xref: /freebsd-10-stable/contrib/libstdc++/include/std/std_memory.h

// <memory> -*- C++ -*-

// Copyright (C) 2001, 2002 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 * Copyright (c) 1997-1999
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 */

/** @file memory
 *  This is a Standard C++ Library header.  You should @c #include this header
 *  in your programs, rather than any of the "st[dl]_*.h" implementation files.
 */

#ifndef _CPP_MEMORY
#define _CPP_MEMORY 1

#pragma GCC system_header

#include <bits/stl_algobase.h>
#include <bits/stl_alloc.h>
#include <bits/stl_construct.h>
#include <bits/stl_iterator_base_types.h> //for iterator_traits
#include <bits/stl_uninitialized.h>
#include <bits/stl_raw_storage_iter.h>

// Since this entire file is within namespace std, there's no reason to
// waste two spaces along the left column.  Thus the leading indentation is
// slightly violated from here on.
namespace std
{
/**
 *  @if maint
 *  This is a helper function.  The unused second parameter exists to
 *  permit the real get_temporary_buffer to use template parameter deduction.
 *
 *  XXX This should perhaps use the pool.
 *  @endif
*/
template <typename _Tp>
pair<_Tp*, ptrdiff_t>
__get_temporary_buffer(ptrdiff_t __len, _Tp*)
{
  if (__len > ptrdiff_t(INT_MAX / sizeof(_Tp)))
    __len = INT_MAX / sizeof(_Tp);

  while (__len > 0) {
    _Tp* __tmp = (_Tp*) std::malloc((std::size_t)__len * sizeof(_Tp));
    if (__tmp != 0)
      return pair<_Tp*, ptrdiff_t>(__tmp, __len);
    __len /= 2;
  }

  return pair<_Tp*, ptrdiff_t>((_Tp*)0, 0);
}

/**
 *  @brief This is a mostly-useless wrapper around malloc().
 *  @param  len  The number of objects of type Tp.
 *  @return   See full description.
 *
 *  Reinventing the wheel, but this time with prettier spokes!
 *
 *  This function tries to obtain storage for @c len adjacent Tp objects.
 *  The objects themselves are not constructed, of course.  A pair<> is
 *  returned containing "the buffer s address and capacity (in the units of
 *  sizeof(Tp)), or a pair of 0 values if no storage can be obtained."
 *  Note that the capacity obtained may be less than that requested if the
 *  memory is unavailable; you should compare len with the .second return
 *  value.
*/
template<typename _Tp>
  inline pair<_Tp*,ptrdiff_t>
  get_temporary_buffer(ptrdiff_t __len)
  {
    return __get_temporary_buffer(__len, (_Tp*) 0);
  }

/**
 *  @brief The companion to get_temporary_buffer().
 *  @param  p  A buffer previously allocated by get_temporary_buffer.
 *  @return   None.
 *
 *  Frees the memory pointed to by p.
 */
template<typename _Tp>
  void
  return_temporary_buffer(_Tp* __p)
  {
    std::free(__p);
  }


/**
 *  A wrapper class to provide auto_ptr with reference semantics.  For
 *  example, an auto_ptr can be assigned (or constructed from) the result of
 *  a function which returns an auto_ptr by value.
 *
 *  All the auto_ptr_ref stuff should happen behind the scenes.
*/
template<typename _Tp1>
  struct auto_ptr_ref
{
   _Tp1* _M_ptr;

   explicit
   auto_ptr_ref(_Tp1* __p)
   : _M_ptr(__p) {}
};


/**
 *  @brief  A simple smart pointer providing strict ownership semantics.
 *
 *  The Standard says:
 *  <pre>
 *  An @c auto_ptr owns the object it holds a pointer to.  Copying an
 *  @c auto_ptr copies the pointer and transfers ownership to the destination.
 *  If more than one @c auto_ptr owns the same object at the same time the
 *  behavior of the program is undefined.
 *
 *  The uses of @c auto_ptr include providing temporary exception-safety for
 *  dynamically allocated memory, passing ownership of dynamically allocated
 *  memory to a function, and returning dynamically allocated memory from a
 *  function.  @c auto_ptr does not meet the CopyConstructible and Assignable
 *  requirements for Standard Library <a href="tables.html#65">container</a>
 *  elements and thus instantiating a Standard Library container with an
 *  @c auto_ptr results in undefined behavior.
 *  </pre>
 *  Quoted from [20.4.5]/3.
 *
 *  Good examples of what can and cannot be done with auto_ptr can be found
 *  in the libstdc++ testsuite.
 *
 *  @if maint
 *  _GLIBCPP_RESOLVE_LIB_DEFECTS
 *  127.  auto_ptr<> conversion issues
 *  These resolutions have all been incorporated.
 *  @endif
*/
template<typename _Tp>
  class auto_ptr
{
private:
  _Tp* _M_ptr;

public:
  /// The pointed-to type.
  typedef _Tp element_type;

  /**
   *  @brief  An %auto_ptr is usually constructed from a raw pointer.
   *  @param  p  A pointer (defaults to NULL).
   *
   *  This object now @e owns the object pointed to by @a p.
  */
  explicit
  auto_ptr(element_type* __p = 0) throw()
  : _M_ptr(__p) { }

