smart_ptr.tpp

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/*
    The STL+ C++ Library Collection

    Website <http://stlplus.sourceforge.net/> Collection <index.html>


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        * License for using the STLplus Library Collection <#license>
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        License for using the STLplus Library Collection

    *© 1999-2008 Andy Rushton. All rights reserved.*

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:

        * Redistributions of source code must retain the above Copyright
          notice, this list of conditions and the following disclaimer.
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          notice, this list of conditions and the following disclaimer in
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        * Neither the name of the STLplus library nor the names of its
          contributors may be used to endorse or promote products derived
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    This software is provided by the Copyright holders and contributors "as
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/*
    Modified version of STL+ sources shipped with the Mobile Robot 
        Programming Toolkit (MRPT).
        
        Sources have been modified to support thred-safe smart pointers
        through atomic operations.
        
        2009, Jose Luis Blanco. University of Malaga. 
*/

#ifndef MRPT_SMARTPTR_H
#define MRPT_SMARTPTR_H

////////////////////////////////////////////////////////////////////////////////

//   Author:    Andy Rushton
//   Copyright: (c) Andy Rushton, 2007
//   License:   BSD License, see ../docs/license.html

////////////////////////////////////////////////////////////////////////////////

namespace stlplus
{

  ////////////////////////////////////////////////////////////////////////////////
  // internal holder data structure
  ////////////////////////////////////////////////////////////////////////////////

  template<typename T,typename COUNTER>
  class smart_ptr_holder
  {
  private:
        COUNTER m_count;  //JL: It was...  unsigned m_count;
    T* m_data;

    // make these private to disallow copying because the holder doesn't know how to copy
    inline smart_ptr_holder(const smart_ptr_holder& s) :
      m_count(0), m_data(0)
      {
      }

    inline smart_ptr_holder& operator=(const smart_ptr_holder& s)
      {
        return *this;
      }

  public:
    inline smart_ptr_holder(T* p = 0) : 
      m_count(1), m_data(p)
      {
      }

    ~smart_ptr_holder(void)
      {
        clear();
      }

    inline unsigned long count(void) const
      {
        return m_count;
      }

    inline void increment(void)
      {
        ++m_count;
      }

    inline bool decrement(void)
      {
        return (--m_count)==0;
      }

    inline bool null(void)
      {
        return m_data == 0;
      }

    inline void clear(void)
      {
        if(m_data)
          delete m_data;
        m_data = 0;
      }

    inline void set(T* p = 0)
      {
        clear();
        m_data = p;
      }

    inline T*& pointer(void)
      {
        return m_data;
      }

    inline const T* pointer(void) const
      {
        return m_data;
      }

    inline T& value(void)
      {
        return *m_data;
      }

    inline const T& value(void) const
      {
        return *m_data;
      }
  };

  ////////////////////////////////////////////////////////////////////////////////
  // smart_ptr_base class
  ////////////////////////////////////////////////////////////////////////////////

  ////////////////////////////////////////////////////////////////////////////////
  // constructors, assignments and destructors

  // create a null pointer
  template <typename T, typename C, typename COUNTER>
  smart_ptr_base<T,C,COUNTER>::smart_ptr_base(void) :
    m_holder(new smart_ptr_holder<T,COUNTER>)
  {
  }

  // create a pointer containing a *copy* of the object pointer
  template <typename T, typename C, typename COUNTER>
  smart_ptr_base<T,C,COUNTER>::smart_ptr_base(const T& data) throw(illegal_copy) :
    m_holder(new smart_ptr_holder<T,COUNTER>)
  {
    m_holder->set(C()(data));
  }

  // create a pointer containing a dynamically created object
  // Note: the object must be allocated *by the user* with new
  // constructor form - must be called in the form smart_ptr<type> x(new type(args))
  template <typename T, typename C, typename COUNTER>
  smart_ptr_base<T,C,COUNTER>::smart_ptr_base(T* data) :
    m_holder(new smart_ptr_holder<T,COUNTER>)
  {
    m_holder->set(data);
  }

  // copy constructor implements counted referencing - no copy is made
  template <typename T, typename C, typename COUNTER>
  smart_ptr_base<T,C,COUNTER>::smart_ptr_base(const smart_ptr_base<T,C,COUNTER>& r) :
    m_holder(0)
  {
    m_holder = r.m_holder;
    m_holder->increment();
  }

  // destructor decrements the reference count and delete only when the last reference is destroyed
  template <typename T, typename C, typename COUNTER>
  smart_ptr_base<T,C,COUNTER>::~smart_ptr_base(void)
  {
    if(m_holder->decrement())
      delete m_holder;
  }

  //////////////////////////////////////////////////////////////////////////////
  // logical tests to see if there is anything contained in the pointer since it can be null

  template <typename T, typename C, typename COUNTER>
  inline bool smart_ptr_base<T,C,COUNTER>::null(void) const
  {
    return m_holder->null();
  }

  template <typename T, typename C, typename COUNTER>
  inline bool smart_ptr_base<T,C,COUNTER>::present(void) const
  {
    return !m_holder->null();
  }

  template <typename T, typename C, typename COUNTER>
  bool smart_ptr_base<T,C,COUNTER>::operator!(void) const
  {
    return m_holder->null();
  }

  template <typename T, typename C, typename COUNTER>
  smart_ptr_base<T,C,COUNTER>::operator bool(void) const
  {
    return !m_holder->null();
  }

