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Further improvement to StackableStreambuf.

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The ownership model is more shored up.
This commit is contained in:
ADAM David Alan Martin
2023-10-20 03:09:01 -04:00
parent 8520b87689
commit f61710bfdb
4 changed files with 82 additions and 57 deletions
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62
Utility/StackableStreambuf.h
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@ -7,6 +7,8 @@ static_assert( __cplusplus > 2020'00 );
#include <ostream>
#include <exception>
#include <stdexcept>
#include <memory>
#include <stack>
namespace Alepha::Hydrogen::Utility ::detail:: stackable_streambuf
{
@ -23,19 +25,25 @@ namespace Alepha::Hydrogen::Utility ::detail:: stackable_streambuf
inline namespace impl
{
void releaseStack( std::ios_base &ios );
bool releaseTop( std::ostream &os );
void iosCallback( const std::ios_base::event event, std::ios_base &ios, const int idx );
}
inline auto &
getStack( std::ios_base &ios )
{
auto &ownership= reinterpret_cast< std::stack< std::unique_ptr< StackableStreambuf > > *& >( ios.pword( index ) );
if( not ownership ) ownership= new std::decay_t< decltype( *ownership ) >{};
return *ownership;
}
struct exports::StackableStreambuf
: virtual public std::streambuf
{
public:
std::streambuf *underlying;
~StackableStreambuf() {}
~StackableStreambuf() override {}
// Children must be created by `new`.
explicit
@ -45,9 +53,10 @@ namespace Alepha::Hydrogen::Utility ::detail:: stackable_streambuf
// TODO: Atomicity for this:
if( not host.iword( index ) ) host.register_callback( iosCallback, index );
host.iword( index )= 1;
getStack( host ).emplace( this );
}
std::ostream out() const { return std::ostream{ underlying }; }
auto out() const { return std::ostream{ underlying }; }
virtual void writeChar( const char ch )= 0;
virtual void drain()= 0;
@ -69,22 +78,36 @@ namespace Alepha::Hydrogen::Utility ::detail:: stackable_streambuf
}
};
inline bool
impl::releaseTop( std::ostream &os )
{
auto *const streambuf= os.rdbuf();
if( not streambuf ) return false;
auto *const stacked= dynamic_cast< StackableStreambuf * >( streambuf );
if( not stacked ) return false;
enum { token };
inline bool
releaseTop( std::ios_base &ios, decltype( token )= token )
{
auto &ownership= getStack( ios );
// Since it's owned, delete happens at scope exit.
const std::unique_ptr top= std::move( ownership.top() );
ownership.pop();
top->drain();
return not ownership.empty();
}
inline bool
releaseTop( std::ostream &os )
{
const auto *const current= dynamic_cast< StackableStreambuf * >( os.rdbuf() );
if( not current ) return false;
os.rdbuf( current->underlying );
releaseTop( os, token );
stacked->drain();
os.rdbuf( stacked->underlying );
delete stacked;
return true;
}
inline void
impl::releaseStack( std::ios_base &ios )
releaseStack( std::ios_base &ios )
{
auto &os= dynamic_cast< std::ostream & >( ios );
@ -94,9 +117,16 @@ namespace Alepha::Hydrogen::Utility ::detail:: stackable_streambuf
inline void
impl::iosCallback( const std::ios_base::event event, std::ios_base &ios, const int idx )
{
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wterminate"
if( index != idx ) throw std::logic_error{ "Wrong index." };
if( event == std::ios_base::erase_event ) releaseStack( ios );
else if( event == std::ios_base::imbue_event ) {}
else if( event == std::ios_base::copyfmt_event ) throw std::runtime_error{ "Can't copy?" };
#pragma GCC diagnostic pop
}
template< typename T >