  /**
   *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
   *  @param  a  Another %auto_ptr of the same type.
   *
   *  This object now @e owns the object previously owned by @a a, which has
   *  given up ownsership.
  */
  auto_ptr(auto_ptr& __a) throw()
  : _M_ptr(__a.release()) { }

  /**
   *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
   *  @param  a  Another %auto_ptr of a different but related type.
   *
   *  A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
   *
   *  This object now @e owns the object previously owned by @a a, which has
   *  given up ownsership.
  */
  template<typename _Tp1>
    auto_ptr(auto_ptr<_Tp1>& __a) throw()
    : _M_ptr(__a.release()) { }

  /**
   *  @brief  %auto_ptr assignment operator.
   *  @param  a  Another %auto_ptr of the same type.
   *
   *  This object now @e owns the object previously owned by @a a, which has
   *  given up ownsership.  The object that this one @e used to own and
   *  track has been deleted.
  */
  auto_ptr&
  operator=(auto_ptr& __a) throw()
    {
      reset(__a.release());
      return *this;
    }

  /**
   *  @brief  %auto_ptr assignment operator.
   *  @param  a  Another %auto_ptr of a different but related type.
   *
   *  A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
   *
   *  This object now @e owns the object previously owned by @a a, which has
   *  given up ownsership.  The object that this one @e used to own and
   *  track has been deleted.
  */
  template <typename _Tp1>
    auto_ptr&
    operator=(auto_ptr<_Tp1>& __a) throw()
    {
      reset(__a.release());
      return *this;
    }

  /**
   *  When the %auto_ptr goes out of scope, the object it owns is deleted.
   *  If it no longer owns anything (i.e., @c get() is @c NULL), then this
   *  has no effect.
   *
   *  @if maint
   *  The C++ standard says there is supposed to be an empty throw
   *  specification here, but omitting it is standard conforming.  Its
   *  presence can be detected only if _Tp::~_Tp() throws, but this is
   *  prohibited.  [17.4.3.6]/2
   *  @end maint
  */
  ~auto_ptr() { delete _M_ptr; }

  /**
   *  @brief  Smart pointer dereferencing.
   *
   *  If this %auto_ptr no longer owns anything, then this operation will
   *  crash.  (For a smart pointer, "no longer owns anything" is the same as
   *  being a null pointer, and you know what happens when you dereference
   *  one of those...)
  */
  element_type&
  operator*() const throw() { return *_M_ptr; }

  /**
   *  @brief  Smart pointer dereferencing.
   *
   *  This returns the pointer itself, which the language then will
   *  automatically cause to be dereferenced.
  */
  element_type*
  operator->() const throw() { return _M_ptr; }

  /**
   *  @brief  Bypassing the smart pointer.
   *  @return  The raw pointer being managed.
   *
   *  You can get a copy of the pointer that this object owns, for
   *  situations such as passing to a function which only accepts a raw
   *  pointer.
   *
   *  @note  This %auto_ptr still owns the memory.
  */
  element_type*
  get() const throw() { return _M_ptr; }

  /**
   *  @brief  Bypassing the smart pointer.
   *  @return  The raw pointer being managed.
   *
   *  You can get a copy of the pointer that this object owns, for
   *  situations such as passing to a function which only accepts a raw
   *  pointer.
   *
   *  @note  This %auto_ptr no longer owns the memory.  When this object
   *  goes out of scope, nothing will happen.
  */
  element_type*
  release() throw()
    {
      element_type* __tmp = _M_ptr;
      _M_ptr = 0;
      return __tmp;
    }

  /**
   *  @brief  Forcibly deletes the managed object.
   *  @param  p  A pointer (defaults to NULL).
   *
   *  This object now @e owns the object pointed to by @a p.  The previous
   *  object has been deleted.
  */
  void
  reset(element_type* __p = 0) throw()
    {
      if (__p != _M_ptr)
        {
          delete _M_ptr;
          _M_ptr = __p;
        }
    }

  /** @{
   *  @brief  Automatic conversions
   *
   *  These operations convert an %auto_ptr into and from an auto_ptr_ref
   *  automatically as needed.  This allows constructs such as
   *  @code
   *    auto_ptr<Derived>  func_returning_auto_ptr(.....);
   *    ...
   *    auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
   *  @endcode
  */
  auto_ptr(auto_ptr_ref<element_type> __ref) throw()
    : _M_ptr(__ref._M_ptr) {}

  auto_ptr&
  operator=(auto_ptr_ref<element_type> __ref) throw()
    {
      if (__ref._M_ptr != this->get())
        {
          delete _M_ptr;
          _M_ptr = __ref._M_ptr;
        }
      return *this;
    }

  template<typename _Tp1>
    operator auto_ptr_ref<_Tp1>() throw()
      { return auto_ptr_ref<_Tp1>(this->release()); }

  template<typename _Tp1>
    operator auto_ptr<_Tp1>() throw()
      { return auto_ptr<_Tp1>(this->release()); }
  /** @}  */
};

} // namespace std

#endif /* _CPP_MEMORY */