fsm: add osmo_fsm_inst_state_chg_keep_or_start_timer()
During FSM design for osmo-msc, I noticed that the current behavior that
keep_timer=true doesn't guarantee a running timer can make FSM design a bit
complex, especially when using osmo_tdef for timeout definitions.
A desirable keep_timer=true behavior is one that keeps the previous timer
running, but starts a timer if no timer is running yet.
The simplest example is: a given state repeatedly transitions back to itself,
but wants to set a timeout only on first entering, avoiding to restart the
timeout on re-entering.
Another example is a repeated transition between two or more states, where the
first time we enter this group a timeout should start, but it should not
restart from scratch on every transition.
When using osmo_tdef timeout definitions for this, so far separate meaningless
states have to be introduced that merely set a fixed timeout.
To simplify, add osmo_fsm_inst_state_chg_keep_or_start_timer(), and use this in
osmo_tdef_fsm_inst_state_chg() when both keep_timer == true *and* T != 0.
In tdef_test.ok, the changes show that on first entering state L, the previous
T=1 is now kept with a large remaining timeout. When entering state L from O,
where no timer was running, this time L's T123 is started.
Change-Id: Id647511a4b18e0c4de0e66fb1f35dc9adb9177db
diff --git a/tests/tdef/tdef_test_range_64bit.ok b/tests/tdef/tdef_test_range_64bit.ok
index eed58e6..7ec295d 100644
--- a/tests/tdef/tdef_test_range_64bit.ok
+++ b/tests/tdef/tdef_test_range_64bit.ok
@@ -158,9 +158,9 @@
--> A (configured as T1 100 s) rc=0; state=A T=1, 100.000000 s remaining
Time passes: 23.045678 s
state=A T=1, 76.954322 s remaining
- --> L (configured as T123(keep_timer) 1 s) rc=0; state=L T=123, 76.954322 s remaining
+ --> L (configured as T123(keep_timer) 1 s) rc=0; state=L T=1, 76.954322 s remaining
--> O (no timer configured for this state) rc=0; state=O T=0, no timeout
- --> L (configured as T123(keep_timer) 1 s) rc=0; state=L T=123, no timeout
+ --> L (configured as T123(keep_timer) 1 s) rc=0; state=L T=123, 1.000000 s remaining
- test T=0:
--> O (no timer configured for this state) rc=0; state=O T=0, no timeout
- test no timer: