libs/sig: triangle wave; sig_ops_tri / sig_new_tri()

Added a triangle wave

3 files changed, 31 insertions, 1 deletions

diff --git a/src/libs/sig/ops_sin.c b/src/libs/sig/ops_sin.c
index da5b371..4acc8e5 100644
--- a/src/libs/sig/ops_sin.c
+++ b/src/libs/sig/ops_sin.c
@@ -50,6 +50,15 @@ static float output_sqr(float rads)
 }
 
 
+static float output_tri(float rads)
+{
+	/* This approximation comes from:
+	 * https://calculushowto.com/triangle-wave-function/
+	 */
+	return M_2_PI * asinf(fabsf(sinf(M_PI * rads)));
+}
+
+
 static float output(void *context, unsigned ticks_ms, float (*output_fn)(float rads))
 {
 	ops_sin_ctxt_t	*ctxt = context;
@@ -87,6 +96,12 @@ static float ops_sqr_output(void *context, unsigned ticks_ms)
 }
 
 
+static float ops_tri_output(void *context, unsigned ticks_ms)
+{
+	return output(context, ticks_ms, output_tri);
+}
+
+
 sig_ops_t	sig_ops_sin = {
 	.size = ops_sin_size,
 	.init = ops_sin_init,
@@ -101,3 +116,11 @@ sig_ops_t	sig_ops_sqr = {
 	.destroy = ops_sin_destroy,
 	.output = ops_sqr_output,
 };
+
+
+sig_ops_t	sig_ops_tri = {
+	.size = ops_sin_size,
+	.init = ops_sin_init,
+	.destroy = ops_sin_destroy,
+	.output = ops_tri_output,
+};
diff --git a/src/libs/sig/sig.c b/src/libs/sig/sig.c
index 87a76c4..203a37a 100644
--- a/src/libs/sig/sig.c
+++ b/src/libs/sig/sig.c
@@ -240,6 +240,12 @@ sig_t * sig_new_sqr(sig_t *hz)
 }
 
 
+sig_t * sig_new_tri(sig_t *hz)
+{
+	return sig_new(&sig_ops_tri, hz);
+}
+
+
 sig_t * sig_new_sub(sig_t *a, sig_t *b)
 {
 	return sig_new(&sig_ops_sub, a, b);
diff --git a/src/libs/sig/sig.h b/src/libs/sig/sig.h
index 917dbc4..9be3012 100644
--- a/src/libs/sig/sig.h
+++ b/src/libs/sig/sig.h
@@ -38,15 +38,16 @@ sig_t * sig_new_round(sig_t *x);
 sig_t * sig_new_scale(sig_t *x, sig_t *min, sig_t *max);
 sig_t * sig_new_sin(sig_t *hz);
 sig_t * sig_new_sqr(sig_t *hz);
+sig_t * sig_new_tri(sig_t *hz);
 sig_t * sig_new_sub(sig_t *a, sig_t *b);
 
 extern sig_ops_t	sig_ops_const;
 extern sig_ops_t	sig_ops_rand;
 extern sig_ops_t	sig_ops_sin;
 extern sig_ops_t	sig_ops_sqr;
+extern sig_ops_t	sig_ops_tri;
 
 /* TODO:
-extern sig_ops_t	sig_ops_tri;
 extern sig_ops_t	sig_ops_saw;
 */