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Add optimized implementation of find_last_not_of

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This commit is contained in:
Peter Dimov
2021-10-09 07:08:48 +03:00
parent 408cd96595
commit b01f2fe4d2
1 changed files with 105 additions and 25 deletions
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130
include/boost/core/string_view.hpp
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@ -235,6 +235,84 @@ template<class Ch> BOOST_CXX14_CONSTEXPR std::size_t find_first_not_of( Ch const
return static_cast<std::size_t>( -1 );
}
template<class Ch> BOOST_CXX14_CONSTEXPR std::size_t find_last_not_of( Ch const* p_, Ch const* s, std::size_t pos, std::size_t n ) BOOST_NOEXCEPT
{
typedef typename sv_to_uchar<Ch>::type UCh;
unsigned char table[ 256 ] = {};
bool use_table = true;
for( std::size_t j = 0; j < n; ++j )
{
UCh ch = s[ j ];
if( ch >= 0 && ch < 256 )
{
table[ ch ] = 1;
}
else
{
use_table = false;
break;
}
}
std::size_t const npos = static_cast< std::size_t >( -1 );
std::size_t i = pos;
if( use_table )
{
do
{
UCh ch = p_[ i ];
if( !( ch >= 0 && ch < 256 && table[ ch ] ) ) return i;
--i;
}
while( i != npos );
}
else if( n >= 16 )
{
do
{
Ch ch = p_[ i ];
if( std::char_traits<Ch>::find( s, n, ch ) == 0 ) return i;
--i;
}
while( i != npos );
}
else
{
do
{
Ch ch = p_[ i ];
bool r = false;
for( std::size_t j = 0; j < n; ++j )
{
if( s[ j ] == ch )
{
r = true;
break;
}
}
if( !r ) return i;
--i;
}
while( i != npos );
}
return npos;
}
} // namespace detail
template<class Ch> class basic_string_view
@ -728,36 +806,21 @@ public:
BOOST_CXX14_CONSTEXPR size_type find_last_not_of( basic_string_view str, size_type pos = npos ) const BOOST_NOEXCEPT
{
if( size() == 0 )
{
return npos;
}
if( pos > size() - 1 )
{
pos = size() - 1;
}
do
{
if( !str.contains( p_[ pos ] ) ) return pos;
--pos;
}
while( pos != npos );
return npos;
return find_last_not_of( str.data(), pos, str.size() );
}
BOOST_CXX14_CONSTEXPR size_type find_last_not_of( Ch c, size_type pos = npos ) const BOOST_NOEXCEPT
{
if( size() == 0 )
size_type m = size();
if( m == 0 )
{
return npos;
}
if( pos > size() - 1 )
if( pos > m - 1 )
{
pos = size() - 1;
pos = m - 1;
}
do
@ -770,14 +833,31 @@ public:
return npos;
}
BOOST_CONSTEXPR size_type find_last_not_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR size_type find_last_not_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
{
return find_last_not_of( basic_string_view( s, n ), pos );
if( n == 1 )
{
return find_last_not_of( s[0], pos );
}
size_type m = size();
if( m == 0 )
{
return npos;
}
if( pos > m - 1 )
{
pos = m - 1;
}
return detail::find_last_not_of( data(), s, pos, n );
}
BOOST_CONSTEXPR size_type find_last_not_of( Ch const* s, size_type pos = npos ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR size_type find_last_not_of( Ch const* s, size_type pos = npos ) const BOOST_NOEXCEPT
{
return find_last_not_of( basic_string_view( s ), pos );
return find_last_not_of( s, pos, traits_type::length( s ) );
}
// contains