specialize inventory/storage indices

17 files changed, 407 insertions, 277 deletions

diff --git a/src/map/atcommand.cpp b/src/map/atcommand.cpp
index d2f154f..f405f14 100644
--- a/src/map/atcommand.cpp
+++ b/src/map/atcommand.cpp
@@ -1371,7 +1371,7 @@ ATCE atcommand_item(Session *s, dumb_ptr<map_session_data> sd,
             PickupFail flag;
             if ((flag = pc_additem(sd, &item_tmp, get_count))
                 != PickupFail::OKAY)
-                clif_additem(sd, 0, 0, flag);
+                clif_additem(sd, IOff0::from(0), 0, flag);
         }
         clif_displaymessage(s, "Item created."_s);
     }
@@ -1388,9 +1388,7 @@ static
 ATCE atcommand_itemreset(Session *s, dumb_ptr<map_session_data> sd,
         ZString)
 {
-    int i;
-
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (sd->status.inventory[i].amount
             && sd->status.inventory[i].equip == EPOS::ZERO)
@@ -3118,7 +3116,6 @@ ATCE atcommand_char_wipe(Session *s, dumb_ptr<map_session_data> sd,
         if (pc_isGM(sd).overwhelms(pc_isGM(pl_sd)))
         {
             // you can reset a character only for lower or same GM level
-            int i;
 
             // Reset base level
             pl_sd->status.base_level = 1;
@@ -3139,7 +3136,7 @@ ATCE atcommand_char_wipe(Session *s, dumb_ptr<map_session_data> sd,
             clif_updatestatus(pl_sd, SP::ZENY);
 
             // Clear inventory
-            for (i = 0; i < MAX_INVENTORY; i++)
+            for (IOff0 i : IOff0::iter())
             {
                 if (sd->status.inventory[i].amount)
                 {
@@ -3678,7 +3675,7 @@ ATCE atcommand_chardelitem(Session *s, dumb_ptr<map_session_data> sd,
     XString item_name;
     int i, number = 0;
     ItemNameId item_id;
-    int item_position, count;
+    int count;
     struct item_data *item_data;
 
     if (!asplit(message, &item_name, &number, &character) || number < 1)
@@ -3697,11 +3694,11 @@ ATCE atcommand_chardelitem(Session *s, dumb_ptr<map_session_data> sd,
             if (pc_isGM(sd).overwhelms(pc_isGM(pl_sd)))
             {
                 // you can kill only lower or same level
-                item_position = pc_search_inventory(pl_sd, item_id);
-                if (item_position >= 0)
+                IOff0 item_position = pc_search_inventory(pl_sd, item_id);
+                if (item_position.ok())
                 {
                     count = 0;
-                    for (i = 0; i < number && item_position >= 0; i++)
+                    for (i = 0; i < number && item_position.ok(); i++)
                     {
                         pc_delitem(pl_sd, item_position, 1, 0);
                         count++;
@@ -3849,7 +3846,7 @@ ATCE atcommand_character_item_list(Session *s, dumb_ptr<map_session_data> sd,
         ZString message)
 {
     struct item_data *item_data = NULL;
-    int i, count, counter;
+    int count, counter;
     CharName character;
 
     if (!asplit(message, &character))
@@ -3863,7 +3860,7 @@ ATCE atcommand_character_item_list(Session *s, dumb_ptr<map_session_data> sd,
             // you can look items only lower or same level
             counter = 0;
             count = 0;
-            for (i = 0; i < MAX_INVENTORY; i++)
+            for (IOff0 i : IOff0::iter())
             {
                 if (pl_sd->status.inventory[i].nameid
                     && (item_data =
@@ -3961,7 +3958,7 @@ ATCE atcommand_character_storage_list(Session *s, dumb_ptr<map_session_data> sd,
 {
     Storage *stor;
     struct item_data *item_data = NULL;
-    int i, count, counter;
+    int count, counter;
     CharName character;
 
     if (!asplit(message, &character))
@@ -3977,7 +3974,7 @@ ATCE atcommand_character_storage_list(Session *s, dumb_ptr<map_session_data> sd,
             {
                 counter = 0;
                 count = 0;
-                for (i = 0; i < MAX_STORAGE; i++)
+                for (SOff0 i : SOff0::iter())
                 {
                     if (stor->storage_[i].nameid
                         && (item_data =
@@ -4188,8 +4185,7 @@ static
 ATCE atcommand_dropall(Session *, dumb_ptr<map_session_data> sd,
         ZString)
 {
-    int i;
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (sd->status.inventory[i].amount)
         {
@@ -4212,7 +4208,7 @@ ATCE atcommand_chardropall(Session *s, dumb_ptr<map_session_data>,
     dumb_ptr<map_session_data> pl_sd = map_nick2sd(character);
     if (pl_sd == NULL)
         return ATCE::EXIST;
-    for (int i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (pl_sd->status.inventory[i].amount)
         {
@@ -4232,8 +4228,6 @@ static
 ATCE atcommand_storeall(Session *s, dumb_ptr<map_session_data> sd,
         ZString)
 {
-    int i;
-
     if (!sd->state.storage_open)
     {
         //Open storage.
@@ -4250,7 +4244,7 @@ ATCE atcommand_storeall(Session *s, dumb_ptr<map_session_data> sd,
                 return ATCE::EXIST;
         }
     }
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (sd->status.inventory[i].amount)
         {
@@ -4286,7 +4280,7 @@ ATCE atcommand_charstoreall(Session *s, dumb_ptr<map_session_data> sd,
         clif_displaymessage(s, "run this command again.."_s);
         return ATCE::OKAY;
     }
-    for (int i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (pl_sd->status.inventory[i].amount)
         {
diff --git a/src/map/battle.cpp b/src/map/battle.cpp
index 99252e3..a653cac 100644
--- a/src/map/battle.cpp
+++ b/src/map/battle.cpp
@@ -1327,9 +1327,9 @@ int battle_is_unarmed(dumb_ptr<block_list> bl)
     {
         dumb_ptr<map_session_data> sd = bl->is_player();
 
-        int sidx = sd->equip_index_maybe[EQUIP::SHIELD];
-        int widx = sd->equip_index_maybe[EQUIP::WEAPON];
-        return sidx == -1 && widx == -1;
+        IOff0 sidx = sd->equip_index_maybe[EQUIP::SHIELD];
+        IOff0 widx = sd->equip_index_maybe[EQUIP::WEAPON];
+        return !sidx.ok() && !widx.ok();
     }
     else
         return 0;
@@ -1449,12 +1449,12 @@ struct Damage battle_calc_pc_weapon_attack(dumb_ptr<block_list> src,
     atkmin = atkmin_ = dex;     //最低ATKはDEXで初期化？
     sd->state.arrow_atk = 0;    //arrow_atk初期化
 
-    int widx = sd->equip_index_maybe[EQUIP::WEAPON];
-    int sidx = sd->equip_index_maybe[EQUIP::SHIELD];
+    IOff0 widx = sd->equip_index_maybe[EQUIP::WEAPON];
+    IOff0 sidx = sd->equip_index_maybe[EQUIP::SHIELD];
 
-    if (widx >= 0 && sd->inventory_data[widx])
+    if (widx.ok() && sd->inventory_data[widx])
         atkmin = atkmin * (80 + sd->inventory_data[widx]->wlv * 20) / 100;
-    if (sidx >= 0 && sd->inventory_data[sidx])
+    if (sidx.ok() && sd->inventory_data[sidx])
         atkmin_ = atkmin_ * (80 + sd->inventory_data[sidx]->wlv * 20) / 100;
     if (sd->status.weapon == ItemLook::BOW)
     {                           //武器が弓矢の場合
@@ -2010,8 +2010,8 @@ ATK battle_weapon_attack(dumb_ptr<block_list> src, dumb_ptr<block_list> target,
         // 攻撃対象となりうるので攻撃
         if (sd && sd->status.weapon == ItemLook::BOW)
         {
-            int aidx = sd->equip_index_maybe[EQUIP::ARROW];
-            if (aidx >= 0)
+            IOff0 aidx = sd->equip_index_maybe[EQUIP::ARROW];
+            if (aidx.ok())
             {
                 if (battle_config.arrow_decrement)
                     pc_delitem(sd, aidx, 1, 0);
@@ -2058,9 +2058,9 @@ ATK battle_weapon_attack(dumb_ptr<block_list> src, dumb_ptr<block_list> target,
 
         if (src->bl_type == BL::PC)
         {
-            int weapon_index = sd->equip_index_maybe[EQUIP::WEAPON];
+            IOff0 weapon_index = sd->equip_index_maybe[EQUIP::WEAPON];
             ItemNameId weapon;
-            if (weapon_index >= 0 && sd->inventory_data[weapon_index]
+            if (weapon_index.ok() && sd->inventory_data[weapon_index]
                     && bool(sd->status.inventory[weapon_index].equip & EPOS::WEAPON))
                 weapon = sd->inventory_data[weapon_index]->nameid;
 
diff --git a/src/map/chrif.cpp b/src/map/chrif.cpp
index 3a329f8..ff0adbd 100644
--- a/src/map/chrif.cpp
+++ b/src/map/chrif.cpp
@@ -625,7 +625,6 @@ void chrif_changedgm(Session *, const Packet_Fixed<0x2b0b>& fixed)
 static
 void chrif_changedsex(Session *, const Packet_Fixed<0x2b0d>& fixed)
 {
-    int i;
     dumb_ptr<map_session_data> sd;
 
     AccountId acc = fixed.account_id;
@@ -642,7 +641,7 @@ void chrif_changedsex(Session *, const Packet_Fixed<0x2b0d>& fixed)
             else if (sd->status.sex == SEX::FEMALE)
                 sd->sex = sd->status.sex = SEX::MALE;
             // to avoid any problem with equipment and invalid sex, equipment is unequiped.
-            for (i = 0; i < MAX_INVENTORY; i++)
+            for (IOff0 i : IOff0::iter())
             {
                 if (sd->status.inventory[i].nameid
                     && bool(sd->status.inventory[i].equip))
@@ -942,9 +941,8 @@ void ladmin_itemfrob_c2(dumb_ptr<block_list> bl, ItemNameId source_id, ItemNameI
         {
             dumb_ptr<map_session_data> pc = bl->is_player();
             Storage *stor = account2storage2(pc->status_key.account_id);
-            int j;
 
-            for (j = 0; j < MAX_INVENTORY; j++)
+            for (IOff0 j : IOff0::iter())
                 IFIX(pc->status.inventory[j].nameid);
             // cart is no longer supported
             // IFIX(pc->status.weapon);
@@ -954,10 +952,12 @@ void ladmin_itemfrob_c2(dumb_ptr<block_list> bl, ItemNameId source_id, ItemNameI
             IFIX(pc->status.head_bottom);
 
             if (stor)
-                for (j = 0; j < stor->storage_amount; j++)
+            {
+                for (SOff0 j : SOff0::iter())
                     FIX(stor->storage_[j]);
+            }
 
