Introduction

Avalanche.Emit is a class library for building Types and emitting opcodes by utilizing Avalanche.Service architecture. This library is a helper to the System.Reflection.Emit namespace.

The following example creates a type with method "int MyFunction(int x) => x < 5 ? 0 : 1;"

// Service that handles assembly builder, module builder and type builder
IService service = Services.Create((ServiceHandlers.Instance, EmitHandlers.Instance), CachePolicies.Default);
// Request to create type builder
IRequestFor<TypeBuilder> typeBuilder = new TypeBuilderRequest("MyClass_", TypeAttributes.Public | TypeAttributes.Class | TypeAttributes.AutoClass);
// Request to create method builder for "MyFunction"
IRequestFor<MethodBuilder> myFunc = new MethodBuilderRequest("MyFunction", MethodAttributes.Public | MethodAttributes.Virtual, typeof(int), typeof(int));
// Request to create il generator
IRequestFor<ILGenerator> il = ILGeneratorRequest.Default;
// Define labels
IRequestFor<Label> trueLabel = new LabelRequest(), falseLabel = new LabelRequest();
// "return x < 5 ? 0 : 1"
il = il.Append(OpCodes.Ldarg_1).Append(OpCodes.Ldc_I4_5).Append(OpCodes.Clt).Append(OpCodes.Brtrue_S, falseLabel);
// true: return 1;
il = il.Append(new MarkLabelRequest(trueLabel)).Append(OpCodes.Ldc_I4_1).Append(OpCodes.Ret);
// false: return 0;
il = il.Append(new MarkLabelRequest(falseLabel)).Append(OpCodes.Ldc_I4_0).Append(OpCodes.Ret);
// Add il to "MyFunction"
myFunc = myFunc.Append(il);
// Add "MyFunction"
typeBuilder = typeBuilder.Append(myFunc);

// Request to build type
IRequestFor<Type> type = new TypeRequest(typeBuilder);
// Request to create new instance
IRequestFor<Object> newRequest = type.NewRequest();

// Print request
newRequest.PrintTreeTo(Console.Out);

// Get instance
object instance = service.GetRequired<IRequestFor<object>, object>(newRequest);
// Evaluate: value = 4 < 5 ? 0 : 1;
int value = (int)instance.GetType().GetMethod("MyFunction", new Type[] { typeof(int) })!.Invoke(instance, new object[] { 4 })!;
// Print 
Console.WriteLine(value);

View complete request

NewRequest
└── Type = TypeRequest
    └── Key = ContextRequest<TypeBuilder>
        ├── Key = "System.Reflection.Emit.TypeBuilder"
        ├── Value = TypeBuilderRequest
        │   ├── Name = "MyClass_"
        │   └── Attributes = AutoLayout, AnsiClass, Class, Public, AutoClass
        └── Requests[0] = ContextRequest<MethodBuilder>
            ├── Key = "System.Reflection.Emit.Builder"
            ├── Value = MethodBuilderRequest
            │   ├── Name = "MyFunction"
            │   ├── Attributes = PrivateScope, Public, Virtual
            │   ├── ReturnType = System.Int32
            │   └── ParameterTypes[0] = System.Int32
            └── Requests[0] = ContextRequest<ILGenerator>
                ├── Key = "System.Reflection.Emit.ILGenerator"
                ├── Value = ILGeneratorRequest
                ├── Requests[0] = Emit
                │   └── Opcode = ldarg.1
                ├── Requests[1] = Emit
                │   └── Opcode = ldc.i4.5
                ├── Requests[2] = Emit
                │   └── Opcode = clt
                ├── Requests[3] = Emit
                │   ├── Opcode = brtrue.s
                │   └── Parameters[0] = LabelRequest
                │       └── Id = 49972132
                ├── Requests[4] = MarkLabelRequest
                │   └── Label = LabelRequest
                │       └── Id = 65204782
                ├── Requests[5] = Emit
                │   └── Opcode = ldc.i4.1
                ├── Requests[6] = Emit
                │   └── Opcode = ret
                ├── Requests[7] = MarkLabelRequest
                │   └── Label = LabelRequest
                ├── Requests[8] = Emit
                │   └── Opcode = ldc.i4.0
                └── Requests[9] = Emit
                    └── Opcode = ret

Emit Handlers

EmitHandlers is a collection of handlers that participate in building a type. EmitHandlers requires cache and ServiceHandlers as helper handlers.

