279 lines
14 KiB
C#
279 lines
14 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.Runtime.CompilerServices;
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using System.Runtime.InteropServices;
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using CommunityToolkit.HighPerformance.Enumerables;
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using CommunityToolkit.HighPerformance.Helpers.Internals;
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namespace CommunityToolkit.HighPerformance;
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/// <summary>
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/// Helpers for working with the <see cref="Span{T}"/> type.
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/// </summary>
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public static class SpanExtensions
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{
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/// <summary>
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/// Returns a reference to the first element within a given <see cref="Span{T}"/>, with no bounds checks.
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/// </summary>
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/// <typeparam name="T">The type of elements in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance.</param>
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/// <returns>A reference to the first element within <paramref name="span"/>.</returns>
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/// <remarks>This method doesn't do any bounds checks, therefore it is responsibility of the caller to perform checks in case the returned value is dereferenced.</remarks>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static ref T DangerousGetReference<T>(this Span<T> span)
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{
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return ref MemoryMarshal.GetReference(span);
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}
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/// <summary>
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/// Returns a reference to an element at a specified index within a given <see cref="Span{T}"/>, with no bounds checks.
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/// </summary>
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/// <typeparam name="T">The type of elements in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance.</param>
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/// <param name="i">The index of the element to retrieve within <paramref name="span"/>.</param>
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/// <returns>A reference to the element within <paramref name="span"/> at the index specified by <paramref name="i"/>.</returns>
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/// <remarks>This method doesn't do any bounds checks, therefore it is responsibility of the caller to ensure the <paramref name="i"/> parameter is valid.</remarks>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static ref T DangerousGetReferenceAt<T>(this Span<T> span, int i)
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{
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ref T r0 = ref MemoryMarshal.GetReference(span);
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ref T ri = ref Unsafe.Add(ref r0, (nint)(uint)i);
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return ref ri;
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}
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/// <summary>
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/// Returns a reference to an element at a specified index within a given <see cref="Span{T}"/>, with no bounds checks.
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/// </summary>
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/// <typeparam name="T">The type of elements in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance.</param>
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/// <param name="i">The index of the element to retrieve within <paramref name="span"/>.</param>
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/// <returns>A reference to the element within <paramref name="span"/> at the index specified by <paramref name="i"/>.</returns>
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/// <remarks>This method doesn't do any bounds checks, therefore it is responsibility of the caller to ensure the <paramref name="i"/> parameter is valid.</remarks>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static ref T DangerousGetReferenceAt<T>(this Span<T> span, nint i)
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{
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ref T r0 = ref MemoryMarshal.GetReference(span);
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ref T ri = ref Unsafe.Add(ref r0, i);
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return ref ri;
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}
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#if NETSTANDARD2_1_OR_GREATER
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/// <summary>
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/// Returns a <see cref="Span2D{T}"/> instance wrapping the underlying data for the given <see cref="Span{T}"/> instance.
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/// </summary>
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/// <typeparam name="T">The type of items in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance.</param>
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/// <param name="height">The height of the resulting 2D area.</param>
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/// <param name="width">The width of each row in the resulting 2D area.</param>
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/// <returns>The resulting <see cref="Span2D{T}"/> instance.</returns>
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/// <exception cref="ArgumentOutOfRangeException">
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/// Thrown when one of the input parameters is out of range.
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/// </exception>
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/// <exception cref="ArgumentException">
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/// Thrown when the requested area is outside of bounds for <paramref name="span"/>.
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/// </exception>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static Span2D<T> AsSpan2D<T>(this Span<T> span, int height, int width)
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{
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return new(span, height, width);
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}
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/// <summary>
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/// Returns a <see cref="Span2D{T}"/> instance wrapping the underlying data for the given <see cref="Span{T}"/> instance.
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/// </summary>
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/// <typeparam name="T">The type of items in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance.</param>
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/// <param name="offset">The initial offset within <paramref name="span"/>.</param>
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/// <param name="height">The height of the resulting 2D area.</param>
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/// <param name="width">The width of each row in the resulting 2D area.</param>
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/// <param name="pitch">The pitch in the resulting 2D area.</param>
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/// <returns>The resulting <see cref="Span2D{T}"/> instance.</returns>
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/// <exception cref="ArgumentOutOfRangeException">
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/// Thrown when one of the input parameters is out of range.
