libs/sig: add sig_ops_scale w/test example

This assumes the input value is always 0-1, but may be used to produce
values in any signed range, mapped linearly to the input.

4 files changed, 82 insertions, 1 deletions

diff --git a/src/libs/sig/Makefile.am b/src/libs/sig/Makefile.am
index 64715fe..e53a4bd 100644
--- a/src/libs/sig/Makefile.am
+++ b/src/libs/sig/Makefile.am
@@ -1,3 +1,3 @@
 noinst_LIBRARIES = libsig.a
-libsig_a_SOURCES = ops_abs.c ops_ceil.c ops_clamp.c ops_const.c ops_floor.c ops_inv.c ops_lerp.c ops_max.c ops_min.c ops_mult.c ops_pow.c ops_rand.c ops_round.c ops_sin.c sig.c sig.h
+libsig_a_SOURCES = ops_abs.c ops_ceil.c ops_clamp.c ops_const.c ops_floor.c ops_inv.c ops_lerp.c ops_max.c ops_min.c ops_mult.c ops_pow.c ops_rand.c ops_round.c ops_scale.c ops_sin.c sig.c sig.h
 libsig_a_CPPFLAGS = -I@top_srcdir@/src
diff --git a/src/libs/sig/ops_scale.c b/src/libs/sig/ops_scale.c
new file mode 100644
index 0000000..22c0363
--- /dev/null
+++ b/src/libs/sig/ops_scale.c
@@ -0,0 +1,67 @@
+#include <assert.h>
+
+#include "sig.h"
+
+
+typedef struct ops_scale_ctxt_t {
+	sig_t	*value, *min, *max;
+} ops_scale_ctxt_t;
+
+
+static size_t ops_scale_size(va_list ap)
+{
+	return sizeof(ops_scale_ctxt_t);
+}
+
+
+/* expects three sig_t's: value, min, max.
+ * min is assumed to be always <= max,
+ * and value is assumed to always be 0-1
+ */
+static void ops_scale_init(void *context, va_list ap)
+{
+	ops_scale_ctxt_t	*ctxt = context;
+
+	assert(ctxt);
+
+	ctxt->value = va_arg(ap, sig_t *);
+	ctxt->min = va_arg(ap, sig_t *);
+	ctxt->max = va_arg(ap, sig_t *);
+}
+
+
+static void ops_scale_destroy(void *context)
+{
+	ops_scale_ctxt_t	*ctxt = context;
+
+	assert(ctxt);
+
+	sig_free(ctxt->value);
+	sig_free(ctxt->min);
+	sig_free(ctxt->max);
+}
+
+
+static float ops_scale_output(void *context, unsigned ticks_ms)
+{
+	ops_scale_ctxt_t	*ctxt = context;
+	float			value, min, max;
+
+	assert(ctxt);
+
+	value = sig_output(ctxt->value, ticks_ms);
+	min = sig_output(ctxt->min, ticks_ms);
+	max = sig_output(ctxt->max, ticks_ms);
+
+	assert(max >= min);
+
+	return value * (max - min) + min;
+}
+
+
+sig_ops_t	sig_ops_scale = {
+	.size = ops_scale_size,
+	.init = ops_scale_init,
+	.destroy = ops_scale_destroy,
+	.output = ops_scale_output,
+};
diff --git a/src/libs/sig/sig.c b/src/libs/sig/sig.c
index 4146cd3..c68a420 100644
--- a/src/libs/sig/sig.c
+++ b/src/libs/sig/sig.c
@@ -132,6 +132,19 @@ int main(int argc, char *argv[])
 	for (unsigned i = 0; i < 1000; i++)
 		printf("sin 10hz ^ (sin 1hz * 50) output %i=%f\n", i, sig_output(sig, i));
 	sig = sig_free(sig);
+
+	sig =	sig_new(&sig_ops_scale,								/* scale a */
+			sig_new(&sig_ops_lerp,							/* linear interpolation */
+				sig_new(&sig_ops_sin, sig_new(&sig_ops_const, 10.f)),		/* between one 10hz oscillator */
+				sig_new(&sig_ops_sin, sig_new(&sig_ops_const, 33.f)),		/* and another 33hz oscillator */
+				sig_new(&sig_ops_sin, sig_new(&sig_ops_const, 2.f))		/* weighted by a 2hz oscillator */
+			),
+			sig_new(&sig_ops_const, -100.f), sig_new(&sig_ops_const, 100.f)		/* to the range -100 .. +100 */
+		);
+	for (unsigned i = 0; i < 1000; i++)
+		printf("scale(lerp(sin(10hz), sin(33hz), sin(2hz)), -100, +100)  output %i=%f\n", i, sig_output(sig, i));
+	sig = sig_free(sig);
+
 }
 
 #endif
diff --git a/src/libs/sig/sig.h b/src/libs/sig/sig.h
index 3456af9..b54bfb7 100644
--- a/src/libs/sig/sig.h
+++ b/src/libs/sig/sig.h
@@ -38,5 +38,6 @@ extern sig_ops_t	sig_ops_min;
 extern sig_ops_t	sig_ops_mult;
 extern sig_ops_t	sig_ops_pow;
 extern sig_ops_t	sig_ops_round;
+extern sig_ops_t	sig_ops_scale;
 
 #endif