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systemctl: improve readability of start_unit()

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start_unit() is a little tangled.  There's an easy part we can untangle,
then readers can concentrate on the more necessary complexity.

* Derive (method, action, mode) more clearly, as disjoint cases based on
  the command.  Don't rely on action_table[_ACTION_INVALID].target being
  implicitly initialized to NULL.

  verb_to_method() is now only used on one case, but not because I strongly
  object to the implicit "StartUnit" cases.  It's more a syntax problem.
  I think the old code takes me longer to understand, because the call
  comes just above a similar-looking call to verb_to_action(), but the
  results of the two functions are used in different ways.  It also helps
  that the new code ends up having a more regular form, for the 4 different
  cases.

  These changes cost 6 extra lines.

* Add an assertion to confirm that we do not pass mode=NULL.
This commit is contained in:
Alan Jenkins 2017-08-18 13:18:09 +01:00
parent f886603b7e
commit 913c19161a
1 changed files with 19 additions and 11 deletions
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30
src/systemctl/systemctl.c
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@ -145,7 +145,6 @@ static char *arg_root = NULL;
static usec_t arg_when = 0; static usec_t arg_when = 0;
static char *argv_cmdline = NULL; static char *argv_cmdline = NULL;
static enum action { static enum action {
_ACTION_INVALID,
ACTION_SYSTEMCTL, ACTION_SYSTEMCTL,
ACTION_HALT, ACTION_HALT,
ACTION_POWEROFF, ACTION_POWEROFF,
@ -166,7 +165,8 @@ static enum action {
ACTION_REEXEC, ACTION_REEXEC,
ACTION_RUNLEVEL, ACTION_RUNLEVEL,
ACTION_CANCEL_SHUTDOWN, ACTION_CANCEL_SHUTDOWN,
_ACTION_MAX _ACTION_MAX,
_ACTION_INVALID = -1
} arg_action = ACTION_SYSTEMCTL; } arg_action = ACTION_SYSTEMCTL;
static BusTransport arg_transport = BUS_TRANSPORT_LOCAL; static BusTransport arg_transport = BUS_TRANSPORT_LOCAL;
static const char *arg_host = NULL; static const char *arg_host = NULL;
@ -3052,7 +3052,7 @@ static const struct {
static enum action verb_to_action(const char *verb) { static enum action verb_to_action(const char *verb) {
enum action i; enum action i;
for (i = _ACTION_INVALID; i < _ACTION_MAX; i++) for (i = 0; i < _ACTION_MAX; i++)
if (streq_ptr(action_table[i].verb, verb)) if (streq_ptr(action_table[i].verb, verb))
return i; return i;
@ -3085,22 +3085,30 @@ static int start_unit(int argc, char *argv[], void *userdata) {
if (arg_action == ACTION_SYSTEMCTL) { if (arg_action == ACTION_SYSTEMCTL) {
enum action action; enum action action;
method = verb_to_method(argv[0]);
action = verb_to_action(argv[0]); action = verb_to_action(argv[0]);
if (streq(argv[0], "isolate")) { if (action != _ACTION_INVALID) {
mode = "isolate"; method = "StartUnit";
suffix = ".target"; mode = action_table[action].mode;
} else one_name = action_table[action].target;
mode = action_table[action].mode ?: arg_job_mode; } else {
if (streq(argv[0], "isolate")) {
method = "StartUnit";
mode = "isolate";
one_name = action_table[action].target; suffix = ".target";
} else {
method = verb_to_method(argv[0]);
mode = arg_job_mode;
}
one_name = NULL;
}
} else { } else {
assert(arg_action < ELEMENTSOF(action_table)); assert(arg_action < ELEMENTSOF(action_table));
assert(action_table[arg_action].target); assert(action_table[arg_action].target);
assert(action_table[arg_action].mode);
method = "StartUnit"; method = "StartUnit";
mode = action_table[arg_action].mode; mode = action_table[arg_action].mode;
one_name = action_table[arg_action].target; one_name = action_table[arg_action].target;
} }