stl_tempbuf.h File Reference

#include <bits/stl_algobase.h>
#include <bits/stl_construct.h>

Go to the source code of this file.

Functions
namespace std	_GLIBCXX_VISIBILITY (default)

Detailed Description

This is an internal header file, included by other library headers. Do not attempt to use it directly. {memory}

Function Documentation

namespace std _GLIBCXX_VISIBILITY

(

default

)

Allocates a temporary buffer.

Parameters

__len

The number of objects of type Tp.

Returns

See full description.

Reinventing the wheel, but this time with prettier spokes!

This function tries to obtain storage for __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.

Provides the nothrow exception guarantee.

The companion to get_temporary_buffer().

Parameters

__p	A buffer previously allocated by get_temporary_buffer.

Returns

None.

Frees the memory pointed to by __p.

This class is used in two places: stl_algo.h and ext/memory, where it is wrapped as the temporary_buffer class. See temporary_buffer docs for more notes.

As per Table mumble.

Returns the size requested by the constructor; may be >size().

As per Table mumble.

As per Table mumble.

Constructs a temporary buffer of a size somewhere between zero and the size of the given range.

{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  template<typename _Tp>
    pair<_Tp*, ptrdiff_t>
    get_temporary_buffer(ptrdiff_t __len) _GLIBCXX_NOEXCEPT
    {
      const ptrdiff_t __max =
    __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
      if (__len > __max)
    __len = __max;
      
      while (__len > 0) 
    {
      _Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp), 
                            std::nothrow));
      if (__tmp != 0)
        return std::pair<_Tp*, ptrdiff_t>(__tmp, __len);
      __len /= 2;
    }
      return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
    }

  template<typename _Tp>
    inline void
    return_temporary_buffer(_Tp* __p)
    { ::operator delete(__p, std::nothrow); }


  template<typename _ForwardIterator, typename _Tp>
    class _Temporary_buffer
    {
      // concept requirements
      __glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept)

    public:
      typedef _Tp         value_type;
      typedef value_type* pointer;
      typedef pointer     iterator;
      typedef ptrdiff_t   size_type;

    protected:
      size_type  _M_original_len;
      size_type  _M_len;
      pointer    _M_buffer;

    public:
      size_type
      size() const
      { return _M_len; }

      size_type
      requested_size() const
      { return _M_original_len; }

      iterator
      begin()
      { return _M_buffer; }

      iterator
      end()
      { return _M_buffer + _M_len; }

      _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last);

      ~_Temporary_buffer()
      {
    std::_Destroy(_M_buffer, _M_buffer + _M_len);
    std::return_temporary_buffer(_M_buffer);
      }

    private:
      // Disable copy constructor and assignment operator.
      _Temporary_buffer(const _Temporary_buffer&);

      void
      operator=(const _Temporary_buffer&);
    };


  template<bool>
    struct __uninitialized_construct_buf_dispatch
    {
      template<typename _Pointer, typename _ForwardIterator>
        static void
        __ucr(_Pointer __first, _Pointer __last,
          _ForwardIterator __seed)
        {
      if(__first == __last)
        return;

      _Pointer __cur = __first;
      __try
        {
          std::_Construct(std::__addressof(*__first),
                  _GLIBCXX_MOVE(*__seed));
          _Pointer __prev = __cur;
          ++__cur;
          for(; __cur != __last; ++__cur, ++__prev)
        std::_Construct(std::__addressof(*__cur),
                _GLIBCXX_MOVE(*__prev));
          *__seed = _GLIBCXX_MOVE(*__prev);
        }
      __catch(...)
        {
          std::_Destroy(__first, __cur);
          __throw_exception_again;
        }
    }
    };

  template<>
    struct __uninitialized_construct_buf_dispatch<true>
    {
      template<typename _Pointer, typename _ForwardIterator>
        static void
        __ucr(_Pointer, _Pointer, _ForwardIterator) { }
    };

  // Constructs objects in the range [first, last).
  // Note that while these new objects will take valid values,
  // their exact value is not defined. In particular they may
  // be 'moved from'.
  //
  // While *__seed may be altered during this algorithm, it will have
  // the same value when the algorithm finishes, unless one of the
  // constructions throws.
  //
  // Requirements: _Pointer::value_type(_Tp&&) is valid.
  template<typename _Pointer, typename _ForwardIterator>
    inline void
    __uninitialized_construct_buf(_Pointer __first, _Pointer __last,
                  _ForwardIterator __seed)
    {
      typedef typename std::iterator_traits<_Pointer>::value_type
    _ValueType;

      std::__uninitialized_construct_buf_dispatch<
        __has_trivial_constructor(_ValueType)>::
      __ucr(__first, __last, __seed);
    }

  template<typename _ForwardIterator, typename _Tp>
    _Temporary_buffer<_ForwardIterator, _Tp>::
    _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last)
    : _M_original_len(std::distance(__first, __last)),
      _M_len(0), _M_buffer(0)
    {
      __try
    {
      std::pair<pointer, size_type> __p(std::get_temporary_buffer<
                        value_type>(_M_original_len));
      _M_buffer = __p.first;
      _M_len = __p.second;
      if (_M_buffer)
        std::__uninitialized_construct_buf(_M_buffer, _M_buffer + _M_len,
                           __first);
    }
      __catch(...)
    {
      std::return_temporary_buffer(_M_buffer);
      _M_buffer = 0;
      _M_len = 0;
      __throw_exception_again;
    }
    }

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace