sso_string_base.h

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// Short-string-optimized versatile string base -*- C++ -*-

// Copyright (C) 2005, 2006 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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// 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.

/** @file ext/sso_string_base.h
 *  This file is a GNU extension to the Standard C++ Library.
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

#ifndef _SSO_STRING_BASE_H
#define _SSO_STRING_BASE_H 1

namespace __gnu_cxx
{
  template<typename _CharT, typename _Traits, typename _Alloc>
    class __sso_string_base
    : protected __vstring_utility<_CharT, _Traits, _Alloc>
    {
    public:
      typedef _Traits					    traits_type;
      typedef typename _Traits::char_type		    value_type;

      typedef __vstring_utility<_CharT, _Traits, _Alloc>    _Util_Base;
      typedef typename _Util_Base::_CharT_alloc_type        _CharT_alloc_type;
      typedef typename _CharT_alloc_type::size_type	    size_type;
      
    private:
      // The maximum number of individual char_type elements of an
      // individual string is determined by _S_max_size. This is the
      // value that will be returned by max_size().  (Whereas npos
      // is the maximum number of bytes the allocator can allocate.)
      // If one was to divvy up the theoretical largest size string,
      // with a terminating character and m _CharT elements, it'd
      // look like this:
      // npos = m * sizeof(_CharT) + sizeof(_CharT)
      // Solving for m:
      // m = npos / sizeof(_CharT) - 1
      // In addition, this implementation quarters this amount.
      enum { _S_max_size = (((static_cast<size_type>(-1)
			      / sizeof(_CharT)) - 1) / 4) };

      // Data Members (private):
      typename _Util_Base::template _Alloc_hider<_CharT_alloc_type>
                                                            _M_dataplus;
      size_type                                             _M_string_length;

      enum { _S_local_capacity = 15 };
      
      union
      {
	_CharT           _M_local_data[_S_local_capacity + 1];
	size_type        _M_allocated_capacity;
      };

      void
      _M_data(_CharT* __p)
      { _M_dataplus._M_p = __p; }

      void
      _M_length(size_type __length)
      { _M_string_length = __length; }

      void
      _M_capacity(size_type __capacity)
      { _M_allocated_capacity = __capacity; }

      bool
      _M_is_local() const
      { return _M_data() == _M_local_data; }

      // Create & Destroy
      _CharT*
      _M_create(size_type&, size_type);
      
      void
      _M_dispose()
      {
	if (!_M_is_local())
	  _M_destroy(_M_allocated_capacity);
      }

      void
      _M_destroy(size_type) throw();

      // _M_construct_aux is used to implement the 21.3.1 para 15 which
      // requires special behaviour if _InIterator is an integral type
      template<typename _InIterator>
        void
        _M_construct_aux(_InIterator __beg, _InIterator __end, __false_type)
	{
          typedef typename iterator_traits<_InIterator>::iterator_category _Tag;
          _M_construct(__beg, __end, _Tag());
	}

      template<typename _InIterator>
        void
        _M_construct_aux(_InIterator __beg, _InIterator __end, __true_type)
	{ _M_construct(static_cast<size_type>(__beg),
		       static_cast<value_type>(__end)); }

      template<typename _InIterator>
        void
        _M_construct(_InIterator __beg, _InIterator __end)
	{
	  typedef typename std::__is_integer<_InIterator>::__type _Integral;
	  _M_construct_aux(__beg, __end, _Integral());
        }

      // For Input Iterators, used in istreambuf_iterators, etc.
      template<typename _InIterator>
        void
        _M_construct(_InIterator __beg, _InIterator __end,
		     std::input_iterator_tag);
      
      // For forward_iterators up to random_access_iterators, used for
      // string::iterator, _CharT*, etc.
      template<typename _FwdIterator>
        void
        _M_construct(_FwdIterator __beg, _FwdIterator __end,
		     std::forward_iterator_tag);

      void
      _M_construct(size_type __req, _CharT __c);

    public:
      size_type
      _M_max_size() const
      { return size_type(_S_max_size); }

      _CharT*
      _M_data() const
      { return _M_dataplus._M_p; }

      size_type
      _M_length() const
      { return _M_string_length; }

      size_type
      _M_capacity() const
      {
	return _M_is_local() ? size_type(_S_local_capacity)
	                     : _M_allocated_capacity; 
      }

      bool
      _M_is_shared() const
      { return false; }

      void
      _M_set_leaked() { }

      void
      _M_leak() { }

      void
      _M_set_length(size_type __n)
      {
	_M_length(__n);
	traits_type::assign(_M_data()[__n], _CharT());
      }

      __sso_string_base()
      : _M_dataplus(_Alloc(), _M_local_data)
      { _M_set_length(0); }

      __sso_string_base(const _Alloc& __a);

      __sso_string_base(const __sso_string_base& __rcs);

      __sso_string_base(size_type __n, _CharT __c, const _Alloc& __a);

      template<typename _InputIterator>
        __sso_string_base(_InputIterator __beg, _InputIterator __end,
			  const _Alloc& __a);

      ~__sso_string_base()
      { _M_dispose(); }

      _CharT_alloc_type&
      _M_get_allocator()
      { return _M_dataplus; }

      const _CharT_alloc_type&
      _M_get_allocator() const
      { return _M_dataplus; }

      void
      _M_swap(__sso_string_base& __rcs);

      void
      _M_assign(const __sso_string_base& __rcs);

      void
      _M_reserve(size_type __res);

      void
      _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
		size_type __len2);

      void
      _M_erase(size_type __pos, size_type __n);

      bool
      _M_compare(const __sso_string_base&) const
      { return false; }
    };

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    __sso_string_base<_CharT, _Traits, _Alloc>::
    _M_destroy(size_type __size) throw()
    { _M_dataplus._CharT_alloc_type::deallocate(_M_data(), __size + 1); }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    __sso_string_base<_CharT, _Traits, _Alloc>::
    _M_swap(__sso_string_base& __rcs)
    {
      // NB: Implement Option 3 of DR 431 (see N1599).
      std::__alloc_swap<_CharT_alloc_type>::_S_do_it(_M_get_allocator(),
						     __rcs._M_get_allocator());

      if (_M_is_local())
	if (__rcs._M_is_local())
	  {
	    if (_M_length() && __rcs._M_length())
	      {
		_CharT __tmp_data[_S_local_capacity + 1];
		traits_type::copy(__tmp_data, __rcs._M_local_data,
				  _S_local_capacity + 1);
		traits_type::copy(__rcs._M_local_data, _M_local_data,
				  _S_local_capacity + 1);
		traits_type::copy(_M_local_data, __tmp_data,
				  _S_local_capacity + 1);
	      }
	    else if (__rcs._M_length())
	      {
		traits_type::copy(_M_local_data, __rcs._M_local_data,
				  _S_local_capacity + 1);
		_M_length(__rcs._M_length());
		__rcs._M_set_length(0);
		return;
	      }
	    else if (_M_length())
	      {
		traits_type::copy(__rcs._M_local_data, _M_local_data,
				  _S_local_capacity + 1);
		__rcs._M_length(_M_length());
		_M_set_length(0);
		return;
	      }
	  }
	else
	  {
	    const size_type __tmp_capacity = __rcs._M_allocated_capacity;
	    traits_type::copy(__rcs._M_local_data, _M_local_data,
			      _S_local_capacity + 1);
	    _M_data(__rcs._M_data());
	    __rcs._M_data(__rcs._M_local_data);
	    _M_capacity(__tmp_capacity);
	  }