| 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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