mirror of https://github.com/acidanthera/audk.git
68 lines
1.8 KiB
NASM
68 lines
1.8 KiB
NASM
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;/*++
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;
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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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;
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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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;
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;Module Name:
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;
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; GetPowerOfTwo.c
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;
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;Abstract:
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;
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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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;--*/
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;---------------------------------------------------------------------------
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.686
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.model flat,C
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.code
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;---------------------------------------------------------------------------
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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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;
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;Routine Description:
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;
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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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;Arguments:
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;
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; Input - value to calculate power of two
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;
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;Returns:
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;
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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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GetPowerOfTow PROC
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xor eax, eax
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mov edx, eax
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mov ecx, [esp + 8] ; 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, [esp + 4] ; 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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ret
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GetPowerOfTow ENDP
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END
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