How to slice hex data?

Question

I have and Hex data in which there are three data present on which I can separate the information contain in the hex data:

ID (2 bytes)
length of the packet(2 bytes)
information

from the length of the packet, we come to know how long is the data in this hex data for example hex data = 0001001447364B5F48312E305F56312E312E3165000300133836333932313033343330343337310004000838303634000200154D414A3258584D524A32444A363135303900050005010006000843415244000700094341524431000800050000090018383939313035323138303935393533303834300D000A000E706F7274616C6E6D6D73

if we manually separate this HEX data according to the above information then we get this data 0001001447364B5F48312E305F56312E312E3165

here

id=0001

packet lenght=0014=20

information = 47364B5F48312E305F56312E312E3165

i have tried to separate the information by my code but it only separates the first data I want to separate the whole hex data

this is my python code:

data="0001001447364B5F48312E305F56312E312E316500030013383633393231303334333034333731"
t=data[0:4]
l=data[4:8]
hex_to_decimal=int(l, 16)
data1=data[0:hex_to_decimal*2]
print(data1)

can anyone help me to figure it up

Am I reading this correctly, that you want to have all data chunks separated? — André, Jul 23 '21 at 07:12
please check this question https://stackoverflow.com/questions/15036551/best-way-to-split-a-hexadecimal-in-python — Roksolanka Fedkovych, Jul 23 '21 at 07:12
A 20 byte information field would contain `47364B5F48312E305F56312E312E316500030013`. — martineau, Jul 23 '21 at 09:16
0001001447364B5F48312E305F56312E312E3165 this whole packet is of 20 byte — Muhammed, Jul 23 '21 at 09:26

Joran Beasley · Answer 1 · 2021-07-23T07:34:00.853

this is really what the struct package is made for (and bytes.fromhex)

>>> import struct
>>> s = "0001001447364B5F48312E305F56312E312E3165000300133836333932313033343330343337310004000838303634000200154D414A3258584D524A32444A363135303900050005010006000843415244000700094341524431000800050000090018383939313035323138303935393533303834300D000A000E706F7274616C6E6D6D73"
>>> mbytes = bytes.fromhex(s)
>>> msg_id,msg_size = struct.unpack(">hh",mbytes[:4])
# 1, 20
>>> msg_bytes = struct.unpack_from("{}s".format(msg_size),mbytes[4:])[0]
>>> msg_hex = bytes.hex(msg_bytes)
# 47364b5f48312e305f56312e312e316500030013
# which i think is what you actually want... but if you actually think size represents each character in that string you will need to make a modification
>>> alt_hex = s[8:][msg_size] 
# 47364b5f48312e305f56 ( which i think is the wrong value...)

score 0 · Accepted Answer · answered Jul 23 '21 at 07:47

You can loop over the data string and extract the data.

Here is how it would look like:

data="0001001447364B5F48312E305F56312E312E3165000300133836333932313033343330343337310004000838303634000200154D414A3258584D524A32444A363135303900050005010006000843415244000700094341524431000800050000090018383939313035323138303935393533303834300D000A000E706F7274616C6E6D6D73"

i = 0
while i < len(data):
    t = data[i:i+4]
    l = data[i+4:i+8]
    hex_to_decimal = int(l, 16)
    data1 = data[i:i+hex_to_decimal*2]

    print(f'Length: {hex_to_decimal*2}\nData: {data1}\n')
    i += hex_to_decimal*2

Output:

Length: 40
Data: 0001001447364B5F48312E305F56312E312E3165

Length: 38
Data: 00030013383633393231303334333034333731

Length: 16
Data: 0004000838303634

Length: 42
Data: 000200154D414A3258584D524A32444A3631353039

Length: 10
Data: 0005000501

Length: 16
Data: 0006000843415244

Length: 18
Data: 000700094341524431

Length: 10
Data: 0008000500

Length: 48
Data: 00090018383939313035323138303935393533303834300D

Length: 28
Data: 000A000E706F7274616C6E6D6D73

How to slice hex data?

2 Answers2