Allow for item drop rates up to 255

Source/itemdat.cpp

@@ -33,14 +33,6 @@ std::vector<PLStruct> ItemSuffixes;
 
 namespace {
 
-tl::expected<item_drop_rate, std::string> ParseItemDropRate(std::string_view value)
-{
-	if (value == "Never") return IDROP_NEVER;
-	if (value == "Regular") return IDROP_REGULAR;
-	if (value == "Double") return IDROP_DOUBLE;
-	return tl::make_unexpected("Unknown enum value");
-}
-
 tl::expected<item_class, std::string> ParseItemClass(std::string_view value)
 {
 	if (value == "None") return ICLASS_NONE;
@@ -534,7 +526,7 @@ void LoadItemDat()
 		RecordReader reader { record, filename };
 		ItemData &item = AllItemsList.emplace_back();
 		reader.advance(); // Skip the first column (item ID).
-		reader.read("dropRate", item.iRnd, ParseItemDropRate);
+		reader.readInt("dropRate", item.dropRate);
 		reader.read("class", item.iClass, ParseItemClass);
 		reader.read("equipType", item.iLoc, ParseItemEquipType);
 		reader.read("cursorGraphic", item.iCurs, ParseItemCursorGraphic);

Source/itemdat.h

@@ -80,12 +80,6 @@ enum _item_indexes : int16_t { // TODO defines all indexes in AllItemsList
 	IDI_NONE = -1,
 };
 
-enum item_drop_rate : uint8_t {
-	IDROP_NEVER,
-	IDROP_REGULAR,
-	IDROP_DOUBLE,
-};
-
 enum item_class : uint8_t {
 	ICLASS_NONE,
 	ICLASS_WEAPON,
@@ -489,7 +483,7 @@ enum item_misc_id : int8_t {
 };
 
 struct ItemData {
-	enum item_drop_rate iRnd;
+	uint8_t dropRate;
 	enum item_class iClass;
 	enum item_equip_type iLoc;
 	enum item_cursor_graphic iCurs;

Source/items.cpp

@@ -1350,30 +1350,32 @@ void GetItemBonus(const Player &player, Item &item, int minlvl, int maxlvl, bool
 	}
 }
 
+struct WeightedItemIndex {
+	_item_indexes index;
+	unsigned cumulativeWeight;
+};
+
 _item_indexes GetItemIndexForDroppableItem(bool considerDropRate, tl::function_ref<bool(const ItemData &item)> isItemOkay)
 {
-	static std::array<_item_indexes, IDI_LAST * 2> ril;
+	static std::vector<WeightedItemIndex> ril;
+	ril.clear();
 
-	size_t ri = 0;
+	unsigned cumulativeWeight = 0;
 	for (std::underlying_type_t<_item_indexes> i = IDI_GOLD; i <= IDI_LAST; i++) {
 		if (!IsItemAvailable(i))
 			continue;
 		const ItemData &item = AllItemsList[i];
-		if (item.iRnd == IDROP_NEVER)
+		if (item.dropRate == 0)
 			continue;
 		if (IsAnyOf(item.iSpell, SpellID::Resurrect, SpellID::HealOther) && !gbIsMultiplayer)
 			continue;
 		if (!isItemOkay(item))
 			continue;
-		ril[ri] = static_cast<_item_indexes>(i);
-		ri++;
-		if (item.iRnd == IDROP_DOUBLE && considerDropRate) {
-			ril[ri] = static_cast<_item_indexes>(i);
-			ri++;
-		}
+		cumulativeWeight += considerDropRate ? item.dropRate : 1;
+		ril.push_back({ static_cast<_item_indexes>(i), cumulativeWeight });
 	}
-
-	return ril[GenerateRnd(static_cast<int>(ri))];
+	unsigned targetWeight = static_cast<unsigned>(RandomIntLessThan(static_cast<int>(cumulativeWeight)));
+	return std::upper_bound(ril.begin(), ril.end(), targetWeight, [](unsigned target, const WeightedItemIndex &value) { return target < value.cumulativeWeight; })->index;
 }
 
 _item_indexes RndUItem(Monster *monster)

Source/objects.cpp

@@ -4353,7 +4353,7 @@ void ObjChangeMapResync(int x1, int y1, int x2, int y2)
 _item_indexes ItemMiscIdIdx(item_misc_id imiscid)
 {
 	std::underlying_type_t<_item_indexes> i = IDI_GOLD;
-	while (AllItemsList[i].iRnd == IDROP_NEVER || AllItemsList[i].iMiscId != imiscid) {
+	while (AllItemsList[i].dropRate == 0 || AllItemsList[i].iMiscId != imiscid) {
 		i++;
 	}