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@LordJZ
Created August 9, 2018 18:04
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Split for Span
using System;
using System.Diagnostics.Contracts;
using System.Runtime.CompilerServices;
public static class SpanSplitExtensions
{
public ref struct Enumerable1<T> where T : IEquatable<T>
{
public Enumerable1(ReadOnlySpan<T> span, T separator)
{
Span = span;
Separator = separator;
}
ReadOnlySpan<T> Span { get; }
T Separator { get; }
public Enumerator1<T> GetEnumerator() => new Enumerator1<T>(Span, Separator);
}
public ref struct Enumerable2<T> where T : IEquatable<T>
{
public Enumerable2(ReadOnlySpan<T> span, T separator1, T separator2)
{
Span = span;
Separator1 = separator1;
Separator2 = separator2;
}
ReadOnlySpan<T> Span { get; }
T Separator1 { get; }
T Separator2 { get; }
public Enumerator2<T> GetEnumerator() => new Enumerator2<T>(Span, Separator1, Separator2);
}
public ref struct Enumerable3<T> where T : IEquatable<T>
{
public Enumerable3(ReadOnlySpan<T> span, T separator1, T separator2, T separator3)
{
Span = span;
Separator1 = separator1;
Separator2 = separator2;
Separator3 = separator3;
}
ReadOnlySpan<T> Span { get; }
T Separator1 { get; }
T Separator2 { get; }
T Separator3 { get; }
public Enumerator3<T> GetEnumerator() =>
new Enumerator3<T>(Span, Separator1, Separator2, Separator3);
}
public ref struct EnumerableN<T> where T : IEquatable<T>
{
public EnumerableN(ReadOnlySpan<T> span, ReadOnlySpan<T> separators)
{
Span = span;
Separators = separators;
}
ReadOnlySpan<T> Span { get; }
ReadOnlySpan<T> Separators { get; }
public EnumeratorN<T> GetEnumerator() => new EnumeratorN<T>(Span, Separators);
}
public ref struct Enumerator1<T> where T : IEquatable<T>
{
public Enumerator1(ReadOnlySpan<T> span, T separator)
{
Span = span;
Separator = separator;
Current = default;
if (Span.IsEmpty)
TrailingEmptyItem = true;
}
ReadOnlySpan<T> Span { get; set; }
T Separator { get; }
int SeparatorLength => 1;
ReadOnlySpan<T> TrailingEmptyItemSentinel => Unsafe.As<T[]>(nameof(TrailingEmptyItemSentinel)).AsSpan();
bool TrailingEmptyItem
{
get => Span == TrailingEmptyItemSentinel;
set => Span = value ? TrailingEmptyItemSentinel : default;
}
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;
}
public ReadOnlySpan<T> Current { get; private set; }
}
public ref struct Enumerator2<T> where T : IEquatable<T>
{
public Enumerator2(ReadOnlySpan<T> span, T separator1, T separator2)
{
Span = span;
Separator1 = separator1;
Separator2 = separator2;
Current = default;
if (Span.IsEmpty)
TrailingEmptyItem = true;
}
ReadOnlySpan<T> Span { get; set; }
T Separator1 { get; }
T Separator2 { get; }
int SeparatorLength => 1;
ReadOnlySpan<T> TrailingEmptyItemSentinel => Unsafe.As<T[]>(nameof(TrailingEmptyItemSentinel)).AsSpan();
bool TrailingEmptyItem
{
get => Span == TrailingEmptyItemSentinel;
set => Span = value ? TrailingEmptyItemSentinel : default;
}
public bool MoveNext()
{
if (TrailingEmptyItem)
{
TrailingEmptyItem = false;
Current = default;
return true;
}
if (Span.IsEmpty)
{
Span = Current = default;
return false;
}
int idx = Span.IndexOfAny(Separator1, Separator2);
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;
}
public ReadOnlySpan<T> Current { get; private set; }
}
public ref struct Enumerator3<T> where T : IEquatable<T>
{
public Enumerator3(ReadOnlySpan<T> span, T separator1, T separator2, T separator3)
{
Span = span;
Separator1 = separator1;
Separator2 = separator2;
Separator3 = separator3;
Current = default;
if (Span.IsEmpty)
TrailingEmptyItem = true;
}
ReadOnlySpan<T> Span { get; set; }
T Separator1 { get; }
T Separator2 { get; }
T Separator3 { get; }
int SeparatorLength => 1;
