如何SQL服务器store/transfer十进制流

Question

我正在研究 MS-TDS 协议，我想做的是 read/write TDS 流，get/set System.Data.DataTable from/to 它。除了 decimal varchar(max) varbinary(max) columns

在 C# 中，我得到了 12345678912345678912.3456789m 和 1234567891234567891.23456789m

的以下结果

var bits = decimal.GetBits(12345678912345678912.3456789m)
using (var ms = new System.IO.MemoryStream())
{
    foreach (var b in bits)
        ms.Write(BitConverter.GetBytes(b), 0, 4);
    var decimalBytes = ms.ToArray();
}

 10 15 5F 04 7C 9F B1 E3 F2 FD 1E 66 00 00 00 07 00
 10 15 5F 04 7C 9F B1 E3 F2 FD 1E 66 00 00 00 08 00

这些对我来说完全有意义，最后一个字节是十进制大小（位置），即7和8，值部分是相同的。但在 sql 中，它们看起来完全不同：

SELECT CAST(CAST(12345678912345678912.3456789 AS decimal(38,15)) AS varbinary)
SELECT CAST(CAST(1234567891234567891.23456789 AS decimal(38,15)) AS varbinary)
results:
0x260F 0001 0075 AA3F 0AF2 2A3A DB18 0560 B060 0200
0x260F 0001 80D8 5D06 01E5 9D52 7C82 0070 DE3C 0000

并且在 TDS 流 DataType=[0x6A,0x11,0x26,0x0F] decimal(38,15)、sql 服务器 returns 中：

0x81, // token "COLMETADATA"
0x03, 0x00, 0x00, 0x00, // 3 columns

0x00, 0x00, 0x00, 0x00, 0x09, 0x00, // usertype = 0, falgs = 9
0xa7, 0xff, 0xff, 0x09, 0x04, 0xd0, 0x00, 0x34, // 0xA7=BIGVARCHRTYPE  0xffff=MAX, 
0x0e, 0x56, 0x00, 0x41, 0x00, 0x52, 0x00, 0x43, 0x00, 0x48, 0x00, 0x41, 0x00, 0x52, 0x00, 0x4d, 0x00, 0x41, 0x00, 0x58, 0x00, 0x5f, 0x00, 0x43, 0x00, 0x6f, 0x00, 0x6c, 0x00, // unicode "VARCHARMAX_Col"

0x00, 0x00, 0x00, 0x00, 0x09, 0x00, // usertype = 0, falgs = 9
0x6a, 0x11, 0x26, 0x0f, // 0x6A=DECIMAL  0x11=Size, precision = (38,15)
0x0b, 0x44, 0x00, 0x45, 0x00, 0x43, 0x00, 0x49, 0x00, 0x4d, 0x00, 0x41, 0x00, 0x4c, 0x00, 0x5f, 0x00, 0x43, 0x00, 0x6f, 0x00, 0x6c, 0x00, // unicode "DECIMAL_Col"

0x00, 0x00, 0x00, 0x00, 0x09, 0x00, // usertype = 0, falgs = 9
0xa5, 0xff, 0xff, // 0xA5=BIGVARBINTYPE 0xffff=MAX
0x0d, 0x56, 0x00, 0x41, 0x00, 0x52, 0x00, 0x42, 0x00, 0x49, 0x00, 0x4e, 0x00, 0x4d, 0x00, 0x41, 0x00, 0x58, 0x00, 0x5f, 0x00, 0x43, 0x00, 0x6f, 0x00, 0x6c, 0x00, // unicode "VARBINMAX_Col"

0xd1, // token "ROW"
0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, 0x41, 0x41, 0x41, 0x41, 0x42, 0x00, 0x00, 0x00, 0x00, // varchar(max) value, how to read this ?
0x11, 0x01, 0x00, 0x92, 0xa8, 0x7c, 0x7e, 0xe4, 0x25, 0x1a, 0x0e, 0xab, 0x6b, 0x4d, 0x82, 0x84, 0x04, 0x00, // decimal value, how to read this ?
0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, 0x61, 0x61, 0x61, 0x61, 0x62, 0x00, 0x00, 0x00, 0x00, // varbinary(max) value, how to read this ?

0xd1, // token "ROW"
0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, 0x41, 0x41, 0x41, 0x41, 0x43, 0x00, 0x00, 0x00, 0x00,
0x11, 0x01, 0x00, 0x75, 0xaa, 0x3f, 0xa6, 0x63, 0x9d, 0x02, 0x1b, 0x91, 0x57, 0xa1, 0xa6, 0x73, 0x00, 0x00,
0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, 0x61, 0x61, 0x61, 0x61, 0x63, 0x00, 0x00, 0x00, 0x00,

0xd2,  // token "NBCROW"
0x05,  // NullBitmap 00000101:  1st and 3rd columns are null
0x11, 0x01, 0x50, 0x24, 0xc2, 0x2a, 0xf2, 0x77, 0xd5, 0x97, 0x0f, 0x03, 0xee, 0xf5, 0x02, 0x00, 0x00, 0x00,

第一行的十进制值为

0x11, 0x01, 0x00, 0x92, 0xa8, 0x7c, 0x7e, 0xe4, 0x25, 0x1a, 0x0e, 0xab, 0x6b, 0x4d, 0x82, 0x84, 0x04, 0x00,

0x11应该是长度，0x01表示正值（出自post ）问题：如何将这些字节解析为十进制值？我应该如何将 varchar(max) varbinary(max) 值写入 TDS ROW TokenStream？感谢任何帮助

Answer 1

我明白了。不同之处在于TDS stream使用第一个字节作为符号并使用固定小数点，decimal.GetBits使用最后一个字节中的几个位作为符号和小数点

// write decimal to TDS stream
static byte[] DecimalBytes(decimal dec, int precision = 15)
{
    var round = decimal.Round(dec, precision);
    var valueToWrite = round;
    var sign = round < 0 ? (byte)0x00 : (byte)0x01;
    // get the string
    var str = round.ToString();
    // string without Decimal point
    var numbers = str.Replace(".", string.Empty);
    var dotIdx = str.IndexOf('.');
    if (dotIdx > 0)
    {
        // there must be {precision} digits on the right side of "."
        var padding = precision - (numbers.Length - dotIdx);
        // padding numbers with '0' to precision length
        numbers = numbers.PadRight(numbers.Length + padding, '0');
    }
    else
    {
        numbers = numbers.PadRight(numbers.Length + precision, '0');
    }
    if (!decimal.TryParse(numbers, out valueToWrite))
    {
        throw new ArgumentOutOfRangeException($"Invalid decimal value for Database Type decimal(38,{precision})");
    }
    using (var ms = new System.IO.MemoryStream())
    {
        var bits = decimal.GetBits(valueToWrite);
        ms.WriteByte(0x0D); // length=13
        ms.WriteByte(sign);
        ms.Write(BitConverter.GetBytes(bits[0]), 0, 4);
        ms.Write(BitConverter.GetBytes(bits[1]), 0, 4);
        ms.Write(BitConverter.GetBytes(bits[2]), 0, 4);
        return ms.ToArray();
    }
}

如何SQL服务器store/transfer十进制流

How SQL Server store/transfer decimal stream

c#

sql-server

protocols

decimal