Implement your own Urldecode_ application techniques with an ASP application

That
If there are spaces to replace with%20, if there are other characters to replace with%ASCII, if there are characters such as four bytes of character, the use of two%ascii to replace. But sometimes we also need to decode this encoded string, but the ASP does not provide related functions, which gives us some trouble dealing with the problem. In fact, as long as we know the coding rules, we can use the ASP code to implement our own UrlDecode function.
Specifically implemented as follows:

Copy Code code as follows:

function UrlDecode (ENCODESTR)
Newstr= ""
Havechar=false
Lastchar= ""
For I=1 to Len (ENCODESTR)
Char_c=mid (encodestr,i,1)
If char_c= "+" then
Newstr=newstr & ""
ElseIf char_c= "%" then
Next_1_c=mid (encodestr,i+1,2)
Next_1_num=cint ("&h" & Next_1_c)

If Havechar Then
Havechar=false
Newstr=newstr & Chr (CInt ("&h" & Lastchar & Next_1_c))
Else
If ABS (next_1_num) <=127 Then
Newstr=newstr & Chr (next_1_num)
Else
Havechar=true
Lastchar=next_1_c
End If
End If
I=i+2
Else
Newstr=newstr & Char_c
End If
Next
Urldecode=newstr
End Function

Here's a more mature function:

Copy Code code as follows:

'================================================
' Function name: UrlDecode
' Function: URL decoding
'================================================
Function UrlDecode (ByVal urlcode)
Dim Start,final,length,char,i,butf8,pass
Dim Leftstr,rightstr,finalstr
Dim B0,b1,bx,blength,position,u,utf8
On Error Resume Next

B0 = Array (192,224,240,248,252,254)
Urlcode = Replace (Urlcode, "+", "")
Pass = 0
UTF8 =-1

Length = Len (urlcode): start = InStr (Urlcode, "%"): final = InStrRev (Urlcode, "%")
If start = 0 Or Length < 3 Then UrlDecode = Urlcode:exit Function
Leftstr = Left (urlcode,start-1): Rightstr = Right (urlcode,length-2-final)

For i = start to final
char = Mid (urlcode,i,1)
If char = "%" Then
BX = Urldecode_hex (Mid (urlcode,i + 1,2))
If BX > BX < 128 Then
i = i + 2
Finalstr = finalstr & ChrW (BX)
ElseIf BX > 127 Then
i = i + 2
If UTF8 < 0 Then
Butf8 = 1:blength = -1:B1 = bx
For position = 4 to 0 Step-1
If B1 >= B0 (position) and B1 < B0 (position + 1) Then
Blength = Position
Exit for
End If
Next
If blength >-1 Then
For position = 0 to Blength
B1 = Urldecode_hex (Mid (urlcode,i + position * 3 + 2,2))
If B1 < 128 Or B1 > 191 Then Butf8 = 0:exit for
Next
Else
Butf8 = 0
End If
If Butf8 = 1 and blength = 0 Then Butf8 =-2
If Butf8 >-1 and UTF8 =-2 Then i = start-1: Finalstr = "": Pass = 1
UTF8 = Butf8
End If
If pass = 0 Then
If UTF8 = 1 Then
B1 = Bx:u = 0:blength =-1
For position = 4 to 0 Step-1
If B1 >= B0 (position) and B1 < B0 (position + 1) Then
Blength = Position
B1 = (B1 xOr b0 (position)) * (position + 1)
Exit for
End If
Next
If blength >-1 Then
For position = 0 to Blength
BX = Urldecode_hex (Mid (urlcode,i + 2,2)): i = i + 3
If BX < 128 Or bx > 191 Then u = 0:exit for
u = U + (BX and) * ^ (blength-position)
Next
If u > 0 Then finalstr = finalstr & ChrW (B1 + u)
End If
Else
B1 = bx * &h100:u = 0
BX = Urldecode_hex (Mid (urlcode,i + 2,2))
If bx > 0 Then
U = b1 + bx
i = i + 3
Else
If Left (urlcode,1) = "%" Then
U = b1 + Asc (Mid (urlcode,i + 3,1))
i = i + 2
Else
U = b1 + Asc (Mid (urlcode,i + 1,1))
i = i + 1
End If
End If
Finalstr = finalstr & Chr (U)
End If
Else
Pass = 0
End If
End If
Else
Finalstr = finalstr & Char
End If
Next
UrlDecode = leftstr & Finalstr & Rightstr
End Function

Function Urldecode_hex (ByVal h)
On Error Resume Next
h = "&h" & Trim (h): Urldecode_hex =-1
If Len (h) <> 4 Then Exit Function
If isnumeric (h) Then Urldecode_hex = cInt (h)
End Function