1 files changed, 70 insertions, 0 deletions
diff --git a/src/til_tap.c b/src/til_tap.c
new file mode 100644
index 0000000..44550b6
--- /dev/null
+++ b/src/til_tap.c
@@ -0,0 +1,70 @@
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "til_tap.h"
+
+/* A "tap" is a named binding of a local variable+pointer to that variable.
+ *
+ * It's purpose is to facilitate exposing local variables controlling rendering
+ * to potential external influence.
+ *
+ * While the tap alone does get named, this is mostly for ergonomic reasons since
+ * it's convenient and natural to name the tap while specifying its variable and
+ * pointer by name as well.  Putting them all in once place.
+ *
+ * The tap itself is not a registry or otherwise discoverable entity by itself.
+ * This is strictly just the local glue, with a name.  Other pieces must tie taps
+ * into streams or settings stuff for addressing them by name at a path or other
+ * means.
+ *
+ * Note the intended way for taps to work is that the caller will always access their
+ * local variables indirectly via the pointers they provided when creating the taps.
+ * There will be a function for managing the tap the caller must call before accessing
+ * the variable indirectly as well.  It's that function which will update the indirection
+ * pointer to potentially point elsewhere if another tap is driving the variable.
+ */
+
+struct til_tap_t {
+	til_tap_type_t	type;
+	void		*ptr;		/* points at the caller-provided tap-managed indirection pointer */
+	size_t		n_elems;	/* when > 1, *ptr is an array of n_elems elements.  Otherwise individual variable. */
+	void		*elems;		/* points at the first element of type type, may or may not be an array of them */
+	char		name[];
+};
+
+
+/* This is the raw tap creator but use the type-checked wrappers in the header and add one if one's missing */
+til_tap_t * til_tap_new(til_tap_type_t type, void *ptr, const char *name, size_t n_elems, void *elems)
+{
+	til_tap_t	*tap;
+
+	assert(name);
+	assert(type < TIL_TAP_TYPE_MAX);
+	assert(ptr);
+	assert(n_elems);
+	assert(elems);
+
+	tap = calloc(1, sizeof(til_tap_t) + strlen(name) + 1);
+	if (!tap)
+		return NULL;
+
+	strcpy(tap->name, name);
+	tap->type = type;
+	tap->ptr = ptr;
+	tap->n_elems = n_elems;
+	tap->elems = elems;
+
+	*((void **)tap->ptr) = elems;
+
+	return tap;
+}
+
+
+til_tap_t * til_tap_free(til_tap_t *tap)
+{
+	free(tap);
+
+	return NULL;
+}