Error Detection
Sepand Haghighi
Mahmoud EbrahimKhani
Amirkabir University Of Technology
Version 1.2
About This Package
This package written in python 3 and provide this algorithms :
* CRC
* Hamming Code
* Parity
* Repeated Code
* Simple Checksum
Error_Detect.py
* In this file we wrote error_detect object and some method for it , this object get 3 arguments ; message string , method and a flag for repeated code.
* Two function also written in this file for convert and decode that call each algorithm function in case.
func.py
in this file we wrote each algorithm generate and detect functions separately
with __det and __gen at end of each.
parity_even_gen
def parity_even_gen(error_object):
'''
parity_even_gen(error_detect)-> str
This Function Get an Error_Object As Input And Return A String That Modified By Even Parity Code
Default Input In This Mehtod Is Binary
'''
try:
new_str="" #Empty String
if what(error_object.str)=="bin": # Condition For Checking Binary Or Hex (Default Is Binary)
new_str=error_object.str
elif what(error_object.str)=="hex":
new_str=hex_2_bin(error_object.str)
temp=0 #Temp Variable(Default Zero For XOR Operation)
length=len(new_str) # Length Of Input String
for i in range(length): # Loop For Calculate XOR Of All Bits
temp=xor(int(new_str[i]),temp)
output=new_str+str(temp) # Adding Parity Bit To End Of The Original Message
return output #Return Output In Binary For For transmit
except:
print("Error In Generating Even Parity")
return Noneparity_even_det
def parity_even_det(error_object):
'''
parity_even_det(error_detect)-> Boolean
This Function Get an Error_Object As input and return a boolean value that represent that this string has error or not
Default Input Format Is Binary
'''
try:
new_str=error_object.str # Copy Error Object String In New String Variable
temp=0 # Temp Variable (Default Zero For XOR)
length=len(new_str) # Length of Input String
for i in range(length-1): # Loop For Calculate Of XOR Of All Bits - Last
temp=xor(int(new_str[i]),temp)
if xor(temp,int(new_str[-1]))==0: # Compare Loop result With last Bit And Return Boolean
return True
else:
return False
except:
print("Error In Detecting Even Parity")
return Noneparity_odd_gen
def parity_odd_gen(error_object):
'''
parity_odd_gen(error_detect)-> str
This Function Get an Error_Object As Input And Return A String That Modified By Odd Parity Code
Default Input In This Mehtod Is Binary
'''
try:
new_str="" # Empty String
if what(error_object.str)=="bin": # Condition For Checking Binary Or Hex (Default Is Binary)
new_str=error_object.str
elif what(error_object.str)=="hex":
new_str=hex_2_bin(error_object.str)
temp=0 # Temp Variable (Default Zero For XOR)
length=len(new_str) # Length Of Input String
for i in range(length): # Loop For Calculate XOR Of Bits
temp=xor(int(new_str[i]),temp)
result=new_str+str(int(not(temp))) #Convert To XNOR
return result # Return Binary Output
except:
print("Error In Generating Odd parity")
return Noneparity_odd_det
def parity_odd_det(error_object):
'''
parity_odd_det(error_detect)-> Boolean
This Function Get an Error_Object As input and return a boolean value that represent that this string has error or not
Default Input Format Is Binary
'''
try:
new_str=error_object.str # Copy Error Object String In New String Variable
temp=0 # Temp Variable (Default Zero For XOR)
length=len(new_str)-1 # Length Of Input String -1 (To Ignore Last Bit)
for i in range(length): # Loop For Calculate XOR Of Bits
temp=xor(temp,int(new_str[i]))
