22
2012
05

ASP 实现BASE64编码和解码

ASP 实现BASE64编码和解码 主要是实现加密解密字符串使用 可以用于保存一些不想给别人看到的东西

 

<%
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
 //补足位数是为了便于计算
  asContents = asContents & String(3-m3, chrb(0))
  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
 
 
%>
<%
'测试代码
'response.write strAnsi2Unicode(Base64encode(strUnicode2Ansi("who")))
'response.write  strAnsi2Unicode(Base64decode(strUnicode2Ansi("w6m9qMjLw6m9qMjLw6m9qMjLw6m9qMjLw6m9qMjLw6m9qMjLw6m9qMjLw6m9qMjL")))
%>
 



 

 

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