CODEWITHSUNDEEP
c#arrays
Joel Barsotti
Joel Barsotti

Reputation: 3089

C# - Converting uint to byte[]

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?

Upvotes: 14

Views: 50565

Answers (5)

Chris Taylor
Chris Taylor

Reputation: 53699

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

Upvotes: 7

bytefire
bytefire

Reputation: 4422

Following is a method to always get big endian byte array quickly.

    public static byte[] GetBigEndianBytes(UInt32 val, bool isLittleEndian)
    {
        UInt32 bigEndian = val;
        if (isLittleEndian)
        {
            bigEndian = (val & 0x000000FFU) << 24 | (val & 0x0000FF00U) << 8 |
                 (val & 0x00FF0000U) >> 8 | (val & 0xFF000000U) >> 24;
        }
        return BitConverter.GetBytes(bigEndian);
    }

This overload can be handy, although care must be taken when working across machines with different endian-nesses.

    public static byte[] GetBigEndianBytes(UInt32 val)
    {
        return GetBigEndianBytes(val, BitConverter.IsLittleEndian);
    }

Upvotes: 1

Joel Barsotti
Joel Barsotti

Reputation: 3089

So I figured out a big part of my confusion is related to this: 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();
    }
}

Upvotes: 3

C8H10N4O2
C8H10N4O2

Reputation: 1696

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

Upvotes: 5

leppie
leppie

Reputation: 117230

Array.Reverse to change the endianess.

Upvotes: 7

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