Hook virtual functions by offset

[KillStr3aK]

With these changes, we will be able to hook virtual functions based on offset.

Example

Testing StartTouch, Touch, EndTouch hooks on the soccerball in de_dust2

{
    "StartTouch": {
        "offsets": {
            "windows": 143,
            "linux": 142
        }
    },
    "Touch": {
        "offsets": {
            "windows": 144,
            "linux": 143
        }
    },
    "EndTouch": {
        "offsets": {
            "windows": 145,
            "linux": 144
        }
    }
}

public CPhysicsPropMultiplayer? SoccerBall;

public VirtualFunctionVoid<CBaseEntity, CBaseEntity>? OnStartTouch;
public VirtualFunctionVoid<CBaseEntity, CBaseEntity>? OnTouch;
public VirtualFunctionVoid<CBaseEntity, CBaseEntity>? OnEndTouch;

public override void Load(bool hotReload)
{
    RegisterEventHandler<EventRoundStart>((@event, info) =>
    {
        IEnumerable<CPhysicsPropMultiplayer> list = Utilities.FindAllEntitiesByDesignerName<CPhysicsPropMultiplayer>("prop_physics_multiplayer");

        if (!list.Any())
        {
            return HookResult.Continue;
        }

        SoccerBall = list.First();

        if (OnStartTouch == null) (OnStartTouch = new VirtualFunctionVoid<CBaseEntity, CBaseEntity>(SoccerBall, GameData.GetOffset("StartTouch"))).Hook(HookOnStartTouch, HookMode.Pre);
        if (OnTouch == null) (OnTouch = new VirtualFunctionVoid<CBaseEntity, CBaseEntity>(SoccerBall, GameData.GetOffset("Touch"))).Hook(HookOnTouch, HookMode.Pre);
        if (OnEndTouch == null) (OnEndTouch = new VirtualFunctionVoid<CBaseEntity, CBaseEntity>(SoccerBall, GameData.GetOffset("EndTouch"))).Hook(HookOnEndTouch, HookMode.Pre);

        return HookResult.Continue;
    });
}

public override void Unload(bool hotReload)
{
    OnStartTouch?.Unhook(HookOnStartTouch, HookMode.Pre);
    OnTouch?.Unhook(HookOnTouch, HookMode.Pre);
    OnEndTouch?.Unhook(HookOnEndTouch, HookMode.Pre);
}

private HookResult HookOnStartTouch(DynamicHook h)
{
    CBaseEntity entity = h.GetParam<CBaseEntity>(0);
    CBaseEntity otherEntity = h.GetParam<CBaseEntity>(1);

    if (entity != SoccerBall && otherEntity != SoccerBall)
        return HookResult.Continue;

    Console.WriteLine($"[OnStartTouch] {otherEntity.DesignerName} ({otherEntity.Index}) started touching {entity.DesignerName} ({entity.Index})");
    return HookResult.Continue;
}

private HookResult HookOnTouch(DynamicHook h)
{
    CBaseEntity entity = h.GetParam<CBaseEntity>(0);
    CBaseEntity otherEntity = h.GetParam<CBaseEntity>(1);

    if (entity != SoccerBall && otherEntity != SoccerBall)
        return HookResult.Continue;

    Console.WriteLine($"[OnTouch] {otherEntity.DesignerName} ({otherEntity.Index}) is touching {entity.DesignerName} ({entity.Index})");
    return HookResult.Continue;
}

private HookResult HookOnEndTouch(DynamicHook h)
{
    CBaseEntity entity = h.GetParam<CBaseEntity>(0);
    CBaseEntity otherEntity = h.GetParam<CBaseEntity>(1);

    if (entity != SoccerBall && otherEntity != SoccerBall)
        return HookResult.Continue;

    Console.WriteLine($"[OnEndTouch] {otherEntity.DesignerName} ({otherEntity.Index}) is no longer touching {entity.DesignerName} ({entity.Index})");
    return HookResult.Continue;
}

