remove vga page # debugging

[lifeboot.git] / lifeboot.asm

diff --git a/lifeboot.asm b/lifeboot.asm
index b81453c30b616ff0a5eb7910a66a68079eacd9f9..7ada2fa18329d6e0d999990d11fcd3120451175c 100644 (file)
--- a/lifeboot.asm
+++ b/lifeboot.asm
@@ -14,7 +14,7 @@ org 0x7c00
 
 %define COLS 80
 %define ROWS 25
-%define VGAPGSZ (COLS * ROWS * 2)
+%define VGAPGSZ (COLS * ROWS * 2 + 96)  ; why 96 ??????
 
 ; memory layout ---------------------------------------------------------------
 
@@ -52,12 +52,19 @@ mov ah, 0x01                ; set text-mode cursor shape
 int 0x10                    ; video services
 
 ; initialize xss
+
+set_xss_seed:
+
 mov ah, 0x00                ; get
 int 0x1a                    ;  system time
+
+cmp dx, 0
+je set_xss_seed             ; if seed is 0, xs wont work properly
+
 mov [xss], dx               ; cx:dx = number of clock ticks since midnight
 
 ; initialize currvgapg
-mov word [currvgapg], VGAPGSZ
+mov word [currvgapg], 0
 
 ; start simulation from random state ------------------------------------------
 
@@ -69,10 +76,9 @@ call init_grid
 
 next_state:
 
-call flip_vga_page          ; display current state
-call delay                  ; sleep a little
-
-call write_next_vga_page    ; write the next state to the hidden page
+call write_next_vga_page
+call wait_keypress
+call flip_vga_page
 
 jmp next_state
 
@@ -94,6 +100,17 @@ int 0x15                    ; wait
 
 ret
 
+; wait_keypress() - wait for any keypress -------------------------------------
+
+; clobbers: ax
+
+wait_keypress:
+
+mov ah, 0x00        ; read key press
+int 0x16            ; keyboard services
+
+ret
+
 ; vsync_wait() - wait for display to enter the next VBlank cycle --------------
 
 ; clobbers ax, dx
@@ -191,7 +208,7 @@ ret
 ; output:
 ; ax = # alive neighbours
 
-; clobbers ?
+; clobbers ax, bx, dx
 
 alive_neighbours:
 enter 5, 0
@@ -208,25 +225,62 @@ div bl                      ; al = idx / COLS ; ah = idx % COLS
 
 mov [bp - 1], al            ; row = idx / COLS
 mov [bp - 2], ah            ; row = idx % COLS
-mov byte [bp - 6], 0        ; neighbours = 0
+mov byte [bp - 3], 0        ; neighbours = 0
 
-mov byte [bp - 8], -1       ; i = -1
+mov byte [bp - 4], -1       ; i = -1
 .i:                         ; do {
 
-    mov byte [bp - 10], -1          ; j = -1
+    mov byte [bp - 5], -1           ; j = -1
 .j:                                 ; do {
 
-        ; if ((row || col) && get_state (grid, row + i, col + i) == ALIVE)        
-        ;   neighbours++
+        mov al, [bp - 4]
+        or al, [bp - 5]
+        jz .continue                    ; if (!i && !j) continue
+
+        mov al, [bp - 1]
+        add al, [bp - 4]                ; al = row + i
 
-        inc byte [bp - 10]
-        cmp byte [bp - 10], 1
+        cmp al, 0
+        jl .continue                    ; if (row + i < 0) continue
+
+        cmp al, ROWS
+        jge .continue                   ; if (row + i >= ROWS) continue
+
+        mov ah, [bp - 2]
+        add ah, [bp - 5]                ; ah = col + j
+
+        cmp ah, 0
+        jl .continue                    ; if (col + j < 0) continue
+
+        cmp ah, COLS
+        jge .continue                   ; if (col + j >= COLS) continue
+
+        movzx bx, ah                    ; bx = col + j
+
+        mov ah, COLS
+        mul ah                          ; ax = (row + i) * COLS
+
+        add bx, ax                      ; bx = cell index
+        shl bx, 1                       ; bx = grid offset
+
+        mov dx, [es:si + bx]            ; dl = cell state
+
+        cmp dl, ALIVE                   ; if (!ALIVE) continue
+        jne .continue
+
+        inc byte [bp - 3]               ; neighbours++
+
+.continue:
+        inc byte [bp - 5]
+        cmp byte [bp - 5], 1
         jle .j                      ; } while (++j <= 1)
 
-    inc byte [bp - 8]
-    cmp byte [bp - 8], 1
+    inc byte [bp - 4]
+    cmp byte [bp - 4], 1
     jle .i                  ; } while (++i <= 1)
 
+movzx ax, byte [bp - 3]     ; ax = # alive neighbours
+
 leave
 ret
 
@@ -240,7 +294,7 @@ ret
 ; output:
 ; [es:di + cx * 2] = updated cell state
 
-; clobbers ?
+; clobbers ax, bx, dx
 
 write_next_cell_state:
 
@@ -251,20 +305,20 @@ shl bx, 1
 
 mov dx, [es:si + bx]        ; dl = cell current state
 
-test dl, ALIVE              ; if (ALIVE) {
+cmp dl, ALIVE               ; if (ALIVE) {
 jne .else
 
-test ax, 2                  ;     if (n < 2)
+cmp ax, 2                   ;     if (n < 2)
 jl .dead                    ;         return DEAD
 
-test ax, 3                  ;     if (n > 3)
+cmp ax, 3                   ;     if (n > 3)
 jg .dead                    ;         return DEAD
 
 jmp .alive                  ;     return ALIVE
 
 .else:                      ; }
 
-test ax, 3                  ; if (n != 3)
+cmp ax, 3                   ; if (n != 3)
 jne .dead                   ;     return DEAD
 
 .alive:                     ; return ALIVE
@@ -281,7 +335,7 @@ ret
 
 ; write_next_vga_page() -------------------------------------------------------
 
-; clobbers di, si, cx
+; clobbers di, si, ax, bx, cx, dx
 
 write_next_vga_page:
 
@@ -296,7 +350,7 @@ xor cx, cx                  ; i = 0
 call write_next_cell_state
 
 inc cx
-test cx, COLS * ROWS
+cmp cx, COLS * ROWS
 jl .update_loop             ; for i in [0 .. COLS * ROWS - 1]
 
 ret