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/* $Id: ASMBitFirstSet-generic.cpp $ */
/** @file
* IPRT - ASMBitFirstSet - generic C implementation.
*/
/*
* Copyright (C) 2006-2023 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, in version 3 of the
* License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses>.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
* in the VirtualBox distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*
* SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
*/
/*********************************************************************************************************************************
* Header Files *
*********************************************************************************************************************************/
#include <iprt/asm.h>
#include "internal/iprt.h"
#include <iprt/assert.h>
RTDECL(int32_t) ASMBitFirstSet(const volatile void RT_FAR *pvBitmap, uint32_t cBits) RT_NOTHROW_DEF
{
const volatile size_t RT_FAR *pu = (const volatile size_t RT_FAR *)pvBitmap;
Assert(!(cBits & 31));
Assert(!((uintptr_t)pvBitmap & 3));
#if ARCH_BITS > 32
/* Deal with misaligned bitmaps (happens all the time via ASMBitNextClear()). */
if (!((uintptr_t)pvBitmap & 7) && cBits >= 32)
{
uint32_t u32 = *(const volatile uint32_t RT_FAR *)pu;
if (u32 != 0)
{
size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
return iBaseBit + ASMBitFirstSetU32(RT_LE2H_U32(u32)) - 1;
}
pu = (const volatile size_t RT_FAR *)((uintptr_t)pu + sizeof(uint32_t));
cBits -= 32;
}
#endif
/* Main search loop: */
while (cBits >= sizeof(size_t) * 8)
{
size_t u = *pu;
if (u == 0)
{ }
else
{
size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
#if ARCH_BITS == 32
return iBaseBit + ASMBitFirstSetU32(RT_LE2H_U32(u)) - 1;
#elif ARCH_BITS == 64
return iBaseBit + ASMBitFirstSetU64(RT_LE2H_U64(u)) - 1;
#else
# error "ARCH_BITS is not supported"
#endif
}
pu++;
cBits -= sizeof(size_t) * 8;
}
#if ARCH_BITS > 32
/* Final 32-bit item (unlikely)? */
if (cBits < 32)
{ }
else
{
uint32_t u32 = *(const volatile uint32_t RT_FAR *)pu;
if (u32 != 0)
{
size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
return iBaseBit + ASMBitFirstSetU32(RT_LE2H_U32(u32)) - 1;
}
}
#endif
return -1;
}
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