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/// </exception>
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/// <exception cref="ArgumentException">
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/// Thrown when the requested area is outside of bounds for <paramref name="span"/>.
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/// </exception>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static Span2D<T> AsSpan2D<T>(this Span<T> span, int offset, int height, int width, int pitch)
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{
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return new(span, offset, height, width, pitch);
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}
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#endif
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/// <summary>
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/// Casts a <see cref="Span{T}"/> of one primitive type <typeparamref name="T"/> to <see cref="Span{T}"/> of bytes.
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/// </summary>
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/// <typeparam name="T">The type if items in the source <see cref="Span{T}"/>.</typeparam>
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/// <param name="span">The source slice, of type <typeparamref name="T"/>.</param>
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/// <returns>A <see cref="Span{T}"/> of bytes.</returns>
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/// <exception cref="OverflowException">
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/// Thrown if the <see cref="Span{T}.Length"/> property of the new <see cref="Span{T}"/> would exceed <see cref="int.MaxValue"/>.
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/// </exception>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static Span<byte> AsBytes<T>(this Span<T> span)
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where T : unmanaged
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{
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return MemoryMarshal.AsBytes(span);
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}
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/// <summary>
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/// Casts a <see cref="Span{T}"/> of one primitive type <typeparamref name="TFrom"/> to another primitive type <typeparamref name="TTo"/>.
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/// </summary>
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/// <typeparam name="TFrom">The type of items in the source <see cref="Span{T}"/>.</typeparam>
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/// <typeparam name="TTo">The type of items in the destination <see cref="Span{T}"/>.</typeparam>
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/// <param name="span">The source slice, of type <typeparamref name="TFrom"/>.</param>
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/// <returns>A <see cref="Span{T}"/> of type <typeparamref name="TTo"/></returns>
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/// <remarks>
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/// Supported only for platforms that support misaligned memory access or when the memory block is aligned by other means.
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/// </remarks>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static Span<TTo> Cast<TFrom, TTo>(this Span<TFrom> span)
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where TFrom : unmanaged
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where TTo : unmanaged
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{
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return MemoryMarshal.Cast<TFrom, TTo>(span);
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}
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/// <summary>
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/// Gets the index of an element of a given <see cref="Span{T}"/> from its reference.
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/// </summary>
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/// <typeparam name="T">The type if items in the input <see cref="Span{T}"/>.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> to calculate the index for.</param>
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/// <param name="value">The reference to the target item to get the index for.</param>
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/// <returns>The index of <paramref name="value"/> within <paramref name="span"/>, or <c>-1</c>.</returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static int IndexOf<T>(this Span<T> span, ref T value)
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{
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ref T r0 = ref MemoryMarshal.GetReference(span);
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IntPtr byteOffset = Unsafe.ByteOffset(ref r0, ref value);
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nint elementOffset = byteOffset / (nint)(uint)Unsafe.SizeOf<T>();
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if ((nuint)elementOffset >= (uint)span.Length)
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{
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return -1;
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}
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return (int)elementOffset;
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}
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/// <summary>
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/// Counts the number of occurrences of a given value into a target <see cref="Span{T}"/> instance.
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/// </summary>
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/// <typeparam name="T">The type of items in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance to read.</param>
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/// <param name="value">The <typeparamref name="T"/> value to look for.</param>
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/// <returns>The number of occurrences of <paramref name="value"/> in <paramref name="span"/>.</returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static int Count<T>(this Span<T> span, T value)
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where T : IEquatable<T>
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{
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ref T r0 = ref MemoryMarshal.GetReference(span);
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nint length = (nint)(uint)span.Length;
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return (int)SpanHelper.Count(ref r0, length, value);
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}
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/// <summary>
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/// Enumerates the items in the input <see cref="Span{T}"/> instance, as pairs of reference/index values.
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/// This extension should be used directly within a <see langword="foreach"/> loop:
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/// <code>
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/// Span<int> numbers = new[] { 1, 2, 3, 4, 5, 6, 7 };
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///
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/// foreach (var item in numbers.Enumerate())
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/// {
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/// // Access the index and value of each item here...
