Space-Project/dependencies/physx-4.1/source/foundation/include/PsBitUtils.h
2021-01-16 17:11:39 +01:00

110 lines
3.5 KiB
C++

//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
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// documentation and/or other materials provided with the distribution.
// * Neither the name of NVIDIA CORPORATION nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Copyright (c) 2008-2019 NVIDIA Corporation. All rights reserved.
// Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.
// Copyright (c) 2001-2004 NovodeX AG. All rights reserved.
#ifndef PSFOUNDATION_PSBITUTILS_H
#define PSFOUNDATION_PSBITUTILS_H
#include "foundation/PxIntrinsics.h"
#include "foundation/PxAssert.h"
#include "PsIntrinsics.h"
#include "Ps.h"
namespace physx
{
namespace shdfnd
{
PX_INLINE uint32_t bitCount(uint32_t v)
{
// from http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
uint32_t const w = v - ((v >> 1) & 0x55555555);
uint32_t const x = (w & 0x33333333) + ((w >> 2) & 0x33333333);
return (((x + (x >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
}
PX_INLINE bool isPowerOfTwo(uint32_t x)
{
return x != 0 && (x & (x - 1)) == 0;
}
// "Next Largest Power of 2
// Given a binary integer value x, the next largest power of 2 can be computed by a SWAR algorithm
// that recursively "folds" the upper bits into the lower bits. This process yields a bit vector with
// the same most significant 1 as x, but all 1's below it. Adding 1 to that value yields the next
// largest power of 2. For a 32-bit value:"
PX_INLINE uint32_t nextPowerOfTwo(uint32_t x)
{
x |= (x >> 1);
x |= (x >> 2);
x |= (x >> 4);
x |= (x >> 8);
x |= (x >> 16);
return x + 1;
}
/*!
Return the index of the highest set bit. Not valid for zero arg.
*/
PX_INLINE uint32_t lowestSetBit(uint32_t x)
{
PX_ASSERT(x);
return lowestSetBitUnsafe(x);
}
/*!
Return the index of the highest set bit. Not valid for zero arg.
*/
PX_INLINE uint32_t highestSetBit(uint32_t x)
{
PX_ASSERT(x);
return highestSetBitUnsafe(x);
}
// Helper function to approximate log2 of an integer value
// assumes that the input is actually power of two.
// todo: replace 2 usages with 'highestSetBit'
PX_INLINE uint32_t ilog2(uint32_t num)
{
for(uint32_t i = 0; i < 32; i++)
{
num >>= 1;
if(num == 0)
return i;
}
PX_ASSERT(0);
return uint32_t(-1);
}
} // namespace shdfnd
} // namespace physx
#endif // #ifndef PSFOUNDATION_PSBITUTILS_H