| 1 | /* $Id: ASMMemFirstNonZero-generic.cpp 103010 2024-01-24 00:14:44Z vboxsync $ */
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| 2 | /** @file
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| 3 | * IPRT - ASMMemZeroPage - generic C implementation.
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2006-2023 Oracle and/or its affiliates.
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| 8 | *
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| 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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| 11 | *
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| 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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| 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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| 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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| 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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| 33 | *
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| 34 | * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
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| 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-mem.h>
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| 42 | #include "internal/iprt.h"
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| 43 |
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| 44 |
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| 45 | RTDECL(void RT_FAR *) ASMMemFirstNonZero(void const RT_FAR *pv, size_t cb) RT_NOTHROW_DEF
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| 46 | {
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| 47 | uint8_t const *pb = (uint8_t const RT_FAR *)pv;
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| 48 |
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| 49 | /*
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| 50 | * If we've got a large buffer to search, do it in larger units.
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| 51 | */
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| 52 | if (cb >= sizeof(size_t) * 2)
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| 53 | {
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| 54 | /* Align the pointer: */
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| 55 | while ((uintptr_t)pb & (sizeof(size_t) - 1))
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| 56 | {
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| 57 | if (RT_LIKELY(*pb == 0))
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| 58 | { /* likely */ }
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| 59 | else
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| 60 | return (void RT_FAR *)pb;
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| 61 | cb--;
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| 62 | pb++;
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| 63 | }
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| 64 |
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| 65 | /* Scan in size_t sized words: */
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| 66 | while ( cb >= sizeof(size_t)
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| 67 | && *(size_t *)pb == 0)
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| 68 | {
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| 69 | pb += sizeof(size_t);
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| 70 | cb -= sizeof(size_t);
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| 71 | }
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| 72 | }
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| 73 |
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| 74 | /*
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| 75 | * Search byte by byte.
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| 76 | */
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| 77 | for (; cb; cb--, pb++)
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| 78 | if (RT_LIKELY(*pb == 0))
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| 79 | { /* likely */ }
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| 80 | else
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| 81 | return (void RT_FAR *)pb;
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| 82 |
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| 83 | return NULL;
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| 84 | }
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| 85 |
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