boo-os/example.asm

@ $00000:
    label vbuf:

@ $4B000:
    $CB000 ; Set Instruction Pointer to $5B000
   label RAX:
    $0000000 ; RAX
    $0000000 ; R2 - Temp Scratch
    $0000000 ; R3 - Temp Scratch
    $0000000 ; R4 - ARG 1
    $0000000 ; R5 - ARG 2
    $0000000 ; R6 - ARG 3
    $0000000 ; R7 - ARG 4
    $0000000 ; R8 - ARG 5
    $0000000 ; RX
    $0000000 ; RY
        label R(B):
    $0000000 ; RVBUF (RY * 640) + RX
    label R(c):
    $0000001 ; Ghost Post

@ $4B040:
    label CycleCount:
        $0000000; Cycles
    label KeyPressedState:
        $0000000; The ID of a Key Being Pressed (If Any)

@ $4B0C0:

import display.asm ; setpos
import charset.asm ; charset + hex strings
import strings.asm ; draw_char, draw_string
import util.asm ; print_addr
import graphics.asm; draw_vline, draw_hline, draw_rect

; Common Strings
data ascii boo_os_version Boo OS v0.0.1
data ascii HelloWorld Welcome to Boo OS Running on Boo Byte Code!
data ascii Welcome !@#$%^&*()_+=-0987654321
data ascii Introspection We Can Now Do Introspection:
data ascii label_rax RAX:
data ascii label_rip RIP:
data ascii label_cycles Instruction Count:
data ascii label_keypress Current Key Pressed:
data image boo_os.png booos.png
data image boo_os_small.png booos-small.png
data image wallpaper.png wallpaper.png

data ascii quit_label QUIT
data buffer command_line_input 256

meta

; strcmp compares 2 strings in a byte-by-byte manner, incrementing ptrs as it goes. Returns 1 if both bytes
; point to 0. Returns 0 (fail) if it encounters 2 different bytes
; clobbers $1 $2 $4 $5
label strcmp:
    label strcmp_loop:
        ldstore $4 $1
        ldstore $5 $2
        jeq +3 ; if either of these differ then return 0 to indicate these strings don't match
            loadi $1 0
            ret
        loadi $2 0
        jneq +3 ; if both are 0 then we have reached the end of the string
            loadi $1 1
            ret
        inc $4
        inc $5
        jmp strcmp_loop



label handle_keypress:

    ; Check for Backspace
    loadi $1 $7F
    tx $2 $4
    jneq +3
        bdelete $4 command_line_input
        ret

    ; Check for Return
    loadi $1 $0A
    tx $2 $4
    jneq +8
        loadi $4 @command_line_input
        loadi $5 quit_label
        call strcmp
        loadi $2 1
        jneq +2 ; if the command is QUIT, then hlt the machine!! A shell is born
            hlt
        ret

    bappend $4 command_line_input
    ret

; Kernel Begins
@ $CB000:

    loadi $9 $0; 640-64
    loadi $A $0; 480-64
    call set_pos
    loadi $4 wallpaper.png
    call draw_image

    loadi $4 $0
    loadi $5 $0
    loadi $6 $280
    loadi $7 $10
    loadi $8 $222222
    call draw_filled_rect

    loadi $9 $5;
    loadi $A $5;
    call set_pos
    loadi $4 boo_os_version
    call draw_string;

    loadi $9 $1A0;
    loadi $A $5;
    call set_pos
    loadi $4 label_cycles
    call draw_string;

    loadi $4 $4B000
    loadi $2 $40
    add $2 $4 $4
    call print_addr

    loadi $9 1;
    loadi $A 20;
    call set_pos

    loadi $4 HelloWorld
    call draw_string;



    loadi $1 0
    load $2 KeyPressedState
    store $1 KeyPressedState
    jeq +3
        tx $4 $2
        call handle_keypress

    loadi $9 1;
    loadi $A 60;
    call set_pos
    loadi $4 @command_line_input
    call draw_string;



    updsp
    clr
    jmp $CB000;