X-Git-Url: https://git.wirehaze.ovh/lifeboot.git/blobdiff_plain/1f37f09b39ff30c4154b2deaef399eebb594c8db..d2d37470bcaa3af3a9e7bda266c6884b13e9afda:/lifeboot.asm?ds=sidebyside diff --git a/lifeboot.asm b/lifeboot.asm index 7ada2fa..67e7ce9 100644 --- a/lifeboot.asm +++ b/lifeboot.asm @@ -1,43 +1,46 @@ bits 16 -org 0x7c00 +org 7c00h ; ============================================================================= ; settings -------------------------------------------------------------------- %define DEAD ' ' ; char to represent a dead cell -%define ALIVE '#' ; char to represent an alive cell -%define PRINT_COLOR 0x07 ; grey on black -%define WAIT_DELAY 0x02 ; 0.131072 seconds +%define ALIVE '.' ; char to represent an alive cell +%define PRINT_COLOR 07h ; grey on black +%define ITER_LIM 500 ; reset the simulation after this # iterations ; constants ------------------------------------------------------------------- %define COLS 80 %define ROWS 25 -%define VGAPGSZ (COLS * ROWS * 2 + 96) ; why 96 ?????? +%define VGAPGSZ 1000h ; (bytes) ; memory layout --------------------------------------------------------------- -%define ORG 0x7c00 -%define VGA 0xb8000 +%define ORG 7c00h +%define VGA 0b8000h %define DAT ORG + 512 ; static variables ------------------------------------------------------------ %define xss DAT ; xs() state (word) %define currvgapg DAT + 2 ; current vga page near pointer (word) +%define iter DAT + 4 ; current iteration # (word) ; ============================================================================= ; 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 @@ -47,21 +50,19 @@ mov sp, bp cld ; disable cursor -mov ch, 0x3f ; cursor start and options -mov ah, 0x01 ; set text-mode cursor shape -int 0x10 ; video services +mov ch, 3fh ; cursor start and options +mov ah, 01h ; set text-mode cursor shape +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, 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 +mov [xss], dx ; initialize currvgapg mov word [currvgapg], 0 @@ -71,63 +72,43 @@ mov word [currvgapg], 0 start: call init_grid +mov word [iter], 0 + +.next_state: -; apply game of life's rules to determine the next state ---------------------- + call vsync_wait + call update_grid -next_state: + call vsync_wait + call flip_vgapg -call write_next_vga_page -call wait_keypress -call flip_vga_page + inc word [iter] + cmp word [iter], ITER_LIM + jl .next_state -jmp next_state +jmp start ; reset ; ============================================================================= ; functions ------------------------------------------------------------------- -; delay() - suspend program execution temporarily ----------------------------- - -; clobbers ah, cx, dx - -delay: - -mov cx, WAIT_DELAY ; cx:dx = interval in microseconds -mov dx, 0 - -mov ah, 0x86 -int 0x15 ; wait - -ret +; vsync_wait() - wait for display to enter the next retrace cycle ------------- -; 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 +; clobbers al, dx vsync_wait: -mov dx, 0x3da ; input status #1 register +mov dx, 3dah ; input status #1 register -.wait_on: +.wait_retrace_end: in al, dx - test al, 0x08 ; vertical retrace bit - jnz .wait_on + test al, 08h ; vertical retrace bit + jnz .wait_retrace_end -.wait_off: +.wait_retrace_start: in al, dx - test al, 0x08 - jz .wait_off + test al, 08h + jz .wait_retrace_start ret @@ -135,6 +116,7 @@ ret ; output: ; [xss] = updated state +; bx = [xss] ; clobbers bx, dx @@ -168,38 +150,39 @@ mov di, [currvgapg] ; es:di -> grid start mov cx, COLS * ROWS ; for each cell .write_cell: ; do { - call xs ; [xss] = rand + call xs ; bx = random value mov al, DEAD ; al = DEAD (likely) - 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 -call vsync_wait +flip_vgapg: -xor word [currvgapg], VGAPGSZ ; flip currvgapg -setnz al ; al = !(currvgapg == 0) +xor word [currvgapg], VGAPGSZ -mov ah, 0x05 ; select active display page -int 0x10 ; video services +setnz al ; al = !(currvgapg == 0) +mov ah, 05h ; select active display page +int 10h ; bios video services ret -; alive_neighbours() ---------------------------------------------------------- +; alive_neighbours() - get number of alive adjacent cells --------------------- ; input: ; es:si -> current grid @@ -221,7 +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 @@ -234,26 +217,26 @@ 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, 0 ; if (row + i < 0) + jl .continue ; continue - cmp al, ROWS - jge .continue ; if (row + i >= ROWS) continue + cmp al, ROWS ; if (row + i >= ROWS) + jge .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, 0 ; if (col + j < 0) + jl .continue ; continue - cmp ah, COLS - jge .continue ; if (col + j >= COLS) continue + cmp ah, COLS ; if (col + j >= COLS) + jge .continue ; continue movzx bx, ah ; bx = col + j @@ -265,8 +248,8 @@ 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++ @@ -284,7 +267,7 @@ 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 @@ -296,7 +279,7 @@ ret ; clobbers ax, bx, dx -write_next_cell_state: +update_cell: call alive_neighbours ; ax = # alive neighbours @@ -308,11 +291,9 @@ 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 +xor ax, 1 ; if (n != 2 || n != 3) +jnz .dead ; return DEAD (likely) jmp .alive ; return ALIVE @@ -333,25 +314,25 @@ 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 @@ -366,4 +347,4 @@ jmp halt ; ============================================================================= times 510 - ($ - $$) db 0 ; fill remaining bytes with zeroes -dw 0xaa55 ; mbr magic byte +dw 0aa55h ; mbr magic byte