source: xtideuniversalbios/trunk/Configurator/Src/Libraries/prntdos.asm @ 2

; File name     :   prntdos.asm
; Project name  :   Print library
; Created date  :   7.12.2009
; Last update   :   7.12.2009
; Author        :   Tomi Tilli
; Description   :   ASM library to for character and string
;                   printing using DOS.

;--------------- Equates -----------------------------

; Int 21h (DOS) functions
FN_DOS_WR_CHAR_STDOUT   EQU 02h ; Write Character to Standard Output
FN_DOS_WR_STR_STDOUT    EQU 09h ; Write String to Standard Output


;-------------- Public functions ---------------------
; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Prints character. All character printing functions must
; use this macro to print characters (so printing implementation
; can be easily modified when needed).
; 
; PRINT_CHAR
;   Parameters:
;       DL:     Character to print
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
%macro PRINT_CHAR 0
    mov     ah, FN_DOS_WR_CHAR_STDOUT
    int     21h
%endmacro


;--------------------------------------------------------------------
; Prints string. All string printing functions must
; use this macro to print strings (so printing implementation
; can be easily modified when needed).
; 
; PRINT_STR
;   Parameters:
;       DS:DX:      Ptr to '$' terminated string
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
%macro PRINT_STR 0
    mov     ah, FN_DOS_WR_STR_STDOUT
    int     21h
%endmacro


;--------------------------------------------------------------------
; Prints string and returns number of characters printed.
; All string printing functions must use this macro to print strings
; (so printing implementation can be easily modified when needed).
; 
; PRINT_STR_LEN
;   Parameters:
;       DS:DX:      Ptr to STOP terminated string
;   Returns:
;       DX:         Number of characters printed
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
%macro PRINT_STR_LEN 0
    call    Print_DosCharStr
%endmacro

ALIGN JUMP_ALIGN
Print_DosCharStr:
    push    si
    push    cx
    mov     si, dx              ; Load offset to string
    xor     cx, cx              ; Zero character counter
    cld                         ; LODSB to increment SI
ALIGN JUMP_ALIGN
.CharLoop:
    lodsb                       ; Load from [DS:SI] to AL
    cmp     al, STOP            ; End of string?
    je      .Return             ;  If so, return
    mov     dl, al              ; Copy char to DL
    PRINT_CHAR
    inc     cx                  ; Increment characters printed
    jmp     .CharLoop           ; Loop while characters left
ALIGN JUMP_ALIGN
.Return:
    mov     dx, cx              ; Copy chars printed to DX
    pop     cx
    pop     si
    ret