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.

1 files changed, 67 insertions, 0 deletions

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,
+};