新云的一个函数,url解码的.后面部分不是很明白,不知道为什么要分那么多的情况,分两种情况我感觉就可以做到.不知道我忽略了什么?高手给解答下.
 下面是程序代码:
'================================================
'函数名：URLDecode
'作  用：URL解码
'================================================
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 '标记2
    leftstr = Left(urlcode,start - 1) : rightstr = Right(urlcode,length - 2 - final)

    For i = start To final
        char = Mid(urlcode,i,1)
        If char = "%" Then'标记3
            bx = URLDecode_Hex(Mid(urlcode,i + 1,2))
            If bx > 31 And bx < 128 Then
                i = i + 2
                finalstr = finalstr & ChrW(bx)
            ElseIf bx > 127 Then
                i = i + 2
                If utf8 < 0 Then 
                '明确一下，不知道下面这些是做什么用的,后面为什么分了这么多情况
                    butf8 = 1 : blength = -1 : b1 = bx'bx变量弄给b1
                    For position = 4 To 0 Step -1
                        If b1 >= b0(position) And b1 < b0(position + 1) Then
                            blength = position
                            Exit For
                        End If
                    Next
                '截止到这个地方,下面的这个判断是否在上面提供的范围之中
                    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 '如果不在这个范围之中的话
                        butf8 = 0 
                    End If
                    '又一个结束了,butf8默认值就是1,blength的默认值是-1
                    If butf8 = 1 And blength = 0 Then butf8 = -2
                    '一个开始了,下面这句开始设置pass的值了
                    If butf8 > -1 And utf8 = -2 Then i = start - 1 : finalstr = "" : pass = 1
                    utf8 = butf8
                End If
                '结束了
                If pass = 0 Then '//标记1
                '//开始了
                    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)) * 64 ^ (position + 1) '进行异或运

算 
                                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 63) * 64 ^ (blength - position)
                            Next
                            If u > 0 Then finalstr = finalstr & ChrW(b1 + u)
                        End If
                        '//这个结束了
                    Else '//标记1
                        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 '标记3
                    pass = 0
                End If
            End If
        Else '标记2
            finalstr = finalstr & char
        End If
    Next'整个循环结束
    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