code generator that automatically switches endianness
This commit is contained in:
Vinzenz Schroeter
parent
e603c154b9
commit
5532c4f5a8
8 changed files with 291 additions and 34 deletions
227
EndiannessSourceGenerator/EndiannessGenerator.cs
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227
EndiannessSourceGenerator/EndiannessGenerator.cs
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using Microsoft.CodeAnalysis;
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using Microsoft.CodeAnalysis.CSharp;
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using Microsoft.CodeAnalysis.CSharp.Syntax;
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using Microsoft.CodeAnalysis.Text;
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namespace EndiannessSourceGenerator;
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internal class DebugMeException(string message) : Exception(message);
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internal class InvalidUsageException(string message) : Exception(message);
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[Generator]
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public class StructEndiannessSourceGenerator : ISourceGenerator
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{
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private const string Namespace = "EndiannessSourceGenerator";
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private const string AttributeName = "StructEndiannessAttribute";
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private const string IsLittleEndianProperty = "IsLittleEndian";
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private const string AttributeSourceCode =
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$$"""
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// <auto-generated/>
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namespace {{Namespace}}
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{
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[System.AttributeUsage(System.AttributeTargets.Struct)]
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public class {{AttributeName}}: System.Attribute
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{
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public required bool {{IsLittleEndianProperty}} { get; init; }
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}
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}
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""";
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private const string UsingDeclarations =
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"""
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using System;
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using System.Buffers.Binary;
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""";
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public void Initialize(GeneratorInitializationContext context)
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{
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// Register the attribute source
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context.RegisterForPostInitialization(i => { i.AddSource($"{AttributeName}.g.cs", AttributeSourceCode); });
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// context.RegisterForSyntaxNotifications(() => new SyntaxCon);
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}
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private readonly SymbolDisplayFormat _namespacedNameFormat =
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new(typeQualificationStyle: SymbolDisplayTypeQualificationStyle.NameAndContainingTypesAndNamespaces);
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// TODO: generate syntax tree with roslyn to get rid of string wrangling and so code is properly formatted
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public void Execute(GeneratorExecutionContext context)
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{
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var treesWithStructsWithAttributes = context.Compilation.SyntaxTrees
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.Where(st => st.GetRoot().DescendantNodes()
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.OfType<StructDeclarationSyntax>()
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.Any(p => p.DescendantNodes()
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.OfType<AttributeSyntax>()
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.Any()))
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.ToList();
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foreach (var tree in treesWithStructsWithAttributes)
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{
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var semanticModel = context.Compilation.GetSemanticModel(tree);
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var structsWithAttributes = tree.GetRoot().DescendantNodes()
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.OfType<StructDeclarationSyntax>()
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.Where(cd => cd.DescendantNodes()
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.OfType<AttributeSyntax>()
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.Any());
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foreach (var structDeclaration in structsWithAttributes)
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{
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var foundAttribute = GetEndiannessAttribute(structDeclaration, semanticModel);
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// not my type
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if (foundAttribute == null)
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continue;
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HandleStruct(context, structDeclaration, semanticModel, foundAttribute);
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}
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}
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}
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private static void HandleStruct(GeneratorExecutionContext context, StructDeclarationSyntax structDeclaration,
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SemanticModel semanticModel, AttributeSyntax foundAttribute)
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{
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var isPartial = structDeclaration.Modifiers.Any(m => m.IsKind(SyntaxKind.PartialKeyword));
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if (!isPartial)
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throw new InvalidUsageException("struct is not marked partial");
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var accessibilityModifier = structDeclaration.Modifiers.Any(m => m.IsKind(SyntaxKind.InternalKeyword))
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? "internal"
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: "public";
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var structType = semanticModel.GetDeclaredSymbol(structDeclaration);
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if (structType == null)
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throw new DebugMeException("struct type info is null");
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var structNamespace = structType.ContainingNamespace?.ToDisplayString();
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if (structNamespace == null)
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throw new InvalidUsageException("struct has to be contained in a namespace");
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var structIsLittleEndian = GetStructIsLittleEndian(foundAttribute);
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var generatedCode = new StringBuilder();
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generatedCode.AppendLine(UsingDeclarations);
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generatedCode.AppendLine($"namespace {structNamespace};");
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generatedCode.AppendLine($$"""{{accessibilityModifier}} partial struct {{structType.Name}} {""");
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var hasProperties = structDeclaration.Members
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.Any(m => m.IsKind(SyntaxKind.PropertyDeclaration));
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if (hasProperties)
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throw new InvalidUsageException("struct cannot have properties");
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var fieldDeclarations = structDeclaration.Members
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.Where(m => m.IsKind(SyntaxKind.FieldDeclaration)).OfType<FieldDeclarationSyntax>();
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GenerateStructProperties(generatedCode, fieldDeclarations, semanticModel, structIsLittleEndian);
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generatedCode.AppendLine("}"); // end of struct
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context.AddSource($"{structNamespace}.{structType.Name}.g.cs",
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SourceText.From(generatedCode.ToString(), Encoding.UTF8));
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}
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private static void GenerateStructProperties(StringBuilder generatedCode,
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IEnumerable<FieldDeclarationSyntax> fieldDeclarations, SemanticModel semanticModel, bool structIsLittleEndian)
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{
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foreach (var field in fieldDeclarations)
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{
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if (!field.Modifiers.Any(m => m.IsKind(SyntaxKind.PrivateKeyword)))
