C#浮点到二进制字符串，反之亦然

Question

我正在将浮点值转换为二进制字符串表示：

float resulta = 31.0 / 15.0;    //2.0666666
var rawbitsa = ToBinaryString(resulta); //returns 01000000000001000100010001000100

其中 ToBinaryString 编码为：

static string ToBinaryString(float value)
{

        int bitCount = sizeof(float) * 8; // never rely on your knowledge of the size
        // better not use string, to avoid ineffective string concatenation repeated in a loop
        char[] result = new char[bitCount]; 

        // now, most important thing: (int)value would be "semantic" cast of the same
        // mathematical value (with possible rounding), something we don't want; so:
        int intValue = System.BitConverter.ToInt32(BitConverter.GetBytes(value), 0);

        for (int bit = 0; bit < bitCount; ++bit)
        {
            int maskedValue = intValue & (1 << bit); // this is how shift and mask is done.
            if (maskedValue > 0)
                maskedValue = 1;
            // at this point, masked value is either int 0 or 1
            result[bitCount - bit - 1] = maskedValue.ToString()[0];
        }

        return new string(result); // string from character array
}

现在我想将此二进制字符串转换为浮点值。

我尝试了以下方法，但它返回值“2.8293250329111622E-315”

string bstra = "01000000000001000100010001000100";
long w = 0;
for (int i = bstra.Length - 1; i >= 0; i--) w = (w << 1) + (bstra[i] - '0');
double da = BitConverter.ToDouble(BitConverter.GetBytes(w), 0); //returns 2.8293250329111622E-315

通过传入值“01000000000001000100010001000100”，我想要值“2.0666666”

为什么我得到一个错误的值？我错过了什么吗？

Answer 1

你让这件事变得比需要的困难得多；错误似乎大部分在字符解析代码中，但您不需要做所有这些。

你可以这样尝试：

static string ToBinaryString(float value)
{
    const int bitCount = sizeof(float) * 8;
    int intValue = System.BitConverter.ToInt32(BitConverter.GetBytes(value), 0);
    return Convert.ToString(intValue, 2).PadLeft(bitCount, '0');
}

static float FromBinaryString(string bstra)
{
    int intValue = Convert.ToInt32(bstra, 2);
    return BitConverter.ToSingle(BitConverter.GetBytes(intValue), 0);
}

例子：

float resulta = 31.0F / 15.0F; //2.0666666
var rawbitsa = ToBinaryString(resulta);
Console.WriteLine(rawbitsa); //01000000000001000100010001000100
var back = FromBinaryString(rawbitsa);
Console.WriteLine(back); //2.0666666

注意GetBytes 的使用效率有点低；如果你对unsafe 代码没问题，你可以删除所有这些。

另请注意，此代码是特定于 CPU 的 - 它取决于字节序。