How to implement multiplication without using multiplication operator in .NET [closed]

Answer 1

Look, ma, no * operator!

using System;
using System.Reflection.Emit;

static class Program
{
    delegate uint UintOpDelegate(uint a, uint b);

    static void Main()
    {
        var method = new DynamicMethod("Multiply",
            typeof(uint), new Type[] { typeof(uint), typeof(uint) });
        var gen = method.GetILGenerator();
        gen.Emit(OpCodes.Ldarg_0);
        gen.Emit(OpCodes.Ldarg_1);
        gen.Emit(OpCodes.Mul);
        gen.Emit(OpCodes.Ret);

        var del = (UintOpDelegate)method.CreateDelegate(typeof(UintOpDelegate));

        var product = del(2, 3); //product is now 6!
    }
}

Even better:

using System;
using System.Runtime.InteropServices;

delegate uint BinaryOp(uint a, uint b);

static class Program
{
    [DllImport("kernel32.dll", SetLastError = true)]
    static extern bool VirtualProtect(
        IntPtr address, IntPtr size, uint protect, out uint oldProtect);

    static void Main()
    {
        var bytes = IntPtr.Size == sizeof(int) //32-bit? It's slower BTW
            ? Convert.FromBase64String("i0QkBA+vRCQIww==")
            : Convert.FromBase64String("D6/Ki8HD");
        var handle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
        try
        {
            uint old;
            VirtualProtect(handle.AddrOfPinnedObject(),
                (IntPtr)bytes.Length, 0x40, out old);
            var action = (BinaryOp)Marshal.GetDelegateForFunctionPointer(
                handle.AddrOfPinnedObject(), typeof(BinaryOp));
            var temp = action(3, 2); //6!
        }
        finally { handle.Free(); }
    }
}