1 | ; Project name : Assembly Library |
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2 | ; Description : Functions for bit handling. |
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3 | |
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4 | ; Section containing code |
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5 | SECTION .text |
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6 | |
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7 | ;-------------------------------------------------------------------- |
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8 | ; Bit_GetSetCountToCXfromDXAX |
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9 | ; Parameters |
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10 | ; DX:AX: Source DWORD |
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11 | ; Returns: |
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12 | ; CX: Number of bits set in DX:AX |
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13 | ; Corrupts registers: |
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14 | ; Nothing |
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15 | ;-------------------------------------------------------------------- |
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16 | ALIGN JUMP_ALIGN |
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17 | Bit_GetSetCountToCXfromDXAX: |
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18 | push bx |
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19 | |
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20 | call Bit_GetSetCountToCXfromAX |
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21 | mov bx, cx |
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22 | xchg ax, dx |
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23 | call Bit_GetSetCountToCXfromAX |
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24 | xchg ax, dx |
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25 | add cx, bx |
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26 | |
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27 | pop bx |
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28 | ret |
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29 | |
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30 | |
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31 | ;-------------------------------------------------------------------- |
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32 | ; Bit_GetSetCountToCXfromAX |
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33 | ; Parameters |
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34 | ; AX: Source WORD |
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35 | ; Returns: |
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36 | ; CX: Number of bits set in AX |
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37 | ; Corrupts registers: |
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38 | ; Nothing |
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39 | ;-------------------------------------------------------------------- |
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40 | ALIGN JUMP_ALIGN |
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41 | Bit_GetSetCountToCXfromAX: |
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42 | push ax |
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43 | |
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44 | xor cx, cx |
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45 | ALIGN JUMP_ALIGN |
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46 | .BitScanLoop: |
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47 | shr ax, 1 |
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48 | jz SHORT .LastBitInCF |
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49 | adc cl, ch |
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50 | jmp SHORT .BitScanLoop |
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51 | ALIGN JUMP_ALIGN |
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52 | .LastBitInCF: |
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53 | adc cl, ch |
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54 | |
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55 | pop ax |
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56 | ret |
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57 | |
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58 | |
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59 | ;-------------------------------------------------------------------- |
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60 | ; Bit_SetToDXAXfromIndexInCL |
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61 | ; Parameters: |
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62 | ; CL: Index of bit to set (0...31) |
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63 | ; DX:AX: Destination DWORD with flag to be set |
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64 | ; Returns: |
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65 | ; DX:AX: DWORD with wanted bit set |
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66 | ; Corrupts registers: |
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67 | ; Nothing |
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68 | ;-------------------------------------------------------------------- |
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69 | ALIGN JUMP_ALIGN |
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70 | Bit_SetToDXAXfromIndexInCL: |
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71 | cmp cl, 16 |
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72 | jb SHORT Bit_SetToAXfromIndexInCL |
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73 | |
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74 | sub cl, 16 |
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75 | xchg ax, dx |
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76 | call Bit_SetToAXfromIndexInCL |
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77 | xchg dx, ax |
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78 | add cl, 16 |
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79 | ret |
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80 | |
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81 | ;-------------------------------------------------------------------- |
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82 | ; Bit_SetToAXfromIndexInCL |
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83 | ; Parameters: |
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84 | ; CL: Index of bit to set (0...15) |
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85 | ; AX: Destination WORD with flag to be set |
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86 | ; Returns: |
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87 | ; AX: WORD with wanted bit set |
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88 | ; Corrupts registers: |
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89 | ; Nothing |
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90 | ;-------------------------------------------------------------------- |
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91 | ALIGN JUMP_ALIGN |
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92 | Bit_SetToAXfromIndexInCL: |
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93 | push dx |
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94 | |
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95 | mov dx, 1 |
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96 | shl dx, cl |
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97 | or ax, dx |
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98 | |
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99 | pop dx |
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100 | ret |
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