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Add optimized implementation of find_first_not_of

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This commit is contained in:
Peter Dimov
2021-10-09 06:40:59 +03:00
parent 3d4eb536cd
commit b9f1b9f39a
1 changed files with 86 additions and 15 deletions
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101
include/boost/core/string_view.hpp
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@ -97,7 +97,7 @@ std::size_t find_first_of( char8_t const* p_, std::size_t n_, char8_t const* s,
template<class Ch> BOOST_CXX14_CONSTEXPR std::size_t find_last_of( Ch const* p_, Ch const* s, std::size_t pos, std::size_t n ) BOOST_NOEXCEPT
{
constexpr std::size_t npos = static_cast< std::size_t >( -1 );
std::size_t const npos = static_cast< std::size_t >( -1 );
std::size_t i = pos;
@ -144,7 +144,7 @@ BOOST_CXX14_CONSTEXPR std::size_t find_last_of( char const* p_, char const* s, s
table[ ch ] = 1;
}
constexpr std::size_t npos = static_cast< std::size_t >( -1 );
std::size_t const npos = static_cast< std::size_t >( -1 );
std::size_t i = pos;
@ -172,6 +172,79 @@ std::size_t find_last_of( char8_t const* p_, char8_t const* s, std::size_t pos,
#endif
template<class Ch> struct sv_to_uchar
{
typedef Ch type;
};
template<> struct sv_to_uchar<char>
{
typedef unsigned char type;
};
template<class Ch> BOOST_CXX14_CONSTEXPR std::size_t find_first_not_of( Ch const* p_, std::size_t n_, 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;
}
}
if( use_table )
{
for( std::size_t i = pos; i < n_; ++i )
{
UCh ch = p_[ i ];
if( !( ch >= 0 && ch < 256 && table[ ch ] ) ) return i;
}
}
else 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 ];
bool r = false;
for( std::size_t j = 0; j < n; ++j )
{
if( s[ j ] == ch )
{
r = true;
break;
}
}
if( !r ) return i;
}
}
return static_cast<std::size_t>( -1 );
}
} // namespace detail
template<class Ch> class basic_string_view
@ -604,7 +677,7 @@ public:
return rfind( c, pos );
}
BOOST_CONSTEXPR size_type find_last_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR size_type find_last_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
{
if( n == 1 )
{
@ -626,7 +699,7 @@ public:
return detail::find_last_of( data(), s, pos, n );
}
BOOST_CONSTEXPR size_type find_last_of( Ch const* s, size_type pos = npos ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR size_type find_last_of( Ch const* s, size_type pos = npos ) const BOOST_NOEXCEPT
{
return find_last_of( s, pos, traits_type::length( s ) );
}
@ -635,12 +708,7 @@ public:
BOOST_CXX14_CONSTEXPR size_type find_first_not_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_not_of( str.data(), pos, str.size() );
}
BOOST_CXX14_CONSTEXPR size_type find_first_not_of( Ch c, size_type pos = 0 ) const BOOST_NOEXCEPT
@ -653,14 +721,17 @@ public:
return npos;
}
BOOST_CONSTEXPR size_type find_first_not_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR size_type find_first_not_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
{
return find_first_not_of( basic_string_view( s, n ), pos );
if( pos >= size() ) return npos;
if( n == 1 ) return find_first_not_of( s[0], pos );
return detail::find_first_not_of( data(), size(), s, pos, n );
}
BOOST_CONSTEXPR size_type find_first_not_of( Ch const* s, size_type pos = 0 ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR size_type find_first_not_of( Ch const* s, size_type pos = 0 ) const BOOST_NOEXCEPT
{
return find_first_not_of( basic_string_view( s ), pos );
return find_first_not_of( s, pos, traits_type::length( s ) );
}
// find_last_not_of
@ -726,7 +797,7 @@ public:
return find( sv ) != npos;
}
BOOST_CONSTEXPR bool contains( Ch c ) const BOOST_NOEXCEPT
BOOST_CXX14_CONSTEXPR bool contains( Ch c ) const BOOST_NOEXCEPT
{
Ch const* p = data();
size_type n = size();