X-Git-Url: https://git.wirehaze.ovh/lifeboot.git/blobdiff_plain/a8cfbb9937178d02aa35816ac8607b2525ba7263..HEAD:/lifeboot.asm?ds=sidebyside diff --git a/lifeboot.asm b/lifeboot.asm index 9b03696..739df40 100644 --- a/lifeboot.asm +++ b/lifeboot.asm @@ -8,13 +8,13 @@ org 7c00h %define DEAD ' ' ; char to represent a dead cell %define ALIVE '.' ; char to represent an alive cell %define PRINT_COLOR 07h ; grey on black -%define ITER_LIM 500 ; reset the simulation after ITER_LIM iterations +%define ITER_LIM 500 ; reset the simulation after this # iterations ; constants ------------------------------------------------------------------- %define COLS 80 %define ROWS 25 -%define VGAPGSZ 1000h +%define VGAPGSZ 1000h ; (bytes) ; memory layout --------------------------------------------------------------- @@ -32,13 +32,15 @@ org 7c00h ; entry point ----------------------------------------------------------------- +entry: + ; initialize segment registers mov ax, VGA >> 4 -mov es, ax +mov es, ax ; es:0 -> video memory xor ax, ax -mov ds, ax -mov ss, ax +mov ds, ax ; ds = 0 +mov ss, ax ; ss = 0 ; set stack pointers mov bp, ORG @@ -50,19 +52,17 @@ cld ; disable cursor mov ch, 3fh ; cursor start and options mov ah, 01h ; set text-mode cursor shape -int 10h ; video services +int 10h ; bios video services ; initialize xss +.set_xss: + mov ah, 00h ; get system time + int 1ah ; bios time services + ; cx:dx = # clock ticks since midnight + or dx, dx + jz .set_xss ; wait for something meaningful -set_xss_seed: - -mov ah, 00h ; get -int 1ah ; 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 +mov [xss], dx ; initialize currvgapg mov word [currvgapg], 0 @@ -72,21 +72,19 @@ mov word [currvgapg], 0 start: call init_grid -mov word [iter], 1 - -; apply game of life's rules to determine the next state ---------------------- +mov word [iter], 0 -next_state: +.next_state: -call vsync_wait -call write_next_vga_page + call vsync_wait + call update_grid -call vsync_wait -call flip_vga_page + call vsync_wait + call flip_vgapg -inc word [iter] -cmp word [iter], ITER_LIM -jle next_state + inc word [iter] + cmp word [iter], ITER_LIM + jl .next_state jmp start ; reset @@ -94,23 +92,23 @@ jmp start ; reset ; functions ------------------------------------------------------------------- -; vsync_wait() - wait for display to enter the next VBlank cycle -------------- +; vsync_wait() - wait for display to enter the next retrace cycle ------------- -; clobbers ax, dx +; clobbers al, dx vsync_wait: mov dx, 3dah ; input status #1 register -.wait_on: +.wait_retrace_end: in al, dx test al, 08h ; vertical retrace bit - jnz .wait_on + jnz .wait_retrace_end -.wait_off: +.wait_retrace_start: in al, dx test al, 08h - jz .wait_off + jz .wait_retrace_start ret @@ -118,6 +116,7 @@ ret ; output: ; [xss] = updated state +; bx = [xss] ; clobbers bx, dx @@ -151,36 +150,39 @@ mov di, [currvgapg] ; es:di -> grid start mov cx, COLS * ROWS ; for each cell .write_cell: ; do { - call xs ; [xss] = rand - mov al, DEAD ; al = DEAD (likely) + call xs ; bx = random value + mov al, DEAD ; al = DEAD - test word [xss], 0b11 + test bx, 0b11 - jnz .nz ; if ([xss] % 4 == 0) + jnz .nz ; if (bx % 4 == 0) mov al, ALIVE ; al = ALIVE .nz: - stosw ; [es:di] = ax ; di += 2 + stosw ; [es:di] = ax, di += 2 loop .write_cell ; } while (--cx) ret -; flip_vga_page() - flip active display page ---------------------------------- +; flip_vgapg() - flip active display page ------------------------------------- -; clobbers ax, dx +; output: +; [currvgapg] ^= VGAPGSZ -flip_vga_page: +; clobbers ax -xor word [currvgapg], VGAPGSZ ; flip currvgapg -setnz al ; al = !