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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.ComponentModel;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Runtime.Versioning;
#pragma warning disable 0809 //warning CS0809: Obsolete member 'Span<T>.Equals(object)' overrides non-obsolete member 'object.Equals(object)'
namespace System
{
/// <summary>
/// ReadOnlySpan represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
/// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
/// </summary>
[DebuggerTypeProxy(typeof(SpanDebugView<>))]
[DebuggerDisplay("{ToString(),raw}")]
public readonly ref partial struct ReadOnlySpan<T>
{
/// <summary>
/// The number of items in the read-only span.
/// </summary>
public int Length
{
[NonVersionable]
get
{
return _length;
}
}
/// <summary>
/// Returns true if Length is 0.
/// </summary>
public bool IsEmpty
{
[NonVersionable]
get
{
// Workaround for https://github.com/dotnet/coreclr/issues/19620
return 0 >= (uint)_length;
}
}
/// <summary>
/// Returns false if left and right point at the same memory and have the same length. Note that
/// this does *not* check to see if the *contents* are equal.
/// </summary>
public static bool operator !=(ReadOnlySpan<T> left, ReadOnlySpan<T> right) => !(left == right);
/// <summary>
/// This method is not supported as spans cannot be boxed. To compare two spans, use operator==.
/// <exception cref="System.NotSupportedException">
/// Always thrown by this method.
/// </exception>
/// </summary>
[Obsolete("Equals() on ReadOnlySpan will always throw an exception. Use == instead.")]
[EditorBrowsable(EditorBrowsableState.Never)]
public override bool Equals(object? obj)
{
throw new NotSupportedException(SR.NotSupported_CannotCallEqualsOnSpan);
}
/// <summary>
/// This method is not supported as spans cannot be boxed.
/// <exception cref="System.NotSupportedException">
/// Always thrown by this method.
/// </exception>
/// </summary>
[Obsolete("GetHashCode() on ReadOnlySpan will always throw an exception.")]
[EditorBrowsable(EditorBrowsableState.Never)]
public override int GetHashCode()
{
throw new NotSupportedException(SR.NotSupported_CannotCallGetHashCodeOnSpan);
}
/// <summary>
/// Defines an implicit conversion of an array to a <see cref="ReadOnlySpan{T}"/>
/// </summary>
public static implicit operator ReadOnlySpan<T>(T[]? array) => new ReadOnlySpan<T>(array);
/// <summary>
/// Defines an implicit conversion of a <see cref="ArraySegment{T}"/> to a <see cref="ReadOnlySpan{T}"/>
/// </summary>
public static implicit operator ReadOnlySpan<T>(ArraySegment<T> segment)
=> new ReadOnlySpan<T>(segment.Array, segment.Offset, segment.Count);
/// <summary>
/// Returns a 0-length read-only span whose base is the null pointer.
/// </summary>
public static ReadOnlySpan<T> Empty => default;
/// <summary>Gets an enumerator for this span.</summary>
public Enumerator GetEnumerator() => new Enumerator(this);
/// <summary>Enumerates the elements of a <see cref="ReadOnlySpan{T}"/>.</summary>
public ref struct Enumerator
{
/// <summary>The span being enumerated.</summary>
private readonly ReadOnlySpan<T> _span;
/// <summary>The next index to yield.</summary>
private int _index;
/// <summary>Initialize the enumerator.</summary>
/// <param name="span">The span to enumerate.</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal Enumerator(ReadOnlySpan<T> span)
{
_span = span;
_index = -1;
}
/// <summary>Advances the enumerator to the next element of the span.</summary>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public bool MoveNext()
{
int index = _index + 1;
if (index < _span.Length)
{
_index = index;
return true;
}
return false;
}
/// <summary>Gets the element at the current position of the enumerator.</summary>
public ref readonly T Current
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
get => ref _span[_index];
}
}
}
}
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