-            for (j = 0; j < MAX_INVENTORY; j++)
+            for (IOff0 j : IOff0::iter())
             {
                 struct item_data *item = pc->inventory_data[j];
                 if (item && item->nameid == source_id)
diff --git a/src/map/clif.cpp b/src/map/clif.cpp
index 2275023..2ae9825 100644
--- a/src/map/clif.cpp
+++ b/src/map/clif.cpp
@@ -673,20 +673,20 @@ void clif_set0078_main_1d8(dumb_ptr<map_session_data> sd, Buffer& buf)
     fixed_1d8.species = sd->status.species;
     fixed_1d8.hair_style = sd->status.hair;
 
-    int widx = sd->equip_index_maybe[EQUIP::WEAPON];
-    int sidx = sd->equip_index_maybe[EQUIP::SHIELD];
+    IOff0 widx = sd->equip_index_maybe[EQUIP::WEAPON];
+    IOff0 sidx = sd->equip_index_maybe[EQUIP::SHIELD];
     if (sd->attack_spell_override)
         fixed_1d8.weapon = sd->attack_spell_look_override;
     else
     {
-        if (widx >= 0 && sd->inventory_data[widx])
+        if (widx.ok() && sd->inventory_data[widx])
         {
             fixed_1d8.weapon = sd->status.inventory[widx].nameid;
         }
         else
             fixed_1d8.weapon = ItemNameId();
     }
-    if (sidx >= 0 && sidx != widx && sd->inventory_data[sidx])
+    if (sidx.ok() && sidx != widx && sd->inventory_data[sidx])
     {
         fixed_1d8.shield = sd->status.inventory[sidx].nameid;
     }
@@ -727,20 +727,20 @@ void clif_set0078_alt_1d9(dumb_ptr<map_session_data> sd, Buffer& buf)
     fixed_1d8.species = sd->status.species;
     fixed_1d8.hair_style = sd->status.hair;
 
-    int widx = sd->equip_index_maybe[EQUIP::WEAPON];
-    int sidx = sd->equip_index_maybe[EQUIP::SHIELD];
+    IOff0 widx = sd->equip_index_maybe[EQUIP::WEAPON];
+    IOff0 sidx = sd->equip_index_maybe[EQUIP::SHIELD];
     if (sd->attack_spell_override)
         fixed_1d8.weapon = sd->attack_spell_look_override;
     else
     {
-        if (widx >= 0 && sd->inventory_data[widx])
+        if (widx.ok() && sd->inventory_data[widx])
         {
             fixed_1d8.weapon = sd->status.inventory[widx].nameid;
         }
         else
             fixed_1d8.weapon = ItemNameId();
     }
-    if (sidx >= 0 && sidx != widx && sd->inventory_data[sidx])
+    if (sidx.ok() && sidx != widx && sd->inventory_data[sidx])
     {
         fixed_1d8.shield = sd->status.inventory[sidx].nameid;
     }
@@ -784,15 +784,15 @@ void clif_set007b(dumb_ptr<map_session_data> sd, Buffer& buf)
     fixed_1da.option = sd->status.option;
     fixed_1da.species = sd->status.species;
     fixed_1da.hair_style = sd->status.hair;
-    int widx = sd->equip_index_maybe[EQUIP::WEAPON];
-    int sidx = sd->equip_index_maybe[EQUIP::SHIELD];
-    if (widx >= 0 && sd->inventory_data[widx])
+    IOff0 widx = sd->equip_index_maybe[EQUIP::WEAPON];
+    IOff0 sidx = sd->equip_index_maybe[EQUIP::SHIELD];
+    if (widx.ok() && sd->inventory_data[widx])
     {
         fixed_1da.weapon = sd->status.inventory[widx].nameid;
     }
     else
         fixed_1da.weapon = ItemNameId();
-    if (sidx >= 0 && sidx != widx && sd->inventory_data[sidx])
+    if (sidx.ok() && sidx != widx && sd->inventory_data[sidx])
     {
         fixed_1da.shield = sd->status.inventory[sidx].nameid;
     }
@@ -1245,21 +1245,19 @@ int clif_buylist(dumb_ptr<map_session_data> sd, dumb_ptr<npc_data_shop> nd)
  */
 int clif_selllist(dumb_ptr<map_session_data> sd)
 {
-    int i, val;
-
     nullpo_ret(sd);
 
     Session *s = sd->sess;
     std::vector<Packet_Repeat<0x00c7>> repeat_c7;
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (sd->status.inventory[i].nameid && sd->inventory_data[i])
         {
-            val = sd->inventory_data[i]->value_sell;
+            int val = sd->inventory_data[i]->value_sell;
             if (val < 0)
                 continue;
             Packet_Repeat<0x00c7> info;
-            info.ioff2 = i + 2;
+            info.ioff2 = i.shift();
             info.base_price = val;
             info.actual_price = val;
             repeat_c7.push_back(info);
@@ -1359,7 +1357,7 @@ void clif_scriptinputstr(dumb_ptr<map_session_data> sd, BlockId npcid)
  *
  *------------------------------------------
  */
-int clif_additem(dumb_ptr<map_session_data> sd, int n, int amount, PickupFail fail)
+int clif_additem(dumb_ptr<map_session_data> sd, IOff0 n, int amount, PickupFail fail)
 {
     nullpo_ret(sd);
 
@@ -1367,18 +1365,18 @@ int clif_additem(dumb_ptr<map_session_data> sd, int n, int amount, PickupFail fa
     Packet_Fixed<0x00a0> fixed_a0;
     if (fail != PickupFail::OKAY)
     {
-        fixed_a0.ioff2 = n + 2;
+        fixed_a0.ioff2 = n.shift();
         fixed_a0.amount = amount;
         fixed_a0.name_id = ItemNameId();
         fixed_a0.pickup_fail = fail;
     }
     else
     {
-        if (n < 0 || n >= MAX_INVENTORY || !sd->status.inventory[n].nameid
+        if (!n.ok() || !sd->status.inventory[n].nameid
             || sd->inventory_data[n] == NULL)
             return 1;
 
-        fixed_a0.ioff2 = n + 2;
+        fixed_a0.ioff2 = n.shift();
         fixed_a0.amount = amount;
         fixed_a0.name_id = sd->status.inventory[n].nameid;
         fixed_a0.identify = 1;
@@ -1405,13 +1403,13 @@ int clif_additem(dumb_ptr<map_session_data> sd, int n, int amount, PickupFail fa
  *
  *------------------------------------------
  */
-void clif_delitem(dumb_ptr<map_session_data> sd, int n, int amount)
+void clif_delitem(dumb_ptr<map_session_data> sd, IOff0 n, int amount)
 {
     nullpo_retv(sd);
 
     Session *s = sd->sess;
     Packet_Fixed<0x00af> fixed_af;
-    fixed_af.ioff2 = n + 2;
+    fixed_af.ioff2 = n.shift();
     fixed_af.amount = amount;
 
     send_fpacket<0x00af, 6>(s, fixed_af);
@@ -1425,17 +1423,17 @@ void clif_itemlist(dumb_ptr<map_session_data> sd)
 {
     nullpo_retv(sd);
 
-    int arrow = -1;
+    IOff0 arrow = IOff0::from(-1);
     Session *s = sd->sess;
     std::vector<Packet_Repeat<0x01ee>> repeat_1ee;
-    for (int i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (!sd->status.inventory[i].nameid
             || sd->inventory_data[i] == NULL
             || itemdb_isequip2(sd->inventory_data[i]))
             continue;
         Packet_Repeat<0x01ee> info;
-        info.ioff2 = i + 2;
+        info.ioff2 = i.shift();
         info.name_id = sd->status.inventory[i].nameid;
         info.item_type = sd->inventory_data[i]->type;
         info.identify = 1;
@@ -1444,7 +1442,7 @@ void clif_itemlist(dumb_ptr<map_session_data> sd)
         {
             info.epos = EPOS::ARROW;
             if (bool(sd->status.inventory[i].equip))
-                arrow = i;      // ついでに矢装備チェック
+                arrow = i;
         }
         else
             info.epos = EPOS::ZERO;
@@ -1458,7 +1456,7 @@ void clif_itemlist(dumb_ptr<map_session_data> sd)
     {
         send_packet_repeatonly<0x01ee, 4, 18>(s, repeat_1ee);
     }
-    if (arrow >= 0)
+    if (arrow.ok())
         clif_arrowequip(sd, arrow);
 }
 
@@ -1472,14 +1470,14 @@ void clif_equiplist(dumb_ptr<map_session_data> sd)
 
     Session *s = sd->sess;
     std::vector<Packet_Repeat<0x00a4>> repeat_a4;
-    for (int i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (!sd->status.inventory[i].nameid
             || sd->inventory_data[i] == NULL
             || !itemdb_isequip2(sd->inventory_data[i]))
             continue;
         Packet_Repeat<0x00a4> info;
-        info.ioff2 = i + 2;
+        info.ioff2 = i.shift();
         info.name_id = sd->status.inventory[i].nameid;
         info.item_type = (
                 sd->inventory_data[i]->type == ItemType::_7
@@ -1515,7 +1513,7 @@ int clif_storageitemlist(dumb_ptr<map_session_data> sd, Storage *stor)
 
     Session *s = sd->sess;
     std::vector<Packet_Repeat<0x01f0>> repeat_1f0;
-    for (int i = 0; i < MAX_STORAGE; i++)
+    for (SOff0 i : SOff0::iter())
     {
         if (!stor->storage_[i].nameid)
             continue;
@@ -1527,7 +1525,7 @@ int clif_storageitemlist(dumb_ptr<map_session_data> sd, Storage *stor)
             continue;
 
         Packet_Repeat<0x01f0> info;
-        info.soff1 = i + 1;
+        info.soff1 = i.shift();
         info.name_id = stor->storage_[i].nameid;
         info.item_type = id->type;
         info.identify = 0;
@@ -1557,7 +1555,7 @@ int clif_storageequiplist(dumb_ptr<map_session_data> sd, Storage *stor)
 
