Fix: missing header includes and add generator declarations

src/generators.h

@@ -4,6 +4,9 @@
 #ifndef GENERATORS_H_
 #define GENERATORS_H_
 
+#include "math.h"
+#include <cstdint>
+
 #include "wave.h"
 
 /*! Generate sine wave data
@@ -11,4 +14,29 @@
  */
 sample_table_t gen_sin();
 
+/*! Generate square wave data
+    @return a table of values
+ */
+sample_table_t gen_squ();
+
+/*! Generate triangle wave data
+    @return a table of values
+ */
+sample_table_t gen_tri();
+
+/*! Generate triangle wave data
+    @return a table of values
+ */
+sample_table_t gen_tri();
+
+/*! Generate saw wave data
+    @return a table of values
+ */
+sample_table_t gen_saw();
+
+/*! Generate ramp wave data
+    @return a table of values
+ */
+sample_table_t gen_ramp();
+
 #endif // GENERATORS_H_