378 lines
5.0 KiB
NASM
378 lines
5.0 KiB
NASM
[BITS 16]
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; Update the IVT with our interrupt handler
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mov bx, 0
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mov ds, bx
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mov word [ds:136], ihdlr
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mov word [ds:138], cs
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mov ax, 2000h
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mov ds, ax
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pop ax
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mov byte [bootdisk], al
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; Set up kernel specifics
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; Root Directory Entries will be at 2000h:2000h
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; FAT1 will be at 2000h:4000h
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mov ax, 2000h
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mov es, ax
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mov bx, 2000h
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mov ah, 2
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mov al, 16
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mov cl, 20
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mov ch, 0
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mov dh, 0
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mov dl, [bootdisk]
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; Load sectors 20 through 36 to 2000h:2000h
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int 13h
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mov ax, 2000h
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mov es, ax
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mov bx, 4000h
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mov ah, 2
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mov al, 9
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mov cl, 2
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mov ch, 0
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mov dh, 0
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mov dl, [bootdisk]
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; Load sectors 2 through 11 to 2000h:4000h
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int 13h
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push msg
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call print
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cmd_loop:
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push cmd_prompt
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call print
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; Clear command buffer
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mov al, 0
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mov di, user_cmd
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mov cx, 64
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clear_loop:
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stosb
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loop clear_loop
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push user_cmd
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push 64
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call readline
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push newline
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call print
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mov si, user_cmd
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mov di, cmd_help_text
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mov cx, 4
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rep cmpsb
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je cmd_help
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mov si, user_cmd
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mov di, cmd_clear_text
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mov cx, 5
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rep cmpsb
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je cmd_clear
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; If the user hasn't run a command we should determine if they're trying to run a program.
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; Decode input to filename
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push user_cmd
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call decode_filename
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; Search for file
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mov si, ax
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call file_exists
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; If it doesn't exist jump to error
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cmp ax, 0
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je handle_error
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; If the file exists load it at 3000h:0
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push ax
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push 0
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push 3000h
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call load_file
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; Make a call to 3000h:0
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call 3000h:0
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; We've now returned.
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; Recover ds
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mov ax, 2000h
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mov ds, ax
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mov es, ax
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; jmp $
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; Loop
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jmp cmd_loop
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handle_error:
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push cmd_err
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call print
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jmp cmd_loop
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cmd_help:
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push cmd_help_msg
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call print
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jmp cmd_loop
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cmd_help_msg:
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db "XnoeOS Help Dialogue", 13, 10
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db "--------------------", 13, 10
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db "Commands: ", 13, 10
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db " - help", 13, 10
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db " : Displays this message", 13, 10
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db " - clear", 13, 10
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db " : Clears the screen", 13, 10
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db 0
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cmd_clear:
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mov ah, 02h
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mov dh, 0
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mov dl, 0
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int 10h
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mov ah, 0ah
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mov cx, 2000
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mov al, 20h
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int 10h
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jmp cmd_loop
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data:
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msg db "Kernel OK!", 13, 10, 0
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cmd_prompt db ">>> ", 0
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cmd_err db "Bad Command or filename!", 13, 10, 13, 10, 0
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cmd_help_text db "help"
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cmd_clear_text db "clear"
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newline db 13, 10, 0
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bootdisk db 0
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program_two db "HELLO BIN"
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user_cmd:
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times 64 db 0
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; print(str)
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print:
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push bp
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mov bp, sp
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mov si, [bp + 4]
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mov ah, 0eh
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mov cx, 1
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mov bh, 0
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print_loop:
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lodsb
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cmp al, 0
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je print_exit
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int 10h
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jmp print_loop
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print_exit:
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pop bp
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ret 2
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; readline(max length, buffer)
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readline:
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push bp
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mov bp, sp
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mov di, [bp + 6]
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mov bx, 0
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readline_loop:
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mov ah, 0h
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int 16h
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cmp ah, 01ch
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je readline_exit
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cmp ah, 0eh
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je readline_backspace
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mov byte [di], al
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inc di
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inc bx
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mov ah, 0eh
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mov cx, 1
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int 10h
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mov ax, [bp + 4]
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cmp bx, ax
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je readline_exit
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jmp readline_loop
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readline_backspace:
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cmp bx, 0
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je readline_loop
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dec di
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dec bx
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mov ah, 0eh
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mov cx, 1
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int 10h
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mov ah, 0ah
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mov cx, 1
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mov al, 20h
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int 10h
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jmp readline_loop
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readline_exit:
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pop bp
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ret 4
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file_exists:
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push si
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mov bp, sp
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mov cx, 256 ; Hardcode the amount of entries for now
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mov ax, ds
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mov es, ax
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mov ax, 0
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file_exists_loop:
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pop si ; Get value in to si
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push si ; Keep track of original value
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xchg cx, dx
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mov di, 2000h ; Root Entries is at 2000h:2000h
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add di, ax
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mov cx, 11
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rep cmpsb
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je file_exists_found
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add ax, 32
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xchg cx, dx
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loop file_exists_loop
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file_exists_not_found:
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mov ax, 0
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pop si
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ret
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file_exists_found:
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mov ax, [es:di+0fh]
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pop si
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ret
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; loadfile(segment, offset, initsector)
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load_file:
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push bp
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mov bp, sp
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mov ax, word [bp + 4]
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mov es, ax
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load_file_loop:
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mov bx, word [bp + 6]
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mov al, byte [bp + 8]
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add al, 34
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mov cl, al
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mov al, 1
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mov ah, 2
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mov ch, 0
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mov dh, 0
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mov dl, byte [bootdisk]
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int 13h
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add word [bp + 6], 512
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mov si, word [bp + 8]
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shl si, 1
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add si, 4000h
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; add si, 1
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cmp word [ds:si], 0ffffh
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je load_file_loaded
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add word [bp + 8], 1
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jmp load_file_loop
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load_file_loaded:
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pop bp
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ret 6
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decode_filename:
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push bp
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mov bp, sp
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push word [bp + 4]
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; First we want to clear the buffer with 0x20s
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mov al, 20h
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mov cx, 11
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mov di, _decode_buffer
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decode_clear_loop:
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stosb
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loop decode_clear_loop
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pop si
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mov cx, 8
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mov bx, 0
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decode_filename_loop:
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lodsb
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cmp al, "."
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je decode_filename_stage2
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mov byte [_decode_buffer+bx], al
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inc bx
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loop decode_filename_loop
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decode_filename_stage2:
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mov bx, 8
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mov cx, 3
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; add si, 1
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decode_filename_stage2_loop:
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lodsb
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cmp al, 0
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je decode_filename_final
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mov byte [_decode_buffer+bx], al
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inc bx
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loop decode_filename_stage2_loop
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decode_filename_final:
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pop bp
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mov ax, _decode_buffer
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ret 2
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_decode_buffer:
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times 11 db 0
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ihdlr:
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cmp ah, 01h
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jne _ihdlr_2
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push si
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call print
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_ihdlr_2:
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cmp ah, 02h
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jne _ihdlr_3
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push si
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push di
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call readline
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_ihdlr_3:
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iret |