     Session *s = sd->sess;
     std::vector<Packet_Repeat<0x00a6>> repeat_a6;
-    for (int i = 0; i < MAX_STORAGE; i++)
+    for (SOff0 i : SOff0::iter())
     {
         if (!stor->storage_[i].nameid)
             continue;
@@ -1568,7 +1566,7 @@ int clif_storageequiplist(dumb_ptr<map_session_data> sd, Storage *stor)
         if (!itemdb_isequip2(id))
             continue;
         Packet_Repeat<0x00a6> info;
-        info.soff1 = i + 1;
+        info.soff1 = i.shift();
         info.name_id = stor->storage_[i].nameid;
         info.item_type = id->type;
         info.identify = 0;
@@ -1837,8 +1835,8 @@ int clif_changelook_towards(dumb_ptr<block_list> bl, LOOK type, int val,
             EQUIP equip_point = equip_points[type];
 
             fixed_1d7.look_type = type;
-            int idx = sd->equip_index_maybe[equip_point];
-            if (idx >= 0 && sd->inventory_data[idx])
+            IOff0 idx = sd->equip_index_maybe[equip_point];
+            if (idx.ok() && sd->inventory_data[idx])
             {
                 fixed_1d7.weapon_or_name_id_or_value = unwrap<ItemNameId>(sd->status.inventory[idx].nameid);
             }
@@ -1849,20 +1847,20 @@ int clif_changelook_towards(dumb_ptr<block_list> bl, LOOK type, int val,
         else
         {
             fixed_1d7.look_type = LOOK::WEAPON;
-            int widx = sd->equip_index_maybe[EQUIP::WEAPON];
-            int sidx = sd->equip_index_maybe[EQUIP::SHIELD];
+            IOff0 widx = sd->equip_index_maybe[EQUIP::WEAPON];
+            IOff0 sidx = sd->equip_index_maybe[EQUIP::SHIELD];
             if (sd->attack_spell_override)
                 fixed_1d7.weapon_or_name_id_or_value = unwrap<ItemNameId>(sd->attack_spell_look_override);
             else
             {
-                if (widx >= 0 && sd->inventory_data[widx])
+                if (widx.ok() && sd->inventory_data[widx])
                 {
                     fixed_1d7.weapon_or_name_id_or_value = unwrap<ItemNameId>(sd->status.inventory[widx].nameid);
                 }
                 else
                     fixed_1d7.weapon_or_name_id_or_value = unwrap<ItemNameId>(ItemNameId());
             }
-            if (sidx >= 0 && sidx != widx && sd->inventory_data[sidx])
+            if (sidx.ok() && sidx != widx && sd->inventory_data[sidx])
             {
                 fixed_1d7.shield = sd->status.inventory[sidx].nameid;
             }
@@ -1954,7 +1952,7 @@ int clif_initialstatus(dumb_ptr<map_session_data> sd)
  *矢装備
  *------------------------------------------
  */
-int clif_arrowequip(dumb_ptr<map_session_data> sd, int val)
+int clif_arrowequip(dumb_ptr<map_session_data> sd, IOff0 val)
 {
     nullpo_ret(sd);
 
@@ -1962,7 +1960,7 @@ int clif_arrowequip(dumb_ptr<map_session_data> sd, int val)
 
     Session *s = sd->sess;
     Packet_Fixed<0x013c> fixed_13c;
-    fixed_13c.ioff2 = val + 2;
+    fixed_13c.ioff2 = val.shift();
     send_fpacket<0x013c, 4>(s, fixed_13c);
 
     return 0;
@@ -2007,13 +2005,13 @@ int clif_statusupack(dumb_ptr<map_session_data> sd, SP type, int ok, int val)
  *
  *------------------------------------------
  */
-int clif_equipitemack(dumb_ptr<map_session_data> sd, int n, EPOS pos, int ok)
+int clif_equipitemack(dumb_ptr<map_session_data> sd, IOff0 n, EPOS pos, int ok)
 {
     nullpo_ret(sd);
 
     Session *s = sd->sess;
     Packet_Fixed<0x00aa> fixed_aa;
-    fixed_aa.ioff2 = n + 2;
+    fixed_aa.ioff2 = n.shift();
     fixed_aa.epos = pos;
     fixed_aa.ok = ok;
     send_fpacket<0x00aa, 7>(s, fixed_aa);
@@ -2025,13 +2023,13 @@ int clif_equipitemack(dumb_ptr<map_session_data> sd, int n, EPOS pos, int ok)
  *
  *------------------------------------------
  */
-int clif_unequipitemack(dumb_ptr<map_session_data> sd, int n, EPOS pos, int ok)
+int clif_unequipitemack(dumb_ptr<map_session_data> sd, IOff0 n, EPOS pos, int ok)
 {
     nullpo_ret(sd);
 
     Session *s = sd->sess;
     Packet_Fixed<0x00ac> fixed_ac;
-    fixed_ac.ioff2 = n + 2;
+    fixed_ac.ioff2 = n.shift();
     fixed_ac.epos = pos;
     fixed_ac.ok = ok;
     send_fpacket<0x00ac, 7>(s, fixed_ac);
@@ -2087,7 +2085,7 @@ int clif_changeoption(dumb_ptr<block_list> bl)
  *
  *------------------------------------------
  */
-int clif_useitemack(dumb_ptr<map_session_data> sd, int index, int amount,
+int clif_useitemack(dumb_ptr<map_session_data> sd, IOff0 index, int amount,
                      int ok)
 {
     nullpo_ret(sd);
@@ -2096,7 +2094,7 @@ int clif_useitemack(dumb_ptr<map_session_data> sd, int index, int amount,
     {
         Session *s = sd->sess;
         Packet_Fixed<0x00a8> fixed_a8;
-        fixed_a8.ioff2 = index + 2;
+        fixed_a8.ioff2 = index.shift();
         fixed_a8.amount = amount;
         fixed_a8.ok = ok;
         send_fpacket<0x00a8, 7>(s, fixed_a8);
@@ -2104,7 +2102,7 @@ int clif_useitemack(dumb_ptr<map_session_data> sd, int index, int amount,
     else
     {
         Packet_Fixed<0x01c8> fixed_1c8;
-        fixed_1c8.ioff2 = index + 2;
+        fixed_1c8.ioff2 = index.shift();
         fixed_1c8.name_id = sd->status.inventory[index].nameid;
         fixed_1c8.block_id = sd->bl_id;
         fixed_1c8.amount = amount;
@@ -2149,7 +2147,7 @@ void clif_tradestart(dumb_ptr<map_session_data> sd, int type)
  *------------------------------------------
  */
 void clif_tradeadditem(dumb_ptr<map_session_data> sd,
-        dumb_ptr<map_session_data> tsd, int index2, int amount)
+        dumb_ptr<map_session_data> tsd, IOff2 index2, int amount)
 {
     nullpo_retv(sd);
     nullpo_retv(tsd);
@@ -2157,7 +2155,7 @@ void clif_tradeadditem(dumb_ptr<map_session_data> sd,
     Session *s = tsd->sess;
     Packet_Fixed<0x00e9> fixed_e9;
     fixed_e9.amount = amount;
-    if (index2 == 0)
+    if (!index2.ok())
     {
         fixed_e9.name_id = ItemNameId();
         fixed_e9.identify = 0;
@@ -2170,7 +2168,7 @@ void clif_tradeadditem(dumb_ptr<map_session_data> sd,
     }
     else
     {
-        int index0 = index2 - 2;
+        IOff0 index0 = index2.unshift();
         fixed_e9.name_id = sd->status.inventory[index0].nameid;
         fixed_e9.identify = 0;
         fixed_e9.broken_or_attribute = 0;
@@ -2189,7 +2187,7 @@ void clif_tradeadditem(dumb_ptr<map_session_data> sd,
  * アイテム追加成功/失敗
  *------------------------------------------
  */
-int clif_tradeitemok(dumb_ptr<map_session_data> sd, int index2, int amount,
+int clif_tradeitemok(dumb_ptr<map_session_data> sd, IOff2 index2, int amount,
                       int fail)
 {
     nullpo_ret(sd);
@@ -2275,14 +2273,14 @@ int clif_updatestorageamount(dumb_ptr<map_session_data> sd,
  *------------------------------------------
  */
 int clif_storageitemadded(dumb_ptr<map_session_data> sd, Storage *stor,
-                           int index, int amount)
+        SOff0 index, int amount)
 {
     nullpo_ret(sd);
     nullpo_ret(stor);
 
     Session *s = sd->sess;
     Packet_Fixed<0x00f4> fixed_f4;
-    fixed_f4.soff1 = index + 1;
+    fixed_f4.soff1 = index.shift();
     fixed_f4.amount = amount;
     fixed_f4.name_id = stor->storage_[index].nameid;
     fixed_f4.identify = 0;
@@ -2303,14 +2301,14 @@ int clif_storageitemadded(dumb_ptr<map_session_data> sd, Storage *stor,
  * カプラ倉庫からアイテムを取り去る
  *------------------------------------------
  */
-int clif_storageitemremoved(dumb_ptr<map_session_data> sd, int index,
+int clif_storageitemremoved(dumb_ptr<map_session_data> sd, SOff0 index,
                              int amount)
 {
     nullpo_ret(sd);
 
     Session *s = sd->sess;
     Packet_Fixed<0x00f6> fixed_f6;
-    fixed_f6.soff1 = index + 1;
+    fixed_f6.soff1 = index.shift();
     fixed_f6.amount = amount;
     send_fpacket<0x00f6, 8>(s, fixed_f6);
 
@@ -4110,8 +4108,6 @@ RecvResult clif_parse_DropItem(Session *s, dumb_ptr<map_session_data> sd)
     if (rv != RecvResult::Complete)
         return rv;
 
-    int item_index, item_amount;
-
     if (pc_isdead(sd))
     {
         clif_clearchar(sd, BeingRemoveWhy::DEAD);
@@ -4129,8 +4125,10 @@ RecvResult clif_parse_DropItem(Session *s, dumb_ptr<map_session_data> sd)
         return rv;
     }
 
-    item_index = fixed.ioff2 - 2;
-    item_amount = fixed.amount;
+    if (!fixed.ioff2.ok())
+        return RecvResult::Error;
+    IOff0 item_index = fixed.ioff2.unshift();
+    int item_amount = fixed.amount;
 
     pc_dropitem(sd, item_index, item_amount);
 
@@ -4161,7 +4159,9 @@ RecvResult clif_parse_UseItem(Session *s, dumb_ptr<map_session_data> sd)
     if (sd->invincible_timer)
         pc_delinvincibletimer(sd);
 
-    pc_useitem(sd, fixed.ioff2 - 2);
+    if (!fixed.ioff2.ok())
+        return RecvResult::Error;
+    pc_useitem(sd, fixed.ioff2.unshift());
 
     return rv;
 }
@@ -4178,14 +4178,14 @@ RecvResult clif_parse_EquipItem(Session *s, dumb_ptr<map_session_data> sd)
     if (rv != RecvResult::Complete)
         return rv;
 
-    int index;
-
     if (pc_isdead(sd))
     {
         clif_clearchar(sd, BeingRemoveWhy::DEAD);
         return rv;
     }
-    index = fixed.ioff2 - 2;
+    if (!fixed.ioff2.ok())
+        return RecvResult::Error;
+    IOff0 index = fixed.ioff2.unshift();
     if (sd->npc_id)
         return rv;
 
@@ -4214,14 +4214,14 @@ RecvResult clif_parse_UnequipItem(Session *s, dumb_ptr<map_session_data> sd)
     if (rv != RecvResult::Complete)
         return rv;
 
-    int index;
-
     if (pc_isdead(sd))
     {
         clif_clearchar(sd, BeingRemoveWhy::DEAD);
         return rv;
     }
-    index = fixed.ioff2 - 2;
+    if (!fixed.ioff2.ok())
+        return RecvResult::Error;
+    IOff0 index = fixed.ioff2.unshift();
 
     if (sd->npc_id
         || sd->opt1 != Opt1::ZERO)
@@ -4366,6 +4366,8 @@ RecvResult clif_parse_TradeAddItem(Session *s, dumb_ptr<map_session_data> sd)
     if (rv != RecvResult::Complete)
         return rv;
 
+    if (fixed.zeny_or_ioff2.index != 0 && !fixed.zeny_or_ioff2.ok())
+        return RecvResult::Error;
     trade_tradeadditem(sd, fixed.zeny_or_ioff2, fixed.amount);
 
     return rv;
@@ -4577,10 +4579,10 @@ RecvResult clif_parse_MoveToKafra(Session *s, dumb_ptr<map_session_data> sd)
     if (rv != RecvResult::Complete)
         return rv;
 
