The Inventories

In Space Engineers, inventories are objects that are available on a block level. Any block may have any number of inventories available. For example, the standard cargo block has one inventory available, while the assemblers have 2: input (raw materials) and output (product).

We can access these inventories in the programmable block by checking the blocks' InventoryCount property. In this tutorial I will assume you already understand how to use the terminal system, and that you understand the anatomy of a script. I will also assume you have gained an understanding of string interpolation. All of these things are outside of the scope of this tutorial.

MyFixedPoint

Some of the members belonging to the inventory API uses a strange data type called MyFixedPoint. It is a type designed to contain a value much like double or float. The hows and why's of this type is beyond the scope of this tutorial but if you're curious, I found this page explaining the difference between fixed point and floating point decimal values - or you can use your own Google-Fu.

What is important is that you can CAST (convert) the values of these members into a much more useful double type, with which you can do all the operations you'll want easily. All you need to do is this:

double maxVolume = (double) inventory.MaxVolume;

Example 1: Total Cargo Volume and Capacity

The following example will be iterating through all available blocks in the current construct, and adding up how much inventory space we have used and how much inventory space is available. We will not be taking into account block types.

ps: this script will need to be recompiled in order to recognize new blocks placed

readonly List<IMyTerminalBlock> _blocks = new List<IMyTerminalBlock>();
readonly StringBuilder _textBuffer = new StringBuilder(1024);
readonly IMyTextSurface _display;

public Program()
{
    // Retrieve all the blocks which can be found in this construct.
    GridTerminalSystem.GetBlocksOfType<IMyTerminalBlock>(_blocks, block => block.IsSameConstructAs(Me));

    // Configure the programmable block display to show simple text output
    _display = Me.GetSurface(0);
    _display.ContentType = ContentType.TEXT_AND_IMAGE;
    _display.TextPadding = 0.1f;

    // We don't want to do this job too often, so let's just update once every 100 ticks
    Runtime.UpdateFrequency = UpdateFrequency.Update100;
}

public void Main(string argument, UpdateType updateSource)
{
    // A constant for newline - just for readability
    const string br = "\n";

    // Get the cargo information
    var cargoSpace = CalculateCargoSpace(_blocks);

    // Write the cargo information to the programmable block display
    _textBuffer.Clear();
    _textBuffer.Append(br);
    _textBuffer.Append($"  Used volume: {cargoSpace.UsedLiters:N2}L{br}");
    _textBuffer.Append($"  Capacity: {cargoSpace.CapacityLiters:N2}L{br}");
    _textBuffer.Append($"  Usage: {(cargoSpace.UsageRatio * 100):N1} %");
    _display.WriteText(_textBuffer);
}

/// <summary>
///     Calculates the cargo space of the provided blocks
/// </summary>
/// <param name="blocks">A list of blocks to scan for inventories</param>
/// <returns>A value containing cargo space information</returns>
public CargoSpace CalculateCargoSpace(List<IMyTerminalBlock> blocks)
{
    double used = 0;
    double capacity = 0;
    // We iterate through all the blocks,
    foreach (var block in blocks)
    {
        // and then we iterate and retrieve all individual inventories for each of those blocks.
        for (var i = 0; i < block.InventoryCount; i++)
        {
            // If the block has no inventories, block.InventoryCount will be 0,
            // and we will never enter this code block.

            // Get the inventory manager at the index specified by i
            var inventory = block.GetInventory(i);

            // CurrentVolume and MaxVolume are both of the type MyFixedPoint. We will CAST
            // (convert the data type) to a double type instead, which is more useful to us.
            var currentVolume = (double) inventory.CurrentVolume;
            var maxVolume = (double) inventory.MaxVolume;

            // Now we add up the current- and max volumes to our total
            // tally.
            used += currentVolume;
            capacity += maxVolume;
        }
    }

    // When we get here, we've looped through all the inventories in the given blocks,
    // and we can create the final informational object - and return it to the user.
    return new CargoSpace(used, capacity);
}

/// <summary>
///     A simple object to contain the final information about
///     the cargo space
/// </summary>
public struct CargoSpace
{
    /// <summary>
    ///     Create a new CargoSpace object with the given values
    /// </summary>
    /// <param name="usedLiters">The occupied volume in Liters</param>
    /// <param name="capacityLiters">The total available volume in Liters</param>
    public CargoSpace(double usedLiters, double capacityLiters)
    {
        UsedLiters = usedLiters;
        CapacityLiters = capacityLiters;
        UsageRatio = capacityLiters > 0 ? usedLiters / capacityLiters : 1.0;
    }

    /// <summary>
    ///     Contains the occupied inventory volume represented in Liters
    /// </summary>
    public readonly double UsedLiters;

    /// <summary>
    ///     Contains the total available space represented in Liters
    /// </summary>
    public readonly double CapacityLiters;

    /// <summary>
    ///     Contains the usage ratio (a value between 0.0 to 1.0)
    /// </summary>
    public readonly double UsageRatio;
}