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
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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 /// Returns largest previous integer for <tt>log2( n )</tt>
38 static inline size_t log2floor( size_t n )
40 return n ? cds::bitop::MSBnz( n ) : 0;
43 /// Returns smallest following integer for <tt>log2( n )</tt>
44 static inline size_t log2ceil( size_t n )
46 size_t i = log2floor( n );
47 return ( size_t( 1 ) << i ) < n ? i + 1 : i;
50 /// Returns largest previous power of 2 for \p n
64 static inline size_t floor2( size_t n )
66 return size_t(1) << log2floor( n );
69 /// Returns smallest following power of 2 for \p n
83 static inline size_t ceil2( size_t n )
85 return size_t(1) << log2ceil( n );
88 /// Checks if \p n is power of 2
89 CDS_CONSTEXPR static inline bool is_power2( size_t n ) CDS_NOEXCEPT
91 return (n & (n - 1)) == 0 && n;
94 /// Returns binary logarithm of \p n if \p n is power of two, otherwise returns 0
95 static inline size_t log2( size_t n )
97 return is_power2(n) ? log2floor(n) : 0;
100 #if CDS_BUILD_BITS == 32
102 // 64bit specializations
104 /// Returns largest previous integer for <tt>log2( n )</tt>
105 static inline uint64_t log2floor( uint64_t n )
107 return n ? cds::bitop::MSBnz( n ) : 0;
110 /// Returns smallest following integer for <tt>log2( n )</tt>
111 static inline uint64_t log2ceil( uint64_t n )
113 uint64_t i = log2floor( n );
114 return (uint64_t( 1 ) << i) < n ? i + 1 : i;
117 /// Returns largest previous power of 2 for \p n
121 floor2(0) == 1 // !!!
131 static inline uint64_t floor2( uint64_t n )
133 return uint64_t( 1 ) << log2floor( n );
136 /// Returns smallest following power of 2 for \p n
150 static inline uint64_t ceil2( uint64_t n )
152 return uint64_t( 1 ) << log2ceil( n );
155 /// Checks if \p n is power of 2
156 CDS_CONSTEXPR static inline bool is_power2( uint64_t n ) CDS_NOEXCEPT
158 return (n & (n - 1)) == 0 && n;
161 /// Returns binary logarithm of \p n if \p n is power of two, otherwise returns 0
162 static inline uint64_t log2( uint64_t n )
164 return is_power2( n ) ? log2floor( n ) : 0;
168 #endif //#if CDS_BUILD_BITS == 32
170 }} // namespace cds::beans
172 #endif // #ifndef CDSLIB_INT_ALGO_H