-    int item_index, item_amount;
-
-    item_index = fixed.ioff2 - 2;
-    item_amount = fixed.amount;
+    if (!fixed.ioff2.ok())
+        return RecvResult::Error;
+    IOff0 item_index = fixed.ioff2.unshift();
+    int item_amount = fixed.amount;
 
     if ((sd->npc_id && !sd->npc_flags.storage) || sd->trade_partner
         || !sd->state.storage_open)
@@ -4604,10 +4606,10 @@ RecvResult clif_parse_MoveFromKafra(Session *s, dumb_ptr<map_session_data> sd)
     if (rv != RecvResult::Complete)
         return rv;
 
-    int item_index, item_amount;
-
-    item_index = fixed.soff1 - 1;
-    item_amount = fixed.amount;
+    if (!fixed.soff1.ok())
+        return RecvResult::Error;
+    SOff0 item_index = fixed.soff1.unshift();
+    int item_amount = fixed.amount;
 
     if ((sd->npc_id && !sd->npc_flags.storage) || sd->trade_partner
         || !sd->state.storage_open)
diff --git a/src/map/clif.hpp b/src/map/clif.hpp
index 3bed955..0087d78 100644
--- a/src/map/clif.hpp
+++ b/src/map/clif.hpp
@@ -80,8 +80,8 @@ void clif_scriptmenu(dumb_ptr<map_session_data>, BlockId, XString);  //self
 void clif_scriptinput(dumb_ptr<map_session_data>, BlockId); //self
 void clif_scriptinputstr(dumb_ptr<map_session_data> sd, BlockId npcid);  // self
 
-int clif_additem(dumb_ptr<map_session_data>, int, int, PickupFail);   //self
-void clif_delitem(dumb_ptr<map_session_data>, int, int);    //self
+int clif_additem(dumb_ptr<map_session_data>, IOff0, int, PickupFail);   //self
+void clif_delitem(dumb_ptr<map_session_data>, IOff0, int);    //self
 int clif_updatestatus(dumb_ptr<map_session_data>, SP);    //self
 int clif_damage(dumb_ptr<block_list>, dumb_ptr<block_list>,
         tick_t, interval_t, interval_t,
@@ -93,14 +93,14 @@ int clif_takeitem(dumb_ptr<block_list> src, dumb_ptr<block_list> dst)
 }
 int clif_changelook(dumb_ptr<block_list>, LOOK, int);   // area
 void clif_changelook_accessories(dumb_ptr<block_list> bl, dumb_ptr<map_session_data> dst); // area or target; list gloves, boots etc.
-int clif_arrowequip(dumb_ptr<map_session_data> sd, int val);    //self
+int clif_arrowequip(dumb_ptr<map_session_data> sd, IOff0 val);    //self
 int clif_arrow_fail(dumb_ptr<map_session_data> sd, int type);   //self
 int clif_statusupack(dumb_ptr<map_session_data>, SP, int, int);   // self
-int clif_equipitemack(dumb_ptr<map_session_data>, int, EPOS, int);  // self
-int clif_unequipitemack(dumb_ptr<map_session_data>, int, EPOS, int);    // self
+int clif_equipitemack(dumb_ptr<map_session_data>, IOff0, EPOS, int);  // self
+int clif_unequipitemack(dumb_ptr<map_session_data>, IOff0, EPOS, int);    // self
 int clif_misceffect(dumb_ptr<block_list>, int);    // area
 int clif_changeoption(dumb_ptr<block_list>);   // area
-int clif_useitemack(dumb_ptr<map_session_data>, int, int, int);    // self
+int clif_useitemack(dumb_ptr<map_session_data>, IOff0, int, int);    // self
 
 void clif_emotion(dumb_ptr<block_list> bl, int type);
 void clif_sitting(Session *, dumb_ptr<map_session_data> sd);
@@ -109,8 +109,8 @@ void clif_sitting(Session *, dumb_ptr<map_session_data> sd);
 void clif_traderequest(dumb_ptr<map_session_data> sd, CharName name);
 void clif_tradestart(dumb_ptr<map_session_data> sd, int type);
 void clif_tradeadditem(dumb_ptr<map_session_data> sd,
-        dumb_ptr<map_session_data> tsd, int index, int amount);
-int clif_tradeitemok(dumb_ptr<map_session_data> sd, int index, int amount,
+        dumb_ptr<map_session_data> tsd, IOff2 index2, int amount);
+int clif_tradeitemok(dumb_ptr<map_session_data> sd, IOff2 index, int amount,
         int fail);
 int clif_tradedeal_lock(dumb_ptr<map_session_data> sd, int fail);
 int clif_tradecancelled(dumb_ptr<map_session_data> sd);
@@ -123,8 +123,8 @@ int clif_storageequiplist(dumb_ptr<map_session_data> sd,
 int clif_updatestorageamount(dumb_ptr<map_session_data> sd,
         Storage *stor);
 int clif_storageitemadded(dumb_ptr<map_session_data> sd, Storage *stor,
-        int index, int amount);
-int clif_storageitemremoved(dumb_ptr<map_session_data> sd, int index,
+        SOff0 index, int amount);
+int clif_storageitemremoved(dumb_ptr<map_session_data> sd, SOff0 index,
         int amount);
 int clif_storageclose(dumb_ptr<map_session_data> sd);
 
diff --git a/src/map/clif.t.hpp b/src/map/clif.t.hpp
index 5b3d32f..ba9a187 100644
--- a/src/map/clif.t.hpp
+++ b/src/map/clif.t.hpp
@@ -27,8 +27,11 @@
 
 # include "../ints/little.hpp"
 
+# include "../compat/iter.hpp"
+
 # include "../generic/enum.hpp"
 
+# include "../mmo/consts.hpp"
 # include "../mmo/enums.hpp"
 
 
@@ -583,6 +586,132 @@ bool network_to_native(Position2 *native, NetPosition2 network)
     return true;
 }
 
+struct IOff2;
+struct SOff1;
+
+struct IOff0
+{
+    uint16_t index;
+
+    bool ok() const
+    { return get0() < MAX_INVENTORY; }
+    uint16_t get0() const
+    { return index; }
+    static IOff0 from(uint16_t i)
+    { return IOff0{i}; }
+    static IteratorPair<ValueIterator<IOff0>> iter()
+    { return {IOff0::from(0), IOff0::from(MAX_INVENTORY)}; };
+    friend uint16_t convert_for_printf(IOff0 i0) { return i0.index; }
+
+    IOff0& operator ++() { ++index; return *this; }
+    friend bool operator == (IOff0 l, IOff0 r) { return l.index == r.index; }
+    friend bool operator != (IOff0 l, IOff0 r) { return !(l == r); }
+    IOff2 shift() const;
+
+    IOff0() : index(0) {}
+private:
+    explicit IOff0(uint16_t i) : index(i) {}
+};
+
+struct SOff0
+{
+    uint16_t index;
+
+    bool ok() const
+    { return get0() < MAX_STORAGE; }
+    uint16_t get0() const
+    { return index; }
+    static SOff0 from(uint16_t i)
+    { return SOff0{i}; }
+    static IteratorPair<ValueIterator<SOff0>> iter()
+    { return {SOff0::from(0), SOff0::from(MAX_STORAGE)}; };
+    friend uint16_t convert_for_printf(SOff0 s0) { return s0.index; }
+
+    SOff0& operator ++() { ++index; return *this; }
+    friend bool operator == (SOff0 l, SOff0 r) { return l.index == r.index; }
+    friend bool operator != (SOff0 l, SOff0 r) { return !(l == r); }
+    SOff1 shift() const;
+
+    SOff0() : index(0) {}
+private:
+    explicit SOff0(uint16_t i) : index(i) {}
+};
 
+struct IOff2
+{
+    uint16_t index;
+
+    bool ok() const
+    { return get2() < MAX_INVENTORY; }
+    uint16_t get2() const
+    { return index - 2; }
+    static IOff2 from(uint16_t i)
+    { return IOff2{static_cast<uint16_t>(i + 2)}; }
+    static IteratorPair<ValueIterator<IOff2>> iter()
+    { return {IOff2::from(0), IOff2::from(MAX_INVENTORY)}; };
+
+    IOff2& operator ++() { ++index; return *this; }
+    friend bool operator == (IOff2 l, IOff2 r) { return l.index == r.index; }
+    friend bool operator != (IOff2 l, IOff2 r) { return !(l == r); }
+    IOff0 unshift() const
+    { return IOff0::from(get2()); }
+
+    IOff2() : index(0) {}
+private:
+    explicit IOff2(uint16_t i) : index(i) {}
+};
+
+struct SOff1
+{
+    uint16_t index;
+
+    bool ok() const
+    { return get1() < MAX_STORAGE; }
+    uint16_t get1() const
+    { return index - 1; }
+    static SOff1 from(uint16_t i)
+    { return SOff1{static_cast<uint16_t>(i + 1)}; }
+    static IteratorPair<ValueIterator<SOff1>> iter()
+    { return {SOff1::from(0), SOff1::from(MAX_STORAGE)}; };
+
+    SOff1& operator ++() { ++index; return *this; }
+    friend bool operator == (SOff1 l, SOff1 r) { return l.index == r.index; }
+    friend bool operator != (SOff1 l, SOff1 r) { return !(l == r); }
+    SOff0 unshift() const
+    { return SOff0::from(get1()); }
+
+    SOff1() : index(0) {}
+private:
+    explicit SOff1(uint16_t i) : index(i) {}
+};
+
+inline IOff2 IOff0::shift() const
+{ return IOff2::from(get0()); }
+inline SOff1 SOff0::shift() const
+{ return SOff1::from(get0()); }
+
+inline
+bool native_to_network(Little16 *network, IOff2 native)
+{
+    return native_to_network(network, native.index);
+}
+
+inline
+bool network_to_native(IOff2 *native, Little16 network)
+{
+    return network_to_native(&native->index, network);
+}
+
+inline
+bool native_to_network(Little16 *network, SOff1 native)
+{
+    return native_to_network(network, native.index);
+}
+
+inline
+bool network_to_native(SOff1 *native, Little16 network)
+{
+    return network_to_native(&native->index, network);
+}
 
 #endif // TMWA_MAP_CLIF_T_HPP
diff --git a/src/map/magic-expr.cpp b/src/map/magic-expr.cpp
index b0e68fb..1e5c829 100644
--- a/src/map/magic-expr.cpp
+++ b/src/map/magic-expr.cpp
@@ -858,8 +858,8 @@ int fun_is_equipped(dumb_ptr<env_t>, val_t *result, Slice<val_t> args)
 
     for (EQUIP i : EQUIPs)
     {
-        int idx = chr->equip_index_maybe[i];
-        if (idx >= 0 && chr->status.inventory[idx].nameid == item.nameid)
+        IOff0 idx = chr->equip_index_maybe[i];
+        if (idx.ok() && chr->status.inventory[idx].nameid == item.nameid)
         {
             retval = true;
             break;
diff --git a/src/map/map.hpp b/src/map/map.hpp
index 7e61e56..8fc752b 100644
--- a/src/map/map.hpp
+++ b/src/map/map.hpp
@@ -183,8 +183,8 @@ struct map_session_data : block_list, SessionData
     unsigned char tmw_version;  // tmw client version
     CharKey status_key;
     CharData status;
-    Array<struct item_data *, MAX_INVENTORY> inventory_data;
-    earray<short, EQUIP, EQUIP::COUNT> equip_index_maybe;
+    GenericArray<struct item_data *, InventoryIndexing<IOff0, MAX_INVENTORY>> inventory_data;
+    earray<IOff0, EQUIP, EQUIP::COUNT> equip_index_maybe;
     int weight, max_weight;
     MapName mapname_;
     Session *sess; // use this, you idiots!
@@ -284,7 +284,7 @@ struct map_session_data : block_list, SessionData
     short sc_count;
 
