mirror of https://github.com/acidanthera/audk.git
47 lines
1.4 KiB
C
47 lines
1.4 KiB
C
/** @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;
|
|
}
|