asp base64加解密函数代码

<% 

sBASE_64_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" 
sBASE_64_CHARACTERS = strUnicode2Ansi(sBASE_64_CHARACTERS) 

Function strUnicodeLen(asContents) 
'计算unicode字符串的Ansi编码的长度 
asContents1="a"&asContents 
len1=len(asContents1) 
k=0 
for i=1 to len1 
asc1=asc(mid(asContents1,i,1)) 
if asc1<0 then asc1=65536+asc1 
if asc1>255 then 
k=k+2 
else 
k=k+1 
end if 
next 
strUnicodeLen=k-1 
End Function 

Function strUnicode2Ansi(asContents) 
'将Unicode编码的字符串，转换成Ansi编码的字符串 
strUnicode2Ansi="" 
len1=len(asContents) 
for i=1 to len1 
varchar=mid(asContents,i,1) 
varasc=asc(varchar) 
if varasc<0 then varasc=varasc+65536 
if varasc>255 then 
varHex=Hex(varasc) 
varlow=left(varHex,2) 
varhigh=right(varHex,2) 
strUnicode2Ansi=strUnicode2Ansi & chrb("&H" & varlow ) & chrb("&H" & varhigh ) 
else 
strUnicode2Ansi=strUnicode2Ansi & chrb(varasc) 
end if 
next 
End function 

Function strAnsi2Unicode(asContents) 
'将Ansi编码的字符串，转换成Unicode编码的字符串 
strAnsi2Unicode = "" 
len1=lenb(asContents) 
if len1=0 then exit function 
for i=1 to len1 
varchar=midb(asContents,i,1) 
varasc=ascb(varchar) 
if varasc > 127 then 
strAnsi2Unicode = strAnsi2Unicode & chr(ascw(midb(asContents,i+1,1) & varchar)) 
i=i+1 
else 
strAnsi2Unicode = strAnsi2Unicode & chr(varasc) 
end if 
next 
End function 

Function Base64encode(asContents) 
'将Ansi编码的字符串进行Base64编码 
'asContents应当是ANSI编码的字符串（二进制的字符串也可以） 
Dim lnPosition 
Dim lsResult 
Dim Char1 
Dim Char2 
Dim Char3 
Dim Char4 
Dim Byte1 
Dim Byte2 
Dim Byte3 
Dim SaveBits1 
Dim SaveBits2 
Dim lsGroupBinary 
Dim lsGroup64 
Dim m4,len1,len2 

len1=Lenb(asContents) 
if len1<1 then 
Base64encode="" 
exit Function 
end if 

m3=Len1 Mod 3 
If M3 > 0 Then asContents = asContents & String(3-M3, chrb(0)) 
'补足位数是为了便于计算 

IF m3 > 0 THEN 
len1=len1+(3-m3) 
len2=len1-3 
else 
len2=len1 
end if 

lsResult = "" 

For lnPosition = 1 To len2 Step 3 
lsGroup64 = "" 
lsGroupBinary = Midb(asContents, lnPosition, 3) 

Byte1 = Ascb(Midb(lsGroupBinary, 1, 1)): SaveBits1 = Byte1 And 3 
Byte2 = Ascb(Midb(lsGroupBinary, 2, 1)): SaveBits2 = Byte2 And 15 
Byte3 = Ascb(Midb(lsGroupBinary, 3, 1)) 

Char1 = Midb(sBASE_64_CHARACTERS, ((Byte1 And 252) / 4) + 1, 1) 
Char2 = Midb(sBASE_64_CHARACTERS, (((Byte2 And 240) / 16) Or (SaveBits1 * 16) And &HFF) + 1, 1) 
Char3 = Midb(sBASE_64_CHARACTERS, (((Byte3 And 192) / 64) Or (SaveBits2 * 4) And &HFF) + 1, 1) 
Char4 = Midb(sBASE_64_CHARACTERS, (Byte3 And 63) + 1, 1) 
lsGroup64 = Char1 & Char2 & Char3 & Char4 

lsResult = lsResult & lsGroup64 
Next 

'处理最后剩余的几个字符 
if M3 > 0 then 
lsGroup64 = "" 
lsGroupBinary = Midb(asContents, len2+1, 3) 