     AccountId trade_partner;
-    Array<int, TRADE_MAX> deal_item_index;
+    Array<IOff2, TRADE_MAX> deal_item_index;
     Array<int, TRADE_MAX> deal_item_amount;
     int deal_zeny;
     short deal_locked;
diff --git a/src/map/mob.cpp b/src/map/mob.cpp
index 336dbe7..01a1029 100644
--- a/src/map/mob.cpp
+++ b/src/map/mob.cpp
@@ -2203,7 +2203,7 @@ void mob_delay_item_drop(TimerData *, tick_t, struct delay_item_drop ditem)
                 pc_additem(ditem.first_sd, &temp_item, ditem.amount))
             != PickupFail::OKAY)
         {
-            clif_additem(ditem.first_sd, 0, 0, flag);
+            clif_additem(ditem.first_sd, IOff0::from(0), 0, flag);
             map_addflooritem(&temp_item, 1,
                     ditem.m, ditem.x, ditem.y,
                     ditem.first_sd, ditem.second_sd, ditem.third_sd);
@@ -2233,7 +2233,7 @@ void mob_delay_item_drop2(TimerData *, tick_t, struct delay_item_drop2 ditem)
                             ditem.item_data.amount))
             != PickupFail::OKAY)
         {
-            clif_additem(ditem.first_sd, 0, 0, flag);
+            clif_additem(ditem.first_sd, IOff0::from(0), 0, flag);
             map_addflooritem(&ditem.item_data, ditem.item_data.amount,
                     ditem.m, ditem.x, ditem.y,
                     ditem.first_sd, ditem.second_sd, ditem.third_sd);
diff --git a/src/map/npc.cpp b/src/map/npc.cpp
index 3232e4d..7d2b8da 100644
--- a/src/map/npc.cpp
+++ b/src/map/npc.cpp
@@ -890,11 +890,11 @@ int npc_selllist(dumb_ptr<map_session_data> sd,
         return 1;
     for (i = 0, z = 0; i < item_list.size(); i++)
     {
-        if (item_list[i].ioff2 - 2 < 0 || item_list[i].ioff2 - 2 >= MAX_INVENTORY)
+        if (!item_list[i].ioff2.ok())
             return 1;
-        ItemNameId nameid = sd->status.inventory[item_list[i].ioff2 - 2].nameid;
+        ItemNameId nameid = sd->status.inventory[item_list[i].ioff2.unshift()].nameid;
         if (!nameid ||
-            sd->status.inventory[item_list[i].ioff2 - 2].amount < item_list[i].count)
+            sd->status.inventory[item_list[i].ioff2.unshift()].amount < item_list[i].count)
             return 1;
         if (sd->trade_partner)
             return 2;           // cant sell while trading
@@ -907,7 +907,7 @@ int npc_selllist(dumb_ptr<map_session_data> sd,
     pc_getzeny(sd, static_cast<int>(z));
     for (i = 0; i < item_list.size(); i++)
     {
-        int item_id = item_list[i].ioff2 - 2;
+        IOff0 item_id = item_list[i].ioff2.unshift();
         pc_delitem(sd, item_id, item_list[i].count, 0);
     }
 
diff --git a/src/map/pc.cpp b/src/map/pc.cpp
index 4d104d1..d37a7ff 100644
--- a/src/map/pc.cpp
+++ b/src/map/pc.cpp
@@ -497,7 +497,7 @@ int pc_setnewpc(dumb_ptr<map_session_data> sd, AccountId account_id, CharId char
     return 0;
 }
 
-EPOS pc_equippoint(dumb_ptr<map_session_data> sd, int n)
+EPOS pc_equippoint(dumb_ptr<map_session_data> sd, IOff0 n)
 {
     nullpo_retr(EPOS::ZERO, sd);
 
@@ -514,7 +514,7 @@ int pc_setinventorydata(dumb_ptr<map_session_data> sd)
 {
     nullpo_ret(sd);
 
-    for (int i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         ItemNameId id = sd->status.inventory[i].nameid;
         sd->inventory_data[i] = itemdb_search(id);
@@ -571,9 +571,9 @@ int pc_setequipindex(dumb_ptr<map_session_data> sd)
     nullpo_ret(sd);
 
     for (EQUIP i : EQUIPs)
-        sd->equip_index_maybe[i] = -1;
+        sd->equip_index_maybe[i] = IOff0::from(-1);
 
-    for (int i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (!sd->status.inventory[i].nameid)
             continue;
@@ -614,7 +614,7 @@ int pc_setequipindex(dumb_ptr<map_session_data> sd)
 }
 
 static
-int pc_isequip(dumb_ptr<map_session_data> sd, int n)
+int pc_isequip(dumb_ptr<map_session_data> sd, IOff0 n)
 {
     struct item_data *item;
     eptr<struct status_change, StatusChange, StatusChange::MAX_STATUSCHANGE> sc_data;
@@ -970,7 +970,7 @@ int pc_calcstatus(dumb_ptr<map_session_data> sd, int first)
     if (first & 1)
     {
         sd->weight = 0;
-        for (int i = 0; i < MAX_INVENTORY; i++)
+        for (IOff0 i : IOff0::iter())
         {
             if (!sd->status.inventory[i].nameid
                 || sd->inventory_data[i] == NULL)
@@ -1041,8 +1041,8 @@ int pc_calcstatus(dumb_ptr<map_session_data> sd, int first)
 
     for (EQUIP i : EQUIPs_noarrow)
     {
-        int index = sd->equip_index_maybe[i];
-        if (index < 0)
+        IOff0 index = sd->equip_index_maybe[i];
+        if (!index.ok())
             continue;
         if (i == EQUIP::WEAPON && sd->equip_index_maybe[EQUIP::SHIELD] == index)
             continue;
@@ -1077,8 +1077,8 @@ int pc_calcstatus(dumb_ptr<map_session_data> sd, int first)
     // 装備品によるステータス変化はここで実行
     for (EQUIP i : EQUIPs_noarrow)
     {
-        int index = sd->equip_index_maybe[i];
-        if (index < 0)
+        IOff0 index = sd->equip_index_maybe[i];
+        if (!index.ok())
             continue;
         if (i == EQUIP::WEAPON && sd->equip_index_maybe[EQUIP::SHIELD] == index)
             continue;
@@ -1153,10 +1153,10 @@ int pc_calcstatus(dumb_ptr<map_session_data> sd, int first)
         sd->watk_2 += skill_power(sd, SkillID::TMW_BRAWLING) >> 3;  // +25 for 200
     }
 
-    int aidx = sd->equip_index_maybe[EQUIP::ARROW];
-    if (aidx >= 0)
-    {                           // 矢
-        int index = aidx;
+    IOff0 aidx = sd->equip_index_maybe[EQUIP::ARROW];
+    if (aidx.ok())
+    {
+        IOff0 index = aidx;
         if (sd->inventory_data[index])
         {                       //まだ属性が入っていない
             argrec_t arg[2] =
@@ -1824,14 +1824,12 @@ int pc_skill(dumb_ptr<map_session_data> sd, SkillID id, int level, int flag)
  */
 ADDITEM pc_checkadditem(dumb_ptr<map_session_data> sd, ItemNameId nameid, int amount)
 {
-    int i;
-
     nullpo_retr(ADDITEM::ZERO, sd);
 
     if (itemdb_isequip(nameid))
         return ADDITEM::NEW;
 
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (sd->status.inventory[i].nameid == nameid)
         {
@@ -1852,11 +1850,11 @@ ADDITEM pc_checkadditem(dumb_ptr<map_session_data> sd, ItemNameId nameid, int am
  */
 int pc_inventoryblank(dumb_ptr<map_session_data> sd)
 {
-    int i, b;
+    int b = 0;
 
     nullpo_ret(sd);
 
-    for (i = 0, b = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (!sd->status.inventory[i].nameid)
             b++;
@@ -1906,30 +1904,27 @@ int pc_getzeny(dumb_ptr<map_session_data> sd, int zeny)
  * アイテムを探して、インデックスを返す
  *------------------------------------------
  */
-int pc_search_inventory(dumb_ptr<map_session_data> sd, ItemNameId item_id)
+IOff0 pc_search_inventory(dumb_ptr<map_session_data> sd, ItemNameId item_id)
 {
-    int i;
+    nullpo_retr(IOff0::from(-1), sd);
 
-    nullpo_retr(-1, sd);
-
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (sd->status.inventory[i].nameid == item_id &&
             (sd->status.inventory[i].amount > 0 || !item_id))
             return i;
     }
 
-    return -1;
+    return IOff0::from(-1);
 }
 
 int pc_count_all_items(dumb_ptr<map_session_data> player, ItemNameId item_id)
 {
-    int i;
     int count = 0;
 
     nullpo_ret(player);
 
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (player->status.inventory[i].nameid == item_id)
             count += player->status.inventory[i].amount;
@@ -1940,12 +1935,12 @@ int pc_count_all_items(dumb_ptr<map_session_data> player, ItemNameId item_id)
 
 int pc_remove_items(dumb_ptr<map_session_data> player, ItemNameId item_id, int count)
 {
-    int i;
-
     nullpo_ret(player);
 
-    for (i = 0; i < MAX_INVENTORY && count; i++)
+    for (IOff0 i : IOff0::iter())
     {
+        if (!count)
+            break;
         if (player->status.inventory[i].nameid == item_id)
         {
             int to_delete = count;
@@ -1973,7 +1968,7 @@ PickupFail pc_additem(dumb_ptr<map_session_data> sd, Item *item_data,
                 int amount)
 {
     struct item_data *data;
-    int i, w;
+    int w;
 
     MAP_LOG_PC(sd, "PICKUP %d %d"_fmt, item_data->nameid, amount);
 
@@ -1986,12 +1981,13 @@ PickupFail pc_additem(dumb_ptr<map_session_data> sd, Item *item_data,
     if ((w = data->weight * amount) + sd->weight > sd->max_weight)
         return PickupFail::TOO_HEAVY;
 
-    i = MAX_INVENTORY;
+    IOff0 i = IOff0::from(MAX_INVENTORY);
 
     if (!itemdb_isequip2(data))
     {
-        // 装 備品ではないので、既所有品なら個数のみ変化させる
-        for (i = 0; i < MAX_INVENTORY; i++)
+        // TODO see if there's any nicer way to preserve the foreach var
+        for (i = IOff0::from(0); i != IOff0::from(MAX_INVENTORY); ++i)
+        {
             if (sd->status.inventory[i].nameid == item_data->nameid)
             {
                 if (sd->status.inventory[i].amount + amount > MAX_AMOUNT)
@@ -2000,12 +1996,12 @@ PickupFail pc_additem(dumb_ptr<map_session_data> sd, Item *item_data,
                 clif_additem(sd, i, amount, PickupFail::OKAY);
                 break;
             }
+        }
     }
-    if (i >= MAX_INVENTORY)
+    if (!i.ok())
     {
-        // 装 備品か未所有品だったので空き欄へ追加
         i = pc_search_inventory(sd, ItemNameId());
-        if (i >= 0)
+        if (i.ok())
         {
             sd->status.inventory[i] = *item_data;
 
