flesh out synthesizer module

src/wavetable.rs

@@ -1,7 +1,8 @@
 pub trait Wavetable {
-    type OutputType;
+    type OutputType: Default + Copy;
     /// get next sample
     fn next(&mut self) -> Self::OutputType;
+    fn size(&self) -> usize;
 }
 
 /// non-interpolated, simple wavetable that produces the next sample
@@ -13,19 +14,23 @@ pub struct SimpleWavetable<'a, T: Copy> {
     index: usize,
 }
 
-impl<'a, T: Copy> Wavetable for SimpleWavetable<'a, T> {
+impl<'a, T: Copy + Default> Wavetable for SimpleWavetable<'a, T> {
     type OutputType = T;
     fn next(&mut self) -> Self::OutputType {
         let value = self.table[self.index];
         self.index += 1;
-        if self.index > self.table.len() {
+        if self.index > self.table.len() - 1 {
             self.index = 0;
         }
         value
     }
+
+    fn size(&self) -> usize {
+        self.table.len()
+    }
 }
 
-impl<'a, T: Copy> SimpleWavetable<'a, T> {
+impl<'a, T: Copy + Default> SimpleWavetable<'a, T> {
     pub fn new(table: &'a [T]) -> Self {
         Self { table, index: 0 }
     }