mirror of https://github.com/acidanthera/audk.git
63 lines
1.5 KiB
C
63 lines
1.5 KiB
C
/*++
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Copyright (c) 2006, Intel Corporation
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All rights reserved. This program and the accompanying materials
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are licensed and made available under the terms and conditions of the BSD License
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which accompanies this distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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Module Name:
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GetPowerOfTwo.c
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Abstract:
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Calculates the largest integer that is both
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a power of two and less than Input
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--*/
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#include "Tiano.h"
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UINT64
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GetPowerOfTwo (
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IN UINT64 Input
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)
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/*++
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Routine Description:
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Calculates the largest integer that is both
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a power of two and less than Input
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Arguments:
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Input - value to calculate power of two
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Returns:
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the largest integer that is both a power of
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two and less than Input
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--*/
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{
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__asm {
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xor eax, eax
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mov edx, eax
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mov ecx, dword ptr Input[4]
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jecxz _F
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bsr ecx, ecx
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bts edx, ecx
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jmp _Exit
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_F:
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mov ecx, dword ptr Input[0]
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jecxz _Exit
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bsr ecx, ecx
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bts eax, ecx
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_Exit:
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}
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}
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