'威山使用的BASE64编码类模块
Option Explicit
Dim Base64Chr As String
Dim NullChr As String
Dim psBase64Chr(0 To 63) As String
Public Function InitBase(ByVal Base64Chr As String)
'如果没有提供字符串则按照标准编码
If Base64Chr = "" Then Base64Chr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
Dim iPtr As Integer
'初始化 BASE64数组
For iPtr = 0 To 63
psBase64Chr(iPtr) = Mid$(Base64Chr, iPtr + 1, 1)
Next
NullChr = Right(Base64Chr, 1)
End Function
'从一个经过Base64的字符串中解码到源字符串
Public Function DecodeBase64String(str2Decode As String) As String
DecodeBase64String = StrConv(DecodeBase64Byte(str2Decode), vbUnicode)
End Function
'从一个经过Base64的字符串中解码到源字节数组
Public Function DecodeBase64Byte(str2Decode As String) As Byte()
Dim lPtr As Long
Dim iValue As Integer
Dim iLen As Integer
Dim iCtr As Integer
Dim Bits(1 To 4) As Byte
Dim strDecode As String
Dim str As String
Dim Output() As Byte
Dim iIndex As Long
Dim lFrom As Long
Dim lTo As Long
'//除去回车
str = Replace(str2Decode, vbCrLf, "")
'//每4个字符一组（4个字符表示3个字）
For lPtr = 1 To Len(str) Step 4
iLen = 4
For iCtr = 0 To 3
'//查找字符在BASE64字符串中的位置
iValue = InStr(1, Base64Chr, Mid$(str, lPtr + iCtr, 1), vbBinaryCompare)
Select Case iValue 'A~Za~z0~9+/
Case 1 To 64:
Bits(iCtr + 1) = iValue - 1
Case 65 '=
iLen = iCtr
Exit For
'//没有发现
Case 0: Exit Function
End Select
Next
'//转换4个6比特数成为3个8比特数
Bits(1) = Bits(1) * &H4 + (Bits(2) And &H30) \ &H10
Bits(2) = (Bits(2) And &HF) * &H10 + (Bits(3) And &H3C) \ &H4
Bits(3) = (Bits(3) And &H3) * &H40 + Bits(4)
'//计算数组的起始位置
lFrom = lTo
lTo = lTo + (iLen - 1) - 1
'//重新定义输出数组
ReDim Preserve Output(0 To lTo)
For iIndex = lFrom To lTo
Output(iIndex) = Bits(iIndex - lFrom + 1)
Next
lTo = lTo + 1
Next
DecodeBase64Byte = Output
End Function
'将一个字节数组进行Base64编码，并返回字符串
Public Function EncodeBase64Byte(sValue() As Byte) As String
Dim lCtr As Long
Dim lPtr As Long
Dim lLen As Long
Dim sEncoded As String
Dim Bits8(1 To 3) As Byte
Dim Bits6(1 To 4) As Byte
Dim i As Integer
For lCtr = 1 To UBound(sValue) + 1 Step 3
For i = 1 To 3
If lCtr + i - 2 <= UBound(sValue) Then
Bits8(i) = sValue(lCtr + i - 2)
lLen = 3
Else
Bits8(i) = 0
lLen = lLen - 1
End If
Next
'//转换字符串为数组，然后转换为4个6位(0-63)
Bits6(1) = (Bits8(1) And &HFC) \ 4
Bits6(2) = (Bits8(1) And &H3) * &H10 + (Bits8(2) And &HF0) \ &H10
Bits6(3) = (Bits8(2) And &HF) * 4 + (Bits8(3) And &HC0) \ &H40
Bits6(4) = Bits8(3) And &H3F
'//添加4个新字符
For lPtr = 1 To lLen + 1
sEncoded = sEncoded & psBase64Chr(Bits6(lPtr))
Next
Next
'//不足4位，以=填充
Select Case lLen + 1
Case 2: sEncoded = sEncoded & NullChr & NullChr
Case 3: sEncoded = sEncoded & NullChr
Case 4:
End Select
EncodeBase64Byte = sEncoded
End Function
'对字符串进行Base64编码并返回字符串
Public Function EncodeBase64String(str2Encode As String) As String
Dim sValue() As Byte
sValue = StrConv(str2Encode, vbFromUnicode)
EncodeBase64String = EncodeBase64Byte(sValue)
End Function
'对文件进行Base64编码并返回编码后的Base64字符串
Public Function EncodFileToBase64String(strFileSource As String)
Dim lpdata() As Byte, i As Long, n As Long
i = FreeFile
Open strFileSource For Binary Access Read Lock Write As i
n = LOF(i) - 1
ReDim lpdata(0 To n)
Get i, , lpdata
Close i
EncodFileToBase64String = EncodeBase64Byte(lpdata)
End Function
'将一个Base64字符串解码，并写入二进制文件
Public Function DecodeBase64StringToFile(strBase64 As String, strFilePath As String)
Dim i As Integer
i = FreeFile
Open strFilePath For Binary Access Write As i
Put i, , DecodeBase64Byte(strBase64)
Close i
End Function
Private Sub Class_Initialize()
Call InitBase("")
End Sub
