libs/sig: square wave; sig_ops_sqr / sig_new_sqr()

This builds minimally upon the existing sine wave code,
just use the sign to drive the signal high or low.

Wikipedia shows a third state for 0 values, but that's for a -1..+1
signal.  I'm producing all 0-1 signals as it's more convenient for
this application, but it seems like it would be awkward to return
.5f for the 0 case.  So 0 is being treated as just another positive
value; high.

1 files changed, 37 insertions, 2 deletions

diff --git a/src/libs/sig/ops_sin.c b/src/libs/sig/ops_sin.c
index 555a682..da5b371 100644
--- a/src/libs/sig/ops_sin.c
+++ b/src/libs/sig/ops_sin.c
@@ -35,7 +35,22 @@ static void ops_sin_destroy(void *context)
 }
 
 
-static float ops_sin_output(void *context, unsigned ticks_ms)
+static float output_sin(float rads)
+{
+	return sinf(rads) * .5f + .5f;
+}
+
+
+static float output_sqr(float rads)
+{
+	if (sinf(rads) < 0.f)
+		return 0.f;
+
+	return 1.f;
+}
+
+
+static float output(void *context, unsigned ticks_ms, float (*output_fn)(float rads))
 {
 	ops_sin_ctxt_t	*ctxt = context;
 	float		rads_per_ms, rads, hz;
@@ -56,7 +71,19 @@ static float ops_sin_output(void *context, unsigned ticks_ms)
 	rads_per_ms = (M_PI * 2.f) * hz * .001f;
 	rads = (float)ticks_ms * rads_per_ms;
 
-	return sinf(rads) * .5f + .5f;
+	return output_fn(rads);
+}
+
+
+static float ops_sin_output(void *context, unsigned ticks_ms)
+{
+	return output(context, ticks_ms, output_sin);
+}
+
+
+static float ops_sqr_output(void *context, unsigned ticks_ms)
+{
+	return output(context, ticks_ms, output_sqr);
 }
 
 
@@ -66,3 +93,11 @@ sig_ops_t	sig_ops_sin = {
 	.destroy = ops_sin_destroy,
 	.output = ops_sin_output,
 };
+
+
+sig_ops_t	sig_ops_sqr = {
+	.size = ops_sin_size,
+	.init = ops_sin_init,
+	.destroy = ops_sin_destroy,
+	.output = ops_sqr_output,
+};