blob: f815576b0553d58fb9c2b10a595d667d99c89f12 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
/* $Id$ */
/** @file
* IPRT - ASMBitFirstClear - generic C implementation.
*/
/*
* Copyright (C) 2006-2022 Oracle Corporation
*
* This file is part of VirtualBox Open Source Edition (OSE), as
* available from http://www.virtualbox.org. This file is free software;
* you can redistribute it and/or modify it under the terms of the GNU
* General Public License (GPL) as published by the Free Software
* Foundation, in version 2 as it comes in the "COPYING" file of the
* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL) only, as it comes in the "COPYING.CDDL" file of the
* VirtualBox OSE 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.
*/
/*********************************************************************************************************************************
* Header Files *
*********************************************************************************************************************************/
#include <iprt/asm.h>
#include "internal/iprt.h"
#include <iprt/assert.h>
RTDECL(int32_t) ASMBitFirstClear(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 != UINT32_MAX)
{
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 == ~(size_t)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 != UINT32_MAX)
{
size_t const iBaseBit = ((uintptr_t)pu - (uintptr_t)pvBitmap) * 8;
return iBaseBit + ASMBitFirstSetU32(~RT_LE2H_U32(u32)) - 1;
}
}
#endif
return -1;
}
|