@@ -2029,7 +2025,7 @@ PickupFail pc_additem(dumb_ptr<map_session_data> sd, Item *item_data,
  * アイテムを減らす
  *------------------------------------------
  */
-int pc_delitem(dumb_ptr<map_session_data> sd, int n, int amount, int type)
+int pc_delitem(dumb_ptr<map_session_data> sd, IOff0 n, int amount, int type)
 {
     nullpo_retr(1, sd);
 
@@ -2062,14 +2058,14 @@ int pc_delitem(dumb_ptr<map_session_data> sd, int n, int amount, int type)
  * アイテムを落す
  *------------------------------------------
  */
-int pc_dropitem(dumb_ptr<map_session_data> sd, int n, int amount)
+int pc_dropitem(dumb_ptr<map_session_data> sd, IOff0 n, int amount)
 {
     nullpo_retr(1, sd);
 
     if (sd->trade_partner || sd->npc_id || sd->state.storage_open)
         return 0;               // no dropping while trading/npc/storage
 
-    if (n < 0 || n >= MAX_INVENTORY)
+    if (!n.ok())
         return 0;
 
     if (amount <= 0)
@@ -2172,7 +2168,7 @@ int pc_takeitem(dumb_ptr<map_session_data> sd, dumb_ptr<flooritem_data> fitem)
         PickupFail flag = pc_additem(sd, &fitem->item_data, fitem->item_data.amount);
         if (flag != PickupFail::OKAY)
             // 重量overで取得失敗
-            clif_additem(sd, 0, 0, flag);
+            clif_additem(sd, IOff0::from(0), 0, flag);
         else
         {
             // 取得成功
@@ -2185,12 +2181,12 @@ int pc_takeitem(dumb_ptr<map_session_data> sd, dumb_ptr<flooritem_data> fitem)
     }
 
     /* Otherwise, we can't pick up */
-    clif_additem(sd, 0, 0, PickupFail::DROP_STEAL);
+    clif_additem(sd, IOff0::from(0), 0, PickupFail::DROP_STEAL);
     return 0;
 }
 
 static
-int pc_isUseitem(dumb_ptr<map_session_data> sd, int n)
+int pc_isUseitem(dumb_ptr<map_session_data> sd, IOff0 n)
 {
     struct item_data *item;
     ItemNameId nameid;
@@ -2217,13 +2213,13 @@ int pc_isUseitem(dumb_ptr<map_session_data> sd, int n)
  * アイテムを使う
  *------------------------------------------
  */
-int pc_useitem(dumb_ptr<map_session_data> sd, int n)
+int pc_useitem(dumb_ptr<map_session_data> sd, IOff0 n)
 {
     int amount;
 
     nullpo_retr(1, sd);
 
-    if (n >= 0 && n < MAX_INVENTORY && sd->inventory_data[n])
+    if (n.ok() && sd->inventory_data[n])
     {
         amount = sd->status.inventory[n].amount;
         if (!sd->status.inventory[n].nameid
@@ -2716,9 +2712,9 @@ int pc_checkskill(dumb_ptr<map_session_data> sd, SkillID skill_id)
  * 装 備品のチェック
  *------------------------------------------
  */
-int pc_checkequip(dumb_ptr<map_session_data> sd, EPOS pos)
+IOff0 pc_checkequip(dumb_ptr<map_session_data> sd, EPOS pos)
 {
-    nullpo_retr(-1, sd);
+    nullpo_retr(IOff0::from(-1), sd);
 
     for (EQUIP i : EQUIPs)
     {
@@ -2726,7 +2722,7 @@ int pc_checkequip(dumb_ptr<map_session_data> sd, EPOS pos)
             return sd->equip_index_maybe[i];
     }
 
-    return -1;
+    return IOff0::from(-1);
 }
 
 /*==========================================
@@ -3314,13 +3310,13 @@ int pc_resetlvl(dumb_ptr<map_session_data> sd, int type)
     for (EQUIP i : EQUIPs)
     {
         // unequip items that can't be equipped by base 1 [Valaris]
-        short *idx = &sd->equip_index_maybe[i];
-        if (*idx >= 0)
+        IOff0 *idx = &sd->equip_index_maybe[i];
+        if ((*idx).ok())
         {
             if (!pc_isequip(sd, *idx))
             {
                 pc_unequipitem(sd, *idx, CalcStatus::LATER);
-                *idx = -1;
+                *idx = IOff0::from(-1);
             }
         }
     }
@@ -4381,7 +4377,7 @@ int pc_cleareventtimer(dumb_ptr<map_session_data> sd)
  *------------------------------------------
  */
 static
-int pc_signal_advanced_equipment_change(dumb_ptr<map_session_data> sd, int n)
+int pc_signal_advanced_equipment_change(dumb_ptr<map_session_data> sd, IOff0 n)
 {
     if (bool(sd->status.inventory[n].equip & EPOS::SHOES))
         clif_changelook(sd, LOOK::SHOES, 0);
@@ -4396,7 +4392,7 @@ int pc_signal_advanced_equipment_change(dumb_ptr<map_session_data> sd, int n)
     return 0;
 }
 
-int pc_equipitem(dumb_ptr<map_session_data> sd, int n, EPOS)
+int pc_equipitem(dumb_ptr<map_session_data> sd, IOff0 n, EPOS)
 {
     ItemNameId nameid;
     struct item_data *id;
@@ -4404,9 +4400,9 @@ int pc_equipitem(dumb_ptr<map_session_data> sd, int n, EPOS)
 
     nullpo_ret(sd);
 
-    if (n < 0 || n >= MAX_INVENTORY)
+    if (!n.ok())
     {
-        clif_equipitemack(sd, 0, EPOS::ZERO, 0);
+        clif_equipitemack(sd, IOff0::from(0), EPOS::ZERO, 0);
         return 0;
     }
 
@@ -4431,11 +4427,11 @@ int pc_equipitem(dumb_ptr<map_session_data> sd, int n, EPOS)
     {
         // アクセサリ用例外処理
         EPOS epor = EPOS::ZERO;
-        int midx = sd->equip_index_maybe[EQUIP::MISC2];
-        int cidx = sd->equip_index_maybe[EQUIP::CAPE];
-        if (midx >= 0)
+        IOff0 midx = sd->equip_index_maybe[EQUIP::MISC2];
+        IOff0 cidx = sd->equip_index_maybe[EQUIP::CAPE];
+        if (midx.ok())
             epor |= sd->status.inventory[midx].equip;
-        if (cidx >= 0)
+        if (cidx.ok())
             epor |= sd->status.inventory[cidx].equip;
         epor &= (EPOS::MISC2 | EPOS::CAPE);
         pos = (epor == EPOS::CAPE ? EPOS::MISC2 : EPOS::CAPE);
@@ -4445,8 +4441,8 @@ int pc_equipitem(dumb_ptr<map_session_data> sd, int n, EPOS)
     {
         if (bool(pos & equip_pos[i]))
         {
-            short *idx = &sd->equip_index_maybe[i];
-            if (*idx >= 0)    //Slot taken, remove item from there.
+            IOff0 *idx = &sd->equip_index_maybe[i];
+            if ((*idx).ok())    //Slot taken, remove item from there.
                 pc_unequipitem(sd, *idx, CalcStatus::LATER);
             *idx = n;
         }
@@ -4542,7 +4538,7 @@ int pc_equipitem(dumb_ptr<map_session_data> sd, int n, EPOS)
  * 装 備した物を外す
  *------------------------------------------
  */
-int pc_unequipitem(dumb_ptr<map_session_data> sd, int n, CalcStatus type)
+int pc_unequipitem(dumb_ptr<map_session_data> sd, IOff0 n, CalcStatus type)
 {
     nullpo_ret(sd);
 
@@ -4557,7 +4553,7 @@ int pc_unequipitem(dumb_ptr<map_session_data> sd, int n, CalcStatus type)
         for (EQUIP i : EQUIPs)
         {
             if (bool(sd->status.inventory[n].equip & equip_pos[i]))
-                sd->equip_index_maybe[i] = -1;
+                sd->equip_index_maybe[i] = IOff0::from(-1);
         }
         if (bool(sd->status.inventory[n].equip & EPOS::WEAPON))
         {
@@ -4605,7 +4601,7 @@ int pc_unequipitem(dumb_ptr<map_session_data> sd, int n, CalcStatus type)
     return 0;
 }
 
-int pc_unequipinvyitem(dumb_ptr<map_session_data> sd, int n, CalcStatus type)
+int pc_unequipinvyitem(dumb_ptr<map_session_data> sd, IOff0 n, CalcStatus type)
 {
     nullpo_retr(1, sd);
 
@@ -4617,7 +4613,7 @@ int pc_unequipinvyitem(dumb_ptr<map_session_data> sd, int n, CalcStatus type)
         {
             //Slot taken, remove item from there.
             pc_unequipitem(sd, sd->equip_index_maybe[i], type);
-            sd->equip_index_maybe[i] = -1;
+            sd->equip_index_maybe[i] = IOff0::from(-1);
         }
     }
 
@@ -4631,28 +4627,29 @@ int pc_unequipinvyitem(dumb_ptr<map_session_data> sd, int n, CalcStatus type)
  */
 int pc_checkitem(dumb_ptr<map_session_data> sd)
 {
-    int i, j, k, calc_flag = 0;
+    int calc_flag = 0;
 
     nullpo_ret(sd);
 
-    // 所持品空き詰め
-    for (i = j = 0; i < MAX_INVENTORY; i++)
+    IOff0 j = IOff0::from(0);
+    for (IOff0 i : IOff0::iter())
     {
         if (!(sd->status.inventory[i].nameid))
             continue;
-        if (i > j)
+        if (i != j)
         {
             sd->status.inventory[j] = sd->status.inventory[i];
             sd->inventory_data[j] = sd->inventory_data[i];
         }
-        j++;
+        ++j;
     }
-    for (k = j; k < MAX_INVENTORY; ++k)
+    for (IOff0 k = j; k != IOff0::from(MAX_INVENTORY); ++k)
+    {
         sd->status.inventory[k] = Item{};
-    for (k = j; k < MAX_INVENTORY; k++)
         sd->inventory_data[k] = NULL;
+    }
 
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (!sd->status.inventory[i].nameid)
             continue;
diff --git a/src/map/pc.hpp b/src/map/pc.hpp
index 87ed708..6e07070 100644
--- a/src/map/pc.hpp
+++ b/src/map/pc.hpp
@@ -84,10 +84,10 @@ int pc_setnewpc(dumb_ptr<map_session_data>, AccountId, CharId, int, uint32_t /*t
 int pc_authok(AccountId, int, TimeT, short tmw_version, const CharKey *, const CharData *);
 int pc_authfail(AccountId accid);
 
