source: xtideuniversalbios/trunk/Assembly_Library/Src/Util/Bit.asm@ 464

Last change on this file since 464 was 376, checked in by gregli@…, 13 years ago

WIDE checkin... Added copyright and license information to sorce files, as per the GPL instructions for usage.
File size: 2.8 KB
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1; Project name : Assembly Library
2; Description : Functions for bit handling.
3
4;
5; XTIDE Universal BIOS and Associated Tools
6; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 by XTIDE Universal BIOS Team.
7;
8; This program is free software; you can redistribute it and/or modify
9; it under the terms of the GNU General Public License as published by
10; the Free Software Foundation; either version 2 of the License, or
11; (at your option) any later version.
12;
13; This program is distributed in the hope that it will be useful,
14; but WITHOUT ANY WARRANTY; without even the implied warranty of
15; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16; GNU General Public License for more details.
17; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
18;
19
20; Section containing code
21SECTION .text
22
23;--------------------------------------------------------------------
24; Bit_GetSetCountToCXfromDXAX
25; Parameters
26; DX:AX: Source DWORD
27; Returns:
28; CX: Number of bits set in DX:AX
29; Corrupts registers:
30; Nothing
31;--------------------------------------------------------------------
32ALIGN JUMP_ALIGN
33Bit_GetSetCountToCXfromDXAX:
34 push bx
35
36 call Bit_GetSetCountToCXfromAX
37 mov bx, cx
38 xchg ax, dx
39 call Bit_GetSetCountToCXfromAX
40 xchg ax, dx
41 add cx, bx
42
43 pop bx
44 ret
45
46
47;--------------------------------------------------------------------
48; Bit_GetSetCountToCXfromAX
49; Parameters
50; AX: Source WORD
51; Returns:
52; CX: Number of bits set in AX
53; Corrupts registers:
54; Nothing
55;--------------------------------------------------------------------
56ALIGN JUMP_ALIGN
57Bit_GetSetCountToCXfromAX:
58 push ax
59
60 xor cx, cx
61ALIGN JUMP_ALIGN
62.BitScanLoop:
63 shr ax, 1
64 jz SHORT .LastBitInCF
65 adc cl, ch
66 jmp SHORT .BitScanLoop
67ALIGN JUMP_ALIGN
68.LastBitInCF:
69 adc cl, ch
70
71 pop ax
72 ret
73
74
75;--------------------------------------------------------------------
76; Bit_SetToDXAXfromIndexInCL
77; Parameters:
78; CL: Index of bit to set (0...31)
79; DX:AX: Destination DWORD with flag to be set
80; Returns:
81; DX:AX: DWORD with wanted bit set
82; Corrupts registers:
83; Nothing
84;--------------------------------------------------------------------
85ALIGN JUMP_ALIGN
86Bit_SetToDXAXfromIndexInCL:
87 cmp cl, 16
88 jb SHORT Bit_SetToAXfromIndexInCL
89
90 sub cl, 16
91 xchg ax, dx
92 call Bit_SetToAXfromIndexInCL
93 xchg dx, ax
94 add cl, 16
95 ret
96
97;--------------------------------------------------------------------
98; Bit_SetToAXfromIndexInCL
99; Parameters:
100; CL: Index of bit to set (0...15)
101; AX: Destination WORD with flag to be set
102; Returns:
103; AX: WORD with wanted bit set
104; Corrupts registers:
105; Nothing
106;--------------------------------------------------------------------
107ALIGN JUMP_ALIGN
108Bit_SetToAXfromIndexInCL:
109 push dx
110
111 mov dx, 1
112 shl dx, cl
113 or ax, dx
114
115 pop dx
116 ret
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