librespot/playback/src/audio_backend/mod.rs

use crate::config::AudioFormat;
use crate::decoder::AudioPacket;
use std::io;

pub trait Open {
    fn open(_: Option<String>, format: AudioFormat) -> Self;
}

pub trait Sink {
    fn start(&mut self) -> io::Result<()>;
    fn stop(&mut self) -> io::Result<()>;
    fn write(&mut self, packet: &AudioPacket) -> io::Result<()>;
}

pub type SinkBuilder = fn(Option<String>, AudioFormat) -> Box<dyn Sink>;

pub trait SinkAsBytes {
    fn write_bytes(&mut self, data: &[u8]) -> io::Result<()>;
}

fn mk_sink<S: Sink + Open + 'static>(device: Option<String>, format: AudioFormat) -> Box<dyn Sink> {
    Box::new(S::open(device, format))
}

// reuse code for various backends
macro_rules! sink_as_bytes {
    () => {
        fn write(&mut self, packet: &AudioPacket) -> io::Result<()> {
            use crate::convert::{self, i24};
            use zerocopy::AsBytes;
            match packet {
                AudioPacket::Samples(samples) => match self.format {
                    AudioFormat::F32 => self.write_bytes(samples.as_bytes()),
                    AudioFormat::S32 => {
                        let samples_s32: &[i32] = &convert::to_s32(samples);
                        self.write_bytes(samples_s32.as_bytes())
                    }
                    AudioFormat::S24 => {
                        let samples_s24: &[i32] = &convert::to_s24(samples);
                        self.write_bytes(samples_s24.as_bytes())
                    }
                    AudioFormat::S24_3 => {
                        let samples_s24_3: &[i24] = &convert::to_s24_3(samples);
                        self.write_bytes(samples_s24_3.as_bytes())
                    }
                    AudioFormat::S16 => {
                        let samples_s16: &[i16] = &convert::to_s16(samples);
                        self.write_bytes(samples_s16.as_bytes())
                    }
                },
                AudioPacket::OggData(samples) => self.write_bytes(samples),
            }
        }
    };
}

macro_rules! start_stop_noop {
    () => {
        fn start(&mut self) -> io::Result<()> {
            Ok(())
        }
        fn stop(&mut self) -> io::Result<()> {
            Ok(())
        }
    };
}

#[cfg(feature = "alsa-backend")]
mod alsa;
#[cfg(feature = "alsa-backend")]
use self::alsa::AlsaSink;

#[cfg(feature = "portaudio-backend")]
mod portaudio;
#[cfg(feature = "portaudio-backend")]
use self::portaudio::PortAudioSink;

#[cfg(feature = "pulseaudio-backend")]
mod pulseaudio;
#[cfg(feature = "pulseaudio-backend")]
use self::pulseaudio::PulseAudioSink;

#[cfg(feature = "jackaudio-backend")]
mod jackaudio;
#[cfg(feature = "jackaudio-backend")]
use self::jackaudio::JackSink;

#[cfg(feature = "gstreamer-backend")]
mod gstreamer;
#[cfg(feature = "gstreamer-backend")]
use self::gstreamer::GstreamerSink;

#[cfg(any(feature = "rodio-backend", feature = "rodiojack-backend"))]
mod rodio;

#[cfg(feature = "sdl-backend")]
mod sdl;
#[cfg(feature = "sdl-backend")]
use self::sdl::SdlSink;

mod pipe;
use self::pipe::StdoutSink;

mod subprocess;
use self::subprocess::SubprocessSink;

pub const BACKENDS: &[(&str, SinkBuilder)] = &[
    #[cfg(feature = "alsa-backend")]
    ("alsa", mk_sink::<AlsaSink>),
    #[cfg(feature = "portaudio-backend")]
    ("portaudio", mk_sink::<PortAudioSink>),
    #[cfg(feature = "pulseaudio-backend")]
    ("pulseaudio", mk_sink::<PulseAudioSink>),
    #[cfg(feature = "jackaudio-backend")]
    ("jackaudio", mk_sink::<JackSink>),
    #[cfg(feature = "gstreamer-backend")]
    ("gstreamer", mk_sink::<GstreamerSink>),
    #[cfg(feature = "rodio-backend")]
    ("rodio", rodio::mk_rodio),
    #[cfg(feature = "rodiojack-backend")]
    ("rodiojack", rodio::mk_rodiojack),
    #[cfg(feature = "sdl-backend")]
    ("sdl", mk_sink::<SdlSink>),
    ("pipe", mk_sink::<StdoutSink>),
    ("subprocess", mk_sink::<SubprocessSink>),
];

pub fn find(name: Option<String>) -> Option<SinkBuilder> {
    if let Some(name) = name {
        BACKENDS
            .iter()
            .find(|backend| name == backend.0)
            .map(|backend| backend.1)
    } else {
        Some(
            BACKENDS
                .first()
                .expect("No backends were enabled at build time")
                .1,
        )
    }
}