hodec 2: prep: common pick_better_lchan_to_move() function

There are four places deciding which of 2 lchans to move, depending on average
db ratings. Upcoming patches will enrich that decision for better handling of
dynamic timeslots, so have one common function for these to avoid code dup.

Change-Id: I745dc95cf564dd330295cecb4d64dccebf55163f

1 files changed, 27 insertions, 16 deletions

diff --git a/src/osmo-bsc/handover_decision_2.c b/src/osmo-bsc/handover_decision_2.c
index c818dbbde..7df8bb1fb 100644
--- a/src/osmo-bsc/handover_decision_2.c
+++ b/src/osmo-bsc/handover_decision_2.c
@@ -1362,6 +1362,29 @@ static void on_measurement_report(struct gsm_meas_rep *mr)
 	}
 }
 
+/* Given two candidates, pick the one that should rather be moved during handover.
+ * Return the better candidate in out-parameters best_cand and best_avg_db.
+ */
+static void pick_better_lchan_to_move(bool want_highest_db,
+				      struct ho_candidate **best_cand_p, unsigned int *best_avg_db_p,
+				      struct ho_candidate *other_cand, unsigned int other_avg_db)
+{
+	if (!*best_cand_p)
+		goto return_other;
+
+	if (want_highest_db && (*best_avg_db_p < other_avg_db))
+		goto return_other;
+	if (!want_highest_db && (*best_avg_db_p > other_avg_db))
+		goto return_other;
+
+	/* keep the same candidate. */
+	return;
+
+return_other:
+	*best_cand_p = other_cand;
+	*best_avg_db_p = other_avg_db;
+}
+
 /*
  * Handover/assignment check after timer timeout:
  *
@@ -1563,10 +1586,7 @@ next_b1:
 			is_improved = 0;
 		LOGPHOCAND(&clist[i], LOGL_DEBUG, "candidate %d: avg=%d best_avg_db=%d\n",
 			   i, avg, best_avg_db);
-		if (avg > best_avg_db) {
-			best_cand = &clist[i];
-			best_avg_db = avg;
-		}
+		pick_better_lchan_to_move(true, &best_cand, &best_avg_db, &clist[i], avg);
 	}
 
 	/* perform handover, if there is a candidate */
@@ -1636,10 +1656,7 @@ next_b2:
 				is_improved = 1;
 			} else
 				is_improved = 0;
-			if (avg < worst_avg_db) {
-				worst_cand = &clist[i];
-				worst_avg_db = avg;
-			}
+			pick_better_lchan_to_move(false, &worst_cand, &worst_avg_db, &clist[i], avg);
 		}
 	}
 
@@ -1712,10 +1729,7 @@ next_c1:
 			is_improved = 1;
 		} else
 			is_improved = 0;
-		if (avg > best_avg_db) {
-			best_cand = &clist[i];
-			best_avg_db = avg;
-		}
+		pick_better_lchan_to_move(true, &best_cand, &best_avg_db, &clist[i], avg);
 	}
 
 	/* perform handover, if there is a candidate */
@@ -1790,10 +1804,7 @@ next_c2:
 				is_improved = 0;
 			LOGP(DHODEC, LOGL_DEBUG, "candidate %d: avg=%d worst_avg_db=%d\n", i, avg,
 			     worst_avg_db);
-			if (avg < worst_avg_db) {
-				worst_cand = &clist[i];
-				worst_avg_db = avg;
-			}
+			pick_better_lchan_to_move(false, &worst_cand, &worst_avg_db, &clist[i], avg);
 		}
 	}