Zadanie3

@@ -0,0 +1,160 @@
+from sys import argv
+import sys
+import binascii
+import base64
+
+def binnahex(var):
+    all = {"0000": "0",
+            "0001": "1",
+            "0010": "2",
+            "0011": "3",
+            "0100": "4",
+            "0101": "5",
+            "0110": "6",
+            "0111": "7",
+            "1000": "8",
+            "1001": "9",
+            "1010": "A",
+            "1011": "B",
+            "1100": "C",
+            "1101": "D",
+            "1110": "E",
+            "1111": "F"
+            }
+    i = 0
+    output = ""
+
+    while (len(var) % 4 != 0):
+        var = "0" + var
+
+    while (i < len(var)):
+        output = output + all[var[i:i + 4]]
+        i = i + 4
+
+    output = output.lstrip("0")
+    output = "0" if len(output) == 0 else output
+
+    return output
+
+#XOR
+def xor(a, b):
+ 
+    # init
+    result = []
+ 
+    # porownuje znaki
+    for i in range(1, len(b)):
+        if a[i] == b[i]:
+            result.append('0')
+        else:
+            result.append('1')
+ 
+    return ''.join(result)
+ 
+ 
+# dzielenie modulo 2
+def divide(message):
+    poly16 = "10001000000100001"
+    # Ilosc bitow dla operacji XOR 'na raz'
+    step = len(poly16)
+ 
+    # podzial krok po kroku
+    temp = message[0 : step]
+ 
+    while step < len(message):
+ 
+        if temp[0] == '1':
+ 
+            temp = xor(poly16, temp) + message[step]
+ 
+        else:   
+            # jezeli 1 bit po lewej == 0
+            temp = xor('0'*step, temp) + message[step]
+ 
+        # kolejny krok
+        step += 1
+ 
+    if temp[0] == '1':
+        temp = xor(poly16, temp)
+    else:
+        temp = xor('0'*step, temp)
+ 
+    check = temp
+    return check
+
+def decode(message,crc):
+    poly16 = "10001000000100001"
+    l_poly16 = len(poly16)
+    message = bytearray(message, 'ascii')
+    message = format(int.from_bytes(message, "big"), "b")
+    while len(message) % 8 != 0:
+        message = "0" + message
+    dec = int(crc, 16)
+    crc2=bin(dec)[2:]
+    while len(crc2) % 8 != 0:
+        crc2 = "0" + crc2
+    msg=message+crc2
+    while len(msg) % 8 != 0:
+        msg = "0" + msg
+    obroc = list(msg)
+    for i in range(l_poly16 - 1):
+        if obroc[i] == "0":
+            obroc[i] = "1"
+        elif obroc[i] == '1':
+            obroc[i] = "0"
+
+    msg = "".join(obroc)
+
+    remainder = divide(msg)
+
+    suma = 0
+    for i in range(0, len(remainder)):
+            if '1' in remainder:
+                suma = suma+1
+
+    if suma == 0:
+        print("true ")
+    elif suma > 0:
+        print("false")
+
+
+def encode(message):
+    poly16 = "10001000000100001"
+    a=message
+    
+    message = bytearray(message, 'ascii')
+    message = format(int.from_bytes(message, "big"), "b")
+    l_poly16 = len(poly16)
+    message = message + '0'*(l_poly16-1)
+    while len(message) % 8 != 0:
+        message = "0" + message
+    obroc = list(message)
+    for i in range(l_poly16 - 1):
+        if obroc[i] == "0":
+            obroc[i] = "1"
+        elif obroc[i] == '1':
+            obroc[i] = "0"
+
+    message = "".join(obroc)
+    remainder = divide(message)
+    ab=binnahex(remainder)
+    d=str(base64.b16decode(ab))[2:-1]
+    message_final = a + d
+    message_final = bytearray(message_final, 'ascii')
+    d = bytearray(d, 'ascii')
+    print("calosc : ", message_final)
+    print("crc hex : ", ab)   
+    print("crc ascii : ", d)       
+    decode(a,ab)
+
+def main():
+    global message
+    message = list(argv[1])
+    flag = argv[2] 
+    if flag == 'encode':
+        encode(sys.argv[1])
+    elif flag == 'decode':
+        crc = argv[3] 
+        decode(sys.argv[1],sys.argv[3])    
+if __name__ == '__main__':
+    main()