ReadOnlySpan<T> TrailingEmptyItemSentinel => Unsafe.As<T[]>(nameof(TrailingEmptyItemSentinel)).AsSpan();
bool TrailingEmptyItem
{
get => Span == TrailingEmptyItemSentinel;
set => Span = value ? TrailingEmptyItemSentinel : default;
}
public bool MoveNext()
{
if (TrailingEmptyItem)
{
TrailingEmptyItem = false;
Current = default;
return true;
}
if (Span.IsEmpty)
{
Span = Current = default;
return false;
}
int idx = Span.IndexOfAny(Separator1, Separator2, Separator3);
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;
}
public ReadOnlySpan<T> Current { get; private set; }
}
public ref struct EnumeratorN<T> where T : IEquatable<T>
{
public EnumeratorN(ReadOnlySpan<T> span, ReadOnlySpan<T> separators)
{
Span = span;
Separators = separators;
Current = default;
if (Span.IsEmpty)
TrailingEmptyItem = true;
}
ReadOnlySpan<T> Span { get; set; }
ReadOnlySpan<T> Separators { get; }
int SeparatorLength => 1;
ReadOnlySpan<T> TrailingEmptyItemSentinel => Unsafe.As<T[]>(nameof(TrailingEmptyItemSentinel)).AsSpan();
bool TrailingEmptyItem
{
get => Span == TrailingEmptyItemSentinel;
set => Span = value ? TrailingEmptyItemSentinel : default;
}
public bool MoveNext()
{
if (TrailingEmptyItem)
{
TrailingEmptyItem = false;
Current = default;
return true;
}
if (Span.IsEmpty)
{
Span = Current = default;
return false;
}
int idx = Span.IndexOfAny(Separators);
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;
}
public ReadOnlySpan<T> Current { get; private set; }
}
[Pure]
public static Enumerable1<T> Split<T>(this ReadOnlySpan<T> span, T separator)
where T : IEquatable<T> => new Enumerable1<T>(span, separator);
[Pure]
public static Enumerable2<T> Split<T>(this ReadOnlySpan<T> span, T separator1, T separator2)
where T : IEquatable<T> => new Enumerable2<T>(span, separator1, separator2);
[Pure]
public static Enumerable3<T> Split<T>(this ReadOnlySpan<T> span, T separator1, T separator2, T separator3)
where T : IEquatable<T> => new Enumerable3<T>(span, separator1, separator2, separator3);
[Pure]
public static EnumerableN<T> Split<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> values)
where T : IEquatable<T> => new EnumerableN<T>(span, values);
}
[TestFixture]
public class SpanSplitExtensionsTests
{
[TestCase("", 'a')]
[TestCase("a", 'a')]
[TestCase("aaaa", 'a')]
[TestCase("abababab", 'a')]
[TestCase("babababa", 'a')]
[TestCase("aaaaab", 'a')]
[TestCase("baaaaa", 'a')]
[TestCase("zzzzzazzzzazzzzazzz", 'a')]
public void Test(string str, char separator)
{
List<string> parts = new List<string>();
foreach (ReadOnlySpan<char> part in str.AsSpan().Split(separator))
parts.Add(part.ToString());
CollectionAssert.AreEqual(str.Split(separator), parts);
}
}
@MartinZid
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@LordJZ Could you explain to me please, what is the meaning of the property TrailingEmptyItemSentinel.

I think that you can use a classic boolean field - TrailingEmptyItem and ditch the TrailingEmptyItemSentinel completely.

@LordJZ
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Author

LordJZ commented Nov 8, 2019

@LordJZ Could you explain to me please, what is the meaning of the property TrailingEmptyItemSentinel.

I think that you can use a classic boolean field - TrailingEmptyItem and ditch the TrailingEmptyItemSentinel completely.

That's absolutely correct. The sole reason for this sentinel is to avoid having an extra boolean field.

@MartinZid
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That's absolutely correct. The sole reason for this sentinel is to avoid having an extra boolean field.

So it is about size optimization of the Enumerator.

Thank you for your answer @LordJZ.

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