azsteal-SmartSpawnController/src/Utils/Emit.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;
using System.Threading.Tasks;

namespace astealz.SmartSpawnController.Utils
{
    public delegate T PropertyGetter<out T>(object instance);
    public delegate void PropertySetter<in T>(object instance, T value);
    public delegate T MethodInvoker<in T1, out T>(object instance, T1 arg1);
    public delegate void MethodInvoker<in T>(object instance, T value);

    // methods in this class creates a dynamic methods (and return a delegate) for quick access to a property or method which cannot be called by a direct call
    // this approach is about 5x faster than reflection
    static class Emit
    {
        // delegate for property getter
        public static PropertyGetter<T> CreateDynamicPropertyGetter<T>(
            PropertyInfo propertyInfo,
            BindingFlags bindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance)
        {
            if (propertyInfo == null)
                throw new ArgumentNullException(nameof(propertyInfo));

            if (!typeof(T).IsAssignableFrom(propertyInfo.PropertyType))
                throw new ArgumentException($"Property type '{propertyInfo.PropertyType}' does not match return type '{typeof(T)}'");

            var getterMethodInfo = propertyInfo.GetGetMethod(true);
            if (getterMethodInfo == null)
                throw new InvalidOperationException($"Can't find getter for property '{propertyInfo.Name}' in '{propertyInfo.DeclaringType}'");

            var dynMethod = new DynamicMethod($"__get_{typeof(T).Name}_prop_{propertyInfo.Name}", typeof(T), new[] { typeof(object) }, propertyInfo.DeclaringType, true);
            var ilGen = dynMethod.GetILGenerator();
            if (getterMethodInfo.IsStatic)
            {
                ilGen.Emit(OpCodes.Call, getterMethodInfo);
            }
            else
            {
                ilGen.Emit(OpCodes.Ldarg_0);
                ilGen.Emit(OpCodes.Castclass, propertyInfo.DeclaringType);
                ilGen.Emit(OpCodes.Callvirt, getterMethodInfo);
            }
            ilGen.Emit(OpCodes.Ret);
            return (PropertyGetter<T>)dynMethod.CreateDelegate(typeof(PropertyGetter<T>));
        }

        // delegate for property setter
        public static PropertySetter<T> CreateDynamicPropertySetter<T>(
            PropertyInfo propertyInfo,
            BindingFlags bindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance)
        {
            if (propertyInfo == null)
                throw new ArgumentNullException(nameof(propertyInfo));

            if (!typeof(T).IsAssignableFrom(propertyInfo.PropertyType))
                throw new ArgumentException($"Property type '{propertyInfo.PropertyType}' does not match the type of value '{typeof(T)}'");

            var setterMethodInfo = propertyInfo.GetSetMethod(true);
            if (setterMethodInfo == null)
                throw new InvalidOperationException($"Can't find setter for property '{propertyInfo.Name}' in '{propertyInfo.DeclaringType}'");

            var dynMethod = new DynamicMethod($"__set_{typeof(T).Name}_prop_{propertyInfo.Name}", null, new[] { typeof(object), typeof(T) }, propertyInfo.DeclaringType);
            var ilGen = dynMethod.GetILGenerator();
            if (setterMethodInfo.IsStatic)
            {
                ilGen.Emit(OpCodes.Ldarg_1);
                ilGen.Emit(OpCodes.Call, setterMethodInfo);
                ilGen.Emit(OpCodes.Ret);
            }
            else
            {
                ilGen.Emit(OpCodes.Ldarg_0);
                ilGen.Emit(OpCodes.Castclass, propertyInfo.DeclaringType);
                ilGen.Emit(OpCodes.Ldarg_1);
                ilGen.Emit(OpCodes.Callvirt, setterMethodInfo);
            }
            ilGen.Emit(OpCodes.Ret);
            return (PropertySetter<T>)dynMethod.CreateDelegate(typeof(PropertySetter<T>));
        }

        // delegate to invoke a method with one argument and return value
        public static MethodInvoker<T1, TR> CreateDynamicMethodInvoker<T1, TR>(MethodInfo methodInfo)
        {
            if (methodInfo == null)
                throw new ArgumentNullException(nameof(methodInfo));

            if (!typeof(TR).IsAssignableFrom(methodInfo.ReturnType))
                throw new ArgumentException($"Method return type '{methodInfo.ReturnType}' does not match return type '{typeof(TR)}'");

            var dynMethod = new DynamicMethod(
                $"__invoke_{typeof(TR).Name}_method_{methodInfo.Name}", // method name is only for debugging
                typeof(TR),
                new[] { typeof(object), typeof(T1) }, // add method arguments here (T2, T3, T4...)
                methodInfo.DeclaringType,
                true);

            var ilGen = dynMethod.GetILGenerator();
            if (methodInfo.IsStatic)
            {
                // if target method is static push first argument on stack
                ilGen.Emit(OpCodes.Ldarg_1);
                ilGen.Emit(OpCodes.Call, methodInfo);
            }
            else
            {
                // otherwise push instance and cast it to type where method is declared
                ilGen.Emit(OpCodes.Ldarg_0);
                ilGen.Emit(OpCodes.Castclass, methodInfo.DeclaringType);
                // then push method arguments
                ilGen.Emit(OpCodes.Ldarg_1);
                ilGen.Emit(OpCodes.Callvirt, methodInfo);
            }
            ilGen.Emit(OpCodes.Ret);
            return (MethodInvoker<T1, TR>)dynMethod.CreateDelegate(typeof(MethodInvoker<T1, TR>));
        }

        public static MethodInvoker<T> CreateDynamicMethodInvoker<T>(MethodInfo methodInfo)
        {
            if (methodInfo == null)
                throw new ArgumentNullException(nameof(methodInfo));

            if (!typeof(void).Equals(methodInfo.ReturnType))
                throw new ArgumentException($"Method return type '{methodInfo.ReturnType}' does not match return type 'void'");

            var dynMethod = new DynamicMethod(
                $"__invoke_void_method_{methodInfo.Name}", // method name is only for debugging
                typeof(void),
                new[] { typeof(object), typeof(T) }, // add method arguments here (T2, T3, T4...)
                methodInfo.DeclaringType,
                true);

            var ilGen = dynMethod.GetILGenerator();
            if (methodInfo.IsStatic)
            {
                // if target method is static push first argument on stack
                ilGen.Emit(OpCodes.Ldarg_1);
                ilGen.Emit(OpCodes.Call, methodInfo);
            }
            else
            {
                // otherwise push instance and cast it to type where method is declared
                ilGen.Emit(OpCodes.Ldarg_0);
                ilGen.Emit(OpCodes.Castclass, methodInfo.DeclaringType);
                // then push method arguments
                ilGen.Emit(OpCodes.Ldarg_1);
                ilGen.Emit(OpCodes.Callvirt, methodInfo);
            }
            ilGen.Emit(OpCodes.Ret);
            return (MethodInvoker<T>)dynMethod.CreateDelegate(typeof(MethodInvoker<T>));
        }
    }
}