public class ItemStackInventory implements IInventory {
    private final EntityPlayer player;
    private final ItemStack itemStack;
    private ItemStack[] inventory;
    private int size;

    public ItemStackInventory(EntityPlayer player, ItemStack itemStack, int size) {
        this.player = player;
        this.itemStack = itemStack;
        this.size = size;
        this.inventory = new ItemStack[size];
        loadFromNBT();
    }

    private void loadFromNBT() {
        if (!itemStack.hasTagCompound()) {
            itemStack.setTagCompound(new NBTTagCompound());
        }
        NBTTagList tagList = itemStack.getTagCompound().getTagList("Items", 10);
        for (int i = 0; i < tagList.tagCount(); i++) {
            NBTTagCompound tag = tagList.getCompoundTagAt(i);
            int slot = tag.getByte("Slot") & 255;
            if (slot < size) {
                inventory[slot] = ItemStack.loadItemStackFromNBT(tag);
            }
        }
    }

    private void saveToNBT() {
        if (!itemStack.hasTagCompound()) {
            itemStack.setTagCompound(new NBTTagCompound());
        }
        NBTTagList tagList = new NBTTagList();
        for (int i = 0; i < inventory.length; i++) {
            if (inventory[i] != null) {
                NBTTagCompound tag = new NBTTagCompound();
                tag.setByte("Slot", (byte) i);
                inventory[i].writeToNBT(tag);
                tagList.appendTag(tag);
            }
        }
        itemStack.getTagCompound().setTag("Items", tagList);
    }

    @Override
    public int getSizeInventory() {
        return size;
    }

    @Override
    public ItemStack getStackInSlot(int index) {
        return inventory[index];
    }

    @Override
    public void setInventorySlotContents(int index, ItemStack itemStack) {
        inventory[index] = itemStack;
        markDirty();
    }

    @Override
    public String getInventoryName() {
        return itemStack.getDisplayName();
    }

    @Override
    public boolean hasCustomInventoryName() {
        return true;
    }

    @Override
    public ItemStack decrStackSize(int index, int count) {
        if (inventory[index] != null) {
            ItemStack itemstack;
            if (inventory[index].stackSize <= count) {
                itemstack = inventory[index];
                inventory[index] = null;
            } else {
                itemstack = inventory[index].splitStack(count);
                if (inventory[index].stackSize == 0) {
                    inventory[index] = null;
                }
            }
            markDirty();
            return itemstack;
        }
        return null;
    }

    @Override
    public ItemStack getStackInSlotOnClosing(int index) {
        if (inventory[index] != null) {
            ItemStack itemstack = inventory[index];
            inventory[index] = null;
            markDirty();
            return itemstack;
        }
        return null;
    }

    @Override
    public boolean isUseableByPlayer(EntityPlayer player) {
        return true;
    }

    @Override
    public void openInventory() {
    }

    @Override
    public void closeInventory() {
        System.out.println(itemStack.getTagCompound());
    }

    @Override
    public int getInventoryStackLimit() {
        return 64;
    }

    @Override
    public void markDirty() {
        saveToNBT();
    }

    @Override
    public boolean isItemValidForSlot(int index, ItemStack stack) {
        return true;
    }

}