From 9040d7813d25926e98163647846105d5fe3fa535 Mon Sep 17 00:00:00 2001
From: Peter Nelson <peter1138@openttd.org>
Date: Fri, 8 Sep 2023 20:34:20 +0100
Subject: [PATCH] Codechange: Use std::array and std::unique_ptr for
 PersistentStorageArrays.

This (mostly) avoids the need for manual memory management and copying.
---
 src/newgrf_storage.h         | 36 +++++++++---------------------------
 src/saveload/industry_sl.cpp |  2 +-
 src/saveload/station_sl.cpp  |  2 +-
 3 files changed, 11 insertions(+), 29 deletions(-)

diff --git a/src/newgrf_storage.h b/src/newgrf_storage.h
index 1461581fd2..7ea531443b 100644
--- a/src/newgrf_storage.h
+++ b/src/newgrf_storage.h
@@ -65,26 +65,10 @@ private:
  */
 template <typename TYPE, uint SIZE>
 struct PersistentStorageArray : BasePersistentStorageArray {
-	TYPE storage[SIZE]; ///< Memory to for the storage array
-	TYPE *prev_storage; ///< Memory to store "old" states so we can revert them on the performance of test cases for commands etc.
+	using StorageType = std::array<TYPE, SIZE>;
 
-	/** Simply construct the array */
-	PersistentStorageArray() : prev_storage(nullptr)
-	{
-		memset(this->storage, 0, sizeof(this->storage));
-	}
-
-	/** And free all data related to it */
-	~PersistentStorageArray()
-	{
-		free(this->prev_storage);
-	}
-
-	/** Resets all values to zero. */
-	void ResetToZero()
-	{
-		memset(this->storage, 0, sizeof(this->storage));
-	}
+	StorageType storage{}; ///< Memory for the storage array
+	std::unique_ptr<StorageType> prev_storage{}; ///< Temporary memory to store previous state so it can be reverted, e.g. for command tests.
 
 	/**
 	 * Stores some value at a given position.
@@ -104,10 +88,9 @@ struct PersistentStorageArray : BasePersistentStorageArray {
 
 		/* We do not have made a backup; lets do so */
 		if (AreChangesPersistent()) {
-			assert(this->prev_storage == nullptr);
-		} else if (this->prev_storage == nullptr) {
-			this->prev_storage = MallocT<TYPE>(SIZE);
-			memcpy(this->prev_storage, this->storage, sizeof(this->storage));
+			assert(!this->prev_storage);
+		} else if (!this->prev_storage) {
+			this->prev_storage = std::make_unique<StorageType>(this->storage);
 
 			/* We only need to register ourselves when we made the backup
 			 * as that is the only time something will have changed */
@@ -132,10 +115,9 @@ struct PersistentStorageArray : BasePersistentStorageArray {
 
 	void ClearChanges()
 	{
-		if (this->prev_storage != nullptr) {
-			memcpy(this->storage, this->prev_storage, sizeof(this->storage));
-			free(this->prev_storage);
-			this->prev_storage = nullptr;
+		if (this->prev_storage) {
+			this->storage = *this->prev_storage;
+			this->prev_storage.reset();
 		}
 	}
 };
diff --git a/src/saveload/industry_sl.cpp b/src/saveload/industry_sl.cpp
index 017ab89bec..1c0b79f5b3 100644
--- a/src/saveload/industry_sl.cpp
+++ b/src/saveload/industry_sl.cpp
@@ -246,7 +246,7 @@ struct INDYChunkHandler : ChunkHandler {
 				/* Store the old persistent storage. The GRFID will be added later. */
 				assert(PersistentStorage::CanAllocateItem());
 				i->psa = new PersistentStorage(0, 0, 0);
-				memcpy(i->psa->storage, _old_ind_persistent_storage.storage, sizeof(_old_ind_persistent_storage.storage));
+				std::copy(std::begin(_old_ind_persistent_storage.storage), std::end(_old_ind_persistent_storage.storage), std::begin(i->psa->storage));
 			}
 			if (IsSavegameVersionBefore(SLV_INDUSTRY_CARGO_REORGANISE)) LoadMoveAcceptsProduced(i);
 			Industry::IncIndustryTypeCount(i->type);
diff --git a/src/saveload/station_sl.cpp b/src/saveload/station_sl.cpp
index 76ef03dee4..3ae0dabc5f 100644
--- a/src/saveload/station_sl.cpp
+++ b/src/saveload/station_sl.cpp
@@ -426,7 +426,7 @@ public:
 			/* Store the old persistent storage. The GRFID will be added later. */
 			assert(PersistentStorage::CanAllocateItem());
 			st->airport.psa = new PersistentStorage(0, 0, 0);
-			memcpy(st->airport.psa->storage, _old_st_persistent_storage.storage, sizeof(_old_st_persistent_storage.storage));
+			std::copy(std::begin(_old_st_persistent_storage.storage), std::end(_old_st_persistent_storage.storage), std::begin(st->airport.psa->storage));
 		}
 
 		size_t num_cargo = this->GetNumCargo();