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Add optimized implementation of find_first_of

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This commit is contained in:
Peter Dimov
2021-10-08 07:03:39 +03:00
parent df65ea6600
commit 18334b1614
1 changed files with 92 additions and 10 deletions
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102
include/boost/core/string_view.hpp
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@ -25,6 +25,7 @@
#include <stdexcept>
#include <cstddef>
#include <cstring>
#include <climits>
#if !defined(BOOST_NO_CXX17_HDR_STRING_VIEW)
# include <string_view>
#endif
@ -33,6 +34,89 @@ namespace boost
{
namespace core
{
namespace detail
{
template<class Ch> BOOST_CXX14_CONSTEXPR std::size_t find_first_of( Ch const* p_, std::size_t n_, Ch const* s, std::size_t pos, std::size_t n ) BOOST_NOEXCEPT
{
if( n >= 16 )
{
for( std::size_t i = pos; i < n_; ++i )
{
Ch ch = p_[ i ];
if( std::char_traits<Ch>::find( s, n, ch ) != 0 ) return i;
}
}
else
{
for( std::size_t i = pos; i < n_; ++i )
{
Ch ch = p_[ i ];
for( std::size_t j = 0; j < n; ++j )
{
if( s[ j ] == ch ) return i;
}
}
}
return static_cast<std::size_t>( -1 );
}
#if CHAR_BIT == 8
BOOST_CXX14_CONSTEXPR std::size_t find_first_of( char const* p_, std::size_t n_, char const* s, std::size_t pos, std::size_t n ) BOOST_NOEXCEPT
{
unsigned char table[ 256 ] = {};
unsigned char r = 0;
boost::uint64_t mask = 0;
for( std::size_t j = 0; j < n; ++j )
{
unsigned char ch = s[ j ];
table[ ch ] = 1;
r |= ch;
mask |= boost::uint64_t( 1 ) << ( ch & 0x3F );
}
if( ( r & 0xC0 ) == 0 )
{
for( std::size_t i = pos; i < n_; ++i )
{
unsigned char ch = p_[ i ];
if( mask & ( boost::uint64_t( 1 ) << ch ) ) return i;
}
return static_cast<std::size_t>( -1 );
}
else
{
for( std::size_t i = pos; i < n_; ++i )
{
unsigned char ch = p_[ i ];
if( table[ ch ] ) return i;
}
return static_cast<std::size_t>( -1 );
}
}
#endif
#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
std::size_t find_first_of( char8_t const* p_, std::size_t n_, char8_t const* s, std::size_t pos, std::size_t n ) BOOST_NOEXCEPT
{
return detail::find_first_of( reinterpret_cast< char const* >( p_ ), n_, reinterpret_cast< char const* >( s ), pos, n );
}
#endif
} // namespace detail
template<class Ch> class basic_string_view
{
@ -425,12 +509,7 @@ public:
BOOST_CXX14_CONSTEXPR size_type find_first_of( basic_string_view str, size_type pos = 0 ) const BOOST_NOEXCEPT
{
for( std::size_t i = pos; i < n_; ++i )
{
if( str.contains( p_[ i ] ) ) return i;
}
return npos;
return find_first_of( str.data(), pos, str.size() );
}
BOOST_CONSTEXPR size_type find_first_of( Ch c, size_type pos = 0 ) const BOOST_NOEXCEPT
@ -438,14 +517,17 @@ public:
return find( c, pos );
}
BOOST_CONSTEXPR size_type find_first_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR size_type find_first_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
{
return find_first_of( basic_string_view( s, n ), pos );
if( n == 0 || pos >= size() ) return npos;
if( n == 1 ) return find( s[0], pos );
return detail::find_first_of( data(), size(), s, pos, n );
}
BOOST_CONSTEXPR size_type find_first_of( Ch const* s, size_type pos = 0 ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR size_type find_first_of( Ch const* s, size_type pos = 0 ) const BOOST_NOEXCEPT
{
return find_first_of( basic_string_view( s ), pos );
return find_first_of( s, pos, traits_type::length( s ) );
}
// find_last_of