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authorrubidium <rubidium@openttd.org>2007-12-30 21:35:48 +0000
committerrubidium <rubidium@openttd.org>2007-12-30 21:35:48 +0000
commit1a70eed58c1d42900b0a972403d993c435be8a65 (patch)
tree01e7b3240ff6b76eb9a2d853dae254da23112163
parent566a24d6ee26ca3ed419a1944a690acd00e06426 (diff)
downloadopenttd-1a70eed58c1d42900b0a972403d993c435be8a65.tar.xz
(svn r11724) -Fix: make it impossible (for users) to circumvent the length checking of the NewGRF 'allow wagon attach' callback by moving several wagons at a time.
-rw-r--r--src/train_cmd.cpp92
1 files changed, 83 insertions, 9 deletions
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index c347200f2..12ea3ddaf 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -1027,16 +1027,90 @@ CommandCost CmdMoveRailVehicle(TileIndex tile, uint32 flags, uint32 p1, uint32 p
if (flags & DC_EXEC) src->unitnumber = unit_num;
}
- if (dst_head != NULL) {
- /* Check NewGRF Callback 0x1D */
- uint16 callback = GetVehicleCallbackParent(CBID_TRAIN_ALLOW_WAGON_ATTACH, 0, 0, dst_head->engine_type, src, dst_head);
- if (callback != CALLBACK_FAILED) {
- if (callback == 0xFD) return_cmd_error(STR_INCOMPATIBLE_RAIL_TYPES);
- if (callback < 0xFD) {
- StringID error = GetGRFStringID(GetEngineGRFID(dst_head->engine_type), 0xD000 + callback);
- return_cmd_error(error);
+ /*
+ * Check whether the vehicles in the source chain are in the destination
+ * chain. This can easily be done by checking whether the first vehicle
+ * of the source chain is in the destination chain as the Next/Previous
+ * pointers always make a doubly linked list of it where the assumption
+ * v->Next()->Previous() == v holds (assuming v->Next() != NULL).
+ */
+ bool src_in_dst = false;
+ for (Vehicle *v = dst_head; !src_in_dst && v != NULL; v = v->Next()) src_in_dst = v == src;
+
+ /*
+ * If the source chain is in the destination chain then the user is
+ * only reordering the vehicles, thus not attaching a new vehicle.
+ * Therefor the 'allow wagon attach' callback does not need to be
+ * called. If it would be called strange things would happen because
+ * one 'attaches' an already 'attached' vehicle causing more trouble
+ * than it actually solves (infinite loops and such).
+ */
+ if (dst_head != NULL && !src_in_dst) {
+ /*
+ * When performing the 'allow wagon attach' callback, we have to check
+ * that for each and every wagon, not only the first one. This means
+ * that we have to test one wagon, attach it to the train and then test
+ * the next wagon till we have reached the end. We have to restore it
+ * to the state it was before we 'tried' attaching the train when the
+ * attaching fails or succeeds because we are not 'only' doing this
+ * in the DC_EXEC state.
+ */
+ Vehicle *dst_tail = dst_head;
+ while (dst_tail->Next() != NULL) dst_tail = dst_tail->Next();
+
+ Vehicle *orig_tail = dst_tail;
+ Vehicle *next_to_attach = src;
+ Vehicle *src_previous = src->Previous();
+
+ while (next_to_attach != NULL) {
+ uint16 callback = GetVehicleCallbackParent(CBID_TRAIN_ALLOW_WAGON_ATTACH, 0, 0, dst_head->engine_type, next_to_attach, dst_head);
+ if (callback != CALLBACK_FAILED) {
+ StringID error = STR_NULL;
+
+ if (callback == 0xFD) error = STR_INCOMPATIBLE_RAIL_TYPES;
+ if (callback < 0xFD) error = GetGRFStringID(GetEngineGRFID(dst_head->engine_type), 0xD000 + callback);
+
+ if (error != STR_NULL) {
+ /*
+ * The attaching is not allowed. In this case 'next_to_attach'
+ * can contain some vehicles of the 'source' and the destination
+ * train can have some too. We 'just' add the to-be added wagons
+ * to the chain and then split it where it was previously
+ * separated, i.e. the tail of the original destination train.
+ * Furthermore the 'previous' link of the original source vehicle needs
+ * to be restored, otherwise the train goes missing in the depot.
+ */
+ dst_tail->SetNext(next_to_attach);
+ orig_tail->SetNext(NULL);
+ if (src_previous != NULL) src_previous->SetNext(src);
+
+ return_cmd_error(error);
+ }
}
- }
+
+ /*
+ * Adding a next wagon to the chain so we can test the other wagons.
+ * First 'take' the first wagon from 'next_to_attach' and move it
+ * to the next wagon. Then add that to the tail of the destination
+ * train and update the tail with the new vehicle.
+ */
+ Vehicle *to_add = next_to_attach;
+ next_to_attach = next_to_attach->Next();
+
+ to_add->SetNext(NULL);
+ dst_tail->SetNext(to_add);
+ dst_tail = dst_tail->Next();
+ }
+
+ /*
+ * When we reach this the attaching is allowed. It also means that the
+ * chain of vehicles to attach is empty, so we do not need to merge that.
+ * This means only the splitting needs to be done.
+ * Furthermore the 'previous' link of the original source vehicle needs
+ * to be restored, otherwise the train goes missing in the depot.
+ */
+ orig_tail->SetNext(NULL);
+ if (src_previous != NULL) src_previous->SetNext(src);
}
/* do it? */