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Updated to match 1.30.0 release.

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[SVN r1108]
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Eric Friedman
2003-03-26 00:25:46 +00:00
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include/boost/optional.hpp
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// (C) 2003, Fernando Luis Cacciola Carballal.
//
// This material is provided "as is", with absolutely no warranty expressed
// or implied. Any use is at your own risk.
//
// Permission to use or copy this software for any purpose is hereby granted
// without fee, provided the above notices are retained on all copies.
// Permission to modify the code and to distribute modified code is granted,
// provided the above notices are retained, and a notice that the code was
// modified is included with the above copyright notice.
//
// See http://www.boost.org/lib/optional for documentation.
//
// You are welcome to contact the author at:
// fernando_cacciola@hotmail.com
//
#ifndef BOOST_OPTIONAL_FLC_19NOV2002_HPP
#define BOOST_OPTIONAL_FLC_19NOV2002_HPP
#include<new>
#include<algorithm>
#include "boost/config.hpp"
#include "boost/detail/workaround.hpp"
#include "boost/assert.hpp"
#include "boost/type_traits/alignment_of.hpp"
#include "boost/type_traits/type_with_alignment.hpp"
#if BOOST_WORKAROUND(BOOST_MSVC, == 1200)
// VC6.0 has the following bug:
// When a templated assignment operator exist, an implicit conversion
// constructing an optional<T> is used when assigment of the form:
// optional<T> opt ; opt = T(...);
// is compiled.
// However, optional's ctor is _explicit_ and the assignemt shouldn't compile.
// Therefore, for VC6.0 templated assignment is disabled.
//
#define BOOST_OPTIONAL_NO_CONVERTING_ASSIGNMENT
#endif
#if BOOST_WORKAROUND(BOOST_MSVC, == 1300)
// VC7.0 has the following bug:
// When both a non-template and a template copy-ctor exist
// and the templated version is made 'explicit', the explicit is also
// given to the non-templated version, making the class non-implicitely-copyable.
//
#define BOOST_OPTIONAL_NO_CONVERTING_COPY_CTOR
#endif
namespace boost
{
namespace optional_detail
{
template <class T>
class aligned_storage
{
// Borland ICEs if unnamed unions are used for this!
union dummy_u
{
char data[ sizeof(T) ];
type_with_alignment< ::boost::alignment_of<T>::value > aligner_;
} dummy_ ;
public:
void const* address() const { return &dummy_.data[0]; }
void * address() { return &dummy_.data[0]; }
} ;
}
template<class T>
class optional
{
typedef optional<T> this_type ;
typedef optional_detail::aligned_storage<T> storage_type ;
typedef void (this_type::*unspecified_bool_type)();
public :
typedef T value_type ;
// Creates an optional<T> uninitialized.
// No-throw
optional ()
:
m_initialized(false) {}
// Creates an optional<T> initialized with 'val'.
// Can throw if T::T(T const&) does
explicit optional ( T const& val )
:
m_initialized(false)
{
construct(val);
}
#ifndef BOOST_OPTIONAL_NO_CONVERTING_COPY_CTOR
// NOTE: MSVC needs templated versions first
// Creates a deep copy of another convertible optional<U>
// Requires a valid conversion from U to T.
// Can throw if T::T(U const&) does
template<class U>
explicit optional ( optional<U> const& rhs )
:
m_initialized(false)
{
if ( rhs )
construct(*rhs);
}
#endif
// Creates a deep copy of another optional<T>
// Can throw if T::T(T const&) does
optional ( optional const& rhs )
:
m_initialized(false)
{
if ( rhs )
construct(*rhs);
}
// No-throw (assuming T::~T() doesn't)
~optional() { destroy() ; }
#ifndef BOOST_OPTIONAL_NO_CONVERTING_ASSIGNMENT
// Assigns from another convertible optional<U> (converts && deep-copies the rhs value)
// Requires a valid conversion from U to T.
// Basic Guarantee: If T::T( U const& ) throws, this is left UNINITIALIZED
template<class U>
optional& operator= ( optional<U> const& rhs )
{
destroy(); // no-throw
if ( rhs )
{
// An exception can be thrown here.
// It it happens, THIS will be left uninitialized.
construct(*rhs);
}
return *this ;
}
#endif
// Assigns from another optional<T> (deep-copies the rhs value)
// Basic Guarantee: If T::T( T const& ) throws, this is left UNINITIALIZED
optional& operator= ( optional const& rhs )
{
destroy(); // no-throw
if ( rhs )
{
// An exception can be thrown here.
