Cast float to int without ANY conversion?

Question

I am writing various types to a byte stream by manually casting and shifting values. I have found this to be more than three times faster than using BitConverter or BinaryWriter.

My problem is with floats. I need to cast them to ints in order to perform shift operations on them, but any cast to int will cause an implicit conversion with truncation, etc. I want the keep the exact binary representation the same. Is this possible?

eg. I want to be able to do similar to:

byte[] bytes = new byte[4];
float myFloat = 32.2;

//following won't compile as can't shift floats.
bytes [0] = (byte)myFloat;
bytes [1] = (byte)(myFloat >> 8);
bytes [2] = (byte)(myFloat >> 16);
bytes [3] = (byte)(myFloat >> 24);

Answer 1

The following does not require unsafe code and is proved to work (I used it for years across various .NET versions):

[StructLayout(LayoutKind.Explicit)]
public struct FloatAndUIntUnion
{
    [FieldOffset(0)]
    public uint  UInt32Bits;
    [FieldOffset(0)]
    public float FloatValue;
}


FloatAndUIntUnion f2i = default(FloatAndUIntUnion);
f2i.FloatValue = aFloat;    // write as float
uint i = f2i.UInt32Bits;    // read back as int

Note that the float→int direction can be simpler:

int i = aFloat.GetHashCode();

However, it is much more obscure because not documented (as per MSDN), although confirmed by this post. (That is, the behaviour was the same in 2006 as now in 2013, and I see no reason to change it in the future — but it may happen, and I'm unsure whether it would qualify as a backward-incompatible change or not.)