Byte1 = Ascb(Midb(lsGroupBinary, 1, 1)): SaveBits1 = Byte1 And 3 
Byte2 = Ascb(Midb(lsGroupBinary, 2, 1)): SaveBits2 = Byte2 And 15 
Byte3 = Ascb(Midb(lsGroupBinary, 3, 1)) 

Char1 = Midb(sBASE_64_CHARACTERS, ((Byte1 And 252) / 4) + 1, 1) 
Char2 = Midb(sBASE_64_CHARACTERS, (((Byte2 And 240) / 16) Or (SaveBits1 * 16) And &HFF) + 1, 1) 
Char3 = Midb(sBASE_64_CHARACTERS, (((Byte3 And 192) / 64) Or (SaveBits2 * 4) And &HFF) + 1, 1) 

if M3=1 then 
lsGroup64 = Char1 & Char2 & ChrB(61) & ChrB(61) '用=号补足位数 
else 
lsGroup64 = Char1 & Char2 & Char3 & ChrB(61) '用=号补足位数 
end if 

lsResult = lsResult & lsGroup64 
end if 

Base64encode = lsResult 

End Function 


Function Base64decode(asContents) 
'将Base64编码字符串转换成Ansi编码的字符串 
'asContents应当也是ANSI编码的字符串（二进制的字符串也可以） 
Dim lsResult 
Dim lnPosition 
Dim lsGroup64, lsGroupBinary 
Dim Char1, Char2, Char3, Char4 
Dim Byte1, Byte2, Byte3 
Dim M4,len1,len2 

len1= Lenb(asContents) 
M4 = len1 Mod 4 

if len1 < 1 or M4 > 0 then 
'字符串长度应当是4的倍数 
Base64decode = "" 
exit Function 
end if 

'判断最后一位是不是 = 号 
'判断倒数第二位是不是 = 号 
'这里m4表示最后剩余的需要单独处理的字符个数 
if midb(asContents, len1, 1) = chrb(61) then m4=3 
if midb(asContents, len1-1, 1) = chrb(61) then m4=2 

if m4 = 0 then 
len2=len1 
else 
len2=len1-4 
end if 

For lnPosition = 1 To Len2 Step 4 
lsGroupBinary = "" 
lsGroup64 = Midb(asContents, lnPosition, 4) 
Char1 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, 1, 1)) - 1 
Char2 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, 2, 1)) - 1 
Char3 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, 3, 1)) - 1 
Char4 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, 4, 1)) - 1 
Byte1 = Chrb(((Char2 And 48) / 16) Or (Char1 * 4) And &HFF) 
Byte2 = lsGroupBinary & Chrb(((Char3 And 60) / 4) Or (Char2 * 16) And &HFF) 
Byte3 = Chrb((((Char3 And 3) * 64) And &HFF) Or (Char4 And 63)) 
lsGroupBinary = Byte1 & Byte2 & Byte3 

lsResult = lsResult & lsGroupBinary 
Next 

'处理最后剩余的几个字符 
if M4 > 0 then 
lsGroupBinary = "" 
lsGroup64 = Midb(asContents, len2+1, m4) & chrB(65) 'chr(65)=A，转换成值为0 
if M4=2 then '补足4位，是为了便于计算 
lsGroup64 = lsGroup64 & chrB(65) 
end if 
Char1 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, 1, 1)) - 1 
Char2 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, 2, 1)) - 1 
Char3 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, 3, 1)) - 1 
Char4 = InStrb(sBASE_64_CHARACTERS, Midb(lsGroup64, 4, 1)) - 1 
Byte1 = Chrb(((Char2 And 48) / 16) Or (Char1 * 4) And &HFF) 
Byte2 = lsGroupBinary & Chrb(((Char3 And 60) / 4) Or (Char2 * 16) And &HFF) 
Byte3 = Chrb((((Char3 And 3) * 64) And &HFF) Or (Char4 And 63)) 

if M4=2 then 
lsGroupBinary = Byte1 
elseif M4=3 then 
lsGroupBinary = Byte1 & Byte2 
end if 

lsResult = lsResult & lsGroupBinary 
end if 

Base64decode = lsResult 

End Function 
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