Big Endian float conversion

[piote]

Hi,
I am trying to convert a Big Endian data file to something readable on most Windows PCs. I do ok with integer data but I cannot convert the floating points (32-bit IEEE).
1) Is it possible for a BinaryReader to account for Big Endian, such that .ReadSingle() would return the correct value?

2) If I have to read the bytes one at a time and reverse them, is there a way to type cast it to a float?

I pursued #2 for a while, but C# type-casting seems to convert the actual value and not the binary that represents it. So the result is something like 1.12E9 instead of 89.9.
I really don't know how to make it work correctly. I would be grateful for any help.

Regards,
Piote

 

[BoulderBum]

I didn't know the answer off the top of my head, but these Google hits looked promising:

http://www.thescripts.com/forum/thread454822.html

-and-

http://forums.asp.net/p/1151121/1878503.aspx

That last link you're probably already familiar with, though.

MCP, MCTS - .NET Framework 2.0 Web Applications

 

[phinoppix]

I do not know about #1, but for #2, manually tweaking the byte order is the only way to go to convert big-endian ints to little-endian. Here's how I do it using a struct, which works well for 4-byte numeric types, including float. (Note that you can also use the BitConverter.ToSingle() which takes a byte array.)

[StructLayout(LayoutKind.Explicit)]
struct UnionInt
{
	[FieldOffset(0)] public byte byte0;
	[FieldOffset(1)] public byte byte1;
	[FieldOffset(2)] public byte byte2;
	[FieldOffset(3)] public byte byte3;

	[FieldOffset(0)] public float AsSingle;
	[FieldOffset(0)] public int AsInt32;

	public void FromBigEndian(byte[] bigEndianData)
	{
		this.byte0 = bigEndianData[3];
		this.byte1 = bigEndianData[2];
		this.byte2 = bigEndianData[1];
		this.byte3 = bigEndianData[0];
	}
}

Here's how to use it...

[COLOR=green]// Simulate big endian.[/color]
byte[] b = new byte[] {0x42, 0xb3, 0xcc, 0xcd};
float bf = BitConverter.ToSingle(b, 0);
MessageBox.Show(string.Format("big endian data = {0}", bf));

[COLOR=green]// Convert to little endian. Output is 89.9[/color]
UnionInt val = new UnionInt();
val.FromBigEndian(b);
MessageBox.Show("val = " + val.AsSingle.ToString());

 

[piote]

Thanks for help!

Regards,
Piote