[转]用于Asp的base64编码/解码函数

<!--#include file="base64.inc"-->
<%
'---------------------------------------------------------------------------------
str="我爱你tandy"
encodestr=encode64(str) '编码
response.write encodestr & "<hr>"
response.write decode64(encodestr) & "<hr>" '解码
%>

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

'计算unicode字符串的Ansi编码的长度
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

'将Unicode编码的字符串，转换成Ansi编码的字符串
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

'将Ansi编码的字符串，转换成Unicode编码的字符串
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

'将Ansi编码的字符串进行Base64编码
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

'将Base64编码字符串转换成Ansi编码的字符串
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

function encode64(byval str)
encode64=strAnsi2Unicode(Base64encode(strUnicode2Ansi(str)))
end function

function decode64(byval str)
decode64=strAnsi2Unicode(Base64decode(strUnicode2Ansi(str)))
end function
%>