2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017
6 Source code repo: http://github.com/khizmax/libcds/
7 Download: http://sourceforge.net/projects/libcds/files/
9 Redistribution and use in source and binary forms, with or without
10 modification, are permitted provided that the following conditions are met:
12 * Redistributions of source code must retain the above copyright notice, this
13 list of conditions and the following disclaimer.
15 * Redistributions in binary form must reproduce the above copyright notice,
16 this list of conditions and the following disclaimer in the documentation
17 and/or other materials provided with the distribution.
19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
23 FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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25 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
26 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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31 #ifndef CDSLIB_INT_ALGO_H
32 #define CDSLIB_INT_ALGO_H
34 #include <cds/algo/bitop.h>
36 namespace cds { namespace beans {
37 #if CDS_BUILD_BITS == 64
38 /// Returns largest previous integer for <tt>log2( n )</tt>
39 static inline size_t log2floor( size_t n )
41 return n ? cds::bitop::MSBnz( n ) : 0;
44 /// Returns smallest following integer for <tt>log2( n )</tt>
45 static inline size_t log2ceil( size_t n )
47 size_t i = log2floor( n );
48 return ( size_t( 1 ) << i ) < n ? i + 1 : i;
51 /// Returns largest previous power of 2 for \p n
65 static inline size_t floor2( size_t n )
67 return size_t(1) << log2floor( n );
70 /// Returns smallest following power of 2 for \p n
84 static inline size_t ceil2( size_t n )
86 return size_t(1) << log2ceil( n );
89 /// Checks if \p n is power of 2
90 CDS_CONSTEXPR static inline bool is_power2( size_t n ) CDS_NOEXCEPT
92 return (n & (n - 1)) == 0 && n;
95 /// Returns binary logarithm of \p n if \p n is power of two, otherwise returns 0
96 static inline size_t log2( size_t n )
98 return is_power2(n) ? log2floor(n) : 0;
101 #elif CDS_BUILD_BITS == 32
103 // 64bit specializations
105 /// Returns largest previous integer for <tt>log2( n )</tt>
106 static inline uint64_t log2floor( uint64_t n )
108 return n ? cds::bitop::MSBnz( n ) : 0;
111 /// Returns smallest following integer for <tt>log2( n )</tt>
112 static inline uint64_t log2ceil( uint64_t n )
114 uint64_t i = log2floor( n );
115 return (uint64_t( 1 ) << i) < n ? i + 1 : i;
118 /// Returns largest previous power of 2 for \p n
122 floor2(0) == 1 // !!!
132 static inline uint64_t floor2( uint64_t n )
134 return uint64_t( 1 ) << log2floor( n );
137 /// Returns smallest following power of 2 for \p n
151 static inline uint64_t ceil2( uint64_t n )
153 return uint64_t( 1 ) << log2ceil( n );
156 /// Checks if \p n is power of 2
157 CDS_CONSTEXPR static inline bool is_power2( uint64_t n ) CDS_NOEXCEPT
159 return (n & (n - 1)) == 0 && n;
162 /// Returns binary logarithm of \p n if \p n is power of two, otherwise returns 0
163 static inline uint64_t log2( uint64_t n )
165 return is_power2( n ) ? log2floor( n ) : 0;
171 }} // namespace cds::beans
173 #endif // #ifndef CDSLIB_INT_ALGO_H