boo-os/kernel.asm

@ $00000:
    label vbuf:

@ $4B000:
    $CB000 ; Set Instruction Pointer to $5B000
   label RAX:
    $0000000 ; RAX
    $0000000 ; R2 - Temp Scratch
    $0000000 ; R3 - Temp Scratch
    label ARG1
    $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:

hlt

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 prompt [sarah@boo] >
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 ascii jump_label JUMP
data ascii diss_label DISS

data buffer command_line_input 64


data buffers 48 terminal 64
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 $3 $4 $5
label strcmp:
    loadi $3 $0
    label strcmp_loop:
        rload $4 $1
        rload $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
        inc $3
        tx $1 $3 ;check expected length
        tx $2 $6 ;check max length

        jneq +3 ; if expected_length == max_length
             loadi $1 1 ; return true
             ret

        jmp strcmp_loop


label shift_terminal:

        ; copy terminal 0 to terminal 1
        loadi $4 terminal[2] ;src
        bcopy $4 terminal[3] ; dest

        ; copy terminal 0 to terminal 1
        loadi $4 terminal[1] ;src
        bcopy $4 terminal[2] ; dest

        ; copy terminal 0 to terminal 1
        loadi $4 terminal[0] ;src
        bcopy $4 terminal[1] ; dest

        ; copy command line to terminal 0
        loadi $4 command_line_input ;src
        bcopy $4 terminal[0] ; dest

        bzero command_line_input

        ret

data ascii diss_load LOAD
data ascii diss_call CALL
data ascii diss_unknown UNKNOWN

label _disassemble_cmd:
    loadi $1 $20
    bappend $1 command_line_input ; space

    loadi $1 1c ; 28 bits
    shift $4 $1 $2 ;
    loadi $5 diss_unknown

    loadi $1 $3
    jneq +2
        loadi $5 diss_load

    loadi $1 $C
    jneq +2
        loadi $5 diss_call

    label _disassemble_cmd_inner:
        rload $5 $1
        loadi $2 0
        jneq +2
            ret
        bappend $1 command_line_input
        inc $5
        jmp _disassemble_cmd_inner


label disassemble:
    call string_to_num
    ; $1 contains a actual address we want to diss
    loadi $2 $FFFFFF;
    jlt +2
        ret
    rload $1 $8 ;
    call shift_terminal
    bzero command_line_input
    loadi $6 7
    label _disassemble_inner:
        tx $4 $8 ; temp store for command
        loadi $5 4 ; number of bits to shift
        mul $6 $5 $5 ; number of bits to shift command >> (count * 8) (3*8, 2*8, 1*8, 0*8)
        shift $4 $5 $1 ; do the actual shift
        loadi $5 $00000F
        and $1 $5 $4
        ; clobbers 1 2 3 4
        call num_to_char;
        bappend $4 command_line_input
        tx $1 $6
        loadi $2 0
        jneq +4
            tx $4 $8
            call _disassemble_cmd
            ret
    dec $6
    jmp _disassemble_inner

label jump:
    call string_to_num
    ijmp $1 ;;lol
    ret

label do_shell:
        loadi $4 @command_line_input
        loadi $5 quit_label
        loadi $6 4
        call strcmp
        loadi $2 1
        jneq +2 ; if the command is QUIT, then hlt the machine!! A shell is born
            hlt

        loadi $4 @command_line_input
        loadi $5 diss_label
        loadi $6 4
        call strcmp
        loadi $2 1
        jneq +6 ; if the command is QUIT, then hlt the machine!! A shell is born
            loadi $4 @command_line_input
            loadi $5 5
            add $4 $5 $4
            call disassemble
            ret

        loadi $4 @command_line_input
        loadi $5 jump_label
        loadi $6 4
        call strcmp
        loadi $2 1
        jneq +5 ; if the command is QUIT, then hlt the machine!! A shell is born
            loadi $4 @command_line_input
            loadi $5 5
            add $4 $5 $4
            call jump

        ret

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


    ; print some shell history
    loadi $9 5;
    loadi $A 180;
    call set_pos
    loadi $4 @terminal[3]
    call draw_string;

    loadi $9 5;
    loadi $A 190;
    call set_pos
    loadi $4 @terminal[2]
    call draw_string;

    loadi $9 5;
    loadi $A 1A0;
    call set_pos
    loadi $4 @terminal[1]
    call draw_string;

    loadi $9 5;
    loadi $A 1B0;
    call set_pos
    loadi $4 @terminal[0]
    call draw_string;

    loadi $9 5;
    loadi $A 1C0;
    call set_pos

    loadi $4 prompt
    call draw_string;

    loadi $9 70;
    loadi $A 1C0;
    call set_pos

    loadi $4 @command_line_input
    call draw_string;

    updsp
    clr
    jmp $CB000;