@Override
public ItemStack decrStackSize (int slot, int amount) {
if (contents[slot] != null) {
ItemStack ret;
if (contents[slot].stackSize <= amount) { //not enough items
ret = contents[slot];
contents[slot] = null;
} else { //enough items
ret = contents[slot].splitStack(amount);
if (contents[slot].stackSize == 0) contents[slot] = null;
}
this.markDirty();
return ret;
}
return null;
}