How to convert float to uint by float representation?

Question

In C I will do this to convert float representation of number into DWORD. Take the value from the address and cast the content to DWORD.

dwordVal = *(DWORD*)&floatVal;

So for example 44.54321 will become 0x42322C3F.

How can I do the same in C#?

Temper

Actually *(DWORD*)&floatVal is the wrong way to do it in C as it breaks strict aliasing rules that C compilers rely on for optimisation. Correct ways involve a union (see C99tc3 footnote 82) or memcpy(). – Olympiaolympiad

Answer 1

You can use the BitConverter class:

uint value = BitConverter.ToUInt32(BitConverter.GetBytes(44.54321F), 0);
Console.WriteLine("{0:x}", value); // 42322c3f

You could also do this more directly using an unsafe context:

float floatVal = 44.54321F;
uint value;
unsafe { 
    value = *((uint*)(&floatVal));
}
Console.WriteLine("{0:x}", value); // 42322c3f

However, I'd strongly recommend avoiding this. See Should you use pointers (unsafe code) in C#?

Scala

Answer 2

Use the BitConverter class:

float f = 44.54321f;
uint u = BitConverter.ToUInt32(BitConverter.GetBytes(f), 0);
System.Diagnostics.Debug.Assert(u == 0x42322C3F);

Rms

Answer 3

In .NET Core 2.0 you can use BitConverter.SingleToInt32Bits(). The reverse operation is BitConverter.Int32BitsToSingle()

.NET 6 added 2 more utilities:

• BitConverter.UInt32BitsToSingle()
• BitConverter.SingleToUInt32Bits()

Lexine

Answer 4

bitconvert creates a new byte array on every call. this is the solution:

    unsafe public static float ToDecibel(this float x)
    {
        uint* y = (uint*)&x;
        (*y) &= 0x7fffffff;
        return (*y) * 7.17711438e-7f - 764.6161886f;
    }

Constanta

+1 for remembering unsafe. BUT ... This changes x! Better to use uint y = *(uint*)&x; y &= 0x7fffffff; return y * 7.17711438e-7f - 764.6161886f; to avoid changing x. – Meraree