job: use a lookup table for merging of job types

It is easier to see what job_type_merge() is doing when the merging
rules are written in the form of a table.

job_type_is_superset() contained redundant information. It can be
simplified to a simple rule: Type A is a superset of B iff merging A
with B gives A.

Two job types are conflicting iff they are not mergeable.

Make job_type_lookup_merge() the core function to decide the type
merging. All other job_type_*() are just short wrappers around it.
They can be inline.

test-job-type gives the same results as before.
btw, the systemd binary is smaller by almost 1 KB.

1 files changed, 25 insertions, 4 deletions

diff --git a/src/job.h b/src/job.h
index 2121426b33..60a43e074d 100644
--- a/src/job.h
+++ b/src/job.h
@@ -24,6 +24,7 @@
 
 #include <stdbool.h>
 #include <inttypes.h>
+#include <errno.h>
 
 typedef struct Job Job;
 typedef struct JobDependency JobDependency;
@@ -37,6 +38,7 @@ typedef enum JobResult JobResult;
 #include "hashmap.h"
 #include "list.h"
 
+/* Be careful when changing the job types! Adjust job_merging_table[] accordingly! */
 enum JobType {
         JOB_START,                  /* if a unit does not support being started, we'll just wait until it becomes active */
         JOB_VERIFY_ACTIVE,
@@ -145,10 +147,29 @@ bool job_is_anchor(Job *j);
 
 int job_merge(Job *j, Job *other);
 
-int job_type_merge(JobType *a, JobType b);
-bool job_type_is_mergeable(JobType a, JobType b);
-bool job_type_is_superset(JobType a, JobType b);
-bool job_type_is_conflicting(JobType a, JobType b);
+JobType job_type_lookup_merge(JobType a, JobType b);
+
+static inline int job_type_merge(JobType *a, JobType b) {
+        JobType t = job_type_lookup_merge(*a, b);
+        if (t < 0)
+                return -EEXIST;
+        *a = t;
+        return 0;
+}
+
+static inline bool job_type_is_mergeable(JobType a, JobType b) {
+        return job_type_lookup_merge(a, b) >= 0;
+}
+
+static inline bool job_type_is_conflicting(JobType a, JobType b) {
+        return !job_type_is_mergeable(a, b);
+}
+
+static inline bool job_type_is_superset(JobType a, JobType b) {
+        /* Checks whether operation a is a "superset" of b in its actions */
+        return a == job_type_lookup_merge(a, b);
+}
+
 bool job_type_is_redundant(JobType a, UnitActiveState b);
 
 bool job_is_runnable(Job *j);