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Optimize HexConverter.FromChar #81146

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Optimize HexConverter.FromChar #81146

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ce5873c
Eliminate FromChar bounds checks
xtqqczze Jan 25, 2023
3b3d0db
Optimize conditions
xtqqczze Jan 25, 2023
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4 changes: 2 additions & 2 deletions src/libraries/Common/src/System/HexConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -275,13 +275,13 @@ public static bool TryDecodeFromUtf16(ReadOnlySpan<char> chars, Span<byte> bytes
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static int FromChar(int c)
{
return c >= CharToHexLookup.Length ? 0xFF : CharToHexLookup[c];
return (uint)c >= CharToHexLookup.Length ? 0xFF : CharToHexLookup[c];
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static int FromUpperChar(int c)
{
return c > 71 ? 0xFF : CharToHexLookup[c];
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This looks like an off-by-one error in the original code since 'F' is 70.

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It's not an actual error because c being 70 will return 0xFF anyway (from the lookup)

return (uint)c >= 72 ? 0xFF : CharToHexLookup[c];
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
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