Created
January 18, 2021 13:39
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ReadOnlySpan Split
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| using System; | |
| using System.Runtime.CompilerServices; | |
| using JetBrains.Annotations; | |
| // Reduced-down and slightly refactored version of https://gist.github.com/LordJZ/92b7decebe52178a445a0b82f63e585a | |
| // It exposes only (T separator) overload of the Split method which was enough for my needs. | |
| public static class SpanExtensions | |
| { | |
| public readonly ref struct Enumerable<T> | |
| where T : IEquatable<T> | |
| { | |
| private readonly ReadOnlySpan<T> _span; | |
| private readonly T _separator; | |
| public Enumerable(ReadOnlySpan<T> span, T separator) | |
| { | |
| _span = span; | |
| _separator = separator; | |
| } | |
| [PublicAPI] | |
| public Enumerator<T> GetEnumerator() => new Enumerator<T>(_span, _separator); | |
| } | |
| public ref struct Enumerator<T> | |
| where T : IEquatable<T> | |
| { | |
| private const int SeparatorLength = 1; | |
| private readonly ReadOnlySpan<T> _trailingEmptyItemSentinel; | |
| private readonly T _separator; | |
| private ReadOnlySpan<T> _span; | |
| private ReadOnlySpan<T> _current; | |
| public Enumerator(ReadOnlySpan<T> span, T separator) | |
| { | |
| _span = span; | |
| _separator = separator; | |
| _current = default; | |
| _trailingEmptyItemSentinel = Unsafe.As<T[]>(nameof(_trailingEmptyItemSentinel)).AsSpan(); | |
| if (_span.IsEmpty) | |
| TrailingEmptyItem = true; | |
| } | |
| [PublicAPI] | |
| public ReadOnlySpan<T> Current => _current; | |
| private bool TrailingEmptyItem | |
| { | |
| get => _span == _trailingEmptyItemSentinel; | |
| set => _span = value ? _trailingEmptyItemSentinel : default; | |
| } | |
| [PublicAPI] | |
| public bool MoveNext() | |
| { | |
| if (TrailingEmptyItem) | |
| { | |
| TrailingEmptyItem = false; | |
| _current = default; | |
| return true; | |
| } | |
| if (_span.IsEmpty) | |
| { | |
| _span = _current = default; | |
| return false; | |
| } | |
| int idx = _span.IndexOf(_separator); | |
| if (idx < 0) | |
| { | |
| _current = _span; | |
| _span = default; | |
| } | |
| else | |
| { | |
| _current = _span.Slice(0, idx); | |
| _span = _span.Slice(idx + SeparatorLength); | |
| if (_span.IsEmpty) | |
| TrailingEmptyItem = true; | |
| } | |
| return true; | |
| } | |
| } | |
| [Pure, PublicAPI] | |
| public static Enumerable<T> Split<T>(this ReadOnlySpan<T> span, T separator) | |
| where T : IEquatable<T> => new Enumerable<T>(span, separator); | |
| } |
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