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1、Option ExplicitPrivate Declare Sub CopyMemory Lib “kernel32“ Alias “RtlMoveMemory“ (Destination As Any, Source As Any, ByVal Length As Long)Private Sub cmdSinHex_Click()Text3 = “Dim i As IntegerDim hexData As StringDim a As SingleDim Buffer(3) As Bytea = Val(Text1)CopyMemory Buffer(0), a, 4For i = 0
2、 To 3If Len(Hex(Buffer(i) = 1 ThenhexData = “0“ & Hex(Buffer(i) + hexDataElsehexData = Hex(Buffer(i) + hexDataEnd IfNextText2 = hexDataFor i = 1 To Len(hexData) Step 2Text3 = Text3 & ChrW(Val(“&H“ & Mid(hexData, i, 2) & “ “Next End SubPrivate Sub Form_Load()Text1 = “Text2 = “Text3 = “ End SubVB 串口通信
3、中经常会遇到 10 进制浮点数转为多字节 Byte 数据类型的情况，以及在接收后 需转为 10 进制浮点数需求。 VB 有专门的 API 函数 CopyMemory 能处理 2-10 进制浮点数转换和 10-2 进制浮点数转换。 下列代码演示了 10 进制 Single（单精度浮点型转为 16 进制字符显示的浮点数和其相反运 算：Option Explicit Private Declare Sub CopyMemory Lib “kernel32“ Alias “RtlMoveMemory“ (Destination As Any, Source As Any, ByVal Length A
4、s Long) Private Sub BinToSin_Click()Dim sinStr As StringDim sinSj As SingleDim Buffer(3) As ByteDim i As IntegersinStr = Text2For i = 1 To Len(Text2) Step 2Buffer(7 - i) / 2) = Val(“&H“ & Mid(sinStr, i, 2)NextCopyMemory ByVal VarPtr(sinSj), ByVal VarPtr(Buffer(0), 4Text3 = sinSj End SubPrivate Sub S
5、inToBin_Click()Dim i As IntegerDim hexData As StringDim a As SingleDim Buffer(3) As Bytea = Val(Text1)CopyMemory Buffer(0), a, 4For i = 0 To 3If Len(Hex(Buffer(i) = 1 ThenhexData = “0“ & Hex(Buffer(i) + hexDataElsehexData = Hex(Buffer(i) + hexDataEnd IfNextText2 = hexData End Sub 下列代码演示了 10 进制 Doubl
6、e（双精度浮点型）转为 16 进制字符显示的浮点数和其相反 运算：Option Explicit Private Declare Sub CopyMemory Lib “kernel32“ Alias “RtlMoveMemory“ (Destination As Any, Source As Any, ByVal Length As Long) Private Sub cmdDoubHex_Click()Dim i As IntegerDim hexData As StringDim a As DoubleDim Buffer(7) As Bytea = Val(Text1)CopyMemo
7、ry Buffer(0), a, 8For i = 0 To 7If Len(Hex(Buffer(i) = 1 ThenhexData = “0“ & Hex(Buffer(i) + hexDataElsehexData = Hex(Buffer(i) + hexDataEnd IfNextText2 = hexData End SubPrivate Sub cmdHexDec_Click()Dim sinStr As StringDim sinSj As DoubleDim bytes(7) As ByteDim i As IntegersinStr = Text2For i = 1 To
8、 Len(Text2) Step 2bytes(15 - i) / 2) = Val(“&H“ & Mid(sinStr, i, 2)NextCopyMemory ByVal VarPtr(sinSj), ByVal VarPtr(bytes(0), 8Text3 = sinSj End Sub但从中无法了解它是如何进行运算处理的。以下通过对 Single（单精度浮点型）和 Double（双精度浮点型）在内存的储存方式进行分析。 VB 的 Single 数据类型 Single（单精度浮点型）变量存储为 IEEE 32 位（4 个字节）浮点数值的形式，它的范围 在负数的时候是从 -3.40282
