get a table struct with informations about a bunch of containers

container.lua

function tablelength(T)
  local count = 0
  for _ in pairs(T) do count = count + 1 end
  return count
end

function makeInventoriesHash (containers)
  inputHash = {
    -- Inventory by inputs
    inputs = {},
    -- Consolidated inventories
    global = {},
    -- All item names found
    names = {},
    -- Containers with more than one type of items, by index
    multiItemContainers = {}
  }

  for i, input in pairs(containers) do
    inventoryHash = {}
    inventory = input.chest:getInventories()[1]
    size = inventory.size - 1;

    for i = 0, size, 1 do
      stack = inventory:getstack(i)

      if stack.item.type then
        name = stack.item.type.name
        qty = stack.count
        if not inventoryHash[name] then 
         inventoryHash[name] = 0
         table.insert(inputHash.names, name)
        end
        if not inputHash.global[name] then
          inputHash.global[name] = 0
        end
        inventoryHash[name] = inventoryHash[name] + qty
        inputHash.global[name] = inputHash.global[name] + qty
      end
    end
    inputHash.inputs[i] = inventoryHash;

    if tablelength(inventoryHash) > 1 then 
      table.insert(inputHash.multiItemContainers, i)
    end
  end

  return inputHash;
end