libs/sig: add sig_ops_expand convenience

This is a specialized version of sig_ops_scale which assumes a
min..max range of -1..+1

nvidia register combiners docs describe this operation as "expand
normal", and they have several variants, but I don't want to go
too crazy here right now.  Plain expand it is.

1 files changed, 56 insertions, 0 deletions

diff --git a/src/libs/sig/ops_expand.c b/src/libs/sig/ops_expand.c
new file mode 100644
index 0000000..76791e4
--- /dev/null
+++ b/src/libs/sig/ops_expand.c
@@ -0,0 +1,56 @@
+#include <assert.h>
+
+#include "sig.h"
+
+
+typedef struct ops_expand_ctxt_t {
+	sig_t	*value;
+} ops_expand_ctxt_t;
+
+
+static size_t ops_expand_size(va_list ap)
+{
+	return sizeof(ops_expand_ctxt_t);
+}
+
+
+/* expects a single sig_t: value
+ * input range is assumed to be 0..1, outputs expanded
+ * range of -1..+1
+ */
+static void ops_expand_init(void *context, va_list ap)
+{
+	ops_expand_ctxt_t	*ctxt = context;
+
+	assert(ctxt);
+
+	ctxt->value = va_arg(ap, sig_t *);
+}
+
+
+static void ops_expand_destroy(void *context)
+{
+	ops_expand_ctxt_t	*ctxt = context;
+
+	assert(ctxt);
+
+	sig_free(ctxt->value);
+}
+
+
+static float ops_expand_output(void *context, unsigned ticks_ms)
+{
+	ops_expand_ctxt_t	*ctxt = context;
+
+	assert(ctxt);
+
+	return sig_output(ctxt->value, ticks_ms) * 2.f + 1.f;
+}
+
+
+sig_ops_t	sig_ops_expand = {
+	.size = ops_expand_size,
+	.init = ops_expand_init,
+	.destroy = ops_expand_destroy,
+	.output = ops_expand_output,
+};