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Avoid reflection when validating enums #2676

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Merged
joshua-spacetime merged 1 commit into from
Apr 29, 2025
Merged

Avoid reflection when validating enums #2676

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18 changes: 17 additions & 1 deletion crates/bindings-csharp/BSATN.Runtime/BSATN/Runtime.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,9 +50,25 @@ public interface IReadWrite<T>
public readonly struct Enum<T> : IReadWrite<T>
where T : struct, Enum
{
private static readonly ulong NumVariants;

static Enum()
{
NumVariants = (ulong)Enum.GetValues(typeof(T)).Length;
}

private static T Validate(T value)
{
if (!Enum.IsDefined(typeof(T), value))
// Previously this was: `if (!Enum.IsDefined(typeof(T), value))`.
// This was quite expensive because:
// 1. It uses reflection
// 2. It allocates
// 3. It is called on each row when decoding
//
// However, enum values are guaranteed to be sequential and zero based.
// Hence we only ever need to do an upper bound check.
// See `SpacetimeDB.Type.ParseEnum` for the syntax analysis.
if (Convert.ToUInt64(value) >= NumVariants)
{
throw new ArgumentOutOfRangeException(
nameof(value),
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