From 24317fc8608ee433ac34573a111ac1b921b815f5 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Thu, 26 May 2016 23:39:50 -0700
Subject: [PATCH] chip8

---
 beautiful-racket/br/demo/chip8.rkt | 51 ++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 16 deletions(-)

diff --git a/beautiful-racket/br/demo/chip8.rkt b/beautiful-racket/br/demo/chip8.rkt
index 4ea33f3..ba92a96 100644
--- a/beautiful-racket/br/demo/chip8.rkt
+++ b/beautiful-racket/br/demo/chip8.rkt
@@ -3,7 +3,7 @@
 ; http://devernay.free.fr/hacks/chip8/C8TECH10.HTM
 ; http://mattmik.com/files/chip8/mastering/chip8.html
 
-(define (explode-bytes val)
+(define (split-bytes val)
   (cond
     [(zero? val) (list 0)]
     [else
@@ -17,21 +17,21 @@
 
 (module+ test
   (require rackunit)
-  (check-equal? (explode-bytes #x2B45) (list #x2 #xB #x4 #x5))
-  (check-equal? (explode-bytes #xCD) (list #xC #xD))
-  (check-equal? (explode-bytes #xA) (list #xA))
-  (check-equal? (explode-bytes #x0) (list #x0)))
+  (check-equal? (split-bytes #x2B45) (list #x2 #xB #x4 #x5))
+  (check-equal? (split-bytes #xCD) (list #xC #xD))
+  (check-equal? (split-bytes #xA) (list #xA))
+  (check-equal? (split-bytes #x0) (list #x0)))
 
-(define (glue-bytes bytes)
+(define (join-bytes bytes)
   (for/sum ([b (in-list (reverse bytes))]
             [i (in-naturals)])
            (* b (expt 16 i))))
 
 (module+ test
-  (check-equal? #x2B45 (glue-bytes (list #x2 #xB #x4 #x5)))
-  (check-equal? #xCD (glue-bytes (list #xC #xD)))
-  (check-equal? #xA (glue-bytes (list #xA)))
-  (check-equal? #x0 (glue-bytes (list #x0))))
+  (check-equal? #x2B45 (join-bytes (list #x2 #xB #x4 #x5)))
+  (check-equal? #xCD (join-bytes (list #xC #xD)))
+  (check-equal? #xA (join-bytes (list #xA)))
+  (check-equal? #x0 (join-bytes (list #x0))))
 
 (define-macro (define-memory-vector ID [FIELD LENGTH SIZE] ...)
   (with-pattern
@@ -50,7 +50,7 @@
        (define (PREFIXED-ID-REF idx)
          (unless (< idx LENGTH)
            (raise-argument-error 'PREFIXED-ID-REF (format "index less than field length ~a" LENGTH) idx))
-         (glue-bytes
+         (join-bytes
           (for/list ([i (in-range SIZE)])
                     (vector-ref ID (+ FIELD-OFFSET i idx)))))
        ...
@@ -60,19 +60,38 @@
          (unless (< val (expt 16 SIZE))
            (raise-argument-error 'PREFIXED-ID-SET! (format "value less than field size ~a" (expt 16 SIZE)) val))
          (for ([i (in-range SIZE)]
-               [b (in-list (explode-bytes val))])
+               [b (in-list (split-bytes val))])
               (vector-set! ID (+ FIELD-OFFSET i idx) b))) ...)))
 
-(define-memory-vector chip 
+(define-memory-vector chip8 
   [opcode 1 2] ; two bytes
   [memory 4096 1] ; one byte per
   [V 16 1] ; one byte per
-  [I 3 1] ; index register, 0x000 to 0xFFF
-  [pc 3 1] ; program counter, 0x000 to 0xFFF
+  [I 2 1] ; index register, 0x000 to 0xFFF (1.5 bytes)
+  [pc 2 1] ; program counter, 0x000 to 0xFFF (1.5 bytes)
   [gfx (* 64 32) 1] ; pixels
   [delay_timer 1 1]
   [sound_timer 1 1]
   [stack 16 2] ; 2 bytes each
-  [sp 1 1] ; stack pointer
+  [sp 1 2] ; stack pointer
   [key 16 1]) ; keys
 
+;; Set up render system and register input callbacks
+;(setup-graphics chip8)
+;(setup-input chip8)
+
+;; Initialize the Chip8 system and load the game into the memory  
+;(initialize chip8)
+;(load-game chip8 "pong")
+
+;; Emulation loop
+#;(let loop ()
+  ;; Emulate one cycle
+  (emulate-cycle chip8)
+  ;; If the draw flag is set, update the screen
+  (when (draw-flag? chip8)
+    (draw-graphics chip8))
+  
+  ;; Store key press state (Press and Release)
+  (set-keys chip8)
+  (loop))
\ No newline at end of file