[41] | 1 | ; Project name : Assembly Library |
---|
| 2 | ; Description : Functions for bit handling. |
---|
| 3 | |
---|
| 4 | ; Section containing code |
---|
| 5 | SECTION .text |
---|
| 6 | |
---|
| 7 | ;-------------------------------------------------------------------- |
---|
| 8 | ; Bit_GetSetCountToCXfromDXAX |
---|
| 9 | ; Parameters |
---|
| 10 | ; DX:AX: Source DWORD |
---|
| 11 | ; Returns: |
---|
| 12 | ; CX: Number of bits set in DX:AX |
---|
| 13 | ; Corrupts registers: |
---|
| 14 | ; Nothing |
---|
| 15 | ;-------------------------------------------------------------------- |
---|
| 16 | ALIGN JUMP_ALIGN |
---|
| 17 | Bit_GetSetCountToCXfromDXAX: |
---|
| 18 | push bx |
---|
| 19 | |
---|
| 20 | call Bit_GetSetCountToCXfromAX |
---|
| 21 | mov bx, cx |
---|
| 22 | xchg ax, dx |
---|
| 23 | call Bit_GetSetCountToCXfromAX |
---|
| 24 | xchg ax, dx |
---|
| 25 | add cx, bx |
---|
| 26 | |
---|
| 27 | pop bx |
---|
| 28 | ret |
---|
| 29 | |
---|
| 30 | |
---|
| 31 | ;-------------------------------------------------------------------- |
---|
| 32 | ; Bit_GetSetCountToCXfromAX |
---|
| 33 | ; Parameters |
---|
| 34 | ; AX: Source WORD |
---|
| 35 | ; Returns: |
---|
| 36 | ; CX: Number of bits set in AX |
---|
| 37 | ; Corrupts registers: |
---|
| 38 | ; Nothing |
---|
| 39 | ;-------------------------------------------------------------------- |
---|
| 40 | ALIGN JUMP_ALIGN |
---|
| 41 | Bit_GetSetCountToCXfromAX: |
---|
| 42 | push ax |
---|
| 43 | |
---|
| 44 | xor cx, cx |
---|
| 45 | ALIGN JUMP_ALIGN |
---|
| 46 | .BitScanLoop: |
---|
| 47 | shr ax, 1 |
---|
| 48 | jz SHORT .LastBitInCF |
---|
[103] | 49 | adc cl, ch |
---|
[41] | 50 | jmp SHORT .BitScanLoop |
---|
| 51 | ALIGN JUMP_ALIGN |
---|
| 52 | .LastBitInCF: |
---|
[103] | 53 | adc cl, ch |
---|
[41] | 54 | |
---|
| 55 | pop ax |
---|
| 56 | ret |
---|
| 57 | |
---|
| 58 | |
---|
| 59 | ;-------------------------------------------------------------------- |
---|
| 60 | ; Bit_SetToDXAXfromIndexInCL |
---|
| 61 | ; Parameters: |
---|
| 62 | ; CL: Index of bit to set (0...31) |
---|
| 63 | ; DX:AX: Destination DWORD with flag to be set |
---|
| 64 | ; Returns: |
---|
| 65 | ; DX:AX: DWORD with wanted bit set |
---|
| 66 | ; Corrupts registers: |
---|
| 67 | ; Nothing |
---|
| 68 | ;-------------------------------------------------------------------- |
---|
| 69 | ALIGN JUMP_ALIGN |
---|
| 70 | Bit_SetToDXAXfromIndexInCL: |
---|
| 71 | cmp cl, 16 |
---|
| 72 | jb SHORT Bit_SetToAXfromIndexInCL |
---|
| 73 | |
---|
| 74 | sub cl, 16 |
---|
| 75 | xchg ax, dx |
---|
| 76 | call Bit_SetToAXfromIndexInCL |
---|
| 77 | xchg dx, ax |
---|
| 78 | add cl, 16 |
---|
| 79 | ret |
---|
| 80 | |
---|
| 81 | ;-------------------------------------------------------------------- |
---|
| 82 | ; Bit_SetToAXfromIndexInCL |
---|
| 83 | ; Parameters: |
---|
| 84 | ; CL: Index of bit to set (0...15) |
---|
| 85 | ; AX: Destination WORD with flag to be set |
---|
| 86 | ; Returns: |
---|
| 87 | ; AX: WORD with wanted bit set |
---|
| 88 | ; Corrupts registers: |
---|
| 89 | ; Nothing |
---|
| 90 | ;-------------------------------------------------------------------- |
---|
| 91 | ALIGN JUMP_ALIGN |
---|
| 92 | Bit_SetToAXfromIndexInCL: |
---|
| 93 | push dx |
---|
| 94 | |
---|
| 95 | mov dx, 1 |
---|
| 96 | shl dx, cl |
---|
| 97 | or ax, dx |
---|
| 98 | |
---|
| 99 | pop dx |
---|
| 100 | ret |
---|