Since OsmoMSC has built-in SMSC, it needs to store the messages
somewhere. Currently we use libdbi and SQLite3 back-end for that.
For a long time, the db_sms_* API remained uncovered by unit tests.
This change aims to fix that, and does cover the following calls:
- db_sms_store(),
- db_sms_get(),
- db_sms_get_next_unsent(),
- db_sms_mark_delivered(),
- db_sms_delete_sent_message_by_id(),
- db_sms_delete_by_msisdn(),
- db_sms_delete_oldest_expired_message().
Due to performance reasons, the test database is initialized in
RAM using the magic filename ':memory:'. This is a feature of
SQLite3 (and not libdbi), see:
https://www.sqlite.org/inmemorydb.html
Of course, this unit test helped to discover some problems:
1) Storing an SMS with empty TP-User-Data (TP-UDL=0) causes
buffer overruns in both db_sms_store() and db_sms_get().
2) TP-User-Data-Length is always being interpreted in octets,
regardless of DCS (Data Coding Scheme). This results in
storing garbage in the database if the default 7-bit
encoding is used. Fortunately, the 'user_data' buffer
in structure 'gsm_sms' is large emough, so we don't
experience buffer overruns.
3) db_sms_delete_oldest_expired_message() doesn't work
as expected. Instead of removing the *oldest* expired
message, it tries to remove the *newest* one.
The current test expectations do reflect these problems.
All of them will be fixed in the follow-up patches.
Change-Id: Id94ad35b6f78f839137db2e17010fbf9b40111a3
e1e7247500