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, unsigned long& index)
00039     {
00040 #if defined(CS_HAVE___BUILTIN_CTZ)
00041       index = __builtin_ctz (value);
00042       return value != 0;
00043 #elif defined(CS_HAVE_BITSCAN_INTRINSICS)
00044       return _BitScanForward (&index, value) != 0;
00045 #else
00046       // Generic c++ version
00047       index = 0;
00048 
00049       while (value)
00050       {
00051         if (value & 0x01)
00052         {
00053           return true;
00054         }
00055         value >>= 0x01;
00056         index++;
00057       }
00058 
00059       return false;
00060 #endif
00061     }
00062 
00069     CS_FORCEINLINE bool ScanBitReverse (uint32 value, unsigned long& index)
00070     {
00071 #if defined(CS_HAVE___BUILTIN_CLZ)
00072       index = __builtin_clz (value);
00073       return value != 0;
00074 #elif defined(CS_HAVE_BITSCAN_INTRINSICS)
00075       return _BitScanReverse (&index, value) != 0;
00076 #else
00077       index = 0;
00078 
00079       while (value)
00080       {
00081         if (value & 0x80000000)
00082         {
00083           return true;
00084         }
00085         value <<= 0x01;
00086         index++;
00087       }
00088 
00089       return false;
00090 #endif
00091     }
00092 
00096     CS_FORCEINLINE uint32 ComputeBitsSet (uint32 v)
00097     {
00098 #if defined(CS_HAVE___BUILTIN_POPCOUNT)
00099       return __builtin_popcount (v);
00100 #else
00101       v = v - ((v >> 1) & 0x55555555);
00102       v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
00103       return (((v + (v >> 4)) & 0x0f0f0f0f) * 0x01010101) >> 24;
00104 #endif
00105     }
00106 
00107     }
00108   }
00109 
00110 }
00111 
00112 #endif

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