C# - Converting uint to byte[]

Question

So I was using BitConverter.GetBytes() to convert uint32 to byte[], but my the order in the array seems to be backwards. http://msdn.microsoft.com/en-us/library/1184xdy4.aspx (shows that it's byte[] seems to be little endian).

Is there a better way handle this than just using linq to reverse the byte arrays?

Answer 1

Array.Reverse to change the endianess.

Answer 2

Microsoft discusses the little-endian / big-endian issue with the GetBytes() method on the documentation page for BitConverter.

Answer 3

    static byte[] GetBytes(int num)
    {
        byte[] bytes = new byte[4];
        int x, i = bytes.Length;
        while (num > 0)
        {
            num = Math.DivRem(num, 256, out x);
            bytes[--i] = (byte)x;
        }
        return bytes;
    }

Answer 4

If you are going to be moving between platform architectures simply reversing the array might be correct on one platform, but fail on a platform that is already using big endian.

You use the IPAddress.HostToNetworkOrder functions, which will ensure that the data is always in network order (big endian).

uint number = 234234233;
uint bigEndian = IPAddress.HostToNetworkOrder(number);
byte[] b = BitConverter.GetBytes(bigEndian);

Answer 5

So I figured out a big part of my confusion is related to this: http://stackoverflow.com/questions/2023672/islittleendian-field-reports-false-but-it-must-be-little-endian

What I ended up doing was wrapping all the BitConverter calls with call that took an extra parameter to specifiy endianness, then added a function that gets called to check to see if the bytes need to be revered.

public static class BitEndianConverter
{
    public static byte[] GetBytes(bool value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }

    public static byte[] GetBytes(char value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }
    public static byte[] GetBytes(double value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }
    public static byte[] GetBytes(float value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }
    public static byte[] GetBytes(int value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }
    public static byte[] GetBytes(long value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }
    public static byte[] GetBytes(short value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }
    public static byte[] GetBytes(uint value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }
    public static byte[] GetBytes(ulong value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }
    public static byte[] GetBytes(ushort value, bool littleEndian)
    {
        return ReverseAsNeeded(BitConverter.GetBytes(value), littleEndian);
    }

    private static byte[] ReverseAsNeeded(byte[] bytes, bool wantsLittleEndian)
    {
        if (wantsLittleEndian == BitConverter.IsLittleEndian)
            return bytes;
        else
            return (byte[])bytes.Reverse().ToArray();
    }
}