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throw new InvalidUsageException("fields have to be private");
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var variableDeclaration = field.DescendantNodes()
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.OfType<VariableDeclarationSyntax>()
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.FirstOrDefault();
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if (variableDeclaration == null)
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throw new DebugMeException("variable declaration of field declaration null");
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var variableTypeInfo = semanticModel.GetTypeInfo(variableDeclaration.Type).Type;
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if (variableTypeInfo == null)
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throw new DebugMeException("variable type info of field declaration null");
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var typeName = variableTypeInfo.ToDisplayString();
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var fieldName = variableDeclaration.Variables.First().Identifier.ToString();
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var propertyName = GeneratePropertyName(fieldName);
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GenerateProperty(generatedCode, typeName, propertyName, structIsLittleEndian, fieldName);
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}
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}
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private static void GenerateProperty(StringBuilder generatedCode, string typeName, string propertyName,
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bool structIsLittleEndian, string fieldName)
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{
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generatedCode.AppendLine($$"""public {{typeName}} {{propertyName}} {""");
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var maybeNegator = structIsLittleEndian ? string.Empty : "!";
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var sameEndiannessExpression = $"{maybeNegator}BitConverter.IsLittleEndian";
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generatedCode.AppendLine($"get => {sameEndiannessExpression}");
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generatedCode.AppendLine($" ? {fieldName}");
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generatedCode.AppendLine($" : BinaryPrimitives.ReverseEndianness({fieldName});");
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generatedCode.AppendLine($"set => {fieldName} = {sameEndiannessExpression}");
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generatedCode.AppendLine(" ? value");
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generatedCode.AppendLine(" : BinaryPrimitives.ReverseEndianness(value);");
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generatedCode.AppendLine("}"); // end of property
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}
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private static string GeneratePropertyName(string fieldName)
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{
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var propertyName = fieldName;
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if (propertyName.StartsWith("_"))
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propertyName = propertyName.Substring(1);
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if (!char.IsLetter(propertyName, 0) || char.IsUpper(propertyName, 0))
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throw new InvalidUsageException("field names have to start with a lower case letter");
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propertyName = propertyName.Substring(0, 1).ToUpperInvariant()
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+ propertyName.Substring(1);
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return propertyName;
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}
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private static AttributeSyntax? GetEndiannessAttribute(StructDeclarationSyntax structDeclaration,
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SemanticModel semanticModel)
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{
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AttributeSyntax? foundAttribute = null;
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foreach (var attributeSyntax in structDeclaration.DescendantNodes().OfType<AttributeSyntax>())
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{
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var attributeTypeInfo = semanticModel.GetTypeInfo(attributeSyntax).Type;
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if (attributeTypeInfo == null)
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throw new DebugMeException("attribute type info is null");
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if (attributeTypeInfo.ContainingNamespace?.Name != Namespace)
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continue;
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if (attributeTypeInfo.Name != AttributeName)
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continue;
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foundAttribute = attributeSyntax;
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break;
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}
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return foundAttribute;
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}
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private static bool GetStructIsLittleEndian(AttributeSyntax foundAttribute)
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{
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var endiannessArguments = foundAttribute.ArgumentList;
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if (endiannessArguments == null)
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throw new InvalidUsageException("endianness attribute has no arguments");
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var isLittleEndianArgumentSyntax = endiannessArguments.Arguments
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.FirstOrDefault(argumentSyntax =>
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argumentSyntax.NameEquals?.Name.Identifier.ToString() == IsLittleEndianProperty);
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if (isLittleEndianArgumentSyntax == null)
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throw new InvalidUsageException("endianness attribute argument not found");
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bool? structIsLittleEndian = isLittleEndianArgumentSyntax.Expression.Kind() switch
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{
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SyntaxKind.FalseLiteralExpression => false,
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SyntaxKind.TrueLiteralExpression => true,
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SyntaxKind.DefaultLiteralExpression => false,
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_ => throw new InvalidUsageException($"{IsLittleEndianProperty} has to be set with a literal")
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};
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return structIsLittleEndian.Value;
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}
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}
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23
EndiannessSourceGenerator/EndiannessSourceGenerator.csproj
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23
EndiannessSourceGenerator/EndiannessSourceGenerator.csproj
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@ -0,0 +1,23 @@
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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<TargetFramework>netstandard2.0</TargetFramework>
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<IsPackable>false</IsPackable>
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<Nullable>enable</Nullable>
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<LangVersion>latest</LangVersion>
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<EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
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<IsRoslynComponent>true</IsRoslynComponent>
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<PackageId>EndiannessSourceGenerator</PackageId>
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</PropertyGroup>
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<ItemGroup>
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<PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4">
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<PrivateAssets>all</PrivateAssets>
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<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
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</PackageReference>
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<PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.9.2" PrivateAssets="all" />
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<PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.9.2"/>
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</ItemGroup>
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</Project>
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5
EndiannessSourceGenerator/Readme.md
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5
EndiannessSourceGenerator/Readme.md
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# Endianness Source Generator
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When annotating a struct with the `StructEndianness` attribute, this code generator will generate properties for the declared fields.
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Each time a property is read or written, the endianness is converted from runtime endianness to struct endianness or vice-versa.
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