X-Git-Url: https://git.wirehaze.ovh/lifeboot.git/blobdiff_plain/0d9586ff094ca3530341657b0ded38e747286de8..d2d37470bcaa3af3a9e7bda266c6884b13e9afda:/lifeboot.asm?ds=inline diff --git a/lifeboot.asm b/lifeboot.asm index 2d1542f..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) +%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 xss + 2 ; current vga page near pointer (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 ds, ax -mov es, ax +mov es, ax ; es:0 -> video memory xor ax, ax -mov ss, ax +mov ds, ax ; ds = 0 +mov ss, ax ; ss = 0 ; set stack pointers mov bp, ORG @@ -47,63 +50,65 @@ 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 -mov ah, 0x00 ; get -int 0x1a ; system time -mov [xss], dx ; cx:dx = number of clock ticks since midnight +.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 + +mov [xss], dx ; initialize currvgapg -mov word [currvgapg], VGAPGSZ +mov word [currvgapg], 0 -; setup ----------------------------------------------------------------------- +; start simulation from random state ------------------------------------------ -setup: +start: call init_grid -call flip_vga_page -call delay +mov word [iter], 0 -jmp setup +.next_state: -; ============================================================================= - -; functions ------------------------------------------------------------------- + call vsync_wait + call update_grid -; delay() - suspend program execution temporarily ----------------------------- + call vsync_wait + call flip_vgapg -; clobbers ah, cx, dx + inc word [iter] + cmp word [iter], ITER_LIM + jl .next_state -delay: +jmp start ; reset -mov cx, WAIT_DELAY ; cx:dx = interval in microseconds -mov dx, 0 - -mov ah, 0x86 -int 0x15 ; wait +; ============================================================================= -ret +; functions ------------------------------------------------------------------- -; vsync() - 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: +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 @@ -111,6 +116,7 @@ ret ; output: ; [xss] = updated state +; bx = [xss] ; clobbers bx, dx @@ -144,34 +150,189 @@ 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 ------------------------------------- + +; output: +; [currvgapg] ^= VGAPGSZ + +; clobbers ax + +flip_vgapg: + +xor word [currvgapg], VGAPGSZ + +setnz al ; al = !(currvgapg == 0) +mov ah, 05h ; select active display page +int 10h ; bios video services + +ret + +; alive_neighbours() - get number of alive adjacent cells --------------------- + +; input: +; es:si -> current grid +; cx -> cell index + +; output: +; ax = # alive neighbours + +; clobbers ax, bx, dx + +alive_neighbours: +enter 5, 0 + +; [bp - 1]: row +; [bp - 2]: col +; [bp - 3]: neighbours +; [bp - 4]: i +; [bp - 5]: j + +mov ax, cx ; ax = idx +mov bl, COLS ; bl = COLS +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 - 3], 0 ; neighbours = 0 + +mov byte [bp - 4], -1 ; i = -1 +.i: ; do { + + mov byte [bp - 5], -1 ; j = -1 +.j: ; do { + + mov al, [bp - 4] + or al, [bp - 5] ; if (!i && !j) + jz .continue ; continue + + mov al, [bp - 1] + add al, [bp - 4] ; al = row + i + + cmp al, 0 ; if (row + i < 0) + jl .continue ; 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 ; if (col + j < 0) + jl .continue ; continue + + cmp ah, COLS ; if (col + j >= COLS) + jge .continue ; 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) + jne .continue ; continue + + inc byte [bp - 3] ; neighbours++ + +.continue: + inc byte [bp - 5] + cmp byte [bp - 5], 1 + jle .j ; } while (++j <= 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 + +; update_cell() - write next cell state --------------------------------------- + +; input: +; es:si -> current grid +; es:di -> next grid +; cx -> cell index + +; output: +; [es:di + cx * 2] = updated cell state + +; clobbers ax, bx, dx + +update_cell: + +call alive_neighbours ; ax = # alive neighbours + +mov bx, cx +shl bx, 1 + +mov dx, [es:si + bx] ; dl = cell current state + +cmp dl, ALIVE ; if (ALIVE) { +jne .else + +shr ax, 1 +xor ax, 1 ; if (n != 2 || n != 3) +jnz .dead ; return DEAD (likely) + +jmp .alive ; return ALIVE + +.else: ; } + +cmp ax, 3 ; if (n != 3) +jne .dead ; return DEAD + +.alive: ; return ALIVE +mov dl, ALIVE +jmp .write + +.dead: +mov dl, DEAD + +.write: +mov [es:di + bx], dx + +ret + +; update_grid() - write next grid (inactive vga page) ------------------------- + +; clobbers di, si, ax, bx, cx, dx + +update_grid: + +mov si, [currvgapg] ; es:si -> current page -; clobbers ax, dx +mov di, VGAPGSZ +xor di, si ; es:di -> next page -flip_vga_page: +mov cx, COLS * ROWS - 1 ; for each cell (index) -call vsync +.update_loop: ; do { -xor word [currvgapg], VGAPGSZ ; flip currvgapg -setnz al ; al = !(currvgapg == 0) + call update_cell -mov ah, 0x05 ; select active display page -int 0x10 ; video services + dec cx + jns .update_loop ; } while (--cx > 0) ret @@ -186,4 +347,4 @@ jmp halt ; ============================================================================= times 510 - ($ - $$) db 0 ; fill remaining bytes with zeroes -dw 0xaa55 ; mbr magic byte +dw 0aa55h ; mbr magic byte