From e7191fc57a9ef00e6495014f1da5a2ea67b839ca Mon Sep 17 00:00:00 2001
From: peter1138 <peter1138@openttd.org>
Date: Tue, 19 Jun 2007 16:40:59 +0000
Subject: [PATCH] (svn r10222) -Fix [FS#892]: Only 2 trains could crash at one
 time as collision checking stopped on the first hit. This could cause desyncs
 in network games as the collision hash order is not guaranteed. (patch by B.
 N. Smatz)

---
 src/train_cmd.cpp | 88 +++++++++++++++++++++++++----------------------
 1 file changed, 47 insertions(+), 41 deletions(-)

diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index f04121db63..0aca1b08d4 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -2659,28 +2659,6 @@ static void TrainMovedChangeSignals(TileIndex tile, DiagDirection dir)
 }
 
 
-struct TrainCollideChecker {
-	const Vehicle *v;
-	const Vehicle *v_skip;
-};
-
-static void *FindTrainCollideEnum(Vehicle *v, void *data)
-{
-	const TrainCollideChecker* tcc = (TrainCollideChecker*)data;
-
-	if (v != tcc->v &&
-			v != tcc->v_skip &&
-			v->type == VEH_TRAIN &&
-			v->u.rail.track != TRACK_BIT_DEPOT &&
-			myabs(v->z_pos - tcc->v->z_pos) < 6 &&
-			myabs(v->x_pos - tcc->v->x_pos) < 6 &&
-			myabs(v->y_pos - tcc->v->y_pos) < 6) {
-		return v;
-	} else {
-		return NULL;
-	}
-}
-
 static void SetVehicleCrashed(Vehicle *v)
 {
 	if (v->u.rail.crash_anim_pos != 0) return;
@@ -2704,6 +2682,47 @@ static uint CountPassengersInTrain(const Vehicle* v)
 	return num;
 }
 
+struct TrainCollideChecker {
+	Vehicle *v;
+	const Vehicle *v_skip;
+	uint num;
+};
+
+static void *FindTrainCollideEnum(Vehicle *v, void *data)
+{
+	TrainCollideChecker* tcc = (TrainCollideChecker*)data;
+
+	if (v != tcc->v &&
+			v != tcc->v_skip &&
+			v->type == VEH_TRAIN &&
+			v->u.rail.track != TRACK_BIT_DEPOT &&
+			myabs(v->z_pos - tcc->v->z_pos) < 6 &&
+			myabs(v->x_pos - tcc->v->x_pos) < 6 &&
+			myabs(v->y_pos - tcc->v->y_pos) < 6 ) {
+
+		Vehicle *coll = GetFirstVehicleInChain(v);
+
+		/* it can't collide with its own wagons */
+		if (tcc->v == coll ||
+			(tcc->v->u.rail.track == TRACK_BIT_WORMHOLE && (tcc->v->direction & 2) != (v->direction & 2)))
+			return NULL;
+
+		/* two drivers + passengers killed in train tcc->v (if it was not crashed already) */
+		if (!(tcc->v->vehstatus & VS_CRASHED)) {
+			tcc->num += 2 + CountPassengersInTrain(tcc->v);
+			SetVehicleCrashed(tcc->v);
+		}
+
+		if (!(coll->vehstatus & VS_CRASHED)) {
+			/* two drivers + passengers killed in train coll (if it was not crashed already) */
+			tcc->num += 2 + CountPassengersInTrain(coll);
+			SetVehicleCrashed(coll);
+		}
+	}
+
+	return NULL;
+}
+
 /**
  * Checks whether the specified train has a collision with another vehicle. If
  * so, destroys this vehicle, and the other vehicle if its subtype has TS_Front.
@@ -2720,28 +2739,15 @@ static void CheckTrainCollision(Vehicle *v)
 	TrainCollideChecker tcc;
 	tcc.v = v;
 	tcc.v_skip = v->next;
+	tcc.num = 0;
 
-	/* find colliding vehicle */
-	Vehicle *realcoll = (Vehicle*)VehicleFromPosXY(v->x_pos, v->y_pos, &tcc, FindTrainCollideEnum);
-	if (realcoll == NULL) return;
+	/* find colliding vehicles */
+	VehicleFromPosXY(v->x_pos, v->y_pos, &tcc, FindTrainCollideEnum);
 
-	Vehicle *coll = GetFirstVehicleInChain(realcoll);
+	/* any dead -> no crash */
+	if (tcc.num == 0) return;
 
-	/* it can't collide with its own wagons */
-	if (v == coll ||
-			(v->u.rail.track == TRACK_BIT_WORMHOLE && (v->direction & 2) != (realcoll->direction & 2)))
-		return;
-
-	/* two drivers + passengers killed in train v */
-	uint num = 2 + CountPassengersInTrain(v);
-	if (!(coll->vehstatus & VS_CRASHED))
-		/* two drivers + passengers killed in train coll (if it was not crashed already) */
-		num += 2 + CountPassengersInTrain(coll);
-
-	SetVehicleCrashed(v);
-	if (IsFrontEngine(coll)) SetVehicleCrashed(coll);
-
-	SetDParam(0, num);
+	SetDParam(0, tcc.num);
 	AddNewsItem(STR_8868_TRAIN_CRASH_DIE_IN_FIREBALL,
 		NEWS_FLAGS(NM_THIN, NF_VIEWPORT | NF_VEHICLE, NT_ACCIDENT, 0),
 		v->index,