add logic to read and write persistent volume

connect/src/spirc.rs

@@ -196,7 +196,17 @@ fn calc_logarithmic_volume(volume: u16) -> u16 {
     val
 }
 
-fn volume_to_mixer(volume: u16, linear_volume: bool) -> u16 {
+// write linear volume (0..100) to file
+fn write_volume(volume: u16, filepath: Option<String>) {
+    let volume = volume as i32 * 100 / 0xFFFF;
+    let mut file = File::create(filepath.unwrap()).expect("Could not create persistent volume");
+    file.write_all(volume.to_string().as_bytes()).expect("Could not write persistent volume");
+}
+
+fn volume_to_mixer(volume: u16, linear_volume: bool, persist_volume: Option<String>) -> u16 {
+    if persist_volume.is_some() {
+        write_volume(volume, persist_volume);
+    }
     if linear_volume {
         debug!("linear volume: {}", volume);
         volume

src/main.rs

@@ -87,6 +87,19 @@ fn list_backends() {
     }
 }
 
+// read linear volume (0..100) from file
+// convert to 0..0xFFFF scale
+fn read_volume(filepath: String) -> i32 {
+    let mut data = String::new();
+    let mut file = File::open(filepath).expect("Could not open persistent volume");
+    file.read_to_string(&mut data).expect("Could not read persistent volume");
+    let volume = data.trim().parse::<i32>().expect("Persistent volume must be an integer");
+    if volume < 0 || volume > 100 {
+        panic!("Initial volume must be in the range 0-100");
+    }
+    volume * 0xFFFF / 100
+}
+
 #[derive(Clone)]
 struct Setup {
     backend: fn(Option<String>) -> Box<Sink>,
@@ -211,7 +224,7 @@ fn setup(args: &[String]) -> Setup {
     let mixer_name = matches.opt_str("mixer");
     let mixer = mixer::find(mixer_name.as_ref()).expect("Invalid mixer");
 
-    let initial_volume = matches
+    let mut initial_volume = matches
         .opt_str("initial-volume")
         .map(|volume| {
             let volume = volume.parse::<i32>().unwrap();
@@ -222,6 +235,13 @@ fn setup(args: &[String]) -> Setup {
         })
         .unwrap_or(0x8000);
 
+    // check if user has requested persistent volume
+    // if the file exists, override initial volume
+    let persist_volume = matches.opt_str("persist-volume");
+    if persist_volume.is_some() && Path::new(&persist_volume.clone().unwrap()).exists() {
+        initial_volume = read_volume(persist_volume.clone().unwrap());
+    }
+
     let zeroconf_port = matches
         .opt_str("zeroconf-port")
         .map(|port| port.parse::<u16>().unwrap())