  //////////////////////////////////////////////////////////////////////////////
  // dereference operators and functions

  template <typename T, typename C, typename COUNTER>
  inline T& smart_ptr_base<T,C,COUNTER>::operator*(void) throw(null_dereference)
  {
    if (m_holder->null()) throw null_dereference("null pointer dereferenced in smart_ptr::operator*");
    return m_holder->value();
  }

  template <typename T, typename C, typename COUNTER>
  inline const T& smart_ptr_base<T,C,COUNTER>::operator*(void) const throw(null_dereference)
  {
    if (m_holder->null()) throw null_dereference("null pointer dereferenced in smart_ptr::operator*");
    return m_holder->value();
  }

  template <typename T, typename C, typename COUNTER>
  inline T* smart_ptr_base<T,C,COUNTER>::operator->(void) throw(null_dereference)
  {
    if (m_holder->null()) throw null_dereference("null pointer dereferenced in smart_ptr::operator->");
    return m_holder->pointer();
  }

  template <typename T, typename C, typename COUNTER>
  inline const T* smart_ptr_base<T,C,COUNTER>::operator->(void) const throw(null_dereference)
  {
    if (m_holder->null()) throw null_dereference("null pointer dereferenced in smart_ptr::operator->");
    return m_holder->pointer();
  }

  //////////////////////////////////////////////////////////////////////////////
  // explicit function forms of the above assignment dereference operators

  template <typename T, typename C, typename COUNTER>
  inline void smart_ptr_base<T,C,COUNTER>::set_value(const T& data) throw(illegal_copy)
  {
    m_holder->set(C()(data));
  }

  template <typename T, typename C, typename COUNTER>
  inline T& smart_ptr_base<T,C,COUNTER>::value(void) throw(null_dereference)
  {
    if (m_holder->null()) throw null_dereference("null pointer dereferenced in smart_ptr::value");
    return m_holder->value();
  }

  template <typename T, typename C, typename COUNTER>
  inline const T& smart_ptr_base<T,C,COUNTER>::value(void) const throw(null_dereference)
  {
    if (m_holder->null()) throw null_dereference("null pointer dereferenced in smart_ptr::value");
    return m_holder->value();
  }

  template <typename T, typename C, typename COUNTER>
  void smart_ptr_base<T,C,COUNTER>::set(T* data)
  {
    m_holder->set(data);
  }

  template <typename T, typename C, typename COUNTER>
  inline T* smart_ptr_base<T,C,COUNTER>::pointer(void)
  {
    return m_holder->pointer();
  }

  template <typename T, typename C, typename COUNTER>
  inline const T* smart_ptr_base<T,C,COUNTER>::pointer(void) const
  {
    return m_holder->pointer();
  }

  ////////////////////////////////////////////////////////////////////////////////
  // functions to manage counted referencing

  // make this an alias of the passed object
  template <typename T, typename C, typename COUNTER>
  void smart_ptr_base<T,C,COUNTER>::alias(const smart_ptr_base<T,C,COUNTER>& r)
  {
    // make it alias-copy safe - this means that I don't try to do the
    // assignment if r is either the same object or an alias of it
    //   if (m_holder == r.m_holder) return;
    //   if (m_holder->decrement())
    //     delete m_holder;
    //   m_holder = r.m_holder;
    //   m_holder->increment();
    make_alias(r.m_holder);
  }

  template <typename T, typename C, typename COUNTER>
  bool smart_ptr_base<T,C,COUNTER>::aliases(const smart_ptr_base<T,C,COUNTER>& r) const
  {
    return m_holder == r.m_holder;
  }

  template <typename T, typename C, typename COUNTER>
  unsigned smart_ptr_base<T,C,COUNTER>::alias_count(void) const
  {
    return m_holder->count();
  }

  template <typename T, typename C, typename COUNTER>
  void smart_ptr_base<T,C,COUNTER>::clear(void)
  {
    m_holder->clear();
  }

  template <typename T, typename C, typename COUNTER>
  void smart_ptr_base<T,C,COUNTER>::clear_unique(void)
  {
    if (m_holder->count() == 1)
      m_holder->clear();
    else
    {
      m_holder->decrement();
      m_holder = 0;
      m_holder = new smart_ptr_holder<T,COUNTER>;
    }
  }

  template <typename T, typename C, typename COUNTER>
  void smart_ptr_base<T,C,COUNTER>::make_unique(void) throw(illegal_copy)
  {
    if (m_holder->count() > 1)
    {
      smart_ptr_holder<T,COUNTER>* old_holder = m_holder;
      m_holder->decrement();
      m_holder = 0;
      m_holder = new smart_ptr_holder<T,COUNTER>;
      if (old_holder->pointer())
        m_holder->set(C()(old_holder->value()));
    }
  }

  template <typename T, typename C, typename COUNTER>
  void smart_ptr_base<T,C,COUNTER>::copy(const smart_ptr_base<T,C,COUNTER>& data) throw(illegal_copy)
  {
    alias(data);
    make_unique();
  }

  // internal function for distinguishing unique smart_ptr objects
  // used for example in persistence routines

  template <typename T, typename C, typename COUNTER>
  void* smart_ptr_base<T,C,COUNTER>::handle(void) const
  {
    return m_holder;
  }

  template <typename T, typename C, typename COUNTER>
  void smart_ptr_base<T,C,COUNTER>::make_alias(void* handle)
  {
    smart_ptr_holder<T,COUNTER>* r_holder = (smart_ptr_holder<T,COUNTER>*)handle;
    if (m_holder != r_holder)
    {
      if (m_holder->decrement())
        delete m_holder;
      m_holder = r_holder;
      m_holder->increment();
    }
  }

  ////////////////////////////////////////////////////////////////////////////////

} // end namespace stlplus

#endif