| 1 | ; File name : prntdos.asm
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| 2 | ; Project name : Print library
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| 3 | ; Created date : 7.12.2009
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| 4 | ; Last update : 7.12.2009
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| 5 | ; Author : Tomi Tilli
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| 6 | ; Description : ASM library to for character and string
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| 7 | ; printing using DOS.
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| 8 |
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| 9 | ;--------------- Equates -----------------------------
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| 10 |
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| 11 | ; Int 21h (DOS) functions
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| 12 | FN_DOS_WR_CHAR_STDOUT EQU 02h ; Write Character to Standard Output
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| 13 | FN_DOS_WR_STR_STDOUT EQU 09h ; Write String to Standard Output
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| 14 |
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| 15 |
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| 16 | ;-------------- Public functions ---------------------
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| 17 | ; Section containing code
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| 18 | SECTION .text
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| 19 |
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| 20 | ;--------------------------------------------------------------------
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| 21 | ; Prints character. All character printing functions must
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| 22 | ; use this macro to print characters (so printing implementation
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| 23 | ; can be easily modified when needed).
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| 24 | ;
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| 25 | ; PRINT_CHAR
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| 26 | ; Parameters:
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| 27 | ; DL: Character to print
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| 28 | ; Returns:
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| 29 | ; Nothing
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| 30 | ; Corrupts registers:
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| 31 | ; AX
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| 32 | ;--------------------------------------------------------------------
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| 33 | %macro PRINT_CHAR 0
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| 34 | mov ah, FN_DOS_WR_CHAR_STDOUT
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| 35 | int 21h
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| 36 | %endmacro
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| 37 |
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| 38 |
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| 39 | ;--------------------------------------------------------------------
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| 40 | ; Prints string. All string printing functions must
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| 41 | ; use this macro to print strings (so printing implementation
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| 42 | ; can be easily modified when needed).
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| 43 | ;
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| 44 | ; PRINT_STR
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| 45 | ; Parameters:
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| 46 | ; DS:DX: Ptr to '$' terminated string
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| 47 | ; Returns:
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| 48 | ; Nothing
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| 49 | ; Corrupts registers:
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| 50 | ; AX
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| 51 | ;--------------------------------------------------------------------
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| 52 | %macro PRINT_STR 0
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| 53 | mov ah, FN_DOS_WR_STR_STDOUT
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| 54 | int 21h
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| 55 | %endmacro
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| 56 |
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| 57 |
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| 58 | ;--------------------------------------------------------------------
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| 59 | ; Prints string and returns number of characters printed.
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| 60 | ; All string printing functions must use this macro to print strings
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| 61 | ; (so printing implementation can be easily modified when needed).
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| 62 | ;
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| 63 | ; PRINT_STR_LEN
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| 64 | ; Parameters:
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| 65 | ; DS:DX: Ptr to STOP terminated string
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| 66 | ; Returns:
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| 67 | ; DX: Number of characters printed
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| 68 | ; Corrupts registers:
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| 69 | ; AX
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| 70 | ;--------------------------------------------------------------------
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| 71 | %macro PRINT_STR_LEN 0
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| 72 | call Print_DosCharStr
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| 73 | %endmacro
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| 74 |
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| 75 | ALIGN JUMP_ALIGN
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| 76 | Print_DosCharStr:
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| 77 | push si
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| 78 | push cx
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| 79 | mov si, dx ; Load offset to string
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| 80 | xor cx, cx ; Zero character counter
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| 81 | cld ; LODSB to increment SI
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| 82 | ALIGN JUMP_ALIGN
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| 83 | .CharLoop:
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| 84 | lodsb ; Load from [DS:SI] to AL
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| 85 | cmp al, STOP ; End of string?
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| 86 | je .Return ; If so, return
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| 87 | mov dl, al ; Copy char to DL
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| 88 | PRINT_CHAR
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| 89 | inc cx ; Increment characters printed
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| 90 | jmp .CharLoop ; Loop while characters left
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| 91 | ALIGN JUMP_ALIGN
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| 92 | .Return:
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| 93 | mov dx, cx ; Copy chars printed to DX
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| 94 | pop cx
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| 95 | pop si
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| 96 | ret
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