Added simple GetHashCodeFromChars extension.

Author: electricessence

Benchmarks/EnumParseTests.cs

@@ -3,6 +3,18 @@
 
 namespace Open.Text.Benchmarks;
 
+/*
+|                  Method | UseValid | IgnoreCase |     Mean |    Error |   StdDev | Ratio | RatioSD | Allocated |
+|------------------------ |--------- |----------- |---------:|---------:|---------:|------:|--------:|----------:|
+| CompiledSwitchByLengths |     True |      False | 12.63 ns | 0.285 ns | 0.776 ns |  1.00 |    0.00 |         - |
+|          EnumValueParse |     True |      False | 50.22 ns | 0.543 ns | 0.481 ns |  3.98 |    0.17 |         - |
+|           FastEnumParse |     True |      False | 46.10 ns | 0.780 ns | 0.730 ns |  3.62 |    0.22 |         - |
+|                         |          |            |          |          |          |       |         |           |
+| CompiledSwitchByLengths |     True |       True | 17.29 ns | 0.185 ns | 0.173 ns |  1.00 |    0.00 |         - |
+|          EnumValueParse |     True |       True | 59.01 ns | 0.340 ns | 0.284 ns |  3.41 |    0.04 |         - |
+|           FastEnumParse |     True |       True | 72.12 ns | 0.451 ns | 0.352 ns |  4.17 |    0.05 |         - |
+*/
+
 [MemoryDiagnoser]
 public class EnumParseTests
 {
@@ -16,7 +28,7 @@ void SetTests()
 			? (ignoreCase ? new ValidTestsIC() : new ValidTests())
 			: (ignoreCase ? new InvalidTestsIC() : new InvalidTests());
 
-	[Params(true, false)]
+	[Params(true/*, false*/)]
 	public bool UseValid
 	{
 		get => useValid;

Benchmarks/Program.cs

@@ -1,8 +1,8 @@
 using BenchmarkDotNet.Running;
 using Open.Text.Benchmarks;
 
-//BenchmarkRunner.Run<EnumParseTests>();
-BenchmarkRunner.Run<EnumToStringTests>();
+BenchmarkRunner.Run<EnumParseTests>();
+//enchmarkRunner.Run<EnumToStringTests>();
 //BenchmarkRunner.Run<CharAssumptionTests>();
 //BenchmarkRunner.Run<EnumAttributeTests>();
 //BenchmarkRunner.Run<IsDefinedTests>();

Source/Extensions._.cs

@@ -433,4 +433,25 @@ public static string Supplant<T>(this string format, T[]? values, CultureInfo? c
 			1 => string.Format(cultureInfo ?? CultureInfo.InvariantCulture, format, values[0]),
 			_ => string.Format(cultureInfo ?? CultureInfo.InvariantCulture, format, values as object[] ?? values.Cast<object>().ToArray()),
 		};
+
+	/// <summary>
+	/// A hashing algorithm that is nearly as fast as the default string.GetHashCode()
+	/// but can be used for any sequence of characters reliably.
+	/// </summary>
+	/// <remarks>
+	/// Setting the <paramref name="maxChars"/> parameter to a lower number
+	/// will dramatically increase the speed as more characters requires more iterations.
+	/// </remarks>
+	public static int GetHashCodeFromChars(this ReadOnlySpan<char> chars, int maxChars = int.MaxValue)
+	{
+		int hash_value = 0;
+		int length = Math.Min(chars.Length, maxChars);
+		for (var i = 0; i < length; i++)
+		{
+			ref readonly char c = ref chars[i];
+			hash_value = (hash_value * 31) ^ c;
+		}
+
+		return hash_value;
+	}
 }