如何将十六进制字符串转为字节数组计算正确的CRC32校验值？

开发的窗体程序可从XML文件提取十六进制数据，但计算CRC32校验值时遇到问题：使用Encoding.UTF8.GetBytes将十六进制字符串转为字节传入Crc32类，得到的结果与在线CRC32工具「字符串」输入的结果一致，但需要的是工具选择「字节」输入时的结果（匹配原XML中的校验值6889CDCF），目前无法将十六进制字符串转为正确的字节格式传入Crc32类。

待计算的Motorola格式十六进制字符串 #

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

目标CRC32十六进制结果 #

6889CDCF

当前使用的Crc32类代码 #

Public Class Crc32
     Shared table As UInteger()

     Shared Sub New()
         Dim poly As UInteger = &Hedb88320UI
         table = New UInteger(255) {}
         Dim temp As UInteger = 0
         For i As UInteger = 0 To table.Length - 1
             temp = i
             For j As Integer = 8 To 1 Step -1
                 If (temp And 1) = 1 Then
                     temp = CUInt((temp >> 1) Xor poly)
                 Else
                     temp >>= 1
                 End If
             Next
             table(i) = temp
         Next
     End Sub

     Public Shared Function ComputeChecksum(bytes As Byte()) As UInteger
         Dim crc As UInteger = &HFFFFFFFFUI
         For i As Integer = 0 To bytes.Length - 1
             Dim index As Byte = CByte(((crc) And &HFF) Xor bytes(i))
             crc = CUInt((crc >> 8) Xor table(index))
         Next
         Return Not crc
     End Function
 End Class

当前计算代码 #

If xmlR.NodeType = XmlNodeType.Element AndAlso xmlR.Name = "DATEN" Then
    HexData = xmlR.ReadElementContentAsString
    LblRawhex.Text = Microsoft.VisualBasic.Left(HexData, 8)
    LblDataNmeHex.Text = Microsoft.VisualBasic.Mid(HexData, 9, 24)
    TxtFullHex.Text = Microsoft.VisualBasic.Left(HexData, Len(HexData) - 8)
    LblCRC.Text = Hex(Crc32.ComputeChecksum(Encoding.UTF8.GetBytes(TxtFullHex.Text)))
    'LblCRC.Text = Crc32.ComputeChecksum(Hex(TxtFullHex.Text))
End If

解决方案 #

问题核心是：你当前把十六进制字符串作为UTF-8文本转成字节数组，而实际需要把十六进制字符串解析为对应的原始字节（比如字符串中的"42"对应字节0x42）。

1. 实现十六进制字符串转字节数组的函数 #

添加一个工具函数，将十六进制字符串转换为对应的字节数组：

Public Function HexStringToByteArray(hexString As String) As Byte()
    ' 移除字符串中所有非十六进制字符（如空格、换行等，若你的字符串无此类字符可省略）
    hexString = System.Text.RegularExpressions.Regex.Replace(hexString, "[^0-9A-Fa-f]", "")
    
    ' 验证字符串长度为偶数，否则无法完整解析为字节
    If hexString.Length Mod 2 <> 0 Then
        Throw New ArgumentException("十六进制字符串长度必须为偶数")
    End If
    
    Dim byteArray(hexString.Length \ 2 - 1) As Byte
    For i As Integer = 0 To hexString.Length - 1 Step 2
        ' 每两个字符解析为一个字节
        byteArray(i \ 2) = Convert.ToByte(hexString.Substring(i, 2), 16)
    Next
    Return byteArray
End Function

2. 修改CRC计算代码 #

将原来的Encoding.UTF8.GetBytes替换为上述函数，重新计算CRC：

If xmlR.NodeType = XmlNodeType.Element AndAlso xmlR.Name = "DATEN" Then
    HexData = xmlR.ReadElementContentAsString
    LblRawhex.Text = Microsoft.VisualBasic.Left(HexData, 8)
    LblDataNmeHex.Text = Microsoft.VisualBasic.Mid(HexData, 9, 24)
    TxtFullHex.Text = Microsoft.VisualBasic.Left(HexData, Len(HexData) - 8)
    
    ' 使用自定义函数转换十六进制字符串为字节数组
    Dim rawBytes As Byte() = HexStringToByteArray(TxtFullHex.Text)
    ' 计算CRC并转为十六进制字符串
    LblCRC.Text = Hex(Crc32.ComputeChecksum(rawBytes)).ToUpper()
End If

验证 #

使用上述代码转换给定的十六进制字符串后，传入Crc32.ComputeChecksum得到的结果即为目标值6889CDCF。

内容的提问来源于stack exchange，提问作者gadjet