move constants.h and the oscillator into libfm from libfmdsp

lib/constants.h

@@ -0,0 +1,7 @@
+#pragma once
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
+#ifndef M_2PI
+#define M_2PI (M_PI * 2.0)
+#endif

lib/oscillator.c

@@ -0,0 +1,40 @@
+#include "oscillator.h"
+
+void init_oscillator(Oscillator *osc, float frequency, float sample_rate) {
+	osc->phase = 0.0f;
+	osc->phase_increment = (M_2PI * frequency) / sample_rate;
+	osc->sample_rate = sample_rate;
+}
+
+inline void change_oscillator_frequency(Oscillator *osc, float frequency) {
+	osc->phase_increment = (M_2PI * frequency) / osc->sample_rate;
+}
+
+float get_oscillator_sin_sample(Oscillator *osc) {
+	float sample = sinf(osc->phase);
+	advance_oscillator(osc);
+	return sample;
+}
+
+float get_oscillator_cos_sample(Oscillator *osc) {
+	float sample = cosf(osc->phase);
+	advance_oscillator(osc);
+	return sample;
+}
+
+float get_oscillator_sin_multiplier_ni(Oscillator *osc, float multiplier) {
+	float new_phase = osc->phase * multiplier;
+	new_phase -= (new_phase >= M_2PI) ? M_2PI : 0.0f;
+	return sinf(new_phase);
+}
+
+float get_oscillator_cos_multiplier_ni(Oscillator *osc, float multiplier) {
+	float new_phase = osc->phase * multiplier;
+	new_phase -= (new_phase >= M_2PI) ? M_2PI : 0.0f;
+	return cosf(new_phase);
+}
+
+inline void advance_oscillator(Oscillator *osc) {
+	osc->phase += osc->phase_increment;
+	if (osc->phase >= M_2PI) osc->phase -= M_2PI;
+}

lib/oscillator.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "constants.h"
+#include <math.h>
+
+typedef struct {
+	float phase;
+	float phase_increment;
+	float sample_rate;
+} Oscillator;
+
+void init_oscillator(Oscillator *osc, float frequency, float sample_rate);
+void change_oscillator_frequency(Oscillator *osc, float frequency);
+float get_oscillator_sin_sample(Oscillator *osc);
+float get_oscillator_cos_sample(Oscillator *osc);
+float get_oscillator_sin_multiplier_ni(Oscillator *osc, float multiplier);
+float get_oscillator_cos_multiplier_ni(Oscillator *osc, float multiplier);
+void advance_oscillator(Oscillator *osc);