Data Center Modloader

A Rust-based modloader for the Unity game Data Center by Waseku.

Built on MelonLoader with a Rust FFI bridge — write mods in Rust with safe wrappers!

Quick Start

1. Install MelonLoader

Download the MelonLoader installer from GitHub and install it for Data Center.exe.

2. Build the Modloader

cargo build --release
dotnet build -c Release csharp/DataCenterModLoader/

3. Deploy

.\tools\install.ps1

4. Launch the Game

Start Data Center through Steam. You should see the MelonLoader console with the modloader banner.

Writing a Rust Mod

Create a new Rust library crate with crate-type = ["cdylib"] and depend on dc_api:

use dc_api::*;

static mut API: Option<Api> = None;

#[no_mangle]
pub extern "C" fn mod_info() -> ModInfo {
    ModInfo::new("my_mod", "My Mod", "1.0.0", "YourName", "Does cool stuff")
}

#[no_mangle]
pub extern "C" fn mod_init(api: &'static GameAPI) -> bool {
    let api = unsafe { Api::from_raw(api) };
    api.log_info("Hello from Rust!");
    unsafe { API = Some(api); }
    true
}

#[no_mangle]
pub extern "C" fn mod_update(dt: f32) {
    let api = unsafe { API.as_ref().unwrap() };
    // Your per-frame logic here
}

Build it with cargo build --release and copy the .dll to the game's Mods/native/ folder.

Handling Game Events

Mods can optionally export mod_on_event to react to game events dispatched via Harmony hooks:

use dc_api::events::{self, Event};

#[no_mangle]
pub extern "C" fn mod_on_event(event_id: u32, event_data: *const u8, data_size: u32) {
    let Some(event) = events::decode(event_id, event_data, data_size) else { return };
    let api = unsafe { API.as_ref().unwrap() };

    match event {
        Event::MoneyChanged { old_value, new_value, delta } => {
            api.log_info(&format!("Money: ${:.2} -> ${:.2}", old_value, new_value));
        }
        Event::ServerBroken => {
            api.log_warning("A server broke down!");
        }
        Event::DayEnded { day } => {
            api.log_info(&format!("Day {} started", day));
        }
        _ => {}
    }
}

Available Events

ID	Event	Data	Trigger
100	MoneyChanged	old_value, new_value, delta	Player.UpdateCoin
101	XPChanged	old_value, new_value, delta	Player.UpdateXP
102	ReputationChanged	old_value, new_value, delta	Player.UpdateReputation
200	ServerPowered	powered_on: bool	Server.PowerButton
201	ServerBroken	—	Server.ItIsBroken
202	ServerRepaired	—	Server.RepairDevice
203	ServerInstalled	—	Server.ServerInsertedInRack
300	DayEnded	day: u32	Day counter change in TimeController
400	CustomerAccepted	customer_id: i32	MainGameManager.ButtonCustomerChosen
500	ShopCheckout	—	ComputerShop.ButtonCheckOut
600	EmployeeHired	—	HRSystem.ButtonConfirmHire
601	EmployeeFired	—	HRSystem.ButtonConfirmFireEmployee
700	GameSaved	—	SaveSystem.SaveGame
701	GameLoaded	—	SaveSystem.Load

Mod Config System

The modloader includes a runtime configuration system that lets mods register settings (bools, ints, floats) editable through an in-game IMGUI panel.

• Press F8 to toggle the Mod Settings panel
• Or click Settings in the main menu and choose "Mod Settings"
• All values are persisted to UserData/ModConfigs/<modId>.json

For C# MelonLoader Mods

using DataCenterModLoader;

// Set display info (shown in the panel header)
ModConfigSystem.SetModInfo("my_mod", "YourName", "1.0.0");

// Register options
ModConfigSystem.RegisterBoolOption("my_mod", "god_mode", "God Mode", false, "Prevents all damage");
ModConfigSystem.RegisterIntOption("my_mod", "speed", "Move Speed", 5, 1, 20, "Speed multiplier");
ModConfigSystem.RegisterFloatOption("my_mod", "gravity", "Gravity", 1.0f, 0.0f, 3.0f);

// Read values at any time
bool godMode = ModConfigSystem.GetBoolValue("my_mod", "god_mode");
int speed    = ModConfigSystem.GetIntValue("my_mod", "speed", 5);

For Rust Native Mods

Rust mods register config entries through the FFI bridge automatically via the dc_api config functions. See crates/dc_api for details.

Full API reference: docs/mod_config_system.md

Architecture

Game (Data Center — Unity 6, IL2CPP)
  └── MelonLoader v0.7.2
        └── RustBridge.dll (C# MelonMod)
              ├── Harmony patches on game methods → Event System
              ├── GameAPI function pointer table  → Polling API (v1/v2)
              └── FFI Bridge
                    └── Mods/native/*.dll (Rust cdylib mods)
                          ├── mod_init(api)       ← receives GameAPI table
                          ├── mod_update(dt)      ← called every frame
                          ├── mod_on_event(id,..) ← receives Harmony events
                          └── mod_shutdown()      ← called on quit

Project Structure

├── csharp/DataCenterModLoader/
│   ├── Core.cs                   MelonMod entry point + Harmony registration
│   ├── FFIBridge.cs              Loads Rust DLLs, resolves exports, dispatches
│   ├── GameAPI.cs                Function pointer table (polling API v1/v2)
│   ├── GameHooks.cs              Safe Il2Cpp accessor wrappers
│   ├── EventSystem.cs            Event IDs, data structs, EventDispatcher
│   └── HarmonyPatches.cs         Harmony patches → fires events to Rust mods
├── crates/dc_api/
│   ├── src/lib.rs                GameAPI struct, Api wrapper, FFI type aliases
│   └── src/events.rs             Event types, data structs, decode() function
├── crates/dc_example_mod/        Example Rust mod (infinite money + events)
├── tools/dump/                   Cpp2IL type dump
├── tools/install.ps1             Build & deploy to game directory
├── tools/dump_types.ps1          Run Cpp2IL type dumper
└── tools/find_type.ps1           Search Il2Cpp types by name

Game Info

Property	Value
Engine	Unity 6000.3.12f1 (IL2CPP)
Developer	Waseku
Install Path	C:\Program Files (x86)\Steam\steamapps\common\Data Center

Documentation

Document	Description
Mod Config System	Developer guide for registering and using mod settings from C# mods
Game API Reference	Il2Cpp API reference for game classes (Server, Technician, PlayerManager, etc.)
Multiplayer Roadmap	Design doc and roadmap for the multiplayer mod
Security & Stability Report	Security and stability analysis of the C#/Rust bridge and runtime behavior

Troubleshooting

Il2CppAssemblyGenerator NullReferenceException after game version/engine change

If you switched to a different Data Center build (or Unity/Il2Cpp metadata changed), cached MelonLoader interop output may no longer match.

1. Close the game.
2. Delete:
   • MelonLoader/Il2CppAssemblies/
   • MelonLoader/Il2CppAssemblyGenerator/
   • MelonLoader/Dependencies/Il2CppAssemblyGenerator/Cpp2IL/cpp2il_out/ (if present)
3. Reinstall/repair MelonLoader v0.7.2 for the current game build.
4. Start once without extra mods to let interop assemblies regenerate.

License

MIT