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.

#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 halfs this amount.
      enum { _S_max_size = (((static_cast<size_type>(-1)
                  / sizeof(_CharT)) - 1) / 2) };

      // 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);

      void
      _M_clear()
      { _M_set_length(0); }

      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);
      }
      else
    {
      const size_type __tmp_capacity = _M_allocated_capacity;
      if (__rcs._M_is_local())
        {
          traits_type::copy(_M_local_data, __rcs._M_local_data,
                _S_local_capacity + 1);
          __rcs._M_data(_M_data());
          _M_data(_M_local_data);
        }
      else
        {
          _CharT* __tmp_ptr = _M_data();
          _M_data(__rcs._M_data());
          __rcs._M_data(__tmp_ptr);
          _M_capacity(__rcs._M_allocated_capacity);
        }
      __rcs._M_capacity(__tmp_capacity);
    }

      const size_type __tmp_length = _M_length();
      _M_length(__rcs._M_length());
      __rcs._M_length(__tmp_length);
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    _CharT*
    __sso_string_base<_CharT, _Traits, _Alloc>::
    _M_create(size_type& __capacity, size_type __old_capacity)
    {
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 83.  String::npos vs. string::max_size()
      if (__capacity > size_type(_S_max_size))
    std::__throw_length_error(__N("__sso_string_base::_M_create"));

      // The below implements an exponential growth policy, necessary to
      // meet amortized linear time requirements of the library: see
      // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
      if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
    {
      __capacity = 2 * __old_capacity;
      // Never allocate a string bigger than _S_max_size.
      if (__capacity > size_type(_S_max_size))
        __capacity = size_type(_S_max_size);
    }

      // NB: Need an array of char_type[__capacity], plus a terminating
      // null char_type() element.
      return _M_dataplus._CharT_alloc_type::allocate(__capacity + 1);
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    __sso_string_base<_CharT, _Traits, _Alloc>::
    __sso_string_base(const _Alloc& __a)
    : _M_dataplus(__a, _M_local_data)
    { _M_set_length(0); }

  template<typename _CharT, typename _Traits, typename _Alloc>
    __sso_string_base<_CharT, _Traits, _Alloc>::
    __sso_string_base(const __sso_string_base& __rcs)
    : _M_dataplus(__rcs._M_get_allocator(), _M_local_data)
    { _M_construct(__rcs._M_data(), __rcs._M_data() + __rcs._M_length()); }

  template<typename _CharT, typename _Traits, typename _Alloc>
    __sso_string_base<_CharT, _Traits, _Alloc>::
    __sso_string_base(size_type __n, _CharT __c, const _Alloc& __a)
    : _M_dataplus(__a, _M_local_data)
    { _M_construct(__n, __c); }

  template<typename _CharT, typename _Traits, typename _Alloc>
    template<typename _InputIterator>
    __sso_string_base<_CharT, _Traits, _Alloc>::
    __sso_string_base(_InputIterator __beg, _InputIterator __end,
              const _Alloc& __a)
    : _M_dataplus(__a, _M_local_data)
    { _M_construct(__beg, __end); }

  // NB: This is the special case for Input Iterators, used in
  // istreambuf_iterators, etc.
  // Input Iterators have a cost structure very different from
  // pointers, calling for a different coding style.
  template<typename _CharT, typename _Traits, typename _Alloc>
    template<typename _InIterator>
      void
      __sso_string_base<_CharT, _Traits, _Alloc>::
      _M_construct(_InIterator __beg, _InIterator __end,
           std::input_iterator_tag)
      {
    size_type __len = 0;
    size_type __capacity = size_type(_S_local_capacity);

    while (__beg != __end && __len < __capacity)
      {
        _M_data()[__len++] = *__beg;
        ++__beg;
      }
    
    try
      {
        while (__beg != __end)
          {
        if (__len == __capacity)
          {
            // Allocate more space.
            __capacity = __len + 1;
            _CharT* __another = _M_create(__capacity, __len);
            _S_copy(__another, _M_data(), __len);
            _M_dispose();
            _M_data(__another);
            _M_capacity(__capacity);
          }
        _M_data()[__len++] = *__beg;
        ++__beg;
          }
      }
    catch(...)
      {
        _M_dispose();
        __throw_exception_again;
      }

