Asp的base64编码、解码函数

<%
dim sBASE_64_CHARACTERS
dim len1,k
dim asc1,asContents1
dim varchar,varasc,varHex,varlow,varhigh
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 = ""
	if isnull(asContents) or asContents="" then exit function
	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
			if midb(asContents,i+1,1)<>"" then
				strAnsi2Unicode = strAnsi2Unicode & chr(ascw(midb(asContents,i+1,1) & varchar))
			end if
			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 m3,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  

str1 = "http://www.mzwu.com/default.asp"
str2 = strAnsi2Unicode(Base64encode(strUnicode2Ansi(str1)))
str3 = strAnsi2Unicode(Base64decode(strUnicode2Ansi(str2)))
Response.Write(str2 & "<br/>")
Response.Write(str3 & "<br/>")
%>