al_get_haptic_effect_duration - Allegro 5 API

       Returns  the  estimated  duration  in  seconds of a single loop of the given haptic effect.  The effect’s
       effect.replay must have been filled in correctly before using this function.

       al_get_haptic_effect_duration - Allegro 5 API

       5.1.9

              [UnstableAPI]: Perhaps could be simplified due to limited support for all  the  exposed  features
              across all of the platforms.  Awaiting feedback from users.

Allegro reference manual                                                  al_get_haptic_effect_duration(3alleg5)

              #include <allegro5/allegro.h>

              double al_get_haptic_effect_duration(ALLEGRO_HAPTIC_EFFECT * effect)