#lang "qb"

REM THE Binary OPS ONLY WORK On SIGNED 16-Bit NUMBERS
REM SO WE STORE THE IP ADDRESS As AN ARRAY OF FOUR OCTETS
Cls
Dim IP(3)
Do
    REM Read DEMO Data
    140 Read CI$
    If CI$ = "" Then Exit Do 'Sleep: End
    REM FIND /
    SL = 0
    For I = Len(CI$) To 1 Step -1
        If Mid$(CI$,I,1) = "/" Then SL = I : I = 1
    Next I
    If SL = 0 Then Print "INVALID CIDR STRING: '"; CI$; "'": Goto 140
    NW = Val(Mid$(CI$,SL+1))
    If NW < 1 Or NW > 32 Then Print "INVALID NETWORK WIDTH:"; NW: Goto 140
    REM PARSE OCTETS INTO IP ARRAY
    BY = 0 : N = 0
    For I = 1 To SL-1
        C$ = Mid$(CI$,I,1)
        If Not (C$ <> ".") Then
            IP(N) = BY : N = N + 1
            BY = 0
            If IP(N-1) < 256 Then 310
            Print "INVALID OCTET VALUE:"; IP(N-1): Goto 140
            Else   C = Val(C$):If C Or (C$="0") Then BY = BY*10+C
        End If
        310 '
    Next I
    IP(N) = BY : N = N + 1
    If IP(N-1) > 255 Then Print "INVALID OCTET VALUE:"; IP(N-1): Goto 140
    REM NUMBER OF COMPLETE OCTETS IN NETWORK PART
    NB = Int(NW/8)
    REM NUMBER OF NETWORK BITS IN PARTIAL OCTET
    XB = NW And 7
    REM ZERO Out HOST BITS IN PARTIAL OCTET
    IP(NB) = IP(NB) And (255 - 2^(8-XB) + 1)
    REM And SET Any ALL-HOST OCTETS To 0
    If NB < 3 Then For I = NB +1 To 3 : IP(I) = 0 : Next I
    REM Print Out THE RESULT
    Print Mid$(Str$(IP(0)),2);
    For I = 1 To 3
        Print "."; Mid$(Str$(IP( I)),2);
    Next I
    Print Mid$(CI$,SL)
Loop
Data "87.70.141.1/22",   "36.18.154.103/12", "62.62.197.11/29"
Data "67.137.119.181/4", "161.214.74.21/24", "184.232.176.184/18"
REM SOME INVALID INPUTS
Data "127.0.0.1", "123.45.67.89/0", "98.76.54.32/100", "123.456.789.0/12"

Sleep