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Use from_chars in operator>>.

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This removes code duplication with from_chars and allows for reusing
a faster implementation of from_chars in operator>>.

Also, align the input character buffer for more efficient memory
accesses.
This commit is contained in:
Andrey Semashev
2026-01-03 03:40:31 +03:00
parent 326e5db863
commit 45910f2ace
1 changed files with 4 additions and 51 deletions
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55
include/boost/uuid/uuid_io.hpp
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@@ -91,63 +91,16 @@ std::basic_ostream<Ch, Traits>& operator<<( std::basic_ostream<Ch, Traits>& os,
template<class Ch, class Traits>
std::basic_istream<Ch, Traits>& operator>>( std::basic_istream<Ch, Traits>& is, uuid& u )
{
Ch tmp[ 37 ] = {};
alignas( 16 ) Ch tmp[ 37 ] = {};
is.width( 37 ); // required for pre-C++20
if( is >> tmp )
{
u = {};
using ctype_t = std::ctype<Ch>;
ctype_t const& ctype = std::use_facet<ctype_t>( is.getloc() );
Ch xdigits[ 17 ];
from_chars_error err = from_chars( tmp, tmp + 36, u ).ec;
if( BOOST_UNLIKELY( err != from_chars_error::none ) )
{
char szdigits[] = "0123456789ABCDEF-";
ctype.widen( szdigits, szdigits + 17, xdigits );
}
Ch* const xdigits_end = xdigits + 16;
ctype.toupper( tmp, tmp + 36 );
int j = 0;
for( std::size_t i = 0; i < 16; ++i )
{
Ch* f = std::find( xdigits, xdigits_end, tmp[ j++ ] );
if( f == xdigits_end )
{
is.setstate( std::ios_base::failbit );
return is;
}
unsigned char byte = static_cast<unsigned char>( f - xdigits );
f = std::find( xdigits, xdigits_end, tmp[ j++ ] );
if( f == xdigits_end )
{
is.setstate( std::ios_base::failbit );
return is;
}
byte <<= 4;
byte |= static_cast<unsigned char>( f - xdigits );
u.data()[ i ] = byte;
if( i == 3 || i == 5 || i == 7 || i == 9 )
{
if( tmp[ j++ ] != xdigits[ 16 ] )
{
is.setstate( std::ios_base::failbit );
return is;
}
}
is.setstate( std::ios_base::failbit );
}
}