Added audio backends, fifo support, see #78

fifo.h

@@ -14,4 +14,26 @@ struct audio_data {
     pthread_mutex_t mutex;
 };
 
-void* input_fifo(void* data);
+struct audio_impl {
+    const char* name;
+    void  (*init)(struct audio_data* data);
+    void* (*entry)(void* data);
+};
+
+#define AUDIO_FUNC(F)                                   \
+    .F = (typeof(((struct audio_impl*) NULL)->F)) &F
+
+extern struct audio_impl* audio_impls[4];
+extern size_t audio_impls_idx;
+
+static inline void register_audio_impl(struct audio_impl* impl) { audio_impls[audio_impls_idx++] = impl; }
+
+#define AUDIO_ATTACH(N)                                         \
+    static struct audio_impl N##_var = {                        \
+        .name = #N,                                             \
+        AUDIO_FUNC(init),                                       \
+        AUDIO_FUNC(entry),                                      \
+    };                                                          \
+    void __attribute__((constructor)) _##N##_construct(void) { \
+        register_audio_impl(&N##_var);                          \
+    }