if xor(temp,int(new_str[-1]))==1: # Comapre Loop Result And Parity Bit And Return Boolean Value
return True
else:
return False
except:
print("Error In Detectting Odd Parity")
return Nonerepeated_code_gen
def repeat_gen(error_object):
'''
repeat_gen(error_object) -> String
This Function Get An Error_Object As Input And Return Modified String As Output , Default Input Is Hex
'''
try:
new_str="" # Empty String
if what(error_object.str)=="hex": # Condition For Checking Binary Or Hex (Default Is Hex)
new_str=error_object.str
elif what(error_object.str)=="bin":
new_str=bin_2_hex(error_object.str)
return new_str*error_object.flag #Return flag number of input string that cat together
except:
print("Error In repeat Generation")
return Nonerepeated_code_det
def repeat_det(error_object):
'''
repeat_det(error_object) -> Boolean
This Function Get An Error_object As Input And Return A Boolean Value As Output , Default Output Is Hex
'''
try:
new_str=error_object.str # Copy Error Object String In New String Variable
temp=None # Temp Variable With Default None
length=len(new_str) #Length Of Input String
repeat_number=int(error_object.flag) #Number Of Repeat That Extract From Method
message_length=length//repeat_number # Calc Orignal Message
original_message=new_str[0:message_length] # Extract Orignal Message From Input String
for i in range(repeat_number): # Loop For Compare Orignal Message With Each Of Repeated
temp=new_str[i*message_length:(i+1)*message_length]
if temp!=original_message: # If One Of The Compare Result Is False Break And Return False Else True
return False
return True
except:
print("Error In Repeat Detection")
return Nonehamming_code_gen
def hamming_gen(error_object):
'''
hamming_gen(error_object) -> String
This Function Get An Error_object As Input and Return Modified String By Hamming Code Method As Output , Default Input Is Binary
'''
try:
new_str="" # Empty String
if what(error_object.str)=="bin": # Condition For Checking Binary Or Hex (Default Is Bin)
new_str=error_object.str
elif what(error_object.str)=="hex":
new_str=hex_2_bin(error_object.str)
length=len(new_str) # Length Of Input String
parity_number=int(log(length,2))+1 # Calc Number Of Needed Parity Code
parity_index=[] # Empty List Of Parity Index
message=[] # Empty List As Message
p1=[0,2,4,6,8,10,12,14,16,18] # Parity-1 Indexs
p2=[1,2,5,6,8,9,13,14,17,18] # Parity-2 Indexs
p4=[3,4,5,6,11,12,13,14,19] # Parity-4 Indexs
p8=[7,8,9,10,11,12,13,14] # Parity-8 Indexs
p16=[15,16,17,18,19] # Parity-16 Indexs
k=0 # Iteration Number
parity_number_index=1 # Parity Number Index
for i in range(length): # Loop For Extract available parity index in input message and added to parity _index
if int(2**i)<=length and parity_number_index<=parity_number:
parity_index.append(int(2**i)-1)
parity_number_index=parity_number_index+1 # nubmer of total parity in string
for i in range(length+len(parity_index)): # Modified A Init List For Hamming Code Output
if i in parity_index: # By Inserting 0 in Parity Location
message.append("0")
else:
message.append(new_str[k]) # And Insert Original Message Between them
k=k+1 # Iter
for i in range(length+len(parity_index)): # Calc Each Parity Bit In Message And Generate Hamming Output
if i in p1:
message[0]=str(xor(int(message[0]),int(message[i])))
if i in p2:
message[1]=str(xor(int(message[1]),int(message[i])))
if i in p4:
message[3]=str(xor(int(message[3]),int(message[i])))
if i in p8:
message[7]=str(xor(int(message[7]),int(message[i])))
