ropeimpl.h

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// SGI's rope class implementation -*- C++ -*-
 
// Copyright (C) 2001-2023 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/>.
 
/*
 * Copyright (c) 1997
 * 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 ropeimpl.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{ext/rope}
 */
 
#include <cstdio>
#include <ostream>
#include <bits/functexcept.h>
 
#include <ext/algorithm> // For copy_n and lexicographical_compare_3way
#include <ext/memory> // For uninitialized_copy_n
#include <ext/numeric> // For power
 
namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
 
  // Set buf_start, buf_end, and buf_ptr appropriately, filling tmp_buf
  // if necessary.  Assumes _M_path_end[leaf_index] and leaf_pos are correct.
  // Results in a valid buf_ptr if the iterator can be legitimately
  // dereferenced.
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _S_setbuf(_Rope_iterator_base<_CharT, _Alloc>& __x)
    {
      using std::size_t;
      const _RopeRep* __leaf = __x._M_path_end[__x._M_leaf_index];
      size_t __leaf_pos = __x._M_leaf_pos;
      size_t __pos = __x._M_current_pos;
 
      switch(__leaf->_M_tag)
        {
        case __detail::_S_leaf:
          __x._M_buf_start = ((_Rope_RopeLeaf<_CharT, _Alloc>*)__leaf)->_M_data;
          __x._M_buf_ptr = __x._M_buf_start + (__pos - __leaf_pos);
          __x._M_buf_end = __x._M_buf_start + __leaf->_M_size;
          break;
        case __detail::_S_function:
        case __detail::_S_substringfn:
          {
            size_t __len = _S_iterator_buf_len;
            size_t __buf_start_pos = __leaf_pos;
            size_t __leaf_end = __leaf_pos + __leaf->_M_size;
            char_producer<_CharT>* __fn = ((_Rope_RopeFunction<_CharT,
                                            _Alloc>*)__leaf)->_M_fn;
            if (__buf_start_pos + __len <= __pos)
              {
                __buf_start_pos = __pos - __len / 4;
                if (__buf_start_pos + __len > __leaf_end)
                  __buf_start_pos = __leaf_end - __len;
              }
            if (__buf_start_pos + __len > __leaf_end)
              __len = __leaf_end - __buf_start_pos;
            (*__fn)(__buf_start_pos - __leaf_pos, __len, __x._M_tmp_buf);
            __x._M_buf_ptr = __x._M_tmp_buf + (__pos - __buf_start_pos);
            __x._M_buf_start = __x._M_tmp_buf;
            __x._M_buf_end = __x._M_tmp_buf + __len;
          }
          break;
        default:
          break;
        }
    }
 
  // Set path and buffer inside a rope iterator.  We assume that
  // pos and root are already set.
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _S_setcache(_Rope_iterator_base<_CharT, _Alloc>& __x)
    {
      using std::size_t;
      const _RopeRep* __path[int(__detail::_S_max_rope_depth) + 1];
      const _RopeRep* __curr_rope;
      int __curr_depth = -1;  /* index into path    */
      size_t __curr_start_pos = 0;
      size_t __pos = __x._M_current_pos;
      unsigned char __dirns = 0; // Bit vector marking right turns in the path
 
      if (__pos >= __x._M_root->_M_size)
        {
          __x._M_buf_ptr = 0;
          return;
        }
      __curr_rope = __x._M_root;
      if (0 != __curr_rope->_M_c_string)
        {
          /* Treat the root as a leaf. */
          __x._M_buf_start = __curr_rope->_M_c_string;
          __x._M_buf_end = __curr_rope->_M_c_string + __curr_rope->_M_size;
          __x._M_buf_ptr = __curr_rope->_M_c_string + __pos;
          __x._M_path_end[0] = __curr_rope;
          __x._M_leaf_index = 0;
          __x._M_leaf_pos = 0;
          return;
        }
      for(;;)
        {
          ++__curr_depth;
          __path[__curr_depth] = __curr_rope;
          switch(__curr_rope->_M_tag)
            {
            case __detail::_S_leaf:
            case __detail::_S_function:
            case __detail::_S_substringfn:
              __x._M_leaf_pos = __curr_start_pos;
              goto done;
            case __detail::_S_concat:
              {
                _Rope_RopeConcatenation<_CharT, _Alloc>* __c =
                  (_Rope_RopeConcatenation<_CharT, _Alloc>*)__curr_rope;
                _RopeRep* __left = __c->_M_left;
                size_t __left_len = __left->_M_size;
 
                __dirns <<= 1;
                if (__pos >= __curr_start_pos + __left_len)
                  {
                    __dirns |= 1;
                    __curr_rope = __c->_M_right;
                    __curr_start_pos += __left_len;
                  }
                else
                  __curr_rope = __left;
              }
              break;
            }
        }
    done:
      // Copy last section of path into _M_path_end.
      {
        int __i = -1;
        int __j = __curr_depth + 1 - int(_S_path_cache_len);
 
        if (__j < 0) __j = 0;
        while (__j <= __curr_depth)
          __x._M_path_end[++__i] = __path[__j++];
        __x._M_leaf_index = __i;
      }
      __x._M_path_directions = __dirns;
      _S_setbuf(__x);
    }
 