9、3E38 到 -1.401298E-45，而在正数的时候是从 1.401298E-45 到 3.402823E38。Single 的类型声明字符为感叹号 (!)。 在内存以 32 位二进制形式存在:XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 第 1 位为符号位 第 2-9 位为阶码位 第 10-32 位为 2 进制小数尾值 即 F2 n * 1. XXXXXXX XXXXXXXX XXXXXXXX 其中 F 为正号或负号(首为为 0 正数,首位为 1 负数 n 为 2-9 位组成的 BYTE 数据值 XXXXXXX XXXXXXXX XXXXXXXX 为尾数 Dou
10、ble（双精度浮点型）变量存储为 IEEE 64 位（8 个字节）浮点数值的形式，它的范围 在负数的时候是从 -1.79769313486232E308 到 -4.94065645841247E-324，而正数的时候是 从 4.94065645841247E-324 到 1.79769313486232E308。Double 的类型声明字符是数字符 号 (#)。 在内存以 64 位二进制形式存在:XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 第 1 位为符号位 第 2-12 位为阶码位 第 13-
11、64 位为 2 进制小数尾值 即 F2 n * 1. XXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 其中 F 为正号或负号(首为为 0 正数,首位为 1 负数 n 为 2-12 位组成的 BYTE 数据值XXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 为尾数 以下代码是基于前叙述的 Single（单精度浮点型）在内存的储存方式进行分析后作出的 2- 10 进制浮点数运算：Option ExplicitDim hexData As StringDim i
12、As SingleDim bindata As StringDim zs As String * 8Dim zssz As StringDim xs As String * 23Dim xs_js() As DoubleDim xs_hj As DoubleDim sinData As SingleDim sHex As StringDim sBin As StringDim fh As StringPrivate Sub Command1_Click()Dim fh As StringsHex = Text1HexToBin (sHex)fh = Mid(bindata, 1, 1) 取符号
13、zs = Mid(bindata, 2, 8) 取指数阶码xs = Mid(bindata, 10, 23) 取 2 进制小数xs_hj = 0zssz = BinToHex(zs)ReDim xs_js(1 To 23)For i = 1 To 23xs_js(i) = Val(Mid(xs, i, 1)xs_hj = xs_hj + xs_js(i) / (2 (i)NextIf zs “000000000000“ ThenShape1.FillColor = vbGreenIf fh = 0 ThensinData = 2 (Val(“&H“ & zssz) - 1023) * (1 +
14、 xs_hj)ElseIf fh = 1 ThensinData = -2 (Val(“&H“ & zssz) - 1023) * (1 + xs_hj)End If ElseIf sHex = “00000000“ ThensinData = 0Shape1.FillColor = vbGreen ElseIf zs = “000000000000“ Then 处理在 0 到 2.2250738585072E-308 及Shape1.FillColor = vbRed 0 到-2.2250738585072E-308 间的浮点数If fh = 0 ThensinData = 2 (Val(“
15、&H“ & zssz) - 1022) * xs_hjElseIf fh = 1 ThensinData = -2 (Val(“&H“ & zssz) - 1022) * xs_hjEnd If End If Text3 = sinData End SubPublic Function HexToBin(ByVal sHex As String) As StringConst s1 = “0000101001101111000“, s2 = “0125A4936DB7FEC8“Dim i As Integer, sBin As StringsHex = UCase(sHex)For i = 1
16、 To Len(sHex)sBin = sBin & Mid(s1, InStr(1, s2, Mid(sHex, i, 1), 4)Next iHexToBin = sBinbindata = sBin End FunctionPublic Function BinToHex(ByVal sBin As String) As StringConst s1 = “0000101001101111000“, s2 = “0125A4936DB7FEC8“Dim i As Integer, sHex As StringsBin = String(3 - (Len(sBin) - 1) Mod 4, “0“) & sBinFor i = 1 To Len(sBin) Step 4sHex = sHex & Mid(s2, InStr(1, s1, Mid(sBin, i, 4), 1)Next iBinToHex = sHex End Function字符串类型转化为
