BigEndianBitConverter in Silverlight?

Question

I'm trying to use the MiscUtil.Conversion utility in Silverlight. http://www.yoda.arachsys.com/csharp/miscutil/

When I try to compile it, I get an error saying Silverlight's BitConverter class does not have these two methods:

DoubleToInt64Bits Int64BitsToDouble

Well, I opened up Reflector and found them in mscorlib:

public unsafe long DoubleToInt64Bits(double value)
{
  return *(((long*)&value));
}

public unsafe double Int64BitsToDouble(long value)
{
  return *(((double*) &value));
}

But the problem with that is that Silverlight does not allow unsafe code. In the project properties menu there's a empty checkbox next to "allow unsafe code", but you cannot change the value.

How can I do this in Silverlight?

Answer 1

Have a look at BitConverter.ToDouble(byte[], int) and BitConverter.GetBytes(double). If they exist in Silverlight, they may well be good enough. I'm going to investigate this for Protocol Buffers anyway - if I find a good solution, I'll port it back to MiscUtil.

Answer 2

I don't know if this will work in Silverlight or not, but it does work in a Console application, and it doesn't require unsafe code.

If you can get your double values into a byte array, you can swap the bytes in the byte array to change endian-ness. The process can also be reversed, changing the byte array back into a double.

The code that follows illustrates how to convert between double and byte array, using System.InteropServices. The Main method returns two values in the console: 8 and 3.14159. The 8 indicates that a byte array of 8 bytes was successfully created from the double, and 3.14159 indicates that the double was correctly extracted from the byte array.

using System;
using System.IO;
using System.Text;
using System.Runtime.InteropServices;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            double d = 3.14159d;
            byte[] b = ToByteArray(d);
            Console.WriteLine(b.Length);
            Console.ReadLine();
            double n = FrpmByteArray(b);
            Console.WriteLine(n.ToString());
            Console.ReadLine();
        }
        public static byte[] ToByteArray(object anything)
        {
            int structsize = Marshal.SizeOf(anything);
            IntPtr buffer = Marshal.AllocHGlobal(structsize);
            Marshal.StructureToPtr(anything, buffer, false);
            byte[] streamdatas = new byte[structsize];
            Marshal.Copy(buffer, streamdatas, 0, structsize);
            Marshal.FreeHGlobal(buffer);
            return streamdatas;
        }
        public static double FromByteArray(byte[] b)
        {
            GCHandle handle = GCHandle.Alloc(b, GCHandleType.Pinned);
            double d = (double)Marshal.PtrToStructure(
                handle.AddrOfPinnedObject(),
                typeof(double));
            handle.Free();
            return d;
        }

    }
}