'of_encod()为算注册码的函数，传入序列号算出注册码
Function of_encode(a_text As String) As String
    Dim is_base64 As String
    Dim encmap(1 To 63) As String
    Dim s_ret As String
    Dim i_first As Integer
    Dim i_second As Integer
    Dim i_third As Integer
    Dim by3 As Integer
    Dim i As Integer
    Dim i_total As Long

    is_base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    is_base64 = is_base64 + "abcdefghijklmnopqrstuvwxyz"
    is_base64 = is_base64 + "0123456789"
    is_base64 = is_base64 + "+/"
   
    For i = 1 To 63
        encmap(i) = Mid(is_base64, i + 1, 1)
    Next
   
    s_ret = ""
   
    If Len(a_text) = 0 Then
        of_encode = s_ret
    End If
   
    by3 = Len(a_text) - (Len(a_text) Mod 3)
    i = 1
   
    Do While i <= by3
        i_first = Asc(Mid(a_text, i + 0, 1))
        i_second = Asc(Mid(a_text, i + 1, 1))
        i_third = Asc(Mid(a_text, i + 2, 1))
        s_ret = s_ret + encmap(Int(i_first / 4))
        s_ret = s_ret + encmap((i_first Mod 4) * 16 + Int(i_second / 16))
        s_ret = s_ret + encmap((i_second Mod 16) * 4 + Int(i_third / 64))
        s_ret = s_ret + encmap(i_third Mod 64)
        i = i + 3
    Loop
   
    If i <= Len(a_text) Then
        i_first = Asc(Mid(a_text, i + 0, 1))
   
        If Len(a_text) Mod 3 = 2 Then
            i_second = Asc(Mid(a_text, i + 1, 1))
            s_ret = s_ret + encmap(Int(i_first / 4))
            s_ret = s_ret + encmap((i_first Mod 4) * 16 + Int(i_second / 16))
            s_ret = s_ret + encmap((i_second Mod 16) * 4)
            s_ret = s_ret + "="
        Else
            s_ret = s_ret + encmap(Int(i_first / 4))
            s_ret = s_ret + encmap((i_first Mod 4) * 16)
            s_ret = s_ret + "=="
        End If
   
    End If
   
    of_encode = s_ret    '返回算好的注册码

End Function

'确定按钮的click()事件
Private Sub Command1_Click()
    Dim li_pos As Integer
    Dim ls_serialcode As String

    li_pos = InStr(ls_serialcode, " ")

    If li_pos >= 1 Then
        ls_serialcode = Left(ls_serialcode, li_pos - 1)
    End If

    ls_serialcode = sle_serialcode.Text（此处提示，实时错误４２４）
    sle_code.Text = of_encode(ls_serialcode)
End Sub

Private Sub Command2_Click()
    End
End Sub

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[课程]Android-CTF解题方法汇总！