blob: ac01b3ce50d4ceedaab96da82d40bfce602e648a (
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
|
/** @file
Implementation of TestAndClearBit using compare-exchange primitive
Copyright (C) 2015, Linaro Ltd.
Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution. The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/
#include <Base.h>
#include <Library/SynchronizationLib.h>
INT32
EFIAPI
TestAndClearBit (
IN INT32 Bit,
IN VOID *Address
)
{
UINT16 Word, Read;
UINT16 Mask;
//
// Calculate the effective address relative to 'Address' based on the
// higher order bits of 'Bit'. Use signed shift instead of division to
// ensure we round towards -Inf, and end up with a positive shift in
// 'Bit', even if 'Bit' itself is negative.
//
Address = (VOID*)((UINT8*) Address + ((Bit >> 4) * sizeof(UINT16)));
Mask = 1U << (Bit & 15);
for (Word = *(UINT16 *) Address; Word & Mask; Word = Read) {
Read = InterlockedCompareExchange16 (Address, Word, Word & ~Mask);
if (Read == Word) {
return 1;
}
}
return 0;
}
|
