librespot/playback/src/mixer/alsamixer.rs

use super::AudioFilter;
use super::Mixer;
use std::env;
use std::error::Error;

use alsa;

#[derive(Clone)]
pub struct AlsaMixer {
    card: String,
    mixer: String,
    index: u32,
}

impl AlsaMixer {

    fn map_volume(&self, set_volume:Option<u16>) -> Result<(u16),Box<Error>> {
        let mixer  = alsa::mixer::Mixer::new(&self.card, false)?;
        let sid    = alsa::mixer::SelemId::new(&*self.mixer, self.index);

        let selem = mixer.find_selem(&sid).expect("Coundn't find SelemId");
        let (min, max) = selem.get_playback_volume_range();
        let cur_vol = selem.get_playback_volume(alsa::mixer::SelemChannelId::mono()).expect("Couldn't get current volume");
        let range = (max - min) as f64;

        let new_vol:u16;

        if let Some(vol) = set_volume {
            let alsa_volume:i64 = ((vol as f64 / 0xFFFF as f64) * range) as i64 + min;
            debug!("Maping volume {:?} [u16] ->> Alsa {:?} [i64]",vol,alsa_volume);
            selem.set_playback_volume_all(alsa_volume).expect("Couldn't set alsa volume");
            new_vol = vol; // Meh
        } else {
            new_vol =  (((cur_vol - min) as f64 / range) * 0xFFFF as f64) as u16;
            debug!("Maping volume {:?} [u16] <<- Alsa {:?} [i64]",new_vol, cur_vol);
        }


        Ok(new_vol)
    }
}

impl Mixer for AlsaMixer {
    fn open(device: Option<String>) -> AlsaMixer {
        let card = env::var("LIBRESPOT_CARD").unwrap_or(device.unwrap_or(String::from("default")));
        let mixer = env::var("LIBRESPOT_MIXER").unwrap_or(String::from("PCM"));
        let index: u32 = 0;
        info!(
            "Setting up new mixer: card:{} mixer:{} index:{}",
            card, mixer, index
        );
        AlsaMixer {
            card: card,
            mixer: mixer,
            index: index,
        }
    }

    fn start(&self) {
    }

    fn stop(&self) {
    }

    fn volume(&self) -> u16 {

        match self.map_volume(None){
                Ok(vol) => vol,
                Err(e)  => {
                        error!("Error getting volume for <{}>, {:?}",self.card, e);
                        0 }
        }
    }

    fn set_volume(&self, volume: u16) {
        match self.map_volume(Some(volume)){
                Ok(_) => (),
                Err(e)  => error!("Error setting volume for <{}>, {:?}",self.card, e),
        }
    }

    fn get_audio_filter(&self) -> Option<Box<AudioFilter + Send>> {
        None
    }
}