[87184] | 1 | /* $Id: ASMBitFirstSet-generic.cpp 98103 2023-01-17 14:15:46Z vboxsync $ */
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| 2 | /** @file
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[87193] | 3 | * IPRT - ASMBitFirstSet - generic C implementation.
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[87184] | 4 | */
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| 5 |
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| 6 | /*
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[98103] | 7 | * Copyright (C) 2006-2023 Oracle and/or its affiliates.
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[87184] | 8 | *
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[96407] | 9 | * This file is part of VirtualBox base platform packages, as
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| 10 | * available from https://www.virtualbox.org.
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[87184] | 11 | *
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[96407] | 12 | * This program is free software; you can redistribute it and/or
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| 13 | * modify it under the terms of the GNU General Public License
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| 14 | * as published by the Free Software Foundation, in version 3 of the
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| 15 | * License.
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| 16 | *
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| 17 | * This program is distributed in the hope that it will be useful, but
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| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 20 | * General Public License for more details.
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| 21 | *
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| 22 | * You should have received a copy of the GNU General Public License
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| 23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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| 24 | *
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[87184] | 25 | * The contents of this file may alternatively be used under the terms
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| 26 | * of the Common Development and Distribution License Version 1.0
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[96407] | 27 | * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
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| 28 | * in the VirtualBox distribution, in which case the provisions of the
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[87184] | 29 | * CDDL are applicable instead of those of the GPL.
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| 30 | *
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| 31 | * You may elect to license modified versions of this file under the
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| 32 | * terms and conditions of either the GPL or the CDDL or both.
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[96407] | 33 | *
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| 34 | * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
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[87184] | 35 | */
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| 36 |
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| 37 |
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| 38 | /*********************************************************************************************************************************
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| 39 | * Header Files *
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| 40 | *********************************************************************************************************************************/
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| 41 | #include <iprt/asm.h>
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| 42 | #include "internal/iprt.h"
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| 43 |
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[87192] | 44 | #include <iprt/assert.h>
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[87184] | 45 |
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[87192] | 46 |
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[87203] | 47 | RTDECL(int32_t) ASMBitFirstSet(const volatile void RT_FAR *pvBitmap, uint32_t cBits) RT_NOTHROW_DEF
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[87184] | 48 | {
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[87192] | 49 | const volatile size_t RT_FAR *pu = (const volatile size_t RT_FAR *)pvBitmap;
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| 50 | Assert(!(cBits & 31));
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[87193] | 51 | Assert(!((uintptr_t)pvBitmap & 3));
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[87192] | 52 |
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[87193] | 53 | #if ARCH_BITS > 32
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| 54 | /* Deal with misaligned bitmaps (happens all the time via ASMBitNextClear()). */
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| 55 | if (!((uintptr_t)pvBitmap & 7) && cBits >= 32)
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| 56 | {
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| 57 | uint32_t u32 = *(const volatile uint32_t RT_FAR *)pu;
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[87229] | 58 | if (u32 != 0)
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[87193] | 59 | {
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| 60 | size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
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| 61 | return iBaseBit + ASMBitFirstSetU32(RT_LE2H_U32(u32)) - 1;
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| 62 | }
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| 63 | pu = (const volatile size_t RT_FAR *)((uintptr_t)pu + sizeof(uint32_t));
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| 64 | cBits -= 32;
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| 65 | }
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| 66 | #endif
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| 67 |
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| 68 | /* Main search loop: */
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[87192] | 69 | while (cBits >= sizeof(size_t) * 8)
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| 70 | {
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| 71 | size_t u = *pu;
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[87193] | 72 | if (u == 0)
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[87192] | 73 | { }
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[87185] | 74 | else
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[87192] | 75 | {
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| 76 | size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
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| 77 | #if ARCH_BITS == 32
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[87193] | 78 | return iBaseBit + ASMBitFirstSetU32(RT_LE2H_U32(u)) - 1;
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[87192] | 79 | #elif ARCH_BITS == 64
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[87193] | 80 | return iBaseBit + ASMBitFirstSetU64(RT_LE2H_U64(u)) - 1;
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[87192] | 81 | #else
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[87193] | 82 | # error "ARCH_BITS is not supported"
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[87192] | 83 | #endif
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| 84 | }
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| 85 |
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| 86 | pu++;
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| 87 | cBits -= sizeof(size_t) * 8;
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| 88 | }
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| 89 |
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| 90 | #if ARCH_BITS > 32
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[87193] | 91 | /* Final 32-bit item (unlikely)? */
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| 92 | if (cBits < 32)
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| 93 | { }
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| 94 | else
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[87192] | 95 | {
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| 96 | uint32_t u32 = *(const volatile uint32_t RT_FAR *)pu;
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[87229] | 97 | if (u32 != 0)
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[87192] | 98 | {
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| 99 | size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
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[87193] | 100 | return iBaseBit + ASMBitFirstSetU32(RT_LE2H_U32(u32)) - 1;
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[87192] | 101 | }
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| 102 | }
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| 103 | #endif
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| 104 |
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| 105 | return -1;
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[87184] | 106 | }
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| 107 |
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