al_get_audio_stream_length_secs - Allegro 5 API

       Return the length of the stream in seconds, if known.  Otherwise returns zero.

       Currently   this   can   only   be   called   on   streams  created  with  al_load_audio_stream(3alleg5),
       al_play_audio_stream(3alleg5), al_load_audio_stream_f(3alleg5) or al_play_audio_stream_f(3alleg5).

       al_get_audio_stream_length_secs - Allegro 5 API

al_get_audio_stream_position_secs(3alleg5)

Allegro reference manual                                                al_get_audio_stream_length_secs(3alleg5)

              #include <allegro5/allegro_audio.h>

              double al_get_audio_stream_length_secs(ALLEGRO_AUDIO_STREAM *stream)