00001 /// @addtogroup struct 00002 /// @{ 00003 00004 ///////////////////////////////////////////////////////////////////////////// 00005 /// 00006 /// @file bitcount.h 00007 /// 00008 /// This file defines a very simple function for counting the number of bits 00009 /// in a byte or a multi-byte integer. 00010 /// 00011 /// @author Pawel Pilarczyk 00012 /// 00013 ///////////////////////////////////////////////////////////////////////////// 00014 00015 // Copyright (C) 1997-2013 by Pawel Pilarczyk. 00016 // 00017 // This file is part of the Homology Library. This library is free software; 00018 // you can redistribute it and/or modify it under the terms of the GNU 00019 // General Public License as published by the Free Software Foundation; 00020 // either version 2 of the License, or (at your option) any later version. 00021 // 00022 // This library is distributed in the hope that it will be useful, 00023 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00024 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00025 // GNU General Public License for more details. 00026 // 00027 // You should have received a copy of the GNU General Public License along 00028 // with this software; see the file "license.txt". If not, write to the 00029 // Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, 00030 // MA 02111-1307, USA. 00031 00032 // Started on November 29, 2005. Last revision: November 29, 2005. 00033 00034 00035 #ifndef _CHOMP_STRUCT_BITCOUNT_H_ 00036 #define _CHOMP_STRUCT_BITCOUNT_H_ 00037 00038 namespace chomp { 00039 namespace homology { 00040 00041 00042 extern unsigned char bitcounttable []; 00043 00044 inline int bitcountbyte (char n) 00045 { 00046 return bitcounttable [static_cast<unsigned char> (n)]; 00047 } /* bitcountbyte */ 00048 00049 inline int bitcount (int number) 00050 { 00051 if (!number) 00052 return 0; 00053 unsigned int n = static_cast<unsigned int> (number); 00054 if (n < 256) 00055 return bitcountbyte (static_cast<unsigned char> (n)); 00056 int c = 0; 00057 while (n > 255) 00058 { 00059 if (n & 1) 00060 ++ c; 00061 n >>= 1; 00062 } 00063 return c + bitcountbyte (static_cast<unsigned char> (n)); 00064 } /* bitcount */ 00065 00066 00067 } // namespace homology 00068 } // namespace chomp 00069 00070 #endif // _CHOMP_STRUCT_BITCOUNT_H_ 00071 00072 /// @} 00073
1.7.2