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#ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED
#define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED
// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif
//
// detail/sp_counted_base_gcc_x86.hpp - g++ on 486+ or AMD64
//
// Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
// Copyright 2004-2005 Peter Dimov
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
//
// Lock-free algorithm by Alexander Terekhov
//
// Thanks to Ben Hitchings for the #weak + (#shared != 0)
// formulation
//
#include <boost/detail/sp_typeinfo.hpp>
namespace boost
{
namespace detail
{
inline int atomic_exchange_and_add( int * pw, int dv )
{
// int r = *pw;
// *pw += dv;
// return r;
int r;
__asm__ __volatile__
(
"lock\n\t"
"xadd %1, %0":
"=m"( *pw ), "=r"( r ): // outputs (%0, %1)
"m"( *pw ), "1"( dv ): // inputs (%2, %3 == %1)
"memory", "cc" // clobbers
);
return r;
}
inline void atomic_increment( int * pw )
{
//atomic_exchange_and_add( pw, 1 );
__asm__
(
"lock\n\t"
"incl %0":
"=m"( *pw ): // output (%0)
"m"( *pw ): // input (%1)
"cc" // clobbers
);
}
inline int atomic_conditional_increment( int * pw )
{
// int rv = *pw;
// if( rv != 0 ) ++*pw;
// return rv;
int rv, tmp;
__asm__
(
"movl %0, %%eax\n\t"
"0:\n\t"
"test %%eax, %%eax\n\t"
"je 1f\n\t"
"movl %%eax, %2\n\t"
"incl %2\n\t"
"lock\n\t"
"cmpxchgl %2, %0\n\t"
"jne 0b\n\t"
"1:":
"=m"( *pw ), "=&a"( rv ), "=&r"( tmp ): // outputs (%0, %1, %2)
"m"( *pw ): // input (%3)
"cc" // clobbers
);
return rv;
}
class sp_counted_base
{
private:
sp_counted_base( sp_counted_base const & );
sp_counted_base & operator= ( sp_counted_base const & );
int use_count_; // #shared
int weak_count_; // #weak + (#shared != 0)
public:
sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
{
}
virtual ~sp_counted_base() // nothrow
{
}
// dispose() is called when use_count_ drops to zero, to release
// the resources managed by *this.
virtual void dispose() = 0; // nothrow
// destroy() is called when weak_count_ drops to zero.
virtual void destroy() // nothrow
{
delete this;
}
virtual void * get_deleter( sp_typeinfo const & ti ) = 0;
virtual void * get_untyped_deleter() = 0;
void add_ref_copy()
{
atomic_increment( &use_count_ );
}
bool add_ref_lock() // true on success
{
return atomic_conditional_increment( &use_count_ ) != 0;
}
void release() // nothrow
{
if( atomic_exchange_and_add( &use_count_, -1 ) == 1 )
{
dispose();
weak_release();
}
}
void weak_add_ref() // nothrow
{
atomic_increment( &weak_count_ );
}
void weak_release() // nothrow
{
if( atomic_exchange_and_add( &weak_count_, -1 ) == 1 )
{
destroy();
}
}
long use_count() const // nothrow
{
return static_cast<int const volatile &>( use_count_ );
}
};
} // namespace detail
} // namespace boost
#endif // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED
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