philfleck/UnityNativeTool

Tool created mainly to solve old problem with reloading native plugins without the need to reopen Unity Editor.

Features / overview

Automaticly unloads native plugins after stopping game and loads them when needed
You can unload/reload them manually, even when game is playing
No code change is required (use usual [DllImport])
Low level interface callbacks UnityPluginLoad and UnityPluginUnload do fire
Works on Windows, Linux and Mac
Ability to log native calls to file in order to diagnose crashes caused by them

Download and add unity package from releases.
In project settings, set Api Compatibility Level to .NET 4.x or above.
Edit > Project Settings > Player > Other Settings > Api Compatibility Level
Check Allow 'unsafe' code.
Edit > Project Settings > Player > Other Settings > Allow 'unsafe' code
Set execution order of script UnityNativeTool.DllManipulatorScript to be the lowest of all scripts in game (at least of scripts that use native functions), e.g -10000.
Edit > Project Settings > Script Execution Order
One game object in the scene needs to have DllManipulatorScript on it. (This script calls DontDestroayOnLoad(gameObject) and deletes itself when dupliacate is found, so you don't have to worry about switching scenes).

Your plugin files must be at path specified in options. By default, add __ (two underscores) at the beginning of your dll files in the Assets/Plugins folder (e.g. on Windows, plugin named FastCalcs should be at path Assets\Plugins\__FastCalcs.dll).
By default, all native functions in main scripts assembly will be mocked (i.e. will be handled by this tool instead of Unity, which allows them to be unloaded). You can change this in options and use provided attributes to specify that by yourself (these are in UnityNativeTool namespace).
If something is not working, first check out available options (and read their descriptions), then report an issue.
Options are accessible via DllManipulatorScript editor or window.
Although this tool presumably works in builded game, it's intended to be used in editor.

Low level callbacks such as UnityPluginLoad are not supported (right now).
Marshaling parameter attributes other than [MarshalAs], [In] and [Out] are not supported.
Properties MarshalCookie, MarshalType, MarshalTypeRef and SafeArrayUserDefinedSubType on [MarshalAs] attribute are not supported (due to Mono bug).
Explicitly specifying UnmanagedType.LPArray in [MarshalAs] is not supported (due to another Mono bug). Note that this should be default for array types, so in trivial situations you wouldn't need to use it.
Properties ExactSpelling and PreserveSig on [DllImport] attribute are not supported (as if anyone uses them).
UnityRenderingExtEvent and UnityRenderingExtQuery callbacks don't fire.
Threads that execute past OnApplicationQuit event are not-very-well handled (usualy not something to worry about).

Some of the sources I based my code on (as you often say, this wouldn't be possible without):