-EPOS pc_equippoint(dumb_ptr<map_session_data> sd, int n);
+EPOS pc_equippoint(dumb_ptr<map_session_data> sd, IOff0 n);
 
 int pc_checkskill(dumb_ptr<map_session_data> sd, SkillID skill_id);
-int pc_checkequip(dumb_ptr<map_session_data> sd, EPOS pos);
+IOff0 pc_checkequip(dumb_ptr<map_session_data> sd, EPOS pos);
 
 int pc_walktoxy(dumb_ptr<map_session_data>, int, int);
 int pc_stop_walking(dumb_ptr<map_session_data>, int);
@@ -98,18 +98,18 @@ int pc_randomwarp(dumb_ptr<map_session_data> sd, BeingRemoveWhy type);
 
 ADDITEM pc_checkadditem(dumb_ptr<map_session_data>, ItemNameId, int);
 int pc_inventoryblank(dumb_ptr<map_session_data>);
-int pc_search_inventory(dumb_ptr<map_session_data> sd, ItemNameId item_id);
+IOff0 pc_search_inventory(dumb_ptr<map_session_data> sd, ItemNameId item_id);
 int pc_payzeny(dumb_ptr<map_session_data>, int);
 PickupFail pc_additem(dumb_ptr<map_session_data>, Item *, int);
 int pc_getzeny(dumb_ptr<map_session_data>, int);
-int pc_delitem(dumb_ptr<map_session_data>, int, int, int);
+int pc_delitem(dumb_ptr<map_session_data>, IOff0, int, int);
 int pc_checkitem(dumb_ptr<map_session_data>);
 int pc_count_all_items(dumb_ptr<map_session_data> player, ItemNameId item_id);
 int pc_remove_items(dumb_ptr<map_session_data> player,
         ItemNameId item_id, int count);
 
 int pc_takeitem(dumb_ptr<map_session_data>, dumb_ptr<flooritem_data>);
-int pc_dropitem(dumb_ptr<map_session_data>, int, int);
+int pc_dropitem(dumb_ptr<map_session_data>, IOff0, int);
 
 int pc_checkweighticon(dumb_ptr<map_session_data> sd);
 
@@ -134,10 +134,10 @@ int pc_skillup(dumb_ptr<map_session_data>, SkillID);
 int pc_resetlvl(dumb_ptr<map_session_data>, int type);
 int pc_resetstate(dumb_ptr<map_session_data>);
 int pc_resetskill(dumb_ptr<map_session_data>);
-int pc_equipitem(dumb_ptr<map_session_data>, int, EPOS);
-int pc_unequipitem(dumb_ptr<map_session_data>, int, CalcStatus);
-int pc_unequipinvyitem(dumb_ptr<map_session_data>, int, CalcStatus);
-int pc_useitem(dumb_ptr<map_session_data>, int);
+int pc_equipitem(dumb_ptr<map_session_data>, IOff0, EPOS);
+int pc_unequipitem(dumb_ptr<map_session_data>, IOff0, CalcStatus);
+int pc_unequipinvyitem(dumb_ptr<map_session_data>, IOff0, CalcStatus);
+int pc_useitem(dumb_ptr<map_session_data>, IOff0);
 
 int pc_damage(dumb_ptr<block_list>, dumb_ptr<map_session_data>, int);
 int pc_heal(dumb_ptr<map_session_data>, int, int);
diff --git a/src/map/script.cpp b/src/map/script.cpp
index ab9f848..73ddea7 100644
--- a/src/map/script.cpp
+++ b/src/map/script.cpp
@@ -1926,7 +1926,7 @@ static
 void builtin_countitem(ScriptState *st)
 {
     ItemNameId nameid;
-    int count = 0, i;
+    int count = 0;
     dumb_ptr<map_session_data> sd;
 
     struct script_data *data;
@@ -1947,7 +1947,7 @@ void builtin_countitem(ScriptState *st)
 
     if (nameid)
     {
-        for (i = 0; i < MAX_INVENTORY; i++)
+        for (IOff0 i : IOff0::iter())
         {
             if (sd->status.inventory[i].nameid == nameid)
                 count += sd->status.inventory[i].amount;
@@ -2050,7 +2050,7 @@ void builtin_getitem(ScriptState *st)
         PickupFail flag;
         if ((flag = pc_additem(sd, &item_tmp, amount)) != PickupFail::OKAY)
         {
-            clif_additem(sd, 0, 0, flag);
+            clif_additem(sd, IOff0::from(0), 0, flag);
             map_addflooritem(&item_tmp, amount,
                     sd->bl_m, sd->bl_x, sd->bl_y,
                     NULL, NULL, NULL);
@@ -2114,7 +2114,7 @@ static
 void builtin_delitem(ScriptState *st)
 {
     ItemNameId nameid;
-    int amount, i;
+    int amount;
     dumb_ptr<map_session_data> sd;
     struct script_data *data;
 
@@ -2140,7 +2140,7 @@ void builtin_delitem(ScriptState *st)
         return;
     }
 
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (sd->status.inventory[i].nameid == nameid)
         {
@@ -2290,7 +2290,7 @@ Array<EPOS, 11> equip //=
 static
 void builtin_getequipid(ScriptState *st)
 {
-    int i, num;
+    int num;
     dumb_ptr<map_session_data> sd;
     struct item_data *item;
 
@@ -2301,8 +2301,8 @@ void builtin_getequipid(ScriptState *st)
         return;
     }
     num = conv_num(st, &AARGO2(2));
-    i = pc_checkequip(sd, equip[num - 1]);
-    if (i >= 0)
+    IOff0 i = pc_checkequip(sd, equip[num - 1]);
+    if (i.ok())
     {
         item = sd->inventory_data[i];
         if (item)
@@ -2323,7 +2323,7 @@ void builtin_getequipid(ScriptState *st)
 static
 void builtin_getequipname(ScriptState *st)
 {
-    int i, num;
+    int num;
     dumb_ptr<map_session_data> sd;
     struct item_data *item;
 
@@ -2331,8 +2331,8 @@ void builtin_getequipname(ScriptState *st)
 
     sd = script_rid2sd(st);
     num = conv_num(st, &AARGO2(2));
-    i = pc_checkequip(sd, equip[num - 1]);
-    if (i >= 0)
+    IOff0 i = pc_checkequip(sd, equip[num - 1]);
+    if (i.ok())
     {
         item = sd->inventory_data[i];
         if (item)
@@ -3522,10 +3522,10 @@ static
 void builtin_getinventorylist(ScriptState *st)
 {
     dumb_ptr<map_session_data> sd = script_rid2sd(st);
-    int i, j = 0;
+    int j = 0;
     if (!sd)
         return;
-    for (i = 0; i < MAX_INVENTORY; i++)
+    for (IOff0 i : IOff0::iter())
     {
         if (sd->status.inventory[i].nameid
             && sd->status.inventory[i].amount > 0)
@@ -3730,8 +3730,8 @@ void builtin_nude(ScriptState *st)
 
     for (EQUIP i : EQUIPs)
     {
-        int idx = sd->equip_index_maybe[i];
-        if (idx >= 0)
+        IOff0 idx = sd->equip_index_maybe[i];
+        if (idx.ok())
             pc_unequipitem(sd, idx, CalcStatus::LATER);
     }
     pc_calcstatus(sd, 0);
@@ -3754,8 +3754,8 @@ void builtin_unequipbyid(ScriptState *st)
 
     if (slot_id >= EQUIP() && slot_id < EQUIP::COUNT)
     {
-        int idx = sd->equip_index_maybe[slot_id];
-        if (idx >= 0)
+        IOff0 idx = sd->equip_index_maybe[slot_id];
+        if (idx.ok())
             pc_unequipitem(sd, idx, CalcStatus::LATER);
     }
 
diff --git a/src/map/storage.cpp b/src/map/storage.cpp
index e9c2cd6..88db8c4 100644
--- a/src/map/storage.cpp
+++ b/src/map/storage.cpp
@@ -105,7 +105,6 @@ int storage_additem(dumb_ptr<map_session_data> sd, Storage *stor,
                             Item *item_data, int amount)
 {
     struct item_data *data;
-    int i;
 
     if (!item_data->nameid || amount <= 0)
         return 1;
@@ -114,7 +113,7 @@ int storage_additem(dumb_ptr<map_session_data> sd, Storage *stor,
 
     if (!itemdb_isequip2(data))
     {                           //Stackable
-        for (i = 0; i < MAX_STORAGE; i++)
+        for (SOff0 i : SOff0::iter())
         {
             if (compare_item(&stor->storage_[i], item_data))
             {
@@ -128,9 +127,12 @@ int storage_additem(dumb_ptr<map_session_data> sd, Storage *stor,
         }
     }
     //Add item
-    for (i = 0; i < MAX_STORAGE && stor->storage_[i].nameid; i++);
-
-    if (i >= MAX_STORAGE)
+    SOff0 i = *std::find_if(SOff0::iter().begin(), SOff0::iter().end(),
+            [&stor](SOff0 i_)
+            {
+                return !stor->storage_[i_].nameid;
+            });
+    if (!i.ok())
         return 1;
 
     stor->storage_[i] = *item_data;
@@ -148,7 +150,7 @@ int storage_additem(dumb_ptr<map_session_data> sd, Storage *stor,
  */
 static
 int storage_delitem(dumb_ptr<map_session_data> sd, Storage *stor,
-                            int n, int amount)
+        SOff0 n, int amount)
 {
 
     if (!stor->storage_[n].nameid || stor->storage_[n].amount < amount)
@@ -171,7 +173,7 @@ int storage_delitem(dumb_ptr<map_session_data> sd, Storage *stor,
  * Add an item to the storage from the inventory.
  *------------------------------------------
  */
-int storage_storageadd(dumb_ptr<map_session_data> sd, int index, int amount)
+int storage_storageadd(dumb_ptr<map_session_data> sd, IOff0 index, int amount)
 {
     Storage *stor;
 
@@ -182,7 +184,7 @@ int storage_storageadd(dumb_ptr<map_session_data> sd, int index, int amount)
     if ((stor->storage_amount > MAX_STORAGE) || !stor->storage_status)
         return 0;               // storage full / storage closed
 
-    if (index < 0 || index >= MAX_INVENTORY)
+    if (!index.ok())
         return 0;
 
     if (!sd->status.inventory[index].nameid)
@@ -206,7 +208,7 @@ int storage_storageadd(dumb_ptr<map_session_data> sd, int index, int amount)
  * Retrieve an item from the storage.
  *------------------------------------------
  */
-int storage_storageget(dumb_ptr<map_session_data> sd, int index, int amount)
+int storage_storageget(dumb_ptr<map_session_data> sd, SOff0 index, int amount)
 {
     Storage *stor;
     PickupFail flag;
@@ -215,7 +217,7 @@ int storage_storageget(dumb_ptr<map_session_data> sd, int index, int amount)
     stor = account2storage2(sd->status_key.account_id);
     nullpo_ret(stor);
 
