Avoid memory allocations!

With this change we avoid all memory allocations. Everything is
pre-allocated. It makes the frame-rate stay steady with no drops
produced by the GC. In order to test this, `gcprof` can be used from
`statprof` module.

1 files changed, 13 insertions, 12 deletions

diff --git a/bytepusher.scm b/bytepusher.scm
index 1182f48..4c8671b 100644
--- a/bytepusher.scm
+++ b/bytepusher.scm
@@ -135,18 +135,19 @@
 
 
 ;; rendering ----
-(define (get-pixels)
-  (let* ((initial   (get-initial-pixel))
-         (len       (* width height))
-         (base      (make-bytevector len))
-         (final     (make-bytevector (* 4 len))))
-    (let loop ((i 0))
-      (bytevector-u32-set! final
-                           (* 4 i)
-                           (pixel->color-fast (get-byte (+ i initial)))
-                           (endianness big))
-      (unless (= i (- len 1)) (loop (+ 1 i))))
-      final))
+(define get-pixels
+  ((lambda ()
+    (define len   (* width height))
+    (define final (make-bytevector (* 4 len)))
+    (lambda ()
+      (let* ((initial   (get-initial-pixel)))
+        (let loop ((i 0))
+          (bytevector-u32-set! final
+                               (* 4 i)
+                               (pixel->color-fast (get-byte (+ i initial)))
+                               (endianness big))
+          (unless (= i (- len 1)) (loop (+ 1 i))))
+        final)))))
 
 (define (make-display-texture renderer)
   (make-texture renderer 'argb8888 'streaming width height))