if i in p16:
message[15]=str(xor(int(message[15]),int(message[i])))
result="".join(message) # Use Join Method to Convert List To String
return result
except:
print("Something Wrong In Generating Hamming Code")
return Nonehamming_code_det
def hamming_det(error_object):
'''
hamming_det(error_object) -> Boolean
This Function Get An Error_Object As Input And Return Boolean Value As Output (Default Input In Binary)
'''
try:
new_str=error_object.str # Copy Error Object String In New String Variable
length=len(new_str) # Length Of Input String
parity_index=[] # Empty List As Parity Index
message=list(new_str) # Convert Input String To List
parity_value=[] # Empty List As Parity Bit Values
p1=[2,4,6,8,10,12,14,16,18] # Parity-1 Indexs-Modified
p2=[2,5,6,8,9,13,14,17,18] # Parity-2 Indexs-Modified
p4=[4,5,6,11,12,13,14,19] # Parity-4 Indexs-Modified
p8=[8,9,10,11,12,13,14] # Parity-8 Indexs-Modified
p16=[16,17,18,19] # Parity-16 Indexs-Modified
for i in range(length): #Loop For Extract Parity Index And Added To Parity_Index
if int(2**i)<=length:
parity_index.append(int(2**i)-1)
parity_value.append(new_str[int(2**i)-1])
else:
break
for i in range(length): # Loop For Calc Each Parity Bit And Store In Parity Value
if i in p1:
parity_value[0]=str(xor(int(parity_value[0]),int(message[i])))
if i in p2:
parity_value[1]=str(xor(int(parity_value[1]),int(message[i])))
if i in p4:
parity_value[2]=str(xor(int(parity_value[2]),int(message[i])))
if i in p8:
parity_value[3]=str(xor(int(parity_value[3]),int(message[i])))
if i in p16:
parity_value[4]=str(xor(int(parity_value[4]),int(message[i])))
if bin_2_dec(parity_value)==0: # If Parity Bits Represent 0 Return True (Without One Bit Error)
return True
else:
output="Error Bit Number : "+str(bin_2_dec(parity_value)) # Else Return The Number Of Error Bits
print(output)
return False
except:
print("Something Wrong With Hamming Code")
return Nonecrc_gen
def crc_gen(error_object,poly):
'''
crc_gen(error_object , str) -> String
This Function Get An Error_object And Polynomial Coef As Input And Return Modified String By CRC Method And That Poly As Output
'''
try:
new_str="" # Empty String
if what(error_object.str)=="bin": # Condition For Checking Binary Or Hex (Default Is Bin)
new_str=error_object.str
elif what(error_object.str)=="hex":
new_str=hex_2_bin(error_object.str)
divider_len=len(poly) # Length Of Divider (Length Of Polynomial)
extra_bit_len=divider_len-1 # Extra Bits = Polynomial Degree
message=new_str+(extra_bit_len)*"0" # Add Zero At The End Of The Orignal Message
length=len(message) # Length Of Modified Message
length_init=len(new_str) # length Of Original Message
message=list(message) # Convert Message String tO lIST
start_index=0 # start_index variable default zero
cond_list=["0"]*length_init # Generate Stop Condition Of CRC Method
while(message[0:length-(extra_bit_len)]!=cond_list ): # Main Codition For Continue Divide
temp=message[start_index:start_index+divider_len] # Subset Message By Divider Length
for i in range(divider_len): # XOR Subset By Divider And Replace In Message
temp[i]=str(xor(int(temp[i]),int(poly[i])))
message[start_index:start_index+divider_len]=temp
for j in range(length): # Find Next Bit 1 And Update strat_index
if message[j]=="1":
start_index=j
break
result="".join(message[length-(extra_bit_len):]) # Convert List To String
return new_str+result # Return Modified String
except:
print("Something Wrong In Generating Error_Detection Object!!")
