芬腾内衣官方旗舰店:VB入门技巧N例(10)
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33. 用键盘方向键控制COMBOX
35.VB下的CRC校验程序
一 计算法
计算法就是依据CRC校验码的产生原理来设计程序。其优点是模块代码少,修改灵活,可移植性好。其缺点为计算量大。为了便于理解,这里假
定了三位数据,而多项式码为A001(hex)。
在窗体上放置一命令按钮Command1,并添加如下代码:
2.查表法
查表法的优缺点与计算法的正好相反。为了便于比较,这里所有的假定与计算法的完全相同,都而在窗体上放置一个Command1的按钮,其
代码部分与上面的也完全一致。下面只介绍CRC函数的编写源代码。
- Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
- (ByVal hwnd As Long, _
- ByVal wMsg As Long, _
- ByVal wParam As Long, _
- lParam As Any) As Long
- Const CB_SHOWDROPDOWN = &H14F
- Dim bDrop As Boolean
- Private isDo As Boolean
- Private Sub Combo1_Click()
- If Not isDo Then
- isDo = True '<----------回置状态
- Exit Sub
- Else: MsgBox "safd"
- End If
- End Sub
- Private Sub Combo1_DropDown()
- bDrop = True
- End Sub
- Private Sub Combo1_KeyDown(KeyCode As Integer, Shift As Integer)
- If KeyCode = 40 Then
- isDo = False
- SendMessage Combo1.hwnd, CB_SHOWDROPDOWN, 1, 0
- ElseIf KeyCode = 38 Then
- isDo = False
- If Combo1.ListIndex = 0 Then
- If bDrop Then
- bDrop = False
- SendMessage Combo1.hwnd, CB_SHOWDROPDOWN, 0, 0
- End If
- End If
- End If
- End Sub
- Private Sub Combo1_KeyUp(KeyCode As Integer, Shift As Integer)
- If Combo1.Text = Combo1.List(0) Then
- isDo = True
- End If
- End Sub
- Private Sub Form_Load()
- isDo = True
- Combo1.AddItem "abcd"
- Combo1.AddItem "abcd1"
- Combo1.AddItem "abcd2"
- Combo1.AddItem "abcd3"
- End Sub
35.VB下的CRC校验程序
一 计算法
计算法就是依据CRC校验码的产生原理来设计程序。其优点是模块代码少,修改灵活,可移植性好。其缺点为计算量大。为了便于理解,这里假
定了三位数据,而多项式码为A001(hex)。
在窗体上放置一命令按钮Command1,并添加如下代码:
- Private Sub Command1_Click()
- Dim CRC() As Byte
- Dim d() As Byte '待传输数据
- ReDim d(2) As Byte
- d(0) = 123
- d(1) = 112
- d(2) = 135
- CRC = CRC16(d) '调用CRC16计算函数
- 'CRC(0)为高位
- 'CRC(1)为低位
- End Sub
- 注意:在数据传输时CRC的低位可能在前,而高位在后。
- Function CRC16(data() As Byte) As String
- Dim CRC16Lo As Byte, CRC16Hi As Byte 'CRC寄存器
- Dim CL As Byte, CH As Byte '多项式码&HA001
- Dim SaveHi As Byte, SaveLo As Byte
- Dim i As Integer
- Dim Flag As Integer
- CRC16Lo = &HFF
- CRC16Hi = &HFF
- CL = &H1
- CH = &HA0
- For i = 0 To UBound(data)
- CRC16Lo = CRC16Lo Xor data(i) '每一个数据与CRC寄存器进行异或
- For Flag = 0 To 7
- SaveHi = CRC16Hi
- SaveLo = CRC16Lo
- CRC16Hi = CRC16Hi \ 2 '高位右移一位
- CRC16Lo = CRC16Lo \ 2 '低位右移一位
- If ((SaveHi And &H1) = &H1) Then '如果高位字节最后一位为1
- CRC16Lo = CRC16Lo Or &H80 '则低位字节右移后前面补1
- End If '否则自动补0
- If ((SaveLo And &H1) = &H1) Then '如果LSB为1,则与多项式码进行异或
- CRC16Hi = CRC16Hi Xor CH
- CRC16Lo = CRC16Lo Xor CL
- End If
- Next Flag
- Next i
- Dim ReturnData(1) As Byte
- ReturnData(0) = CRC16Hi 'CRC高位
- ReturnData(1) = CRC16Lo 'CRC低位
- CRC16 = ReturnData
- End Function
2.查表法
查表法的优缺点与计算法的正好相反。为了便于比较,这里所有的假定与计算法的完全相同,都而在窗体上放置一个Command1的按钮,其
代码部分与上面的也完全一致。下面只介绍CRC函数的编写源代码。
- Private Function CRC16(data() As Byte) As String
- Dim CRC16Hi As Byte
- Dim CRC16Lo As Byte
- CRC16Hi = &HFF
- CRC16Lo = &HFF
- Dim i As Integer
