66 lines
1.9 KiB
C++
66 lines
1.9 KiB
C++
/*******************************************************************************
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Copyright (c) 2005-2009 David Williams
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source
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distribution.
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*******************************************************************************/
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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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