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Smart Pointers to boost your code

, 27 Sep 2004 CPOL
A beginner's introduction to the smart pointers provided by the boost library.
#ifndef BOOST_SHARED_ARRAY_HPP_INCLUDED
#define BOOST_SHARED_ARRAY_HPP_INCLUDED

//
//  shared_array.hpp
//
//  (C) Copyright Greg Colvin and Beman Dawes 1998, 1999.
//  Copyright (c) 2001, 2002 Peter Dimov
//
//  Permission to copy, use, modify, sell and distribute this software
//  is granted provided this copyright notice appears in all copies.
//  This software is provided "as is" without express or implied
//  warranty, and with no claim as to its suitability for any purpose.
//
//  See http://www.boost.org/libs/smart_ptr/shared_array.htm for documentation.
//

#include <boost/config.hpp>   // for broken compiler workarounds

#if defined(BOOST_NO_MEMBER_TEMPLATES) && !defined(BOOST_MSVC6_MEMBER_TEMPLATES)
#include <boost/detail/shared_array_nmt.hpp>
#else

#include <boost/assert.hpp>
#include <boost/checked_delete.hpp>

#include <boost/detail/shared_count.hpp>
#include <boost/detail/workaround.hpp>

#include <cstddef>            // for std::ptrdiff_t
#include <algorithm>          // for std::swap
#include <functional>         // for std::less

namespace boost
{

//
//  shared_array
//
//  shared_array extends shared_ptr to arrays.
//  The array pointed to is deleted when the last shared_array pointing to it
//  is destroyed or reset.
//

template<class T> class shared_array
{
private:

    // Borland 5.5.1 specific workarounds
    typedef checked_array_deleter<T> deleter;
    typedef shared_array<T> this_type;

public:

    typedef T element_type;

    explicit shared_array(T * p = 0): px(p), pn(p, deleter())
    {
    }

    //
    // Requirements: D's copy constructor must not throw
    //
    // shared_array will release p by calling d(p)
    //

    template<class D> shared_array(T * p, D d): px(p), pn(p, d)
    {
    }

//  generated copy constructor, assignment, destructor are fine

    void reset(T * p = 0)
    {
        BOOST_ASSERT(p == 0 || p != px);
        this_type(p).swap(*this);
    }

    template <class D> void reset(T * p, D d)
    {
        this_type(p, d).swap(*this);
    }

    T & operator[] (std::ptrdiff_t i) const // never throws
    {
        BOOST_ASSERT(px != 0);
        BOOST_ASSERT(i >= 0);
        return px[i];
    }
    
    T * get() const // never throws
    {
        return px;
    }

    // implicit conversion to "bool"

#if defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, <= 0x530)

    operator bool () const
    {
        return px != 0;
    }

#elif defined(__MWERKS__) && BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3003))
    typedef T * (this_type::*unspecified_bool_type)() const;
    
    operator unspecified_bool_type() const // never throws
    {
        return px == 0? 0: &this_type::get;
    }

#else 

    typedef T * this_type::*unspecified_bool_type;

    operator unspecified_bool_type() const // never throws
    {
        return px == 0? 0: &this_type::px;
    }

#endif

    bool operator! () const // never throws
    {
        return px == 0;
    }

    bool unique() const // never throws
    {
        return pn.unique();
    }

    long use_count() const // never throws
    {
        return pn.use_count();
    }

    void swap(shared_array<T> & other) // never throws
    {
        std::swap(px, other.px);
        pn.swap(other.pn);
    }

private:

    T * px;                     // contained pointer
    detail::shared_count pn;    // reference counter

};  // shared_array

template<class T> inline bool operator==(shared_array<T> const & a, shared_array<T> const & b) // never throws
{
    return a.get() == b.get();
}

template<class T> inline bool operator!=(shared_array<T> const & a, shared_array<T> const & b) // never throws
{
    return a.get() != b.get();
}

template<class T> inline bool operator<(shared_array<T> const & a, shared_array<T> const & b) // never throws
{
    return std::less<T*>()(a.get(), b.get());
}

template<class T> void swap(shared_array<T> & a, shared_array<T> & b) // never throws
{
    a.swap(b);
}

} // namespace boost

#endif  // #if defined(BOOST_NO_MEMBER_TEMPLATES) && !defined(BOOST_MSVC6_MEMBER_TEMPLATES)

#endif  // #ifndef BOOST_SHARED_ARRAY_HPP_INCLUDED

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peterchen
Klippel
Germany Germany
Peter is tired of being called "Mr. Chen", even so certain individuals insist on it. No, he's not chinese.
 
Peter has seen lots of boxes you youngsters wouldn't even accept as calculators. He is proud of having visited the insides of a 16 Bit Machine.
 
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