NVIDIA(R) PsFoundation Reference: E:/p4/sw/physx/PxShared/1.0/trunk/src/foundation/include/PsBitUtils.h Source File

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E:/p4/sw/physx/PxShared/1.0/trunk/src/foundation/include/PsBitUtils.h

00001 // This code contains NVIDIA Confidential Information and is disclosed to you
00002 // under a form of NVIDIA software license agreement provided separately to you.
00003 //
00004 // Notice
00005 // NVIDIA Corporation and its licensors retain all intellectual property and
00006 // proprietary rights in and to this software and related documentation and
00007 // any modifications thereto. Any use, reproduction, disclosure, or
00008 // distribution of this software and related documentation without an express
00009 // license agreement from NVIDIA Corporation is strictly prohibited.
00010 //
00011 // ALL NVIDIA DESIGN SPECIFICATIONS, CODE ARE PROVIDED "AS IS.". NVIDIA MAKES
00012 // NO WARRANTIES, EXPRESSED, IMPLIED, STATUTORY, OR OTHERWISE WITH RESPECT TO
00013 // THE MATERIALS, AND EXPRESSLY DISCLAIMS ALL IMPLIED WARRANTIES OF NONINFRINGEMENT,
00014 // MERCHANTABILITY, AND FITNESS FOR A PARTICULAR PURPOSE.
00015 //
00016 // Information and code furnished is believed to be accurate and reliable.
00017 // However, NVIDIA Corporation assumes no responsibility for the consequences of use of such
00018 // information or for any infringement of patents or other rights of third parties that may
00019 // result from its use. No license is granted by implication or otherwise under any patent
00020 // or patent rights of NVIDIA Corporation. Details are subject to change without notice.
00021 // This code supersedes and replaces all information previously supplied.
00022 // NVIDIA Corporation products are not authorized for use as critical
00023 // components in life support devices or systems without express written approval of
00024 // NVIDIA Corporation.
00025 //
00026 // Copyright (c) 2008-2014 NVIDIA Corporation. All rights reserved.
00027 // Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.
00028 // Copyright (c) 2001-2004 NovodeX AG. All rights reserved.
00029 
00030 #ifndef PSFOUNDATION_PSBITUTILS_H
00031 #define PSFOUNDATION_PSBITUTILS_H
00032 
00033 #include "foundation/PxIntrinsics.h"
00034 #include "foundation/PxAssert.h"
00035 #include "PsIntrinsics.h"
00036 #include "Ps.h"
00037 
00038 namespace physx
00039 {
00040 namespace shdfnd
00041 {
00042 PX_INLINE uint32_t bitCount(uint32_t v)
00043 {
00044         // from http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
00045         uint32_t const w = v - ((v >> 1) & 0x55555555);
00046         uint32_t const x = (w & 0x33333333) + ((w >> 2) & 0x33333333);
00047         return (((x + (x >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
00048 }
00049 
00050 PX_INLINE bool isPowerOfTwo(uint32_t x)
00051 {
00052         return x != 0 && (x & (x - 1)) == 0;
00053 }
00054 
00055 // "Next Largest Power of 2
00056 // Given a binary integer value x, the next largest power of 2 can be computed by a SWAR algorithm
00057 // that recursively "folds" the upper bits into the lower bits. This process yields a bit vector with
00058 // the same most significant 1 as x, but all 1's below it. Adding 1 to that value yields the next
00059 // largest power of 2. For a 32-bit value:"
00060 PX_INLINE uint32_t nextPowerOfTwo(uint32_t x)
00061 {
00062         x |= (x >> 1);
00063         x |= (x >> 2);
00064         x |= (x >> 4);
00065         x |= (x >> 8);
00066         x |= (x >> 16);
00067         return x + 1;
00068 }
00069 
00074 PX_INLINE uint32_t lowestSetBit(uint32_t x)
00075 {
00076         PX_ASSERT(x);
00077         return lowestSetBitUnsafe(x);
00078 }
00079 
00084 PX_INLINE uint32_t highestSetBit(uint32_t x)
00085 {
00086         PX_ASSERT(x);
00087         return highestSetBitUnsafe(x);
00088 }
00089 
00090 // Helper function to approximate log2 of an integer value
00091 // assumes that the input is actually power of two.
00092 // todo: replace 2 usages with 'highestSetBit'
00093 PX_INLINE uint32_t ilog2(uint32_t num)
00094 {
00095         for(uint32_t i = 0; i < 32; i++)
00096         {
00097                 num >>= 1;
00098                 if(num == 0)
00099                         return i;
00100         }
00101 
00102         PX_ASSERT(0);
00103         return uint32_t(-1);
00104 }
00105 
00106 } // namespace shdfnd
00107 } // namespace physx
00108 
00109 #endif // #ifndef PSFOUNDATION_PSBITUTILS_H
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