- Dim iIndex As Long
- For i = 0 To UBound(data)
- iIndex = CRC16Lo Xor data(i)
- CRC16Lo = CRC16Hi Xor GetCRCLo(iIndex) '低位处理
- CRC16Hi = GetCRCHi(iIndex) '高位处理
- Next i
- Dim ReturnData(1) As Byte
- ReturnData(0) = CRC16Hi 'CRC高位
- ReturnData(1) = CRC16Lo 'CRC低位
- CRC16 = ReturnData
- End Function
- 'CRC低位字节值表
- Function GetCRCLo(Ind As Long) As Byte
- GetCRCLo = Choose(Ind + 1, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40,
- &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1,
- &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80,
- &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0,
- &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0,
- &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81,
- &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _
- &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80,
- &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0,
- &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1,
- &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81,
- &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1,
- &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40)
- End Function
- 'CRC高位字节值表
- Function GetCRCHi(Ind As Long) As Byte
- GetCRCHi = Choose(Ind + 1, &H0, &HC0, &HC1, &H1, &HC3, &H3, &H2, &HC2, &HC6, &H6, &H7, &HC7, &H5, &HC5, &HC4, &H4,
- &HCC, &HC, &HD, &HCD, &HF, &HCF, &HCE, &HE, &HA, &HCA, &HCB, &HB, &HC9, &H9, &H8, &HC8, &HD8, &H18, &H19, &HD9, &H1B, &HDB,
- &HDA, &H1A, &H1E, &HDE, &HDF, &H1F, &HDD, &H1D, &H1C, &HDC, &H14, &HD4, &HD5, &H15, &HD7, &H17, &H16, &HD6, &HD2, &H12, &H13,
- &HD3, &H11, &HD1, &HD0, &H10, &HF0, &H30, &H31, &HF1, &H33, &HF3, &HF2, &H32, &H36, &HF6, &HF7, &H37, &HF5, &H35, &H34, &HF4,
- &H3C, &HFC, &HFD, &H3D, &HFF, &H3F, &H3E, &HFE, &HFA, &H3A, &H3B, &HFB, &H39, &HF9, &HF8, &H38, &H28, &HE8, &HE9, &H29, &HEB,
- &H2B, &H2A, &HEA, &HEE, &H2E, &H2F, &HEF, &H2D, &HED, &HEC, &H2C, &HE4, &H24, &H25, &HE5, &H27, &HE7, &HE6, &H26, &H22, &HE2,
- &HE3, &H23, &HE1, &H21, &H20, &HE0, &HA0, &H60, _
- &H61, &HA1, &H63, &HA3, &HA2, &H62, &H66, &HA6, &HA7, &H67, &HA5, &H65, &H64, &HA4, &H6C, &HAC, &HAD, &H6D, &HAF, &H6F, &H6E,
- &HAE, &HAA, &H6A, &H6B, &HAB, &H69, &HA9, &HA8, &H68, &H78, &HB8, &HB9, &H79, &HBB, &H7B, &H7A, &HBA, &HBE, &H7E, &H7F, &HBF,
- &H7D, &HBD, &HBC, &H7C, &HB4, &H74, &H75, &HB5, &H77, &HB7, &HB6, &H76, &H72, &HB2, &HB3, &H73, &HB1, &H71, &H70, &HB0, &H50,
- &H90, &H91, &H51, &H93, &H53, &H52, &H92, &H96, &H56, &H57, &H97, &H55, &H95, &H94, &H54, &H9C, &H5C, &H5D, &H9D, &H5F, &H9F,
- &H9E, &H5E, &H5A, &H9A, &H9B, &H5B, &H99, &H59, &H58, &H98, &H88, &H48, &H49, &H89, &H4B, &H8B, &H8A, &H4A, &H4E, &H8E, &H8F,
- &H4F, &H8D, &H4D, &H4C, &H8C, &H44, &H84, &H85, &H45, &H87, &H47, &H46, &H86, &H82, &H42, &H43, &H83, &H41, &H81, &H80, &H40)
- End Function
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