ACE3/addons/core/functions/fn_getTurretIndex.sqf

/*
 * Author: commy2
 *
 * Get the turret index of a units current turret.
 *
 * Argument:
 * 0: Unit, not the vehicle (as in not a car but the player) (Object)
 *
 * Return value:
 * Turret index array or config path. E.g: [0] for gunner or [0,0] for commander. Returns empty array if unit is not in a turret. (Array)
 */

private ["_unit", "_vehicle", "_turrets", "_units", "_index"];

_unit = _this select 0;
_vehicle = vehicle _unit;

//_turrets = [typeOf _vehicle] call FUNC(getTurrets);
_turrets = allTurrets [_vehicle, true];

_units = [];
{
  _units pushBack (_vehicle turretUnit _x);
} forEach _turrets;

_index = _units find _unit;

if (_index == -1) exitWith {[]};

_turrets select _index;