voice interface and type checks

synth/ivoice.h

@@ -0,0 +1,25 @@
+#pragma once
+
+namespace trnr {
+struct ivoice {
+    virtual ~ivoice() = default;
+    virtual float process_sample() = 0;
+    virtual bool is_busy() = 0;
+    virtual void set_samplerate(double samplerate) = 0;
+    virtual void note_on(int _note, float _velocity) = 0;
+    virtual void note_off() = 0;
+    virtual void modulate_pitch(float _pitch) = 0;
+};
+
+// check if a template derives from ivoice
+template <class derived>
+struct is_convertible {
+    template <class T>
+    static char test(T*);
+
+    template <class T>
+    static double test(...);
+
+    static const bool value = sizeof(test<ivoice>(static_cast<derived*>(0))) == 1;
+};
+}