| /*++ | |
| Copyright (c) 2006, 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. | |
| Module Name: | |
| GetPowerOfTwo.c | |
| Abstract: | |
| Calculates the largest integer that is both | |
| a power of two and less than Input | |
| --*/ | |
| #include "Tiano.h" | |
| UINT64 | |
| GetPowerOfTwo ( | |
| IN UINT64 Input | |
| ) | |
| /*++ | |
| Routine Description: | |
| Calculates the largest integer that is both | |
| a power of two and less than Input | |
| Arguments: | |
| Input - value to calculate power of two | |
| Returns: | |
| the largest integer that is both a power of | |
| two and less than Input | |
| --*/ | |
| { | |
| __asm { | |
| xor eax, eax | |
| mov edx, eax | |
| mov ecx, dword ptr Input[4] | |
| jecxz _F | |
| bsr ecx, ecx | |
| bts edx, ecx | |
| jmp _Exit | |
| _F: | |
| mov ecx, dword ptr Input[0] | |
| jecxz _Exit | |
| bsr ecx, ecx | |
| bts eax, ecx | |
| _Exit: | |
| } | |
| } |