bbradson
109 lines
3.7 KiB
C#
109 lines
3.7 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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// https://github.com/CommunityToolkit/dotnet/blob/main/CommunityToolkit.HighPerformance/Enumerables/SpanEnumerable%7BT%7D.cs
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using System.ComponentModel;
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using System.Runtime.CompilerServices;
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using JetBrains.Annotations;
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namespace FisheryLib;
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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="Span{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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[PublicAPI]
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public ref struct SpanEnumerable<T>
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{
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/// <summary>
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/// The source <see cref="Span{T}"/> instance.
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/// </summary>
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private readonly Span<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="SpanEnumerable{T}"/> struct.
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/// </summary>
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/// <param name="span">The source <see cref="Span{T}"/> instance.</param>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public SpanEnumerable(Span<T> span)
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{
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_span = span;
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_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="SpanEnumerable{T}"/> instance targeting the current <see cref="Span{T}"/> value.</returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public readonly SpanEnumerable<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() => ++_index < _span.Length;
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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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// On .NET Standard 2.1 and .NET Core (or on any target that offers runtime
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// support for the Span<T> types), we can save 4 bytes by piggybacking the
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// current index in the length of the wrapped span. We're going to use the
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// first item as the target reference, and the length as a host for the
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// current original offset. This is not possible on eg. .NET Standard 2.0,
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// as we lack the API to create Span<T>-s from arbitrary references.
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=> new(ref Unsafe.Add(ref _span.DangerousGetPinnableReference(), (nint)(uint)_index), _index);
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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="Span{T}"/> instance.
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/// </summary>
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private readonly Span<T> _span;
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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) => _span = MemoryMarshal.CreateSpan(ref value, index);
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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 T Value
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{
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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get => ref MemoryMarshal.GetReference(_span);
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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 => _span.Length;
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}
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}
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} |