convert byte array to 16 bits float

问题

I have a network array of 2 bytes that I need to convert to float [values between -1 ... 1-2.E(-15)]
examples :

byte[] Arr1={0x70 , 0x54} //==> Result = 0.660
byte[] Arr2={0x10 , 0x37} //==> Result = 0.430

Any solutions to overpass this ?

回答1:

What standard you have used that gave you {0x70 , 0x54} ?

I have made a sample code for Half-precision floating point conversation according to IEEE 754-2008 standard.
https://en.wikipedia.org/wiki/Half-precision_floating-point_format

public static float toTwoByteFloat(byte HO, byte LO)
{
    var intVal = BitConverter.ToInt32(new byte[] { HO, LO, 0, 0 }, 0);

    int mant = intVal & 0x03ff;
    int exp = intVal & 0x7c00;
    if (exp == 0x7c00) exp = 0x3fc00;
    else if (exp != 0)
    {
        exp += 0x1c000;
        if (mant == 0 && exp > 0x1c400)
            return BitConverter.ToSingle(BitConverter.GetBytes((intVal & 0x8000) << 16 | exp << 13 | 0x3ff), 0);
    }
    else if (mant != 0)
    {
        exp = 0x1c400;
        do
        {
            mant <<= 1;
            exp -= 0x400;
        } while ((mant & 0x400) == 0);
        mant &= 0x3ff;
    }
    return BitConverter.ToSingle(BitConverter.GetBytes((intVal & 0x8000) << 16 | (exp | mant) << 13), 0);
}

private static byte[] I2B(int input)
{
    var bytes = BitConverter.GetBytes(input);
    return new byte[] { bytes[0], bytes[1] };
}

public static byte[] ToInt(float twoByteFloat)
{
    int fbits = BitConverter.ToInt32(BitConverter.GetBytes(twoByteFloat), 0);
    int sign = fbits >> 16 & 0x8000;
    int val = (fbits & 0x7fffffff) + 0x1000;
    if (val >= 0x47800000)
    {
        if ((fbits & 0x7fffffff) >= 0x47800000)
        {
            if (val < 0x7f800000) return I2B(sign | 0x7c00);
            return I2B(sign | 0x7c00 | (fbits & 0x007fffff) >> 13);
        }
        return I2B(sign | 0x7bff);
    }
    if (val >= 0x38800000) return I2B(sign | val - 0x38000000 >> 13);
    if (val < 0x33000000) return I2B(sign);
    val = (fbits & 0x7fffffff) >> 23;
    return I2B(sign | ((fbits & 0x7fffff | 0x800000) + (0x800000 >> val - 102) >> 126 - val));
}

You'll use it like following

private void button1_Click(object sender, EventArgs e)
{
    var x = ToInt(0.660f);  //it's 0x48 0x39
    var y = toTwoByteFloat(x[0], x[1]); //it's 0.66015625 
}

回答2:

It has been answered as this , the value of the bytes is a pourcentage , so it must be divided by 32767 example : byte[] Arr1={0x70 , 0x54} //==> Result =0x5470/0x7fff= 0.660 byte[] Arr2={0x10 , 0x37} //==> Result = 0x3710/0x7fff= 0.430

来源：https://stackoverflow.com/questions/37759848/convert-byte-array-to-16-bits-float

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