*: use fragment generator

Rather than laying out all fragments in a frame up-front in
ray_module_t.prepare_frame(), return a fragment generator
(rototiller_fragmenter_t) which produces the numbered fragment
as needed.

This removes complexity from the serially-executed
prepare_frame() and allows the individual fragments to be
computed in parallel by the different threads.  It also
eliminates the need for a fragments array in the
rototiller_frame_t, indeed rototiller_frame_t is eliminated
altogether.

1 files changed, 4 insertions, 8 deletions

diff --git a/src/rototiller.h b/src/rototiller.h
index 933f733..beafc52 100644
--- a/src/rototiller.h
+++ b/src/rototiller.h
@@ -3,18 +3,14 @@
 
 #include "fb.h"
 
-/* Intentionally setting this larger than any anticipated number of CPUs */
-#define ROTOTILLER_FRAME_MAX_FRAGMENTS	1024
-
-typedef struct rototiller_frame_t {
-	unsigned	n_fragments;
-	fb_fragment_t	fragments[ROTOTILLER_FRAME_MAX_FRAGMENTS];
-} rototiller_frame_t;
+/* rototiller_fragmenter produces fragments from an input fragment, num being the desired fragment for the current call.
+ * return value of 1 means a fragment has been produced, 0 means num is beyond the end of fragments. */
+typedef int (*rototiller_fragmenter_t)(void *context, const fb_fragment_t *fragment, unsigned num, fb_fragment_t *res_fragment);
 
 typedef struct rototiller_module_t {
 	void *	(*create_context)(void);
 	void	(*destroy_context)(void *context);
-	void	(*prepare_frame)(void *context, unsigned n_cpus, fb_fragment_t *fragment, rototiller_frame_t *res_frame);
+	void	(*prepare_frame)(void *context, unsigned n_cpus, fb_fragment_t *fragment, rototiller_fragmenter_t *res_fragmenter);
 	void	(*render_fragment)(void *context, fb_fragment_t *fragment);
 	char	*name;
 	char	*description;