GSM 7bit encoding/decoding
osmocom at ehlers.info
Sat Jan 14 12:26:36 UTC 2012
since I had problems with german umlauts when receiving (and probably also
when sending) SMS, I looked today in the gsm translating part in
I first noticed a problem, when sending "NETZ Number" to "4636" in O2
network, you get a response SMS saying in which network the number is
located. Using osmocombb, I get:
[SMS from 66399]
Sehr geehrter Kunde, die angefragte Nummer ist im Netz von o2 aktiv
(Angabe ohne Gew§hr).
So the umlaut "ae" is converted to "§".
The problem seems to be in the convert table in
src/shared/libosmocore/src/gsm/gsm_utils.c, which is not bijective. "Ae"
in gsm7 is "0x7b" and must be converted to latin1 "0xe4".
Looking in gsm_7bit_alphabet at place "0xe4", the is "0x7b". But there is
also an "0x7b" at place "0xa7", which comes first and is indeed "§".
So the question is, are there mistakes in the table or is there a reason
for the double entries?
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