[Rgen] Add a central location for the aux variable naming. (#22063)

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Author: mandel-macaque

src/rgen/Microsoft.Macios.Generator/DataModel/Parameter.Generator.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Microsoft.Macios.Generator.DataModel;
+
+readonly partial struct Parameter {
+
+	public enum VariableType {
+		Handle,
+		NSArray,
+		BlockLiteral,
+		PrimitivePointer,
+	}
+
+	/// <summary>
+	/// Returns the name of the aux variable that would have needed for the given parameter. Use the
+	/// variable type to name it.
+	/// </summary>
+	/// <param name="variableType">The type of aux variable.</param>
+	/// <returns>The name of the aux variable to use.</returns>
+	public string? GetNameForVariableType (VariableType variableType)
+		=> variableType switch {
+			VariableType.Handle => $"{Name}__handle__",
+			VariableType.NSArray => $"nsa_{Name}",
+			VariableType.BlockLiteral => $"block_ptr_{Name}",
+			VariableType.PrimitivePointer => $"converted_{Name}",
+			_ => null
+		};
+}

tests/rgen/Microsoft.Macios.Generator.Tests/DataModel/ParameterTests.cs

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+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Collections;
+using System.Collections.Generic;
+using Microsoft.Macios.Generator.DataModel;
+using Xunit;
+using static Microsoft.Macios.Generator.Tests.TestDataFactory;
+
+namespace Microsoft.Macios.Generator.Tests.DataModel;
+
+public class ParameterTests {
+
+	class TestDataGetVariableName : IEnumerable<object []> {
+		public IEnumerator<object []> GetEnumerator ()
+		{
+			var exampleParameter = new Parameter (0, ReturnTypeForBool (), "firstParameter");
+			yield return [exampleParameter, Parameter.VariableType.Handle, $"{exampleParameter.Name}__handle__"];
+			yield return [exampleParameter, Parameter.VariableType.BlockLiteral, $"block_ptr_{exampleParameter.Name}"];
+			yield return [exampleParameter, Parameter.VariableType.PrimitivePointer, $"converted_{exampleParameter.Name}"];
+			yield return [exampleParameter, Parameter.VariableType.NSArray, $"nsa_{exampleParameter.Name}"];
+		}
+
+		IEnumerator IEnumerable.GetEnumerator () => GetEnumerator ();
+	}
+
+	[Theory]
+	[ClassData (typeof (TestDataGetVariableName))]
+	void GetNameForVariableTypeTests (Parameter parameter, Parameter.VariableType variableType, string expectedName)
+		=> Assert.Equal (expectedName, parameter.GetNameForVariableType (variableType));
+}