1 files changed, 19 insertions, 8 deletions
diff --git a/bytepusher.scm b/bytepusher.scm
index f28b961..9c8b96b 100644
--- a/bytepusher.scm
+++ b/bytepusher.scm
@@ -1,6 +1,7 @@
 (define-module (bytepusher)
   #:use-module (rnrs bytevectors)
   #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-60)
   #:use-module (ice-9 binary-ports)
   #:use-module (sdl2)
   #:use-module (sdl2 render)
@@ -39,13 +40,14 @@
 ;; memory ----
 
 (define (get-pc)
-  (+ (bytevector-u16-ref memory 3 (endianness big))
-     (ash (bytevector-u8-ref memory 2) 16)))
+  (+ (ash (get-byte 4)  0)
+     (ash (get-byte 3)  8)
+     (ash (get-byte 2) 16)))
 
 (define (set-pc! value)
-  (let ((pc value))
-    (bytevector-u16-set! memory 2 (ash pc -8)  (endianness big))
-    (bytevector-u8-set!  memory 4 (ash pc -16))))
+  (set-byte! 4 (ash value 0))
+  (set-byte! 3 (ash value -8))
+  (set-byte! 2 (ash value -16)))
 
 (define (get-addr pos)
   (+ (bytevector-u16-ref memory (+ 1 pos) (endianness big))
@@ -61,7 +63,7 @@
   (bytevector-u8-ref memory n))
 
 (define (set-byte! n v)
-  (bytevector-u8-set! memory n v))
+  (bytevector-u8-set! memory n (logand v #xFF)))
 
 ;; ---- memory
 
@@ -152,11 +154,20 @@
         (bytevector-copy! program 0 memory 0 (bytevector-length program))))))
 
 (define (execute! instruction-addr)
+  (call-with-values
+    (lambda () (load-instruction instruction-addr))
+    (lambda (a b c)
+      (set-byte! b (get-byte a))
+      (set-pc! c))))
+
+(define (load-instruction instruction-addr)
   (let ((a (get-addr (+ 0 instruction-addr)))
         (b (get-addr (+ 3 instruction-addr)))
         (c (get-addr (+ 6 instruction-addr))))
-    (set-byte! b (get-byte a))
-    (set-pc! c)))
+      #;(display (string-append "a: " (number->string a 16) "  "))
+      #;(display (string-append "b: " (number->string b 16) "  "))
+      #;(display (string-append "c: " (number->string c 16) "\n"))
+    (values a b c)))
 
 (define (loop-frame!)
   (let loop ((count 65536))