// It it happens, THIS will be left uninitialized.
construct(*rhs);
}
return *this ;
}
// Destroys the current value, if any, leaving this UNINITIALIZED
// No-throw (assuming T::~T() doesn't)
void reset()
{
destroy();
}
// Replaces the current value -if any- with 'val'
// Basic Guarantee: If T::T( T const& ) throws this is left UNINITIALIZED.
void reset ( T const& val )
{
destroy();
construct(val);
}
// Returns a pointer to the value if this is initialized, otherwise,
// returns NULL.
// No-throw
T const* get() const { return m_initialized ? static_cast<T const*>(m_storage.address()) : 0 ; }
T* get() { return m_initialized ? static_cast<T*> (m_storage.address()) : 0 ; }
// Returns a pointer to the value if this is initialized, otherwise,
// the behaviour is UNDEFINED
// No-throw
T const* operator->() const { BOOST_ASSERT(m_initialized) ; return get() ; }
T* operator->() { BOOST_ASSERT(m_initialized) ; return get() ; }
// Returns a reference to the value if this is initialized, otherwise,
// the behaviour is UNDEFINED
// No-throw
T const& operator *() const { BOOST_ASSERT(m_initialized) ; return *get() ; }
T& operator *() { BOOST_ASSERT(m_initialized) ; return *get() ; }
// implicit conversion to "bool"
// No-throw
operator unspecified_bool_type() const { return m_initialized ? &this_type::destroy : 0 ; }
// This is provided for those compilers which don't like the conversion to bool
// on some contexts.
bool operator!() const { return !m_initialized ; }
private :
void construct ( T const& val )
{
new (m_storage.address()) T(val) ;
m_initialized = true ;
}
void destroy()
{
if ( m_initialized )
{
get()->~T() ;
m_initialized = false ;
}
}
bool m_initialized ;
storage_type m_storage ;
} ;
// Returns a pointer to the value if this is initialized, otherwise, returns NULL.
// No-throw
template<class T>
inline
T const* get_pointer ( optional<T> const& opt )
{
return opt.get() ;
}
template<class T>
inline
T* get_pointer ( optional<T>& opt )
{
return opt.get() ;
}
// template<class OP> bool equal_pointees(OP const& x, OP const& y);
//
// Being OP a model of OptionalPointee (either a pointer or an optional):
//
// If both x and y have valid pointees, returns the result of (*x == *y)
// If only one has a valid pointee, returns false.
// If none have valid pointees, returns true.
// No-throw
template<class OptionalPointee>
inline
bool equal_pointees ( OptionalPointee const& x, OptionalPointee const& y )
{
return (!x) != (!y) ? false : ( !x ? true : (*x) == (*y) ) ;
}
// optional's operator == and != have deep-semantics (compare values).
// WARNING: This is UNLIKE pointers. Use equal_pointees() in generic code instead.
template<class T>
inline
bool operator == ( optional<T> const& x, optional<T> const& y )
{ return equal_pointees(x,y); }
template<class T>
inline
bool operator != ( optional<T> const& x, optional<T> const& y )
{ return !( x == y ) ; }
//
// The following swap implementation follows the GCC workaround as found in
// "boost/detail/compressed_pair.hpp"
//
namespace optional_detail {
#ifdef __GNUC__
// workaround for GCC (JM):
using std::swap;
#endif
// optional's swap:
// If both are initialized, calls swap(T&, T&), with whatever exception guarantess are given there.
// If only one is initialized, calls I.reset() and U.reset(*I), with the Basic Guarantee
// If both are uninitialized, do nothing (no-throw)
template<class T>
inline
void optional_swap ( optional<T>& x, optional<T>& y )
{
if ( !x && !!y )
{
x.reset(*y); // Basic guarantee.
y.reset();
}
else if ( !!x && !y )
{
y.reset(*x); // Basic guarantee.
x.reset();
}
else if ( !!x && !!y )
{
#ifndef __GNUC__
using std::swap ;
#endif
swap(*x,*y);
}
}
} // namespace optional_detail
template<class T> inline void swap ( optional<T>& x, optional<T>& y )
{
optional_detail::optional_swap(x,y);
}
} // namespace boost
#endif