Convert int bits to float bits

Question

Convert int bits to float bits

I'm in the process of creating a buffer that will read/write in a banner in which I can completely eradicate the problems that comes with TCP-Segmentation. The only problem I've ran into is the float variable, everything else works fine, besides for the float. I can't find any information on how to convert int32 bits into a float.

When converting a float to int bits, the following method is used (Ripped straight out of java's source code, and converted)

private int floatToIntBits(float value)
{
    int result = BitConverter.ToInt32(BitConverter.GetBytes(value), 0);
    if (((result & 0x7F800000) == 0x7F800000) && (result & 0x80000000) != 0)
        result = 0x7fc00000;
    return result;
}

However, now I need to do the opposite, unfortunately, there isn't any functions in the BitConverter class that works with float.

I can';t find much information in the JavaDocs either, not any that I can personally make use of, You can find info here.

c#

bit-manipulation

asked on Stack Overflow Dec 1, 2014 by

Hobbyist • edited Dec 1, 2014 by

abatishchev

6 Answers

Vexingly, if you were using double and long, there is BitConverter.DoubleToInt64Bits and BitConverter.Int64BitsToDouble. I have genuinely no idea why there aren't Single / Int32 equivalents, as it forces you to create a pointless byte[] on the heap (it doesn't even let you pass in a pre-existing buffer).

If you are happy to use unsafe code, you can actually do it all in a simply data thunk, without any method calls or arrays:

public static unsafe int SingleToInt32Bits(float value) {
    return *(int*)(&value);
}
public static unsafe float Int32BitsToSingle(int value) {
    return *(float*)(&value);
}

answered on Stack Overflow Dec 1, 2014 by

Marc Gravell

Use the BitConverter.ToSingle method:

int i = ...;
float f = BitConverter.ToSingle(BitConverter.GetBytes(i), 0);

answered on Stack Overflow Dec 1, 2014 by

Dmitry

The keyword float is an alias for the data type System.Single.

You can use the BitConverter.ToSingle to convert four bytes into a float.

answered on Stack Overflow Dec 1, 2014 by

Guffa

BitConverter creates some overhead and unnecessary buffer. This solution is almost as fast as unsafe conversion:

[StructLayout(LayoutKind.Explicit)]
struct FloatToInt 
{
    [FieldOffset(0)]private float f;
    [FieldOffset(0)]private int i;
    private static FloatToInt inst = new FloatToInt();
    public static int Convert(float value)
    {
        inst.f = value;
        return t.i;
    }
}

answered on Stack Overflow Dec 10, 2019 by

Aberro • edited Dec 10, 2019 by

Aberro

using the System.Runtime.CompilerServices.Unsafe nuget package

Unsafe.As<float, int>(ref value);

Will convert a float to an int

and

Unsafe.As<int, float>(ref value);

will convert an int to a float

answered on Stack Overflow Dec 19, 2018 by

Yair Halberstadt

Targeting .NET Core we are now finally able to simply use BitConverter.SingleToInt32Bits() and BitConverter.Int32BitsToSingle()!

answered on Stack Overflow Sep 21, 2018 by

D.R.

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