bootgame1
annotate boot.asm @ 1:48755f08211a
move a block around
| author | John Tsiombikas <nuclear@member.fsf.org> |
|---|---|
| date | Thu, 08 Jun 2017 01:01:21 +0300 |
| parents | 81facff3a8ae |
| children |
| rev | line source |
|---|---|
| nuclear@1 | 1 xcells equ 40 |
| nuclear@1 | 2 ycells equ 25 |
| nuclear@1 | 3 poffs equ xcells * ycells |
| nuclear@1 | 4 doffs equ poffs + 2 |
| nuclear@1 | 5 ticks_offs equ doffs + 2 |
| nuclear@1 | 6 |
| nuclear@1 | 7 key_w equ 17 |
| nuclear@1 | 8 key_a equ 30 |
| nuclear@1 | 9 key_s equ 31 |
| nuclear@1 | 10 key_d equ 32 |
| nuclear@1 | 11 |
| nuclear@1 | 12 org 0x7c00 |
| nuclear@0 | 13 start: |
| nuclear@0 | 14 mov ax, 0x13 |
| nuclear@0 | 15 int 0x10 |
| nuclear@1 | 16 |
| nuclear@1 | 17 push word 0x7e00 |
| nuclear@1 | 18 pop es |
| nuclear@1 | 19 xor ax, ax |
| nuclear@1 | 20 xor di, di |
| nuclear@1 | 21 mov cx, 0xfffe |
| nuclear@1 | 22 rep stosw |
| nuclear@1 | 23 push es |
| nuclear@1 | 24 pop ds ; cells table segment -> ds |
| nuclear@1 | 25 |
| nuclear@1 | 26 ; init position |
| nuclear@1 | 27 mov [si + poffs + 1], byte xcells / 2 |
| nuclear@1 | 28 mov [si + poffs], byte ycells / 2 |
| nuclear@1 | 29 |
| nuclear@0 | 30 push word 0xa000 |
| nuclear@0 | 31 pop es |
| nuclear@0 | 32 |
| nuclear@0 | 33 mainloop: |
| nuclear@1 | 34 ; keyboard input |
| nuclear@1 | 35 push si |
| nuclear@1 | 36 add si, doffs |
| nuclear@1 | 37 in al, 0x60 |
| nuclear@1 | 38 cmp al, key_s |
| nuclear@1 | 39 jnz .not_s |
| nuclear@1 | 40 mov [si], word 1 |
| nuclear@1 | 41 .not_s: cmp al, key_w |
| nuclear@1 | 42 jnz .not_w |
| nuclear@1 | 43 mov [si], word 0x00ff |
| nuclear@1 | 44 .not_w: |
| nuclear@1 | 45 cmp al, key_d |
| nuclear@1 | 46 jnz .not_d |
| nuclear@1 | 47 mov [si], word 0x100 |
| nuclear@1 | 48 .not_d: cmp al, key_a |
| nuclear@1 | 49 jnz .endkey |
| nuclear@1 | 50 mov [si], word 0xff00 |
| nuclear@1 | 51 .endkey: |
| nuclear@1 | 52 pop si |
| nuclear@1 | 53 |
| nuclear@1 | 54 ; clear screen |
| nuclear@1 | 55 xor ax, ax |
| nuclear@0 | 56 xor di, di |
| nuclear@0 | 57 mov cx, 32000 |
| nuclear@0 | 58 rep stosw |
| nuclear@0 | 59 |
| nuclear@1 | 60 mov ax, [si + poffs] ; grab position |
| nuclear@1 | 61 |
| nuclear@1 | 62 mov cx, [si + ticks_offs] |
| nuclear@1 | 63 inc cx |
| nuclear@1 | 64 and cx, 0x3ff |
| nuclear@1 | 65 jnz .skip_move ; only move every 64 vsyncs |
| nuclear@1 | 66 |
| nuclear@1 | 67 ; move |
| nuclear@1 | 68 add ah, [si + doffs + 1] |
| nuclear@1 | 69 jnz .xnot0 |
| nuclear@1 | 70 neg byte [si + doffs + 1] |
| nuclear@1 | 71 .xnot0: cmp ah, xcells - 1 |
| nuclear@1 | 72 jnz .xnotmax |
| nuclear@1 | 73 neg byte [si + doffs + 1] |
| nuclear@1 | 74 .xnotmax: |
| nuclear@1 | 75 add al, [si + doffs] |
| nuclear@1 | 76 jnz .ynot0 |
| nuclear@1 | 77 neg byte [si + doffs] |
| nuclear@1 | 78 .ynot0: cmp al, ycells |
| nuclear@1 | 79 jnz .ynotmax |
| nuclear@1 | 80 neg byte [si + doffs] |
| nuclear@1 | 81 .ynotmax: |
| nuclear@1 | 82 mov [si + poffs], ax |
| nuclear@1 | 83 .skip_move: |
| nuclear@1 | 84 mov [si + ticks_offs], cx |
| nuclear@1 | 85 |
| nuclear@1 | 86 call draw_block |
| nuclear@1 | 87 |
| nuclear@1 | 88 |
| nuclear@1 | 89 ; wait vsync |
| nuclear@1 | 90 mov dx, 0x3da |
| nuclear@1 | 91 .vbwait:in al, dx |
| nuclear@1 | 92 and al, 8 |
| nuclear@1 | 93 jz .vbwait |
| nuclear@0 | 94 jmp mainloop |
| nuclear@0 | 95 |
| nuclear@1 | 96 ; ah: x, al: y |
| nuclear@1 | 97 draw_block: |
| nuclear@1 | 98 push ax |
| nuclear@1 | 99 xor al, al |
| nuclear@1 | 100 shr ax, 5 |
| nuclear@1 | 101 mov di, ax |
| nuclear@1 | 102 |
| nuclear@1 | 103 pop ax |
| nuclear@1 | 104 xor ah, ah |
| nuclear@1 | 105 shl ax, 3 |
| nuclear@1 | 106 mov bx, 320 |
| nuclear@1 | 107 mul bx |
| nuclear@1 | 108 add di, ax |
| nuclear@1 | 109 mov cx, 6 |
| nuclear@1 | 110 .sline: |
| nuclear@1 | 111 add di, 320 |
| nuclear@1 | 112 mov eax, 0x0f0f0f00 |
| nuclear@1 | 113 stosd |
| nuclear@1 | 114 shr eax, 8 |
| nuclear@1 | 115 stosd |
| nuclear@1 | 116 sub di, 8 |
| nuclear@1 | 117 dec cx |
| nuclear@1 | 118 jnz .sline |
| nuclear@1 | 119 ret |
| nuclear@1 | 120 |
| nuclear@0 | 121 resb 510 - ($ - start) |
| nuclear@0 | 122 db 0x55, 0xaa |