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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