From 3dbd6475fec5ebd63b18004bb94048460c4fb4a3 Mon Sep 17 00:00:00 2001
From: PeterN <peter1138@openttd.org>
Date: Fri, 30 Apr 2021 12:03:07 +0100
Subject: Codechange: Use C++ features for train wagon overrides. (#9141)

This removes the need for C-style array management and allows use of iterators to perform wagon override lookups.
---
 src/engine.cpp        | 11 -----------
 src/engine_base.h     | 12 ++++++++----
 src/newgrf_engine.cpp | 43 +++++--------------------------------------
 src/newgrf_engine.h   |  2 --
 4 files changed, 13 insertions(+), 55 deletions(-)

diff --git a/src/engine.cpp b/src/engine.cpp
index 60b0d4222..41cd9dba8 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -66,12 +66,6 @@ static_assert(lengthof(_orig_rail_vehicle_info) + lengthof(_orig_road_vehicle_in
 
 const uint EngineOverrideManager::NUM_DEFAULT_ENGINES = _engine_counts[VEH_TRAIN] + _engine_counts[VEH_ROAD] + _engine_counts[VEH_SHIP] + _engine_counts[VEH_AIRCRAFT];
 
-Engine::Engine() :
-	overrides_count(0),
-	overrides(nullptr)
-{
-}
-
 Engine::Engine(VehicleType type, EngineID base)
 {
 	this->type = type;
@@ -136,11 +130,6 @@ Engine::Engine(VehicleType type, EngineID base)
 	}
 }
 
-Engine::~Engine()
-{
-	UnloadWagonOverrides(this);
-}
-
 /**
  * Checks whether the engine is a valid (non-articulated part of an) engine.
  * @return true if enabled
diff --git a/src/engine_base.h b/src/engine_base.h
index 2e434b589..7822111e7 100644
--- a/src/engine_base.h
+++ b/src/engine_base.h
@@ -15,6 +15,12 @@
 #include "core/pool_type.hpp"
 #include "newgrf_commons.h"
 
+struct WagonOverride {
+	std::vector<EngineID> engines;
+	CargoID cargo;
+	const SpriteGroup *group;
+};
+
 typedef Pool<Engine, EngineID, 64, 64000> EnginePool;
 extern EnginePool _engine_pool;
 
@@ -56,13 +62,11 @@ struct Engine : EnginePool::PoolItem<&_engine_pool> {
 	 * evaluating callbacks.
 	 */
 	GRFFilePropsBase<NUM_CARGO + 2> grf_prop;
-	uint16 overrides_count;
-	struct WagonOverride *overrides;
+	std::vector<WagonOverride> overrides;
 	uint16 list_position;
 
-	Engine();
+	Engine() {}
 	Engine(VehicleType type, EngineID base);
-	~Engine();
 	bool IsEnabled() const;
 
 	/**
diff --git a/src/newgrf_engine.cpp b/src/newgrf_engine.cpp
index ee14098c2..cd1214855 100644
--- a/src/newgrf_engine.cpp
+++ b/src/newgrf_engine.cpp
@@ -26,62 +26,29 @@
 
 #include "safeguards.h"
 
-struct WagonOverride {
-	EngineID *train_id;
-	uint trains;
-	CargoID cargo;
-	const SpriteGroup *group;
-};
-
 void SetWagonOverrideSprites(EngineID engine, CargoID cargo, const SpriteGroup *group, EngineID *train_id, uint trains)
 {
 	Engine *e = Engine::Get(engine);
-	WagonOverride *wo;
 
 	assert(cargo < NUM_CARGO + 2); // Include CT_DEFAULT and CT_PURCHASE pseudo cargoes.
 
-	e->overrides_count++;
-	e->overrides = ReallocT(e->overrides, e->overrides_count);
-
-	wo = &e->overrides[e->overrides_count - 1];
+	WagonOverride *wo = &e->overrides.emplace_back();
 	wo->group = group;
 	wo->cargo = cargo;
-	wo->trains = trains;
-	wo->train_id = MallocT<EngineID>(trains);
-	memcpy(wo->train_id, train_id, trains * sizeof *train_id);
+	wo->engines.assign(train_id, train_id + trains);
 }
 
 const SpriteGroup *GetWagonOverrideSpriteSet(EngineID engine, CargoID cargo, EngineID overriding_engine)
 {
 	const Engine *e = Engine::Get(engine);
 
-	for (uint i = 0; i < e->overrides_count; i++) {
-		const WagonOverride *wo = &e->overrides[i];
-
-		if (wo->cargo != cargo && wo->cargo != CT_DEFAULT) continue;
-
-		for (uint j = 0; j < wo->trains; j++) {
-			if (wo->train_id[j] == overriding_engine) return wo->group;
-		}
+	for (const WagonOverride &wo : e->overrides) {
+		if (wo.cargo != cargo && wo.cargo != CT_DEFAULT) continue;
+		if (std::find(wo.engines.begin(), wo.engines.end(), overriding_engine) != wo.engines.end()) return wo.group;
 	}
 	return nullptr;
 }
 
-/**
- * Unload all wagon override sprite groups.
- */
-void UnloadWagonOverrides(Engine *e)
-{
-	for (uint i = 0; i < e->overrides_count; i++) {
-		WagonOverride *wo = &e->overrides[i];
-		free(wo->train_id);
-	}
-	free(e->overrides);
-	e->overrides_count = 0;
-	e->overrides = nullptr;
-}
-
-
 void SetCustomEngineSprites(EngineID engine, byte cargo, const SpriteGroup *group)
 {
 	Engine *e = Engine::Get(engine);
diff --git a/src/newgrf_engine.h b/src/newgrf_engine.h
index f830ff499..90d755d3c 100644
--- a/src/newgrf_engine.h
+++ b/src/newgrf_engine.h
@@ -116,8 +116,6 @@ enum VehicleTrigger {
 };
 void TriggerVehicle(Vehicle *veh, VehicleTrigger trigger);
 
-void UnloadWagonOverrides(Engine *e);
-
 void AlterVehicleListOrder(EngineID engine, uint target);
 void CommitVehicleListOrderChanges();
 
-- 
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