Decoding an extravagant binary format 46 06 09 21 43 65 87 F9

[Scott Ribe]

> On Jul 13, 2020, at 10:46 AM, Papa Tana <papa.tana101@REDACTED> wrote:
> 
> Hi All,
> 
> I receive binaries in my application:
> 
> IMSI_CODED in hex_dump
> 0000   46 06 09 21 43 65 87 F9
> 
> In reality, the peer is sending me this IMSI : (64 60 90 12 34 56 78 9F).
> 
> I hard-decode this IMSI_CODED like below:
> 
> 	<<R1:8, R2:8, R3:8, R4:8, R5:8, R6:8, R7:8, R8:8>> = <<IMSI_CODED:64>>,	
> 	
> 	Elements = [
> 		string:right(integer_to_list(R1,16), 2, $0),
> 		string:right(integer_to_list(R2,16), 2, $0),
> 		string:right(integer_to_list(R3,16), 2, $0),
> 		string:right(integer_to_list(R4,16), 2, $0),
> 		string:right(integer_to_list(R5,16), 2, $0),
> 		string:right(integer_to_list(R6,16), 2, $0),
> 		string:right(integer_to_list(R7,16), 2, $0),
> 		string:right(integer_to_list(R8,16), 2, $0)
> 		],                                          	
> 	R = [[B,A] || [A,B] <-Elements ],	%% here, I need to revert each element :-/
> 	L = list_to_tuple(R),
> 	Z = tuple_to_list(L),
> 	Real_IMSI = string:join(Z,"")
> 	
> 	
> => Real_IMSI = 	"646090123456789F"
> 
> I'm using the same hard-coding style to decode some SMS payload in
> binary format..
> 
> But I can feel that there is a much more elegant way to do it, because
> as you can see, despite it's working, it's really dirty etc...
> 
> Can anyone advice please?
> 
> Thanks,
> 
> Best Regards,

Match on 4-bit values and put them in order?