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[API Proposal]: Add SearchValues Overloads to SequenceReader #114451

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grbell-ms opened this issue Apr 9, 2025 · 3 comments
Open

[API Proposal]: Add SearchValues Overloads to SequenceReader #114451

grbell-ms opened this issue Apr 9, 2025 · 3 comments
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api-suggestion Early API idea and discussion, it is NOT ready for implementation area-System.Buffers untriaged New issue has not been triaged by the area owner

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@grbell-ms
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grbell-ms commented Apr 9, 2025 •
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Background and motivation

SequenceReader has methods that take a ReadOnlySpan of delimiter values and advances/reads until finding one of those values. With SearchValues addition in .NET 8, a new set of overloads is a natural addition. They should be more performant than using the existing overloads while being no more complicated for developers to use (and even easier than using AdvancePastAny(T value0, T value1, T value2, T value3)).

API Proposal

namespace System.Buffers;

public ref struct SequenceReader<T>
{
    public bool TryAdvanceToAny(SearchValues<T> delimiters, bool advancePastDelimiter = true);
    public long AdvancePastAny(SearchValues<T> values);
    public bool TryReadToAny(out ReadOnlySequence<T> sequence, SearchValues<T> delimiters, bool advancePastDelimiter = true);
    public bool TryReadToAny(out ReadOnlySpan<T> span, SearchValues<T> delimiters, bool advancePastDelimiter = true);
}

API Usage

var newlines = SearchValues.Create("\r\n");
var sequenceReader = new SequenceReader(buffer);
sequenceReader.TryReadToAny(out ReadOnlySequence<T> line, newlines, false);
sequenceReader.AdvancePastAny(newlines);

Alternative Designs

We could also add extension methods for SequenceReader<char> and SearchValues<string>.

namespace System.Buffers;

public static class SequenceReaderExtensions
{
    public static bool TryAdvanceToAny(this SequenceReader<char> reader, SearchValues<string> delimiters, bool advancePastDelimiter = true);
    public static long AdvancePastAny(this SequenceReader<char> reader, SearchValues<string> values);
    public static bool TryReadToAny(this SequenceReader<char> reader, out ReadOnlySequence<char> sequence, SearchValues<string> delimiters, bool advancePastDelimiter = true);
    public static bool TryReadToAny(this SequenceReader<char> reader, out ReadOnlySpan<char> span, SearchValues<string> delimiters, bool advancePastDelimiter = true);
}

Risks

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@grbell-ms grbell-ms added the api-suggestion Early API idea and discussion, it is NOT ready for implementation label Apr 9, 2025
@dotnet-policy-service dotnet-policy-service bot added the untriaged New issue has not been triaged by the area owner label Apr 9, 2025
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@grbell-ms
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Added the possibility of extension methods for SequenceReader<char> and SearchValues<string>.

@MihaZupan
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The generic overloads sound reasonable.

I would hold off on SearchValues<string> overloads until there's a demonstrated need here since you can't implement those efficiently without support from SearchValues internals (can't search across multiple segments without copying the whole sequence into a single buffer).

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