add support for jack audio connection kit

Cargo.toml

@@ -52,6 +52,7 @@ url = "1.3"
 alsa            = { git = "https://github.com/plietar/rust-alsa", optional = true }
 portaudio-rs    = { version = "0.3.0", optional = true }
 libpulse-sys    = { version = "0.0.0", optional = true }
+jack            = { version = "0.5.3", optional = true }
 
 [build-dependencies]
 rand            = "0.3.13"
@@ -62,6 +63,7 @@ protobuf_macros = { git = "https://github.com/plietar/rust-protobuf-macros", fea
 alsa-backend = ["alsa"]
 portaudio-backend = ["portaudio-rs"]
 pulseaudio-backend = ["libpulse-sys"]
+jackaudio-backend = ["jack"]
 
 with-tremor = ["librespot-audio/with-tremor"]
 with-lewton = ["librespot-audio/with-lewton"]

src/audio_backend/jackaudio.rs

@@ -0,0 +1,79 @@
+use std::io;
+use super::{Open, Sink};
+use jack::prelude::{AudioOutPort, AudioOutSpec, Client, JackControl, ProcessScope, AsyncClient, client_options, ProcessHandler, Port };
+use std::sync::mpsc::{sync_channel, SyncSender, Receiver};
+
+#[allow(dead_code)]
+pub struct JackSink {
+    send: SyncSender<i16>,
+    active_client: AsyncClient<(),JackData>,
+}
+
+pub struct JackData {
+    rec: Receiver<i16>,
+    port_l: Port<AudioOutSpec>,
+    port_r: Port<AudioOutSpec>,
+}
+
+fn pcm_to_f32(sample: i16) -> f32 {
+    let mut f: f32 = sample as f32 / 32768.0;
+    if f > 1.0 { f = 1.0; }
+    if f < -1.0 { f = -1.0; }
+    f
+}
+
+impl ProcessHandler for JackData {
+    fn process(&mut self, _: &Client, ps: &ProcessScope) -> JackControl {
+        // get output port buffers
+        let mut out_r = AudioOutPort::new(&mut self.port_r, ps);
+        let mut out_l = AudioOutPort::new(&mut self.port_l, ps);
+        let buf_r: &mut [f32] = &mut out_r;
+        let buf_l: &mut [f32] = &mut out_l;
+        // get queue iterator
+        let mut queue_iter = self.rec.try_iter();
+
+        let buf_size = buf_r.len();
+        for i in 0..buf_size {
+            buf_r[i] = pcm_to_f32(queue_iter.next().unwrap_or(0));
+            buf_l[i] = pcm_to_f32(queue_iter.next().unwrap_or(0));
+        }
+        JackControl::Continue
+    }
+}
+
+impl Open for JackSink {
+    fn open(client_name: Option<String>) -> JackSink {
+        info!("Using jack sink!");
+
+        let client_name = client_name.unwrap_or("librespot".to_string());
+        let (client, _status) = Client::new(&client_name[..], client_options::NO_START_SERVER).unwrap();
+        let ch_r = client.register_port("out_0", AudioOutSpec::default()).unwrap();
+        let ch_l = client.register_port("out_1", AudioOutSpec::default()).unwrap();
+        // buffer for samples from librespot (~10ms)
+        let (tx, rx) = sync_channel(2*1024*4);
+        let jack_data = JackData { rec: rx, port_l: ch_l, port_r: ch_r };
+        let active_client = AsyncClient::new(client, (), jack_data).unwrap();
+
+        JackSink { send: tx, active_client: active_client }
+   }
+}
+
+impl Sink for JackSink {
+    fn start(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+
+    fn stop(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+
+    fn write(&mut self, data: &[i16]) -> io::Result<()> {
+        for s in data.iter() {
+            let res = self.send.send(*s);
+            if res.is_err() {
+                error!("jackaudio: cannot write to channel");
+            }
+        }
+        Ok(())
+    }
+}

src/audio_backend/mod.rs

@@ -29,6 +29,11 @@ mod pulseaudio;
 #[cfg(feature = "pulseaudio-backend")]
 use self::pulseaudio::PulseAudioSink;
 
+#[cfg(feature = "jackaudio-backend")]
+mod jackaudio;
+#[cfg(feature = "jackaudio-backend")]
+use self::jackaudio::JackSink;
+
 mod pipe;
 use self::pipe::StdoutSink;
 
@@ -41,6 +46,8 @@ pub const BACKENDS : &'static [
     ("portaudio", mk_sink::<PortAudioSink>),
     #[cfg(feature = "pulseaudio-backend")]
     ("pulseaudio", mk_sink::<PulseAudioSink>),
+    #[cfg(feature = "jackaudio-backend")]
+    ("jackaudio", mk_sink::<JackSink>),
     ("pipe", mk_sink::<StdoutSink>),
 ];
 

src/lib.rs

@@ -34,6 +34,9 @@ extern crate portaudio_rs;
 #[cfg(feature = "libpulse-sys")]
 extern crate libpulse_sys;
 
+#[cfg(feature = "jackaudio-backend")]
+extern crate jack;
+
 pub mod audio_backend;
 pub mod discovery;
 pub mod keymaster;