    _M_set_length(__len);
      }

  template<typename _CharT, typename _Traits, typename _Alloc>
    template<typename _InIterator>
      void
      __sso_string_base<_CharT, _Traits, _Alloc>::
      _M_construct(_InIterator __beg, _InIterator __end,
           std::forward_iterator_tag)
      {
    // NB: Not required, but considered best practice.
    if (__builtin_expect(_S_is_null_pointer(__beg) && __beg != __end, 0))
      std::__throw_logic_error(__N("__sso_string_base::"
                       "_M_construct NULL not valid"));

    size_type __dnew = static_cast<size_type>(std::distance(__beg, __end));

    if (__dnew > size_type(_S_local_capacity))
      {
        _M_data(_M_create(__dnew, size_type(0)));
        _M_capacity(__dnew);
      }

    // Check for out_of_range and length_error exceptions.
    try
      { _S_copy_chars(_M_data(), __beg, __end); }
    catch(...)
      {
        _M_dispose();
        __throw_exception_again;
      }

    _M_set_length(__dnew);
      }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    __sso_string_base<_CharT, _Traits, _Alloc>::
    _M_construct(size_type __n, _CharT __c)
    {
      if (__n > size_type(_S_local_capacity))
    {
      _M_data(_M_create(__n, size_type(0)));
      _M_capacity(__n);
    }

      if (__n)
    _S_assign(_M_data(), __n, __c);

      _M_set_length(__n);
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    __sso_string_base<_CharT, _Traits, _Alloc>::
    _M_assign(const __sso_string_base& __rcs)
    {
      if (this != &__rcs)
    {
      const size_type __rsize = __rcs._M_length();
      const size_type __capacity = _M_capacity();

      if (__rsize > __capacity)
        {
          size_type __new_capacity = __rsize;
          _CharT* __tmp = _M_create(__new_capacity, __capacity);
          _M_dispose();
          _M_data(__tmp);
          _M_capacity(__new_capacity);
        }

      if (__rsize)
        _S_copy(_M_data(), __rcs._M_data(), __rsize);

      _M_set_length(__rsize);
    }
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    __sso_string_base<_CharT, _Traits, _Alloc>::
    _M_reserve(size_type __res)
    {
      // Make sure we don't shrink below the current size.
      if (__res < _M_length())
    __res = _M_length();

      const size_type __capacity = _M_capacity();
      if (__res != __capacity)
    {
      if (__res > __capacity
          || __res > size_type(_S_local_capacity))
        {
          _CharT* __tmp = _M_create(__res, __capacity);
          _S_copy(__tmp, _M_data(), _M_length() + 1);
          _M_dispose();
          _M_data(__tmp);
          _M_capacity(__res);
        }
      else if (!_M_is_local())
        {
          _S_copy(_M_local_data, _M_data(), _M_length() + 1);
          _M_destroy(__capacity);
          _M_data(_M_local_data);
        }
    }
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    __sso_string_base<_CharT, _Traits, _Alloc>::
    _M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
          const size_type __len2)
    {
      const size_type __how_much = _M_length() - __pos - __len1;
      
      size_type __new_capacity = _M_length() + __len2 - __len1;
      _CharT* __r = _M_create(__new_capacity, _M_capacity());

      if (__pos)
    _S_copy(__r, _M_data(), __pos);
      if (__s && __len2)
    _S_copy(__r + __pos, __s, __len2);
      if (__how_much)
    _S_copy(__r + __pos + __len2,
        _M_data() + __pos + __len1, __how_much);
      
      _M_dispose();
      _M_data(__r);
      _M_capacity(__new_capacity);
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    __sso_string_base<_CharT, _Traits, _Alloc>::
    _M_erase(size_type __pos, size_type __n)
    {
      const size_type __how_much = _M_length() - __pos - __n;

      if (__how_much && __n)
    _S_move(_M_data() + __pos, _M_data() + __pos + __n,
        __how_much);

      _M_set_length(_M_length() - __n);
    }

  template<>
    inline bool
    __sso_string_base<char, std::char_traits<char>,
              std::allocator<char> >::
    _M_compare(const __sso_string_base& __rcs) const
    {
      if (this == &__rcs)
    return true;
      return false;
    }

  template<>
    inline bool
    __sso_string_base<wchar_t, std::char_traits<wchar_t>,
              std::allocator<wchar_t> >::
    _M_compare(const __sso_string_base& __rcs) const
    {
      if (this == &__rcs)
    return true;
      return false;
    }
} // namespace __gnu_cxx

#endif /* _SSO_STRING_BASE_H */

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