64 lines
1.8 KiB
C++
64 lines
1.8 KiB
C++
#pragma region License
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/******************************************************************************
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This file is part of the PolyVox library
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Copyright (C) 2006 David Williams
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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******************************************************************************/
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#pragma endregion
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#include "PolyVoxImpl/Utility.h"
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#include <cassert>
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#include <stdexcept>
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namespace PolyVox
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{
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//Note: this function only works for inputs which are a power of two and not zero
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//If this is not the case then the output is undefined.
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uint8_t logBase2(uint32_t uInput)
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{
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//Debug mode validation
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assert(uInput != 0);
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assert(isPowerOf2(uInput));
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//Release mode validation
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if(uInput == 0)
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{
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throw std::invalid_argument("Cannot compute the log of zero.");
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}
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if(!isPowerOf2(uInput))
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{
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throw std::invalid_argument("Input must be a power of two in order to compute the log.");
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}
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uint32_t uResult = 0;
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while( (uInput >> uResult) != 0)
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{
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++uResult;
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}
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return static_cast<uint8_t>(uResult-1);
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}
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bool isPowerOf2(uint32_t uInput)
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{
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if(uInput == 0)
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return false;
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else
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return ((uInput & (uInput-1)) == 0);
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}
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}
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