sso_string_base.h

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// Short-string-optimized versatile string base -*- C++ -*-
 
// Copyright (C) 2005-2023 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 3, 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.
 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
 
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.
 
/** @file ext/sso_string_base.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{ext/vstring.h}
 */
 
#ifndef _SSO_STRING_BASE_H
#define _SSO_STRING_BASE_H 1
 
#include <bits/requires_hosted.h> // GNU extensions are currently omitted
 
namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
 
  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:
      // Data Members:
      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 __size) throw()
      { _M_get_allocator().deallocate(_M_data(), __size + 1); }
 
      // _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, 
                         std::__false_type)
        {
          typedef typename std::iterator_traits<_InIterator>::iterator_category
            _Tag;
          _M_construct(__beg, __end, _Tag());
        }
 
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 438. Ambiguity in the "do the right thing" clause
      template<typename _Integer>
        void
        _M_construct_aux(_Integer __beg, _Integer __end, std::__true_type)
        { _M_construct_aux_2(static_cast<size_type>(__beg), __end); }
 
      void
      _M_construct_aux_2(size_type __req, _CharT __c)
      { _M_construct(__req, __c); }
 
      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
      {
        typedef __alloc_traits<_CharT_alloc_type> _ATraits;
        return (_ATraits::max_size(_M_get_allocator()) - 1) / 2;
      }
 
      _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(_M_local_data)
      { _M_set_length(0); }
 
      __sso_string_base(const _Alloc& __a);
 
      __sso_string_base(const __sso_string_base& __rcs);
 
#if __cplusplus >= 201103L
      __sso_string_base(__sso_string_base&& __rcs);
#endif
 
      __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_swap(__sso_string_base& __rcs)
    {
      if (this == &__rcs)
        return;
 
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 431. Swapping containers with unequal allocators.
      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 > _M_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 max_size.
          if (__capacity > _M_max_size())
            __capacity = _M_max_size();
        }
 
      // NB: Need an array of char_type[__capacity], plus a terminating
      // null char_type() element.
      return _M_get_allocator().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()); }
 
#if __cplusplus >= 201103L
  template<typename _CharT, typename _Traits, typename _Alloc>
    __sso_string_base<_CharT, _Traits, _Alloc>::
    __sso_string_base(__sso_string_base&& __rcs)
    : _M_dataplus(__rcs._M_get_allocator(), _M_local_data)
    {
      if (__rcs._M_is_local())
        {
          if (__rcs._M_length())
            traits_type::copy(_M_local_data, __rcs._M_local_data,
                              _S_local_capacity + 1);
        }
      else
        {
          _M_data(__rcs._M_data());
          _M_capacity(__rcs._M_allocated_capacity);
        }
 
      _M_set_length(__rcs._M_length());
      __rcs._M_data(__rcs._M_local_data);
      __rcs._M_set_length(0);
    }
#endif
 
  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);
                    this->_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 (__is_null_pointer(__beg) && __beg != __end)
          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
          { this->_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)
        this->_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)
            this->_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);
              this->_S_copy(__tmp, _M_data(), _M_length() + 1);
              _M_dispose();
              _M_data(__tmp);
              _M_capacity(__res);
            }
          else if (!_M_is_local())
            {
              this->_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,
              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)
        this->_S_copy(__r, _M_data(), __pos);
      if (__s && __len2)
        this->_S_copy(__r + __pos, __s, __len2);
      if (__how_much)
        this->_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)
        this->_S_move(_M_data() + __pos, _M_data() + __pos + __n, __how_much);
 
      _M_set_length(_M_length() - __n);
    }
 
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
 
#endif /* _SSO_STRING_BASE_H */