// Service that handles assembly builder, module builder and type builder
IService service = Services.Create((ServiceHandlers.Instance, EmitHandlers.Instance), CachePolicies.Default);

EmitHandlers
├── TypeBuilderFactory
├── TypeFactory
├── TypeBuiltHandler
├── ConstructorBuilderFactory
├── MethodBuilderFactory
├── FieldBuilderFactory
├── PropertyBuilderFactory
├── DefineMethodOverrideHandler
├── ILGeneratorFactory
├── PropertyBuilderSetSetterHandler
├── PropertyBuilderSetGetterHandler
├── EmitHandler
├── EmitLdIndHandler
├── EmitStIndHandler
├── EmitCastHandler
├── LocalBuilderFactory
├── LabelFactory
└── MarkLabelRequestHandler

Full Example

Full example

using System;
using System.Reflection;
using System.Reflection.Emit;
using Avalanche.Emit;
using Avalanche.Service;

public class index
{
    public static void Run()
    {
        {
            // <1>
            // Service that handles assembly builder, module builder and type builder
            IService service = Services.Create((ServiceHandlers.Instance, EmitHandlers.Instance), CachePolicies.Default);
            // Request to create type builder
            IRequestFor<TypeBuilder> typeBuilder = new TypeBuilderRequest("MyClass_", TypeAttributes.Public | TypeAttributes.Class | TypeAttributes.AutoClass);
            // Request to create method builder for "MyFunction"
            IRequestFor<MethodBuilder> myFunc = new MethodBuilderRequest("MyFunction", MethodAttributes.Public | MethodAttributes.Virtual, typeof(int), typeof(int));
            // Request to create il generator
            IRequestFor<ILGenerator> il = ILGeneratorRequest.Default;
            // Define labels
            IRequestFor<Label> trueLabel = new LabelRequest(), falseLabel = new LabelRequest();
            // "return x < 5 ? 0 : 1"
            il = il.Append(OpCodes.Ldarg_1).Append(OpCodes.Ldc_I4_5).Append(OpCodes.Clt).Append(OpCodes.Brtrue_S, falseLabel);
            // true: return 1;
            il = il.Append(new MarkLabelRequest(trueLabel)).Append(OpCodes.Ldc_I4_1).Append(OpCodes.Ret);
            // false: return 0;
            il = il.Append(new MarkLabelRequest(falseLabel)).Append(OpCodes.Ldc_I4_0).Append(OpCodes.Ret);
            // Add il to "MyFunction"
            myFunc = myFunc.Append(il);
            // Add "MyFunction"
            typeBuilder = typeBuilder.Append(myFunc);

            // Request to build type
            IRequestFor<Type> type = new TypeRequest(typeBuilder);
            // Request to create new instance
            IRequestFor<Object> newRequest = type.NewRequest();

            // Print request
            newRequest.PrintTreeTo(Console.Out);

            // Get instance
            object instance = service.GetRequired<IRequestFor<object>, object>(newRequest);
            // Evaluate: value = 4 < 5 ? 0 : 1;
            int value = (int)instance.GetType().GetMethod("MyFunction", new Type[] { typeof(int) })!.Invoke(instance, new object[] { 4 })!;
            // Print 
            Console.WriteLine(value);
            // </1>
        }
        {
            // <2>
            // Service that handles assembly builder, module builder and type builder
            IService service = Services.Create((ServiceHandlers.Instance, EmitHandlers.Instance), CachePolicies.Default);
            // </2>
            Console.WriteLine(HandlerInfoPrintTreeExtensions.PrintTree(EmitHandlers.Instance));
        }
    }
}