将随机字节转换为.net十进制0.1小数范围

我正在玩TRNG usb设备，并成功地将随机字节转换为c#中的各种可用数据。

我想创建一个介于0..1之间的。net十进制值(例如:0.37327)直接从字节使用二进制读取器(或其他直接字节->十进制)的方法。

// assume: byte[] random_data of appropriate length, patterned for a 0..1 range decimal value = new BinaryReader(new MemoryStream(random_data)).ReadDecimal();

我正在寻找十进制的字节格式，但它看起来可能不是一个标准?

• 如何将字节值转换为小数?
• .NET十进制跨平台标准

这是我的业余爱好，所以我可以接受使用一些将来可能会改变的东西。我已经查看了为示例输入十进制值生成的字节-我看到了负和精确标志(最后int32中的1Ch max ?)，但是最小/最大数据值转储编译器常量让我有点难倒，并且我生成的值高于零或无效值:

• 最接近1的分数值(0.99…9):FFFFFF0F 6102253E 5ECE4F20 00001C00
• 最接近0(.00…1)的小数值:01000000 00000000 00000000 00001C00

你能帮我找到生成完整分数0的正确路径吗?1范围?

编辑"最终"代码，感谢大家!

这是我最终创建一个范围为[0..]的无偏随机小数的c#代码。1]从合适的随机字节流(如TRNG设备，www.Random.org或CSPRNG算法)。生成的值看起来不错，边界测试通过了，只要我避免了令人尴尬的打字错误和复制/粘贴错误，这应该是可用的。

谢谢你的帮助和有趣的讨论!

private decimal RandomDecimalRange01()
{
    // 96 bits of random data; we'll use 94 bits to directly map decimal's max precision 0..1 range
    byte[] data = new byte[12];
    decimal value = 0;
    // loop until valid value is generated, discarding invalids values. Mostly controlled by top 2 bits: 11 is always invalid, 00 or 01, is always valid, 10 has valid and invalid ranges. Odds make loop generally find value in one or a few iterations.
    while (true)
    {
        // Acquire random bytes from random source (like TRNG device or CSPRNG api)
        if (!trng.GetBytes(data))
        {
            throw new Exception("Failed to aquire random bytes from source");
        }
        else
        {
            // Read 94 random bits (pull 96 bits, discard 2)
            BinaryReader reader = new BinaryReader(new MemoryStream(data));
            int low = reader.ReadInt32();
            int mid = reader.ReadInt32();
            int high = reader.ReadInt32() & 0x3FFFFFFF; // don't consume upper 2 random bits - out of range
            // Discard invalid values and reloop (interpret special invalid value as 1)
            if (high > 542101086)
            {
                continue;
            }
            else if (high == 542101086)
            {
                if (mid > 1042612833)
                {
                    continue;
                }
                else if (mid == 1042612833)
                {
                    if (low > 268435455)
                    {
                        // Special override to generate 1 value for inclusive [0..1] range - interpret the smallest invalid value as 1. Remove code for exclusive range [0..1)
                        if (low == 268435456)
                        {
                            value = 1m; // return 1.0
                            break;
                        }
                        continue;
                    }
                }
            }
            // return random decimal created from parts - positive, maximum precision 28 (1C) scale
            value = new decimal(low, mid, high, false, 28);
            break;
        }
    }
    return value;
}

运行TrueRNGPro TRNG设备字节通过算法生成的值示例

0.8086691474438979082567747041
0.4268035919422123276460607186
0.7758625805098585303332549015
0.0701321080502462116399370731
0.3127190777525873850928167447
0.6022236739048965325585049764
0.1244605652187291191393036867

围绕感兴趣的边界值进行测试

// test databyte values for max & min ranges
new byte[] { 0x01, 0x00, 0x00, 0x10, 0x61, 0x02, 0x25, 0x3E, 0x5E, 0xCE, 0x4F, 0x20 }; // boundary: 1 too large for algorithm, will be discarded
new byte[] { 0x00, 0x00, 0x00, 0x10, 0x61, 0x02, 0x25, 0x3E, 0x5E, 0xCE, 0x4F, 0x20 }; // boundary: special 1 more than largest valid .99999..., interpret as 1 value
new byte[] { 0xFF, 0xFF, 0xFF, 0x0F, 0x61, 0x02, 0x25, 0x3E, 0x5E, 0xCE, 0x4F, 0x20 }; // boundary: largest valid value .9999...
new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; // boundary: smallest valid value, should be 0
new byte[] { 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; // boundary: 1 more than smallest valid value, should be .000...1

for (int exponent=0; exponent<=28; exponent++) {
    BigInteger max = BigInteger.Pow(10, exponent);
    for (int i = 0; i <= max; i++) {
        var fmt = "96bitinteger: {0}, exponent: {1}";
        Console.WriteLine(String.Format(fmt, i, exponent));
    }
}

int[] data = new int[] { 0x10000000, 0x3e250261, 0x204fce5e, 0x1C0000 };
var random_data = data.SelectMany(BitConverter.GetBytes).ToArray();
decimal value = new BinaryReader(new MemoryStream(random_data)).ReadDecimal();
Console.WriteLine(value);

if c < 0x204fce5e:
    a can be anything
    b can be anything
elif c = 0x204fce5e:
    if b < 0x3e250261:
        a can be anything
    elif b = 0x3e250261
        constrain a <= 10000000
    b can not be greater than 0x3e250261
c can not be greater than 0x204fce5e.