return Nonecrc_det
def crc_det(error_object,poly):
'''
crc_det(error_object) -> Boolean
This Function Get An Error_Object And Return Boolean Value As Output ( Default Input Is Hex)
'''
try:
new_str=error_object.str # Copy Error Object String In New String Variable
divider_len=len(poly) # Length Of Divider
extra_bit_len=divider_len-1 # Length Of Extra Bits (Polynomial Degree)
message=list(new_str) # Conert Input Message To List
length=len(message) # Length Of Message
start_index=0 # Start Index
cond_list=["0"]*(length-extra_bit_len) # Stop Conditional
while(message[0:length-extra_bit_len]!=cond_list): # Main Condition For Continue CRC Method
temp=message[start_index:start_index+divider_len] # Subset Message By Divider Length
for i in range(divider_len): # Calc XOR Of Poly And Subset And Replace In Message
temp[i]=str(xor(int(temp[i]),int(poly[i])))
message[start_index:start_index+divider_len]=temp
for j in range(length): # Find Next 1 Bit And Update Start_index
if message[j]=="1":
start_index=j
break
if "".join(message[length-extra_bit_len:])==(divider_len-1)*"0": # Check If Reminder Is Equal Zero Return True Else Return False
return True
else:
return False
except:
print("Something Wrong In Detecting Error In Object")
return Nonechecksum_gen
def checksum_gen(error_object):
'''
checksum_gen(error_object) -> String
This Function Get An Error_Object As Input And Return Modified String By Checksum (Default Input Is Hex)
'''
try:
new_str="" # Empty String
if what(error_object.str)=="hex": # Condition For Checking Binary Or Hex (Default Is Bin)
new_str=error_object.str
elif what(error_object.str)=="bin":
new_str=bin_2_hex(error_object.str)
length=len(new_str) # Length Of Input String
temp=0 # Temp Variable
for i in new_str: # Calc Sum Of Bits And Store In Temp
temp=temp+hex_dict[i]
temp=hex(temp) # Convert Decimal To Hex
temp=temp[2:] # Delete Python Hex Sign
final_string=new_str+temp # Add temp To the end of Orignal Message
return final_string # Return Modified String
except:
print("Error In Checksum Generator")
return Nonechecksum_det
def checksum_det(error_object):
'''
checksum_det(error_object) -> Boolean
This Function Get An Error Obejct As Input And Return A Boolean Value As Output (Default Input Is Hex)
'''
try:
new_str=error_object.str # Copy Error Object String In New String Variable
checksum=new_str[-2:] # Extract Checksum number
temp=0 # Temp Variable
for i in new_str[:-2]: # Calc Sum Of The Bits - Checksum
temp=temp+hex_dict[i]
temp=hex(temp) # Convert Decimal to Hex
temp=temp[2:] # Delet Python Hex Sign
if temp==checksum: # Compare To Checksum Value If Its Identical Return True Else False
return True
else:
return False
except:
print("Error in Checksum Detector")Extra Functions 1
def hex_2_bin(hex_input):
'''
hex_2_bin(str)-> str
'''
try:
init_bin=[]
for i in hex_input:
init_bin.append(bin(hex_dict[i])[2:])
result="".join(init_bin)
return result
except:
print("Something Wrong")
return None
def bin_2_dec(bin_input):
'''
bin_2_dec(str)-> str
'''
try:
s=0
input_val=bin_input.reverse()
for i in range(len(bin_input)):
s=s+(2**i)*int(bin_input[i])
return s
except:
print("Something Wrong")
return NoneExtra Functions 2
def what(string):
'''
(str)->str
Find Input Type
'''
length=len(string)
hex_string=[]
bin_string=[]
error_flag=0
for i in range(length):
if string[i] in ["0","1"]:
hex_string.append(1)
bin_string.append(1)
elif string[i] in hex_dict.keys():
hex_string.append(1)
bin_string.append(0)
else:
error_flag=1
if error_flag==0 and all(bin_string):
return "bin"
elif error_flag==0 and all(hex_string):
return "hex"
else:
return "None"
Extra Functions 3
def bin_2_hex(bin_input):
'''
(Str)->Str
Bin Input To Hex
'''
try:
length=len(bin_input)
temp=[]
temp_2=[]
for i in range(4-length%4):
temp.append("0")
temp="".join(temp)
temp=temp+bin_input
for i in range(0,len(temp),4):
if i+3<len(temp):
temp_2.append(str(bin_dict[temp[i:i+4]]))
temp_2="".join(temp_2);
return temp_2
except:
print("Something Wrong In Input")
return NoneLink
Error_Detect
By sepkjaer
