复制代码 代码如下:

FunctionfDecode(sStringToDecode)

'ThisfunctionwilldecodeaBase64encodedstringandreturnsthedecodedstring.

'Thisbecomesusefullwhenattemptingtohidepasswordsfrompryingeyes.

ConstCharList="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

DimiDataLength,sOutputString,iGroupInitialCharacter

sStringToDecode=Replace(Replace(Replace(sStringToDecode,vbCrLf,""),vbTab,""),"","")

iDataLength=Len(sStringToDecode)

IfiDataLengthMod4<>0Then

fDecode="BadstringpassedtofDecode()function."

ExitFunction

EndIf

ForiGroupInitialCharacter=1ToiDataLengthStep4

DimiDataByteCount,iCharacterCounter,sCharacter,iData,iGroup,sPreliminaryOutString

iDataByteCount=3

iGroup=0

ForiCharacterCounter=0To3

sCharacter=Mid(sStringToDecode,iGroupInitialCharacter+iCharacterCounter,1)

IfsCharacter="="Then

iDataByteCount=iDataByteCount-1

iData=0

Else

iData=InStr(1,CharList,sCharacter,0)-1

IfiData=-1Then

fDecode="BadstringpassedtofDecode()function."

ExitFunction

EndIf

EndIf

iGroup=64*iGroup+iData

Next

iGroup=Hex(iGroup)

iGroup=String(6-Len(iGroup),"0")&iGroup

sPreliminaryOutString=Chr(CByte("&H"&Mid(iGroup,1,2)))&Chr(CByte("&H"&Mid(iGroup,3,2)))&Chr(CByte("&H"&Mid(iGroup,5,2)))

sOutputString=sOutputString&Left(sPreliminaryOutString,iDataByteCount)

Next

fDecode=sOutputString

EndFunction

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