function.asp

来自「j2me lan 聊天 server 基于 servlet 使用向导： 」· ASP 代码 · 共 78 行

<%
Const sBASE_64_CHARACTERS = "aH23rDghF8NOcbCefnjlmLMX0Wk5d6UGst49TSxyzIJKq71ABPQRiopuvVEwYZ+/"
' -----------------------------------------------------------------------------
Function Base64decode(ByVal asContents)
	Dim lsResult
	Dim lnPosition
	Dim lsGroup64, lsGroupBinary
	Dim Char1, Char2, Char3, Char4
	Dim Byte1, Byte2, Byte3

	If Len(asContents) Mod 4 > 0 Then asContents = asContents & String(4 - (Len(asContents) Mod 4), " ")

	lsResult = ""
	
	For lnPosition = 1 To Len(asContents) Step 4
		lsGroupBinary = ""
		lsGroup64 = Mid(asContents, lnPosition, 4)

		Char1 = INSTR(sBASE_64_CHARACTERS, Mid(lsGroup64, 1, 1)) - 1
		Char2 = INSTR(sBASE_64_CHARACTERS, Mid(lsGroup64, 2, 1)) - 1
		Char3 = INSTR(sBASE_64_CHARACTERS, Mid(lsGroup64, 3, 1)) - 1
		Char4 = INSTR(sBASE_64_CHARACTERS, Mid(lsGroup64, 4, 1)) - 1

		Byte1 = Chr(((Char2 And 48) \ 16) Or (Char1 * 4) And &HFF)
		Byte2 = lsGroupBinary & Chr(((Char3 And 60) \ 4) Or (Char2 * 16) And &HFF)
		Byte3 = Chr((((Char3 And 3) * 64) And &HFF) Or (Char4 And 63))

		lsGroupBinary = Byte1 & Byte2 & Byte3
		
		lsResult = lsResult + lsGroupBinary
	Next
	Base64decode = lsResult

End Function
' -----------------------------------------------------------------------------
Function Base64encode(ByVal asContents)
	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
	
	If Len(asContents) Mod 3 > 0 Then asContents = asContents & String(3 - (Len(asContents) Mod 3), " ")

	lsResult = ""
	
	For lnPosition = 1 To Len(asContents) Step 3
		lsGroup64 = ""
		lsGroupBinary = Mid(asContents, lnPosition, 3)
      
		Byte1 = Asc(Mid(lsGroupBinary, 1, 1)): SaveBits1 = Byte1 And 3
		Byte2 = Asc(Mid(lsGroupBinary, 2, 1)): SaveBits2 = Byte2 And 15
		Byte3 = Asc(Mid(lsGroupBinary, 3, 1))
      
		Char1 = Mid(sBASE_64_CHARACTERS, ((Byte1 And 252) \ 4) + 1, 1)
		Char2 = Mid(sBASE_64_CHARACTERS, (((Byte2 And 240) \ 16) Or (SaveBits1 * 16) And &HFF) + 1, 1)
		Char3 = Mid(sBASE_64_CHARACTERS, (((Byte3 And 192) \ 64) Or (SaveBits2 * 4) And &HFF) + 1, 1)
		Char4 = Mid(sBASE_64_CHARACTERS, (Byte3 And 63) + 1, 1)

		lsGroup64 = Char1 & Char2 & Char3 & Char4
		
		lsResult = lsResult + lsGroup64
	Next
	
	Base64encode = lsResult
   
End Function
' -----------------------------------------------------------------------------
%>