Reverse String but keep character pairs together

Question

I have analysed the global header of a PCAP file and found out that the magic number is: d4 c3 b2 a1

This means that it uses a little endian and all the bytes that come after it need to processed in reverse order. The other sections of the global header are as follows:

major version =  02 00

minor version =  04 00

time zone =  00 00 00 00

timestamp =  00 00 00 00

snaplen =  ff ff 00 00

linktype =  01 00 00 00

However given that little endian is in use, it should be:

major version =  00 02

minor version =  00 04

time zone =  00 00 00 00

timestamp =  00 00 00 00

snaplen =  00 00 ff ff

linktype =  00 00 00 01

So I need a way to reverse the string but still keep the pairs of characters separated by the spaces in the same order.

So the code [::-1] will not work because it transforms 02 00 into 00 20, whereas it needs to be 00 02

How would I go about doing this?

Answer 1

You need a few more steps to do it:

linktype = "00 00 00 01"
rev_linktype = " ".join(reversed(linktype.split()))

The idea is to first chop the string into tokens instead of characters, then reverse the order of the tokens, and then join them back into one long string.