| 1 | /* $Id: ASMMemFirstNonZero-generic.cpp 87186 2021-01-06 12:47:49Z 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) 2006-2021 Oracle Corporation
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| 8 | *
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| 9 | * This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | * available from http://www.virtualbox.org. This file is free software;
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| 11 | * you can redistribute it and/or modify it under the terms of the GNU
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| 12 | * General Public License (GPL) as published by the Free Software
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| 13 | * Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | *
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| 17 | * The contents of this file may alternatively be used under the terms
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| 18 | * of the Common Development and Distribution License Version 1.0
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| 19 | * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
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| 20 | * VirtualBox OSE distribution, in which case the provisions of the
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| 21 | * CDDL are applicable instead of those of the GPL.
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| 22 | *
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| 23 | * You may elect to license modified versions of this file under the
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| 24 | * terms and conditions of either the GPL or the CDDL or both.
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| 25 | */
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| 26 |
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| 27 |
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| 28 | /*********************************************************************************************************************************
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| 29 | * Header Files *
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| 30 | *********************************************************************************************************************************/
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| 31 | #include <iprt/asm.h>
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| 32 | #include "internal/iprt.h"
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| 33 |
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| 34 |
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| 35 | DECLASM(void RT_FAR *) ASMMemFirstNonZero(void const RT_FAR *pv, size_t cb) RT_NOTHROW_DEF
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| 36 | {
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| 37 | uint8_t const *pb = (uint8_t const RT_FAR *)pv;
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| 38 |
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| 39 | /*
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| 40 | * If we've got a large buffer to search, do it in larger units.
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| 41 | */
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| 42 | if (cb >= sizeof(size_t) * 2)
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| 43 | {
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| 44 | /* Align the pointer: */
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| 45 | while ((uintptr_t)pb & (sizeof(size_t) - 1))
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| 46 | {
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| 47 | if (RT_LIKELY(*pb == 0))
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| 48 | { /* likely */ }
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| 49 | else
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| 50 | return (void RT_FAR *)pb;
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| 51 | cb--;
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| 52 | pb++;
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| 53 | }
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| 54 |
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| 55 | /* Scan in size_t sized words: */
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| 56 | while ( cb >= sizeof(size_t)
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| 57 | && *(size_t *)pb == 0)
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| 58 | {
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| 59 | pb += sizeof(size_t);
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| 60 | cb -= sizeof(size_t);
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| 61 | }
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| 62 | }
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| 63 |
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| 64 | /*
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| 65 | * Search byte by byte.
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| 66 | */
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| 67 | for (; cb; cb--, pb++)
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| 68 | if (RT_LIKELY(*pb == 0))
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| 69 | { /* likely */ }
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| 70 | else
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| 71 | return (void RT_FAR *)pb;
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| 72 |
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| 73 | return NULL;
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| 74 | }
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| 75 |
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