boost_mirror/core
1
0
Fork 0
mirror of https://github.com/boostorg/core.git synced 2025-05-11 05:07:39 +00:00
Code Issues Packages Projects Releases Wiki Activity

Add countl_zero, countl_one

Browse Source
This commit is contained in:
Peter Dimov 2020-12-28 23:40:59 +02:00
parent 123b567051
commit cc877e6b5b
3 changed files with 99 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
include/boost/core/bit.hpp
View File

@ -45,20 +45,66 @@ To bit_cast( From const & from ) BOOST_NOEXCEPT
namespace detail
{
BOOST_CXX14_CONSTEXPR int countl_impl( boost::uint32_t x ) BOOST_NOEXCEPT
inline int countl_impl( boost::uint32_t x ) BOOST_NOEXCEPT
{
return 0;
static unsigned char const mod37[ 37 ] = { 32, 31, 6, 30, 9, 5, 0, 29, 16, 8, 2, 4, 21, 0, 19, 28, 25, 15, 0, 7, 10, 1, 17, 3, 22, 20, 26, 0, 11, 18, 23, 27, 12, 24, 13, 14, 0 };
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
return mod37[ x % 37 ];
}
inline int countl_impl( boost::uint64_t x ) BOOST_NOEXCEPT
{
return static_cast<boost::uint32_t>( x >> 32 ) != 0?
boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x >> 32 ) ):
boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x ) ) + 32;
}
inline int countl_impl( boost::uint8_t x ) BOOST_NOEXCEPT
{
return boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x ) ) - 24;
}
inline int countl_impl( boost::uint16_t x ) BOOST_NOEXCEPT
{
return boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x ) ) - 16;
}
} // namespace detail
template<class T>
BOOST_CORE_BIT_CONSTEXPR int countl_zero( T x ) BOOST_NOEXCEPT;
BOOST_CORE_BIT_CONSTEXPR int countl_zero( T x ) BOOST_NOEXCEPT
{
BOOST_STATIC_ASSERT( sizeof(T) == sizeof(boost::uint8_t) || sizeof(T) == sizeof(boost::uint16_t) || sizeof(T) == sizeof(boost::uint32_t) || sizeof(T) == sizeof(boost::uint64_t) );
if( sizeof(T) == sizeof(boost::uint8_t) )
{
return boost::core::detail::countl_impl( static_cast<boost::uint8_t>( x ) );
}
else if( sizeof(T) == sizeof(boost::uint16_t) )
{
return boost::core::detail::countl_impl( static_cast<boost::uint16_t>( x ) );
}
else if( sizeof(T) == sizeof(boost::uint32_t) )
{
return boost::core::detail::countl_impl( static_cast<boost::uint32_t>( x ) );
}
else
{
return boost::core::detail::countl_impl( static_cast<boost::uint64_t>( x ) );
}
}
template<class T>
BOOST_CORE_BIT_CONSTEXPR int countl_one( T x ) BOOST_NOEXCEPT
{
return boost::core::countl_zero( ~x );
return boost::core::countl_zero( static_cast<T>( ~x ) );
}
namespace detail
@ -66,7 +112,7 @@ namespace detail
inline int countr_impl( boost::uint32_t x ) BOOST_NOEXCEPT
{
static unsigned char const mod37[] = { 32, 0, 1, 26, 2, 23, 27, 0, 3, 16, 24, 30, 28, 11, 0, 13, 4, 7, 17, 0, 25, 22, 31, 15, 29, 10, 12, 6, 0, 21, 14, 9, 5, 20, 8, 19, 18 };
static unsigned char const mod37[ 37 ] = { 32, 0, 1, 26, 2, 23, 27, 0, 3, 16, 24, 30, 28, 11, 0, 13, 4, 7, 17, 0, 25, 22, 31, 15, 29, 10, 12, 6, 0, 21, 14, 9, 5, 20, 8, 19, 18 };
return mod37[ ( -(boost::int32_t)x & x ) % 37 ];
}
@ -115,7 +161,7 @@ BOOST_CORE_BIT_CONSTEXPR int countr_zero( T x ) BOOST_NOEXCEPT
template<class T>
BOOST_CORE_BIT_CONSTEXPR int countr_one( T x ) BOOST_NOEXCEPT
{
return boost::core::countr_zero( ~x );
return boost::core::countr_zero( static_cast<T>( ~x ) );
}
template<class T>

1
test/Jamfile.v2
View File

@ -225,6 +225,7 @@ run cmath_test.cpp ;
run bit_cast_test.cpp ;
run bit_rotate_test.cpp ;
run bit_countr_test.cpp ;
run bit_countl_test.cpp ;
use-project /boost/core/swap : ./swap ;
build-project ./swap ;

46
test/bit_countl_test.cpp Normal file
View File

@ -0,0 +1,46 @@
// Test for boost/core/bit.hpp (countl_zero, countl_one)
//
// Copyright 2020 Peter Dimov
// Distributed under the Boost Software License, Version 1.0.
// https://www.boost.org/LICENSE_1_0.txt
#include <boost/core/bit.hpp>
#include <boost/core/lightweight_test.hpp>
#include <boost/core/detail/splitmix64.hpp>
#include <boost/cstdint.hpp>
#include <limits>
template<class T> void test_countl( T x )
{
x |= static_cast<T>( 1 ) << ( std::numeric_limits<T>::digits - 1 );
for( int i = 0; i <= std::numeric_limits<T>::digits; ++i, x >>= 1 )
{
BOOST_TEST_EQ( boost::core::countl_zero( x ), i );
BOOST_TEST_EQ( boost::core::countl_one( static_cast<T>( ~x ) ), i );
}
}
int main()
{
test_countl( static_cast<unsigned char>( 0 ) );
test_countl( static_cast<unsigned short>( 0 ) );
test_countl( static_cast<unsigned int>( 0 ) );
test_countl( static_cast<unsigned long>( 0 ) );
test_countl( static_cast<unsigned long long>( 0 ) );
boost::detail::splitmix64 rng;
for( int i = 0; i < 1000; ++i )
{
boost::uint64_t x = rng();
test_countl( static_cast<unsigned char>( x ) );
test_countl( static_cast<unsigned short>( x ) );
test_countl( static_cast<unsigned int>( x ) );
test_countl( static_cast<unsigned long>( x ) );
test_countl( static_cast<unsigned long long>( x ) );
}
return boost::report_errors();
}