ACNL Inventory Item Whitelist RE

ACNL-Inv_Item_WL-RE.c

/*

Reverse Engineering of ACNL's Inventory Whitelist by Slattz
Any hardcoded pointer offsets are based on EUR

Code.bin Offsets of functions below:
0x769864: CheckInventoryItemWhitelist
0x535908: ItemValidity
0x53589C: CheckIfValidItem
0x768DC4: CheckItemValidity

*/

//#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>

typedef uint8_t u8;   //<  8-bit unsigned integer
typedef uint16_t u16; //< 16-bit unsigned integer
typedef uint32_t u32; //< 32-bit unsigned integer
typedef uint64_t u64; //< 64-bit unsigned integer

int CheckItemValidity(u32 *invslot_addr)
{
    /* Checks if the item is valid/obtainable.
    It disregards wrapping paper as it has already bypassed this function. */

    int result = 0;
    u16 maxID = 0x172B; //Real Max ID is 0x372B but game takes 0x2000 from the item ID for these checks
    u16 itemID = *(u16 *)invslot_addr; //Read itemID from specified Inventory Slot
    itemID = itemID & ~0x8000;
    u16 chk = itemID - 0x2000; //To cover items lower than 0x2000 (Enviroment Items)
    
    if (chk < maxID) //If item passes this check, it's 'valid'
        result = itemID - 0x2000; 
    
 if (chk >= maxID) //If item passes this check, it's 'invalid'
        result = -1;
    
    return result;
}

int CheckIfValidItem(u32 *invslot_addr)
{
    int valid = CheckItemValidity(invslot_addr);
    if (valid < 0) //If item is 'invalid'
        return 0;

    u32 point = *(u32 *)0xA18390;
    if (point != 0)
    {
        u16 maxID = 0x172B;
        if (valid <= maxID)
        {
            valid = (valid << 4) - valid;
            valid = point + (valid << 1);
            return valid;
        }
    }

    else return 0;
}

int ItemValidity(u32 *invslot_addr)
{
    int valid = CheckIfValidItem(invslot_addr);
    if (valid == 0)
        return 0;

    u8 point = *(u8 *)(valid+0xA);
    u32 point2 = *(u32 *)0xA183A0;

    if (0x9B >= point)
        point = 0;

    if (point2 == 0)
        return 0;

    if (point < 0x9B)
    {
        point = point + (point << 1);
        point = point + point2;
        return point;
    }

    else return 0;
}

bool CheckInventoryItemWhitelist(u32 *invslot_addr)
{
    u16 itemID = *(u16 *)invslot_addr;
    itemID &= 0x6000;
    if (itemID == 0x4000) //If item is wrapping paper / Any item ID between 0x4000 - 0x5FFF
        goto ItemIsInventoryWhitelisted;
    
    u32 offset = ItemValidity(invslot_addr);
    if (offset == 0)
        goto ItemNotInventoryWhitelisted;

    u8 point = *(u8 *)(offset+1);
    point = (point << 27);
    point = (point >> 31);

    ItemIsInventoryWhitelisted:
    return 1;
    
    ItemNotInventoryWhitelisted:
    return 0;
}