance.
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/// </summary>
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[EditorBrowsable(EditorBrowsableState.Never)]
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public readonly ref struct Item
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{
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/// <summary>
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/// The source <see cref="ReadOnlySpan{T}"/> instance.
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/// </summary>
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private readonly ReadOnlySpan<T> span;
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#if NETSTANDARD2_1_OR_GREATER
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/// <summary>
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/// Initializes a new instance of the <see cref="Item"/> struct.
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/// </summary>
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/// <param name="value">A reference to the target value.</param>
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/// <param name="index">The index of the target value.</param>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public Item(ref T value, int index)
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{
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this.span = MemoryMarshal.CreateReadOnlySpan(ref value, index);
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}
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#else
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/// <summary>
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/// The current index within <see cref="span"/>.
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/// </summary>
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private readonly int index;
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/// <summary>
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/// Initializes a new instance of the <see cref="Item"/> struct.
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/// </summary>
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/// <param name="span">The source <see cref="ReadOnlySpan{T}"/> instance.</param>
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/// <param name="index">The current index within <paramref name="span"/>.</param>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public Item(ReadOnlySpan<T> span, int index)
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{
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this.span = span;
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this.index = index;
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}
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#endif
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/// <summary>
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/// Gets the reference to the current value.
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/// </summary>
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public ref readonly T Value
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{
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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get
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{
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#if NETSTANDARD2_1_OR_GREATER
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return ref MemoryMarshal.GetReference(this.span);
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#else
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ref T r0 = ref MemoryMarshal.GetReference(this.span);
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ref T ri = ref Unsafe.Add(ref r0, (nint)(uint)this.index);
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return ref ri;
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#endif
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}
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}
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/// <summary>
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/// Gets the current index.
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/// </summary>
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public int Index
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{
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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get
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{
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#if NETSTANDARD2_1_OR_GREATER
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return this.span.Length;
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#else
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return this.index;
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#endif
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}
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}
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}
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}
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