用asp实现base64编码

<%


function bin2dec(binStr)
towPow=1
numLen=len(binStr)
bin2Dec=0
decPos=numLen
do while decPos>0
cChar=mid(binStr,decPos,1)
nChar=Cint(cChar)
bin2Dec=bin2Dec+nChar*towPow
towPow=towPow*2
decPos=decPos-1
Loop
end function

function dec2bin(octNumber)
vara=octNumber
do
dec2bin=cstr(vara mod 2) & dec2bin
vara=vara / 2
loop until vara=0
end function

Bstr_base64="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
function enCode_base64(strBin)
bins=""
for i=1 to lenB(strBin)
varTm=AscB(midB(strBin,i,1))
bins=bins & right("00000000" & dec2bin(varTm),8)
if i mod 3=0 then
for w=0 to 3
sixBin=mid(bins,w*6+1,6)
nChar=bin2Dec(sixBin)+1
enCode_base64=enCode_base64 & mid(Bstr_base64,nChar,1)
next
bins=""
end if
next

if bins<>"" then
pads=3-len(bins) / 8
exitLoop=false
do while not exitLoop
nChar=left(bins,6)
if len(nChar)<6 then
nChar=left(nChar & "000000",6)
exitLoop=true
end if
nNum=bin2dec(nChar)+1
enCode_base64=enCode_base64 & mid(Bstr_base64,nNum,1)
bins=mid(bins,7)
Loop
enCode_base64=enCode_base64 & String(pads,"=")
end if
end function

function deCode_base64(baseStr)
if len(baseStr) mod 4 <>0 then
exit function
end if
bins=""
for i=1 to Len(baseStr)
nChar=mid(baseStr,i,1)
if nChar="=" then
exit for
end if
oldValue=inStr(Bstr_base64,nChar)-1
binValue=right("000000" & dec2bin(oldValue),6)
bins=bins & binValue

if len(bins)>=8 then
deChar=left(bins,8)
bins=mid(bins,9)
deCode_base64=deCode_base64 & chrB(bin2Dec(deChar))
end if
next
end function



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