VirtualBox

source: vbox/trunk/src/VBox/Runtime/common/asm/ASMBitFirstClear-generic.cpp@ 103795

Last change on this file since 103795 was 98103, checked in by vboxsync, 2 years ago

Copyright year updates by scm.

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1/* $Id: ASMBitFirstClear-generic.cpp 98103 2023-01-17 14:15:46Z vboxsync $ */
2/** @file
3 * IPRT - ASMBitFirstClear - generic C implementation.
4 */
5
6/*
7 * Copyright (C) 2006-2023 Oracle and/or its affiliates.
8 *
9 * This file is part of VirtualBox base platform packages, as
10 * available from https://www.virtualbox.org.
11 *
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation, in version 3 of the
15 * License.
16 *
17 * This program is distributed in the hope that it will be useful, but
18 * WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * General Public License for more details.
21 *
22 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, see <https://www.gnu.org/licenses>.
24 *
25 * The contents of this file may alternatively be used under the terms
26 * of the Common Development and Distribution License Version 1.0
27 * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
28 * in the VirtualBox distribution, in which case the provisions of the
29 * CDDL are applicable instead of those of the GPL.
30 *
31 * You may elect to license modified versions of this file under the
32 * terms and conditions of either the GPL or the CDDL or both.
33 *
34 * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
35 */
36
37
38/*********************************************************************************************************************************
39* Header Files *
40*********************************************************************************************************************************/
41#include <iprt/asm.h>
42#include "internal/iprt.h"
43
44#include <iprt/assert.h>
45
46
47RTDECL(int32_t) ASMBitFirstClear(const volatile void RT_FAR *pvBitmap, uint32_t cBits) RT_NOTHROW_DEF
48{
49 const volatile size_t RT_FAR *pu = (const volatile size_t RT_FAR *)pvBitmap;
50 Assert(!(cBits & 31));
51 Assert(!((uintptr_t)pvBitmap & 3));
52
53#if ARCH_BITS > 32
54 /* Deal with misaligned bitmaps (happens all the time via ASMBitNextClear()). */
55 if (!((uintptr_t)pvBitmap & 7) && cBits >= 32)
56 {
57 uint32_t u32 = *(const volatile uint32_t RT_FAR *)pu;
58 if (u32 != UINT32_MAX)
59 {
60 size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
61 return iBaseBit + ASMBitFirstSetU32(~RT_LE2H_U32(u32)) - 1;
62 }
63 pu = (const volatile size_t RT_FAR *)((uintptr_t)pu + sizeof(uint32_t));
64 cBits -= 32;
65 }
66#endif
67
68 /* Main search loop: */
69 while (cBits >= sizeof(size_t) * 8)
70 {
71 size_t u = *pu;
72 if (u == ~(size_t)0)
73 { }
74 else
75 {
76 size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
77#if ARCH_BITS == 32
78 return iBaseBit + ASMBitFirstSetU32(~RT_LE2H_U32(u)) - 1;
79#elif ARCH_BITS == 64
80 return iBaseBit + ASMBitFirstSetU64(~RT_LE2H_U64(u)) - 1;
81#else
82# error "ARCH_BITS is not supported"
83#endif
84 }
85
86 pu++;
87 cBits -= sizeof(size_t) * 8;
88 }
89
90#if ARCH_BITS > 32
91 /* Final 32-bit item (unlikely)? */
92 if (cBits < 32)
93 { }
94 else
95 {
96 uint32_t u32 = *(const volatile uint32_t RT_FAR *)pu;
97 if (u32 != UINT32_MAX)
98 {
99 size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
100 return iBaseBit + ASMBitFirstSetU32(~RT_LE2H_U32(u32)) - 1;
101 }
102 }
103#endif
104
105 return -1;
106}
107
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