initial commit, asm operating system with the MikeOS bootloader

source/features/screen.asm

@@ -0,0 +1,152 @@
+; ==================================================================
+; MikeOS -- The Mike Operating System kernel
+; Copyright (C) 2006 - 2021 MikeOS Developers -- see doc/LICENSE.TXT
+;
+; SCREEN HANDLING SYSTEM CALLS
+; ==================================================================
+
+; ------------------------------------------------------------------
+; os_print_string -- Displays text
+; IN: SI = message location (zero-terminated string)
+; OUT: Nothing (registers preserved)
+
+os_print_string:
+	pusha
+
+	mov ah, 0Eh			; int 10h teletype function, we're telling the BIOS we will print something
+
+.repeat:
+	lodsb				; Get char from si into al
+	cmp al, 0			; Compare al to 0
+	je .done			; If char is zero, end of string
+
+	int 10h				; Otherwise, print it
+	jmp .repeat			; And move on to next char
+
+.done:
+	popa
+	ret
+
+; Exact same as the above procedure, but this adds a newline 
+; after priting, similar to the difference between Rust's print! and println!
+os_print_string_nl:				pusha
+
+	mov ah, 0Eh			; int 10h teletype function, we're telling the BIOS we will print something
+
+.repeat:
+	lodsb				; Get char from si into al
+	cmp al, 0			; Compare al to 0
+	je .done			; If char is zero, end of string
+
+	int 10h				; Otherwise, print it
+	jmp .repeat			; And move on to next char
+
+.done:
+	call os_print_newline
+	popa
+	ret
+
+; --------------------------------------------
+
+os_print_newline:
+	pusha
+
+	mov ah, 03h
+	int 10h
+	
+	mov ah, 02h
+	add dh, 1
+	mov dl, 0
+	int 10h
+	
+	popa
+	ret
+		
+
+; -------------------------------------------
+
+os_clear_screen:
+        pusha
+
+	mov ah, 00h
+	mov al, 03h 		; Set video mode to textmode (80x25). 16 colors, 8 pages
+	int 10h
+
+	mov ah, 02h
+	mov dh, 0
+	mov dl, 0
+	int 10h
+
+        popa
+        ret
+
+; -------------------------------------------
+
+; AX = key pressed
+os_read_input:
+	mov ah, 11h			; BIOS call to check for key
+	int 16h				; Interrupt
+	jnz .key_pressed		; Jump if input isn't 0
+	
+	hlt
+	jmp os_read_input
+
+.key_pressed:
+	mov ah, 10h
+	int 16h
+	ret
+
+; -------------------------------------------
+
+os_display_input:
+	pusha
+	
+	call .check_key_pressed
+
+        jmp os_display_input
+
+.check_key_pressed:	
+        call os_read_input
+
+	cmp al, 08h
+	je .backspace
+
+	cmp al, 0Dh
+	je .enter_key
+
+	cmp al, 1Bh
+	je .esc_key
+
+	call .print_current_input
+	ret
+
+.esc_key:
+	call os_reboot
+
+.enter_key:
+	mov al, 0
+	stosb
+	mov di, user_input
+	
+	call os_read_cli
+
+.backspace:
+	mov ah, 0Eh
+
+	mov al, 08h
+	int 10h
+	mov al, 20h
+	int 10h
+	mov al, 08h
+	int 10h
+
+	dec di
+	jmp os_display_input
+
+.print_current_input:
+	stosb
+	
+	mov ah, 0Eh
+	int 10h
+
+	ret