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/// int index = item.Index;
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/// ref int value = ref item.Value;
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/// }
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/// </code>
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/// The compiler will take care of properly setting up the <see langword="foreach"/> loop with the type returned from this method.
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/// </summary>
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/// <typeparam name="T">The type of items to enumerate.</typeparam>
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/// <param name="span">The source <see cref="Span{T}"/> to enumerate.</param>
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/// <returns>A wrapper type that will handle the reference/index enumeration for <paramref name="span"/>.</returns>
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/// <remarks>The returned <see cref="SpanEnumerable{T}"/> value shouldn't be used directly: use this extension in a <see langword="foreach"/> loop.</remarks>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static SpanEnumerable<T> Enumerate<T>(this Span<T> span)
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{
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return new(span);
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}
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/// <summary>
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/// Tokenizes the values in the input <see cref="Span{T}"/> instance using a specified separator.
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/// This extension should be used directly within a <see langword="foreach"/> loop:
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/// <code>
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/// Span<char> text = "Hello, world!".ToCharArray();
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///
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/// foreach (var token in text.Tokenize(','))
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/// {
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/// // Access the tokens here...
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/// }
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/// </code>
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/// The compiler will take care of properly setting up the <see langword="foreach"/> loop with the type returned from this method.
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/// </summary>
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/// <typeparam name="T">The type of items in the <see cref="Span{T}"/> to tokenize.</typeparam>
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/// <param name="span">The source <see cref="Span{T}"/> to tokenize.</param>
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/// <param name="separator">The separator <typeparamref name="T"/> item to use.</param>
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/// <returns>A wrapper type that will handle the tokenization for <paramref name="span"/>.</returns>
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/// <remarks>The returned <see cref="SpanTokenizer{T}"/> value shouldn't be used directly: use this extension in a <see langword="foreach"/> loop.</remarks>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static SpanTokenizer<T> Tokenize<T>(this Span<T> span, T separator)
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where T : IEquatable<T>
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{
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return new(span, separator);
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}
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/// <summary>
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/// Gets a content hash from the input <see cref="Span{T}"/> instance using the Djb2 algorithm.
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/// For more info, see the documentation for <see cref="ReadOnlySpanExtensions.GetDjb2HashCode{T}"/>.
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/// </summary>
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/// <typeparam name="T">The type of items in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance.</param>
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/// <returns>The Djb2 value for the input <see cref="Span{T}"/> instance.</returns>
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/// <remarks>The Djb2 hash is fully deterministic and with no random components.</remarks>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static int GetDjb2HashCode<T>(this Span<T> span)
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where T : notnull
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{
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ref T r0 = ref MemoryMarshal.GetReference(span);
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nint length = (nint)(uint)span.Length;
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return SpanHelper.GetDjb2HashCode(ref r0, length);
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}
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/// <summary>
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/// Copies the contents of a given <see cref="Span{T}"/> into destination <see cref="RefEnumerable{T}"/> instance.
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/// </summary>
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/// <typeparam name="T">The type of items in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance.</param>
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/// <param name="destination">The <see cref="RefEnumerable{T}"/> instance to copy items into.</param>
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/// <exception cref="ArgumentException">
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/// Thrown when the destination <see cref="RefEnumerable{T}"/> is shorter than the source <see cref="Span{T}"/>.
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/// </exception>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static void CopyTo<T>(this Span<T> span, RefEnumerable<T> destination)
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{
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destination.CopyFrom(span);
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}
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/// <summary>
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/// Attempts to copy the contents of a given <see cref="Span{T}"/> into destination <see cref="RefEnumerable{T}"/> instance.
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/// </summary>
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/// <typeparam name="T">The type of items in the input <see cref="Span{T}"/> instance.</typeparam>
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/// <param name="span">The input <see cref="Span{T}"/> instance.</param>
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/// <param name="destination">The <see cref="RefEnumerable{T}"/> instance to copy items into.</param>
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/// <returns>Whether or not the operation was successful.</returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static bool TryCopyTo<T>(this Span<T> span, RefEnumerable<T> destination)
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{
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return destination.TryCopyFrom(span);
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}
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}
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