Hooks - Starline Lua API

Hook a function by address.

ffi.cdef[[ typedef float (__fastcall *fnGetViewmodelFov)(void*); ]]

local addr = cheat.FindPattern("client.dll", "40 53 48 83 EC 20 ...")
local oGetViewmodelFov
oGetViewmodelFov = hooks.Add(addr, ffi.typeof("fnGetViewmodelFov"), function(self)
    return 120.0
end)

The callback runs on the calling thread. Lua execution is serialized across threads. Callback errors are logged instead of propagating into the game.

hooks.Add

local original = hooks.Add(address, ctype, callback)

Installs an inline hook at address. Returns the original function as a callable FFI pointer of the same type.

Param	Type
`address`	number	target function address (from `cheat.FindPattern`, `cheat.FindExport`, etc.)
`ctype`	ffi ctype	function pointer type created with `ffi.typeof`
`callback`	function	your Lua function, receives the same args as the original

The callback must match the function type. On x64, __fastcall is suitable for all calling conventions.

ffi.cdef[[ typedef void (__fastcall *fnFrameStageNotify)(void*, int); ]]

local oFrameStageNotify
oFrameStageNotify = hooks.Add(
    cheat.FindPattern("client.dll", "..."),
    ffi.typeof("fnFrameStageNotify"),
    function(self, stage)
        if stage == 6 then
            -- pre FRAME_RENDER_START
        end
        oFrameStageNotify(self, stage)
    end
)

hooks.Remove

hooks.Remove(address)

Removes a hook by its target address. Restores the original function bytes. Unknown addresses are ignored silently. Hooks are matched only by address. Do not remove a hook from inside its own detour.

Calling the original

hooks.Add returns the original function as a typed FFI pointer. Call it like any other function:

local result = oGetViewmodelFov(self)

Omit the call to replace the original function.

Lifecycle

hooks.Add is load-time only, same as events.On
Detours are uninstalled when a script is unloaded or disabled
Maximum 32 hooks per script
Cannot hook the address of a function inside Starline’s own module
The FFI callback stays alive until the hook is removed

Low-level API

For advanced use, the raw primitives are available:

local orig_addr, err = hooks.Create(target_addr, detour_addr)
hooks.Remove(target_addr)

hooks.Create takes two raw addresses and returns the trampoline address. Null, duplicate, and protected targets error. Installation failure returns nil, error. hooks.Add is built on top of these and handles FFI callback creation, type casting, and GC anchoring for you.

​hooks.Add

​hooks.Remove

​Calling the original

​Lifecycle

​Low-level API

hooks.Add

hooks.Remove

Calling the original

Lifecycle

Low-level API