| 1 | /* $Id: ASMBitNextSet-generic.cpp 93115 2022-01-01 11:31:46Z vboxsync $ */
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| 2 | /** @file
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| 3 | * IPRT - ASMBitNextSet - 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) 2006-2022 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 | #include <iprt/assert.h>
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| 35 |
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| 36 |
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| 37 | RTDECL(int) ASMBitNextSet(const volatile void RT_FAR *pvBitmap, uint32_t cBits, uint32_t iBitPrev) RT_NOTHROW_DEF
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| 38 | {
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| 39 | const volatile uint32_t RT_FAR *pau32Bitmap = (const volatile uint32_t RT_FAR *)pvBitmap;
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| 40 | int iBit = ++iBitPrev & 31;
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| 41 | Assert(!(cBits & 31));
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| 42 | Assert(!((uintptr_t)pvBitmap & 3));
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| 43 | if (iBit)
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| 44 | {
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| 45 | /*
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| 46 | * Inspect the 32-bit word containing the unaligned bit.
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| 47 | */
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| 48 | uint32_t u32 = RT_LE2H_U32(pau32Bitmap[iBitPrev / 32]) >> iBit;
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| 49 | if (u32)
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| 50 | return iBitPrev + ASMBitFirstSetU32(u32) - 1;
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| 51 |
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| 52 | /*
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| 53 | * Skip ahead and see if there is anything left to search.
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| 54 | */
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| 55 | iBitPrev |= 31;
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| 56 | iBitPrev++;
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| 57 | if (cBits <= (uint32_t)iBitPrev)
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| 58 | return -1;
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| 59 | }
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| 60 |
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| 61 | /*
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| 62 | * 32-bit aligned search, let ASMBitFirstSet do the dirty work.
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| 63 | */
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| 64 | iBit = ASMBitFirstSet(&pau32Bitmap[iBitPrev / 32], cBits - iBitPrev);
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| 65 | if (iBit >= 0)
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| 66 | iBit += iBitPrev;
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| 67 | return iBit;
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| 68 | }
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| 69 |
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