Reduce allocations in ChecksumUtilities.BytesToString #12359
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This method was previously allocating a string for each byte being converted and then allocating another string for the stringbuilder.ToString call. Instead: if >NET9 use Convert.ToHexStringLower else create stack alloc'ed char[] and put converted chars in there and allocate a single string from that
src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/ChecksumUtilities.cs
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| return buffer.ToString(); | ||
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| static char GetHexChar(int value) | ||
| => (char)(value < 10 ? '0' + value : 'a' + (value - 10)); |
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Is this faster than indexing into a pre-allocated array of chars?
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Probably slightly slower, but I didn't want to duplicate HexConverter.CharToHexLookup, especially as this won't be used OOP once we move to net9
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I wouldn't duplicate all of that either! I was just thinking of something like this:
private static char GetHexChar(int value) => s_hexChars[value];
private static readonly char[] s_hexChars = new[] { '0', '1', '2', '3', '4', '5', '6', '7, '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
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FWIW, that's definitely into the micro-optimization level. I agree that it's not needed for just netstandard2.0. 👍
src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/ChecksumUtilities.cs
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2) Avoid ImmutableCollectionsMarshal, and just pass the span to Convert.ToHexString
davidwengier
approved these changes
Oct 17, 2025
This was referenced Oct 21, 2025
This was referenced Oct 22, 2025
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This method was previously allocating a string for each byte being converted and then allocating another string for the stringbuilder.ToString call. Instead:
This method was accounting for 1.4% of allocations during the typing scenario in the razoreditingtests.ScrollingAndTypingInCohosting speedometer test. The final string allocation was only 0.3%, which is equivalent to what the new implementation should allocate.