-    if (index < 0 || index >= MAX_STORAGE)
+    if (!index.ok())
         return 0;
 
     if (!stor->storage_[index].nameid)
@@ -227,7 +229,7 @@ int storage_storageget(dumb_ptr<map_session_data> sd, int index, int amount)
     if ((flag = pc_additem(sd, &stor->storage_[index], amount)) == PickupFail::OKAY)
         storage_delitem(sd, stor, index, amount);
     else
-        clif_additem(sd, 0, 0, flag);
+        clif_additem(sd, IOff0::from(0), 0, flag);
 //  log_fromstorage(sd, index, 0);
     return 1;
 }
diff --git a/src/map/storage.hpp b/src/map/storage.hpp
index 3eab087..fe29664 100644
--- a/src/map/storage.hpp
+++ b/src/map/storage.hpp
@@ -27,9 +27,11 @@
 
 # include "../mmo/fwd.hpp"
 
+# include "clif.t.hpp"
+
 int storage_storageopen(dumb_ptr<map_session_data> sd);
-int storage_storageadd(dumb_ptr<map_session_data> sd, int index, int amount);
-int storage_storageget(dumb_ptr<map_session_data> sd, int index, int amount);
+int storage_storageadd(dumb_ptr<map_session_data> sd, IOff0 index, int amount);
+int storage_storageget(dumb_ptr<map_session_data> sd, SOff0 index, int amount);
 int storage_storageclose(dumb_ptr<map_session_data> sd);
 void do_final_storage(void);
 Storage *account2storage(AccountId account_id);
diff --git a/src/map/trade.cpp b/src/map/trade.cpp
index af5d1aa..7a4913a 100644
--- a/src/map/trade.cpp
+++ b/src/map/trade.cpp
@@ -123,7 +123,7 @@ void trade_tradeack(dumb_ptr<map_session_data> sd, int type)
  * アイテム追加
  *------------------------------------------
  */
-void trade_tradeadditem(dumb_ptr<map_session_data> sd, int index, int amount)
+void trade_tradeadditem(dumb_ptr<map_session_data> sd, IOff2 index, int amount)
 {
     dumb_ptr<map_session_data> target_sd;
     struct item_data *id;
@@ -131,27 +131,26 @@ void trade_tradeadditem(dumb_ptr<map_session_data> sd, int index, int amount)
     int trade_weight = 0;
     int free_ = 0;
     int c;
-    int i;
 
     nullpo_retv(sd);
 
     if (((target_sd = map_id2sd(account_to_block(sd->trade_partner))) != NULL)
         && (sd->deal_locked < 1))
     {
-        if (index < 2 || index >= MAX_INVENTORY + 2)
+        if (!index.ok())
         {
-            if (index == 0 && amount > 0 && amount <= sd->status.zeny)
+            if (index.index == 0 && amount > 0 && amount <= sd->status.zeny)
             {
                 sd->deal_zeny = amount;
-                clif_tradeadditem(sd, target_sd, 0, amount);
+                clif_tradeadditem(sd, target_sd, index, amount);
             }
         }
         // note: amount is overridden below!
-        else if (amount <= sd->status.inventory[index - 2].amount
+        else if (amount <= sd->status.inventory[index.unshift()].amount
                  && amount > 0)
         {
             // determine free slots of receiver
-            for (i = 0; i < MAX_INVENTORY; i++)
+            for (IOff0 i : IOff0::iter())
             {
                 if (!target_sd->status.inventory[i].nameid
                     && target_sd->inventory_data[i] == NULL)
@@ -163,13 +162,13 @@ void trade_tradeadditem(dumb_ptr<map_session_data> sd, int index, int amount)
                 {
                     // calculate trade weight
                     trade_weight +=
-                        sd->inventory_data[index - 2]->weight * amount;
+                        sd->inventory_data[index.unshift()]->weight * amount;
 
                     // determine if item is a stackable already in receivers inventory, and up free count
-                    for (i = 0; i < MAX_INVENTORY; i++)
+                    for (IOff0 i : IOff0::iter())
                     {
                         if (target_sd->status.inventory[i].nameid ==
-                            sd->status.inventory[index - 2].nameid
+                            sd->status.inventory[index.unshift()].nameid
                             && target_sd->inventory_data[i] != NULL)
                         {
                             id = target_sd->inventory_data[i];
@@ -205,7 +204,7 @@ void trade_tradeadditem(dumb_ptr<map_session_data> sd, int index, int amount)
                                 return;
                             }
                         }
-                        pc_unequipinvyitem(sd, index - 2, CalcStatus::NOW);
+                        pc_unequipinvyitem(sd, index.unshift(), CalcStatus::NOW);
                         sd->deal_item_index[trade_i] = index;
                         sd->deal_item_amount[trade_i] += amount;
                         clif_tradeitemok(sd, index, amount, 0);    //success to add item
@@ -217,15 +216,15 @@ void trade_tradeadditem(dumb_ptr<map_session_data> sd, int index, int amount)
                 {
                     // calculate weight for stored deal
                     trade_weight +=
-                        sd->inventory_data[sd->deal_item_index[trade_i] -
-                                           2]->weight *
+                        sd->inventory_data[sd->deal_item_index[trade_i].unshift()
+                                           ]->weight *
                         sd->deal_item_amount[trade_i];
                     // count free stackables in stored deal
-                    for (i = 0; i < MAX_INVENTORY; i++)
+                    for (IOff0 i : IOff0::iter())
                     {
                         if (target_sd->status.inventory[i].nameid ==
                             sd->status.
-                            inventory[sd->deal_item_index[trade_i] - 2].nameid
+                            inventory[sd->deal_item_index[trade_i].unshift()].nameid
                             && target_sd->inventory_data[i] != NULL)
                         {
                             id = target_sd->inventory_data[i];
@@ -260,11 +259,11 @@ void trade_tradeok(dumb_ptr<map_session_data> sd)
 
     for (trade_i = 0; trade_i < TRADE_MAX; trade_i++)
     {
-        int index = sd->deal_item_index[trade_i];
-        if (index < 2 || index >= MAX_INVENTORY + 2)
+        IOff2 index = sd->deal_item_index[trade_i];
+        if (!index.ok())
             continue;
         if (sd->deal_item_amount[trade_i] >
-            sd->status.inventory[index - 2].amount
+            sd->status.inventory[index.unshift()].amount
             || sd->deal_item_amount[trade_i] < 0)
         {
             trade_tradecancel(sd);
@@ -276,7 +275,7 @@ void trade_tradeok(dumb_ptr<map_session_data> sd)
     if ((target_sd = map_id2sd(account_to_block(sd->trade_partner))) != NULL)
     {
         sd->deal_locked = 1;
-        clif_tradeitemok(sd, 0, 0, 0);
+        clif_tradeitemok(sd, IOff2::from(0), 0, 0);
         clif_tradedeal_lock(sd, 0);
         clif_tradedeal_lock(target_sd, 1);
     }
@@ -299,20 +298,22 @@ void trade_tradecancel(dumb_ptr<map_session_data> sd)
         {                       //give items back (only virtual)
             if (sd->deal_item_amount[trade_i] != 0)
             {
+                assert (sd->deal_item_index[trade_i].ok());
                 clif_additem(sd,
-                        sd->deal_item_index[trade_i] - 2,
+                        sd->deal_item_index[trade_i].unshift(),
                         sd->deal_item_amount[trade_i],
                         PickupFail::OKAY);
-                sd->deal_item_index[trade_i] = 0;
+                sd->deal_item_index[trade_i] = IOff2::from(0);
                 sd->deal_item_amount[trade_i] = 0;
             }
             if (target_sd->deal_item_amount[trade_i] != 0)
             {
+                assert (target_sd->deal_item_index[trade_i].ok());
                 clif_additem(target_sd,
-                        target_sd->deal_item_index[trade_i] - 2,
+                        target_sd->deal_item_index[trade_i].unshift(),
                         target_sd->deal_item_amount[trade_i],
                         PickupFail::OKAY);
-                target_sd->deal_item_index[trade_i] = 0;
+                target_sd->deal_item_index[trade_i] = IOff2::from(0);
                 target_sd->deal_item_amount[trade_i] = 0;
             }
         }
@@ -379,7 +380,8 @@ void trade_tradecommit(dumb_ptr<map_session_data> sd)
                 {
                     if (sd->deal_item_amount[trade_i] != 0)
                     {
-                        int n = sd->deal_item_index[trade_i] - 2;
+                        assert (sd->deal_item_index[trade_i].ok());
+                        IOff0 n = sd->deal_item_index[trade_i].unshift();
                         PickupFail flag = pc_additem(target_sd,
                                 &sd->status.inventory[n],
                                 sd->deal_item_amount[trade_i]);
@@ -390,12 +392,13 @@ void trade_tradecommit(dumb_ptr<map_session_data> sd)
                             clif_additem(sd, n,
                                     sd->deal_item_amount[trade_i],
                                     PickupFail::OKAY);
-                        sd->deal_item_index[trade_i] = 0;
+                        sd->deal_item_index[trade_i] = IOff2::from(0);
                         sd->deal_item_amount[trade_i] = 0;
                     }
                     if (target_sd->deal_item_amount[trade_i] != 0)
                     {
-                        int n = target_sd->deal_item_index[trade_i] - 2;
+                        assert (target_sd->deal_item_index[trade_i].ok());
+                        IOff0 n = target_sd->deal_item_index[trade_i].unshift();
                         PickupFail flag = pc_additem(sd,
                                 &target_sd->status.inventory[n],
                                 target_sd->deal_item_amount[trade_i]);
@@ -405,10 +408,9 @@ void trade_tradecommit(dumb_ptr<map_session_data> sd)
                                         1);
                         else
                             clif_additem(target_sd, n,
-
                                     target_sd->deal_item_amount[trade_i],
                                     PickupFail::OKAY);
-                        target_sd->deal_item_index[trade_i] = 0;
+                        target_sd->deal_item_index[trade_i] = IOff2::from(0);
                         target_sd->deal_item_amount[trade_i] = 0;
                     }
                 }
@@ -454,7 +456,7 @@ void trade_verifyzeny(dumb_ptr<map_session_data> sd)
         if (sd->deal_zeny > sd->status.zeny)
         {
             if (sd->deal_locked < 1)
-                trade_tradeadditem(sd, 0, sd->status.zeny);    // Fix money ammount
+                trade_tradeadditem(sd, IOff2::from(0), sd->status.zeny);    // Fix money ammount
             else
                 trade_tradecancel(sd); // Or cancel the trade if we can't fix it
         }
diff --git a/src/map/trade.hpp b/src/map/trade.hpp
index 9d542a4..370fcdf 100644
--- a/src/map/trade.hpp
+++ b/src/map/trade.hpp
@@ -25,9 +25,11 @@
 
 # include "../generic/fwd.hpp"
 
+# include "clif.t.hpp"
+
 void trade_traderequest(dumb_ptr<map_session_data> sd, BlockId target_id);
 void trade_tradeack(dumb_ptr<map_session_data> sd, int type);
-void trade_tradeadditem(dumb_ptr<map_session_data> sd, int index, int amount);
+void trade_tradeadditem(dumb_ptr<map_session_data> sd, IOff2 index, int amount);
 void trade_tradeok(dumb_ptr<map_session_data> sd);
 void trade_tradecancel(dumb_ptr<map_session_data> sd);
 void trade_tradecommit(dumb_ptr<map_session_data> sd);