/*
This file is a part of libcds - Concurrent Data Structures library
- (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
+ (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017
Source code repo: http://github.com/khizmax/libcds/
Download: http://sourceforge.net/projects/libcds/files/
#include <cds/algo/bitop.h>
namespace cds { namespace beans {
-
+#if CDS_BUILD_BITS == 64
/// Returns largest previous integer for <tt>log2( n )</tt>
static inline size_t log2floor( size_t n )
{
return is_power2(n) ? log2floor(n) : 0;
}
-#if CDS_BUILD_BITS == 32
+#elif CDS_BUILD_BITS == 32
//@cond
// 64bit specializations
+/// Returns largest previous integer for <tt>log2( n )</tt>
static inline uint64_t log2floor( uint64_t n )
{
return n ? cds::bitop::MSBnz( n ) : 0;
}
+/// Returns smallest following integer for <tt>log2( n )</tt>
static inline uint64_t log2ceil( uint64_t n )
{
uint64_t i = log2floor( n );
return (uint64_t( 1 ) << i) < n ? i + 1 : i;
}
+/// Returns largest previous power of 2 for \p n
+ /**
+ Examples:
+ \code
+ floor2(0) == 1 // !!!
+ floor2(1) == 1
+ floor2(2) == 2
+ floor2(3) == 2
+ floor2(4) == 4
+ floor2(15) == 8
+ floor2(16) == 16
+ floor2(17) == 16
+ \endcode
+ */
static inline uint64_t floor2( uint64_t n )
{
return uint64_t( 1 ) << log2floor( n );
}
+/// Returns smallest following power of 2 for \p n
+ /**
+ Examples:
+ \code
+ ceil2(0) == 1 // !!!
+ ceil2(1) == 1
+ ceil2(2) == 2
+ ceil2(3) == 4
+ ceil2(4) == 4
+ ceil2(15) == 16
+ ceil2(16) == 16
+ ceil2(17) == 32
+ \endcode
+ */
static inline uint64_t ceil2( uint64_t n )
{
return uint64_t( 1 ) << log2ceil( n );
}
+/// Checks if \p n is power of 2
CDS_CONSTEXPR static inline bool is_power2( uint64_t n ) CDS_NOEXCEPT
{
return (n & (n - 1)) == 0 && n;
}
+/// Returns binary logarithm of \p n if \p n is power of two, otherwise returns 0
static inline uint64_t log2( uint64_t n )
{
return is_power2( n ) ? log2floor( n ) : 0;