VirtualBox

source: vbox/trunk/src/VBox/Runtime/common/asm/ASMBitNextClear-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: ASMBitNextClear-generic.cpp 98103 2023-01-17 14:15:46Z vboxsync $ */
2/** @file
3 * IPRT - ASMBitNextClear - 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(int) ASMBitNextClear(const volatile void RT_FAR *pvBitmap, uint32_t cBits, uint32_t iBitPrev) RT_NOTHROW_DEF
48{
49 const volatile uint32_t RT_FAR *pau32Bitmap = (const volatile uint32_t RT_FAR *)pvBitmap;
50 int iBit = ++iBitPrev & 31;
51 Assert(!(cBits & 31));
52 Assert(!((uintptr_t)pvBitmap & 3));
53 if (iBit)
54 {
55 /*
56 * Inspect the 32-bit word containing the unaligned bit.
57 */
58 uint32_t u32 = ~RT_LE2H_U32(pau32Bitmap[iBitPrev / 32]) >> iBit;
59 if (u32)
60 return iBitPrev + ASMBitFirstSetU32(u32) - 1;
61
62 /*
63 * Skip ahead and see if there is anything left to search.
64 */
65 iBitPrev |= 31;
66 iBitPrev++;
67 if (cBits <= (uint32_t)iBitPrev)
68 return -1;
69 }
70
71 /*
72 * 32-bit aligned search, let ASMBitFirstClear do the dirty work.
73 */
74 iBit = ASMBitFirstClear(&pau32Bitmap[iBitPrev / 32], cBits - iBitPrev);
75 if (iBit >= 0)
76 iBit += iBitPrev;
77 return iBit;
78}
79
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