Large Chest Overflow Protection

Large Chest Overflow Protection & Math Safety

The Integer Overflow Problem

In Java and Minecraft, inventory stack calculations use 32-bit signed integers (int). The maximum representable value of a signed 32-bit integer is: $$I_{\max} = 2^{31} - 1 = 2,147,483,647$$

When a Large Chest (54 inventory slots) contains maximum stacks of items, calculating the sum total of items inside the container sums across all 54 slots.

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🧮 Safety Threshold Calculation

If every slot in a 54-slot Large Chest holds a stack of size $L$: $$\text{Total Chest Items} = 54 \times L$$

To prevent $\text{Total Chest Items}$ from exceeding $I_{\max}$: $$54 \times L \le 2,147,483,647$$ $$L \le \frac{2,147,483,647}{54} \approx 39,768,215.68$$

Thus, the Absolute Safety Threshold for stack limits is: $$L_{\text{safe}} = 39,768,215$$

Overflow Impact Table

Stack Limit ($L$)	54-Slot Chest Total Items	Integer Status	Risk
128 (Default)	$6,912$	Safe ($< 2.14\text{B}$)	Zero risk
1,000,000	$54,000,000$	Safe ($< 2.14\text{B}$)	Zero risk
39,768,215	$2,147,483,610$	Safe ($< 2.14\text{B}$)	Recommended Maximum Safe Cap
40,000,000	$2,160,000,000$	Overflow! (Wraps to $-2,134,967,296$)	Item deletion / container corruption

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🛠️ Double-Precision Quick-Crafting Math

In AbstractContainerMenuMixin, vanilla quick-crafting division math is overwritten to use 64-bit double precision floating point math to prevent precision loss and negative integer wrapping when dragging huge stack sizes:

@Mixin(AbstractContainerMenu.class)
public class AbstractContainerMenuMixin {
    @Overwrite
    public static int getQuickCraftPlaceCount(int quickCraftSlotsSize, int quickCraftingType, ItemStack itemStack) {
        return switch (quickCraftingType) {
            case 0 -> (int) ((double) itemStack.getCount() / (double) quickCraftSlotsSize);
            case 1 -> 1;
            case 2 -> itemStack.getMaxStackSize();
            default -> itemStack.getCount();
        };
    }
}