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Add optimized implementation of find_last_of

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This commit is contained in:
Peter Dimov
2021-10-09 05:13:23 +03:00
parent a51364c5d3
commit 3d4eb536cd
1 changed files with 121 additions and 23 deletions
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144
include/boost/core/string_view.hpp
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@ -95,6 +95,83 @@ std::size_t find_first_of( char8_t const* p_, std::size_t n_, char8_t const* s,
#endif
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 i = pos;
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 ];
for( std::size_t j = 0; j < n; ++j )
{
if( s[ j ] == ch ) return i;
}
--i;
}
while( i != npos );
}
return npos;
}
#if CHAR_BIT == 8
BOOST_CXX14_CONSTEXPR std::size_t find_last_of( char const* p_, char const* s, std::size_t pos, std::size_t n ) BOOST_NOEXCEPT
{
unsigned char table[ 256 ] = {};
for( std::size_t j = 0; j < n; ++j )
{
unsigned char ch = s[ j ];
table[ ch ] = 1;
}
constexpr std::size_t npos = static_cast< std::size_t >( -1 );
std::size_t i = pos;
do
{
unsigned char ch = p_[ i ];
if( table[ ch ] ) return i;
--i;
}
while( i != npos );
return npos;
}
#endif
#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
std::size_t find_last_of( char8_t const* p_, char8_t const* s, std::size_t pos, std::size_t n ) BOOST_NOEXCEPT
{
return detail::find_last_of( reinterpret_cast< char const* >( p_ ), reinterpret_cast< char const* >( s ), pos, n );
}
#endif
} // namespace detail
template<class Ch> class basic_string_view
@ -450,8 +527,14 @@ public:
pos = n - 1;
}
const_reverse_iterator r = std::find( rbegin() + n - 1 - pos, rend(), c );
return r == rend()? npos: n - 1 - ( r - rbegin() );
do
{
if( p_[ pos ] == c ) return pos;
--pos;
}
while( pos != npos );
return npos;
}
BOOST_CXX14_CONSTEXPR size_type rfind( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
@ -513,24 +596,7 @@ public:
BOOST_CXX14_CONSTEXPR size_type find_last_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_of( str.data(), pos, str.size() );
}
BOOST_CONSTEXPR size_type find_last_of( Ch c, size_type pos = npos ) const BOOST_NOEXCEPT
@ -540,12 +606,29 @@ public:
BOOST_CONSTEXPR size_type find_last_of( Ch const* s, size_type pos, size_type n ) const BOOST_NOEXCEPT
{
return find_last_of( basic_string_view( s, n ), pos );
if( n == 1 )
{
return rfind( s[0], pos );
}
size_type m = size();
if( m == 0 )
{
return npos;
}
if( pos > m - 1 )
{
pos = m - 1;
}
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
{
return find_last_of( basic_string_view( s ), pos );
return find_last_of( s, pos, traits_type::length( s ) );
}
// find_first_not_of
@ -645,7 +728,22 @@ public:
BOOST_CONSTEXPR bool contains( Ch c ) const BOOST_NOEXCEPT
{
return traits_type::find( data(), size(), c ) != 0;
Ch const* p = data();
size_type n = size();
if( n >= 16 )
{
return traits_type::find( p, n, c ) != 0;
}
else
{
for( size_type i = 0; i < n; ++i )
{
if( p[ i ] == c ) return true;
}
return false;
}
}
BOOST_CONSTEXPR bool contains( Ch const* s ) const BOOST_NOEXCEPT