libs/sig: intrduce sig_ops_const

The simplest of signals: a constant value.

The immediate need for this is to convert ops_sin_ctxt_t.hz to
another sig_t enabling varying hz with time, while still being
able to have a fixed hz as well.

3 files changed, 45 insertions, 1 deletions

diff --git a/src/libs/sig/Makefile.am b/src/libs/sig/Makefile.am
index 4787b5a..4c41f41 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_mult.c ops_sin.c sig.c sig.h
+libsig_a_SOURCES = ops_const.c ops_mult.c ops_sin.c sig.c sig.h
 libsig_a_CPPFLAGS = -I@top_srcdir@/src
diff --git a/src/libs/sig/ops_const.c b/src/libs/sig/ops_const.c
new file mode 100644
index 0000000..aa7e862
--- /dev/null
+++ b/src/libs/sig/ops_const.c
@@ -0,0 +1,43 @@
+#include <assert.h>
+#include <math.h>
+
+#include "sig.h"
+
+
+typedef struct ops_const_ctxt_t {
+	float	value;
+} ops_const_ctxt_t;
+
+
+static size_t ops_const_size(va_list ap)
+{
+	return sizeof(ops_const_ctxt_t);
+}
+
+
+static void ops_const_init(void *context, va_list ap)
+{
+	ops_const_ctxt_t	*ctxt = context;
+
+	assert(ctxt);
+
+	ctxt->value = va_arg(ap, double);
+}
+
+
+static float ops_const_output(void *context, unsigned ticks_ms)
+{
+	ops_const_ctxt_t	*ctxt = context;
+
+	assert(ctxt);
+
+	return ctxt->value;
+}
+
+
+sig_ops_t	sig_ops_const = {
+	.size = ops_const_size,
+	.init = ops_const_init,
+	.output = ops_const_output,
+};
+
diff --git a/src/libs/sig/sig.h b/src/libs/sig/sig.h
index cd22d4d..f377f00 100644
--- a/src/libs/sig/sig.h
+++ b/src/libs/sig/sig.h
@@ -17,6 +17,7 @@ sig_t * sig_new(const sig_ops_t *ops, ...);
 sig_t * sig_free(sig_t *sig);
 float sig_output(sig_t *sig, unsigned ticks_ms);
 
+extern sig_ops_t	sig_ops_const;
 extern sig_ops_t	sig_ops_sin;
 
 /* TODO: