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Expand small value sets to all case permutations in SearchValues<string> #98902
Expand small value sets to all case permutations in SearchValues<string> #98902
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Tagging subscribers to this area: @dotnet/area-system-buffers Issue DetailsImplements #98791 (comment) If we have a set of values like This optimization is a bit niche (unlikely to be applicable often), but it's really cheap to check whether it could apply, and can help cases with many non-letter characters in their prefixes. public class IgnoreCaseToOrdinal
{
private static readonly SearchValues<string> s_values = SearchValues.Create(["ab", "c!"], StringComparison.OrdinalIgnoreCase);
private readonly string _text = new('\n', 1000);
[Benchmark]
public int IndexOfAny() => _text.AsSpan().IndexOfAny(s_values);
}
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src/libraries/System.Private.CoreLib/src/System/SearchValues/Strings/StringSearchValues.cs
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src/libraries/System.Private.CoreLib/src/System/SearchValues/Strings/StringSearchValues.cs
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src/libraries/System.Private.CoreLib/src/System/SearchValues/Strings/StringSearchValues.cs
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src/libraries/System.Private.CoreLib/src/System/SearchValues/Strings/StringSearchValues.cs
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Implements #98791 (comment)
If we have a set of values like
["ab", "c!"]
, we can expand it to["ab", "Ab" "aB", "AB", "c!", "C!"]
and switch to case-sensitive searching.As long as we're making use of buckets that would otherwise have been empty, this is going to be an improvement as the prefix search loop is a bit simpler due to not needing to deal with casing. In the below benchmark, it means eliminating this step from the loop.
This optimization is a bit niche (unlikely to be applicable often), but it's really cheap to check whether it could apply, and can help cases with many non-letter characters in their prefixes.