CrystalSpace

Public API Reference

csutil/bitops.h

00001 /*
00002   Copyright (C) 2007 by Marten Svanfeldt
00003 
00004   This library is free software; you can redistribute it and/or
00005   modify it under the terms of the GNU Library General Public
00006   License as published by the Free Software Foundation; either
00007   version 2 of the License, or (at your option) any later version.
00008 
00009   This library is distributed in the hope that it will be useful,
00010   but WITHOUT ANY WARRANTY; without even the implied warranty of
00011   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012   Library General Public License for more details.
00013 
00014   You should have received a copy of the GNU Library General Public
00015   License along with this library; if not, write to the Free
00016   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00017 */
00018 
00019 #ifndef __CSUTIL_BITOPS_H__
00020 #define __CSUTIL_BITOPS_H__
00021 
00022 
00023 namespace CS
00024 {
00025   namespace Utility
00026   {
00030     namespace BitOps
00031     {
00038     CS_FORCEINLINE bool ScanBitForward (uint32 value, size_t& index)
00039     {
00040 #ifdef CS_HAVE_BITSCAN_INTRINSICS
00041       return _BitScanForward ((unsigned long*)&index, value) != 0;
00042 #else
00043       // Generic c++ version
00044       index = 0;
00045 
00046       while (value)
00047       {
00048         if (value & 0x01)
00049         {
00050           return true;
00051         }
00052         value >>= 0x01;
00053         index++;
00054       }
00055 
00056       return false;
00057 #endif
00058     }
00059 
00066     CS_FORCEINLINE bool ScanBitReverse (uint32 value, size_t& index)
00067     {
00068 #ifdef CS_HAVE_BITSCAN_INTRINSICS
00069       return _BitScanReverse ((unsigned long*)&index, value) != 0;
00070 #else
00071       index = 0;
00072 
00073       while (value)
00074       {
00075         if (value & 0x80000000)
00076         {
00077           return true;
00078         }
00079         value <<= 0x01;
00080         index++;
00081       }
00082 
00083       return false;
00084 #endif
00085     }
00086 
00090     CS_FORCEINLINE uint32 ComputeBitsSet (uint32 v)
00091     {
00092       v = v - ((v >> 1) & 0x55555555);
00093       v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
00094       return ((v + (v >> 4) & 0x0f0f0f0f) * 0x01010101) >> 24;
00095     }
00096 
00097     }
00098   }
00099 
00100 }
00101 
00102 #endif

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