123 lines
4.2 KiB
C#
123 lines
4.2 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.Buffers;
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using System.Runtime.CompilerServices;
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using System.Runtime.InteropServices;
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using CommunityToolkit.HighPerformance.Buffers.Internals.Interfaces;
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using RuntimeHelpers = CommunityToolkit.HighPerformance.Helpers.Internals.RuntimeHelpers;
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namespace CommunityToolkit.HighPerformance.Buffers.Internals;
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/// <summary>
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/// A custom <see cref="MemoryManager{T}"/> that casts data from a <see cref="string"/> to <typeparamref name="TTo"/> values.
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/// </summary>
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/// <typeparam name="TTo">The target type to cast the source characters to.</typeparam>
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internal sealed class StringMemoryManager<TTo> : MemoryManager<TTo>, IMemoryManager
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where TTo : unmanaged
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{
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/// <summary>
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/// The source <see cref="string"/> to read data from.
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/// </summary>
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private readonly string text;
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/// <summary>
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/// The starting offset within <see name="array"/>.
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/// </summary>
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private readonly int offset;
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/// <summary>
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/// The original used length for <see name="array"/>.
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/// </summary>
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private readonly int length;
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/// <summary>
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/// Initializes a new instance of the <see cref="StringMemoryManager{T}"/> class.
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/// </summary>
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/// <param name="text">The source <see cref="string"/> to read data from.</param>
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/// <param name="offset">The starting offset within <paramref name="text"/>.</param>
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/// <param name="length">The original used length for <paramref name="text"/>.</param>
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public StringMemoryManager(string text, int offset, int length)
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{
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this.text = text;
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this.offset = offset;
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this.length = length;
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}
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/// <inheritdoc/>
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public override Span<TTo> GetSpan()
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{
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#if NETSTANDARD2_1_OR_GREATER
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ref char r0 = ref this.text.DangerousGetReferenceAt(this.offset);
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ref TTo r1 = ref Unsafe.As<char, TTo>(ref r0);
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int length = RuntimeHelpers.ConvertLength<char, TTo>(this.length);
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return MemoryMarshal.CreateSpan(ref r1, length);
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#else
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ReadOnlyMemory<char> memory = this.text.AsMemory(this.offset, this.length);
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Span<char> span = MemoryMarshal.AsMemory(memory).Span;
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return MemoryMarshal.Cast<char, TTo>(span);
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#endif
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}
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/// <inheritdoc/>
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public override unsafe MemoryHandle Pin(int elementIndex = 0)
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{
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if ((uint)elementIndex >= (uint)(this.length * Unsafe.SizeOf<char>() / Unsafe.SizeOf<TTo>()))
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{
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ThrowArgumentOutOfRangeExceptionForInvalidIndex();
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}
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int bytePrefix = this.offset * Unsafe.SizeOf<char>();
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int byteSuffix = elementIndex * Unsafe.SizeOf<TTo>();
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int byteOffset = bytePrefix + byteSuffix;
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GCHandle handle = GCHandle.Alloc(this.text, GCHandleType.Pinned);
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ref char r0 = ref this.text.DangerousGetReference();
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ref byte r1 = ref Unsafe.As<char, byte>(ref r0);
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ref byte r2 = ref Unsafe.Add(ref r1, byteOffset);
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void* pi = Unsafe.AsPointer(ref r2);
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return new(pi, handle);
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}
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/// <inheritdoc/>
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public override void Unpin()
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{
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}
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/// <inheritdoc/>
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protected override void Dispose(bool disposing)
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{
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}
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/// <inheritdoc/>
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public Memory<T> GetMemory<T>(int offset, int length)
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where T : unmanaged
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{
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int absoluteOffset = this.offset + RuntimeHelpers.ConvertLength<TTo, char>(offset);
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int absoluteLength = RuntimeHelpers.ConvertLength<TTo, char>(length);
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if (typeof(T) == typeof(char))
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{
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ReadOnlyMemory<char> memory = this.text.AsMemory(absoluteOffset, absoluteLength);
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return (Memory<T>)(object)MemoryMarshal.AsMemory(memory);
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}
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return new StringMemoryManager<T>(this.text, absoluteOffset, absoluteLength).Memory;
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}
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/// <summary>
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/// Throws an <see cref="ArgumentOutOfRangeException"/> when the target index for <see cref="Pin"/> is invalid.
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/// </summary>
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private static void ThrowArgumentOutOfRangeExceptionForInvalidIndex()
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{
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throw new ArgumentOutOfRangeException("elementIndex", "The input index is not in the valid range");
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}
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}
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