Debug output:

10:52:04 [INFO] (cssharp:Core) Creating function CBaseEntity_142
[Info] - Trampoline - Bounds of relative addresses accessed [0xffffffffffffffff, (nil)]
[Info] - Trampoline - Attempting to allocate trampoline within +-2GB range of 0x7f66a15159c0
[Info] - Trampoline - Allocated trampoline at 0x7f6721514000 (using 1 attempts)
10:52:04 [INFO] (cssharp:Core) Creating function CBaseEntity_143
[Info] - Trampoline - Bounds of relative addresses accessed [0xffffffffffffffff, (nil)]
[Info] - Trampoline - Attempting to allocate trampoline within +-2GB range of 0x7f66a1050e60
[Info] - Trampoline - Allocated trampoline at 0x7f672104f000 (using 1 attempts)
10:52:04 [INFO] (cssharp:Core) Creating function CBaseEntity_144
[Info] - Trampoline - Bounds of relative addresses accessed [0xffffffffffffffff, (nil)]
[Info] - Trampoline - Attempting to allocate trampoline within +-2GB range of 0x7f66a1050a40
[Info] - Trampoline - Allocated trampoline at 0x7f66d0e97000 (using 1 attempts)
[OnStartTouch] worldent (0) started touching prop_physics_multiplayer (269)
[OnTouch] worldent (0) is touching prop_physics_multiplayer (269)
[OnTouch] prop_physics_multiplayer (269) is touching worldent (0)

Developers should be aware that they are hooking the virtual function, which is shared between instances (same as with signatures)

[KillStr3aK]

This and related constructors are internal because they should not be used randomly. People should only use the exposed VirtualFunctionVoid and VirtualFunctionWithReturn versions

[Prefix]

@roflmuffin +1 on this

[KillStr3aK]

@roflmuffin +1 on this

my second review has to be resolved before this pr is ready

[Prefix]

@roflmuffin +1 on this

my second review has to be resolved before this pr is ready

what is second pr? can community help you somehow?

[KillStr3aK]

@roflmuffin +1 on this

my second review has to be resolved before this pr is ready

what is second pr? can community help you somehow?

#617 (comment)

this is the second review

[KillStr3aK]

virtual functions that has been created by an offset are now stored as {typeof(TArg1).Name}_{OffsetNum}, for e.g.:
10:52:04 [INFO] (cssharp:Core) Creating function CBaseEntity_142

TArg1 is meant to represent the originating class of the function

@roflmuffin Unsure of the interaction if someone hooks a CBaseEntity and a CCSPlayerPawn with the same offset.

12:40:05 [INFO] (cssharp:Core) Creating function CBaseEntity_142
[Info] - Trampoline - Bounds of relative addresses accessed [0xffffffffffffffff, (nil)]
[Info] - Trampoline - Attempting to allocate trampoline within +-2GB range of 0x7fc5331159c0
[Info] - Trampoline - Allocated trampoline at 0x7fc5b3114000 (using 1 attempts)

12:40:05 [INFO] (cssharp:Core) Creating function CPhysicsPropMultiplayer_142

12:40:05 [INFO] (cssharp:Core) Creating function CBaseEntity_143
[Info] - Trampoline - Bounds of relative addresses accessed [0xffffffffffffffff, (nil)]
[Info] - Trampoline - Attempting to allocate trampoline within +-2GB range of 0x7fc532c50e60
[Info] - Trampoline - Allocated trampoline at 0x7fc5b2c4f000 (using 1 attempts)

12:40:05 [INFO] (cssharp:Core) Creating function CBaseEntity_144
[Info] - Trampoline - Bounds of relative addresses accessed [0xffffffffffffffff, (nil)]
[Info] - Trampoline - Attempting to allocate trampoline within +-2GB range of 0x7fc532c50a40

the hook itself is reused, but currently only the latter is called, I believe this could also happen if the same function is hooked with 2 different signatures? (tested it and yes)