I'm new to c# and I'm learning it just now to switch from Godot to Stride so I'm interested in Data Oriented Design. I was just now experimenting with structs with a silly example and was focused on struct padding; the string should be 8 bytes while the enum is 1 byte so i expected not more than 1 or 3 byte of padding, but the sum ends up being 16 no matter the order... does it always have to allign with the biggest field? how does this work?
using System.Runtime.InteropServices;
[StructLayout(LayoutKind.Explicit)]
struct Entity {
public enum Race : byte { ALIEN, HUMAN };
static private int _max_rand_num = 9999;
static private string[][] _possibleNames = {
new string[]{"Vorp", "Zeep", "Bizr", "Zub", "Wobt"}, // alien names
new string[]{"Carl", "Greta", "Seb", "Xiang", "Sierra"} // human names
};
[FieldOffset(0)] public readonly string name;
[FieldOffset(8)] public readonly Race race;
public Entity()
{
Random rand = new Random();
race = (Race)rand.Next(Enum.GetValues(typeof(Race)).Length);
string[] race_names = _possibleNames[(int)race];
name = race_names[rand.Next(0, race_names.Length)] + rand.Next(_max_rand_num);
}
public override string ToString()
{
return $"Race: {race}, Name: {name}";
}
}
class Program {
public static unsafe void Main(string[] args)
{
Entity rand_entity = new Entity();
Console.WriteLine(
$"{rand_entity}, string size = {sizeof(string*)}, enum size = {sizeof(Entity.Race)}, together = {sizeof(Entity)}");
}
}