(currvgapg == 0) +flip_vgapg: +xor word [currvgapg], VGAPGSZ + +setnz al ; al = !(currvgapg == 0) mov ah, 05h ; select active display page -int 10h ; video services +int 10h ; bios video services ret -; alive_neighbours() ---------------------------------------------------------- +; alive_neighbours() - get number of alive adjacent cells --------------------- ; input: ; es:si -> current grid @@ -202,7 +204,7 @@ enter 5, 0 mov ax, cx ; ax = idx mov bl, COLS ; bl = COLS -div bl ; al = idx / COLS ; ah = idx % COLS +div bl ; al = idx / COLS, ah = idx % COLS mov [bp - 1], al ; row = idx / COLS mov [bp - 2], ah ; row = idx % COLS @@ -215,26 +217,20 @@ mov byte [bp - 4], -1 ; i = -1 .j: ; do { mov al, [bp - 4] - or al, [bp - 5] - jz .continue ; if (!i && !j) continue + or al, [bp - 5] ; if (!i && !j) + jz .continue ; continue mov al, [bp - 1] add al, [bp - 4] ; al = row + i - cmp al, 0 - jl .continue ; if (row + i < 0) continue - - cmp al, ROWS - jge .continue ; if (row + i >= ROWS) continue + cmp al, ROWS ; if ((unsigned)(row + i) >= ROWS) + jae .continue ; 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 + cmp ah, COLS ; if ((unsigned)(col + j) >= COLS) + jae .continue ; continue movzx bx, ah ; bx = col + j @@ -246,8 +242,8 @@ mov byte [bp - 4], -1 ; i = -1 mov dx, [es:si + bx] ; dl = cell state - cmp dl, ALIVE ; if (!ALIVE) continue - jne .continue + cmp dl, ALIVE ; if (!ALIVE) + jne .continue ; continue inc byte [bp - 3] ; neighbours++ @@ -265,7 +261,7 @@ movzx ax, byte [bp - 3] ; ax = # alive neighbours leave ret -; write_next_cell_state() ----------------------------------------------------- +; update_cell() - write next cell state --------------------------------------- ; input: ; es:si -> current grid @@ -277,7 +273,7 @@ ret ; clobbers ax, bx, dx -write_next_cell_state: +update_cell: call alive_neighbours ; ax = # alive neighbours @@ -289,11 +285,9 @@ mov dx, [es:si + bx] ; dl = cell current state cmp dl, ALIVE ; if (ALIVE) { jne .else -cmp ax, 2 ; if (n < 2) -jl .dead ; return DEAD - -cmp ax, 3 ; if (n > 3) -jg .dead ; return DEAD +shr ax, 1 +cmp ax, 1 ; if (n != 2 || n != 3) +jne .dead ; return DEAD jmp .alive ; return ALIVE @@ -314,25 +308,25 @@ mov [es:di + bx], dx ret -; write_next_vga_page() ------------------------------------------------------- +; update_grid() - write next grid (inactive vga page) ------------------------- ; clobbers di, si, ax, bx, cx, dx -write_next_vga_page: +update_grid: mov si, [currvgapg] ; es:si -> current page mov di, VGAPGSZ xor di, si ; es:di -> next page -xor cx, cx ; i = 0 +mov cx, COLS * ROWS - 1 ; for each cell (index) + +.update_loop: ; do { -.update_loop: -call write_next_cell_state + call update_cell -inc cx -cmp cx, COLS * ROWS -jl .update_loop ; for i in [0 .. COLS * ROWS - 1] + dec cx + jns .update_loop ; } while (--cx > 0) ret