  // Specialized version of the above.  Assumes that
  // the path cache is valid for the previous position.
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _S_setcache_for_incr(_Rope_iterator_base<_CharT, _Alloc>& __x)
    {
      using std::size_t;
      int __current_index = __x._M_leaf_index;
      const _RopeRep* __current_node = __x._M_path_end[__current_index];
      size_t __len = __current_node->_M_size;
      size_t __node_start_pos = __x._M_leaf_pos;
      unsigned char __dirns = __x._M_path_directions;
      _Rope_RopeConcatenation<_CharT, _Alloc>* __c;
 
      if (__x._M_current_pos - __node_start_pos < __len)
        {
          /* More stuff in this leaf, we just didn't cache it. */
          _S_setbuf(__x);
          return;
        }
      //  node_start_pos is starting position of last_node.
      while (--__current_index >= 0)
        {
          if (!(__dirns & 1) /* Path turned left */)
            break;
          __current_node = __x._M_path_end[__current_index];
          __c = (_Rope_RopeConcatenation<_CharT, _Alloc>*)__current_node;
          // Otherwise we were in the right child.  Thus we should pop
          // the concatenation node.
          __node_start_pos -= __c->_M_left->_M_size;
          __dirns >>= 1;
        }
      if (__current_index < 0)
        {
          // We underflowed the cache. Punt.
          _S_setcache(__x);
          return;
        }
      __current_node = __x._M_path_end[__current_index];
      __c = (_Rope_RopeConcatenation<_CharT, _Alloc>*)__current_node;
      // current_node is a concatenation node.  We are positioned on the first
      // character in its right child.
      // node_start_pos is starting position of current_node.
      __node_start_pos += __c->_M_left->_M_size;
      __current_node = __c->_M_right;
      __x._M_path_end[++__current_index] = __current_node;
      __dirns |= 1;
      while (__detail::_S_concat == __current_node->_M_tag)
        {
          ++__current_index;
          if (int(_S_path_cache_len) == __current_index)
            {
              int __i;
              for (__i = 0; __i < int(_S_path_cache_len) - 1; __i++)
                __x._M_path_end[__i] = __x._M_path_end[__i+1];
              --__current_index;
            }
          __current_node =
            ((_Rope_RopeConcatenation<_CharT, _Alloc>*)__current_node)->_M_left;
          __x._M_path_end[__current_index] = __current_node;
          __dirns <<= 1;
          // node_start_pos is unchanged.
        }
      __x._M_leaf_index = __current_index;
      __x._M_leaf_pos = __node_start_pos;
      __x._M_path_directions = __dirns;
      _S_setbuf(__x);
    }
 
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _M_incr(std::size_t __n)
    {
      _M_current_pos += __n;
      if (0 != _M_buf_ptr)
        {
          std::size_t __chars_left = _M_buf_end - _M_buf_ptr;
          if (__chars_left > __n)
            _M_buf_ptr += __n;
          else if (__chars_left == __n)
            {
              _M_buf_ptr += __n;
              _S_setcache_for_incr(*this);
            }
          else
            _M_buf_ptr = 0;
        }
    }
 
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _M_decr(std::size_t __n)
    {
      if (0 != _M_buf_ptr)
        {
          std::size_t __chars_left = _M_buf_ptr - _M_buf_start;
          if (__chars_left >= __n)
            _M_buf_ptr -= __n;
          else
            _M_buf_ptr = 0;
        }
      _M_current_pos -= __n;
    }
 
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator<_CharT, _Alloc>::
    _M_check()
    {
      if (_M_root_rope->_M_tree_ptr != this->_M_root)
        {
          // _Rope was modified.  Get things fixed up.
          _RopeRep::_S_unref(this->_M_root);
          this->_M_root = _M_root_rope->_M_tree_ptr;
          _RopeRep::_S_ref(this->_M_root);
          this->_M_buf_ptr = 0;
        }
    }
 
  template <class _CharT, class _Alloc>
    inline
    _Rope_const_iterator<_CharT, _Alloc>::
    _Rope_const_iterator(const _Rope_iterator<_CharT, _Alloc>& __x)
    : _Rope_iterator_base<_CharT, _Alloc>(__x)
    { }
 
  template <class _CharT, class _Alloc>
    inline
    _Rope_iterator<_CharT, _Alloc>::
    _Rope_iterator(rope<_CharT, _Alloc>& __r, std::size_t __pos)
    : _Rope_iterator_base<_CharT,_Alloc>(__r._M_tree_ptr, __pos),
      _M_root_rope(&__r)
    { _RopeRep::_S_ref(this->_M_root); }
 
  template <class _CharT, class _Alloc>
    inline std::size_t
    rope<_CharT, _Alloc>::
    _S_char_ptr_len(const _CharT* __s)
    {
      const _CharT* __p = __s;
      
      while (!_S_is0(*__p))
        ++__p;
      return (__p - __s);
    }
 
 
#ifndef __GC
 
  template <class _CharT, class _Alloc>
    inline void
    _Rope_RopeRep<_CharT, _Alloc>::
    _M_free_c_string()
    {
      _CharT* __cstr = _M_c_string;
      if (0 != __cstr)
        {
          std::size_t __size = this->_M_size + 1;
          std::_Destroy(__cstr, __cstr + __size, _M_get_allocator());
          this->_Data_deallocate(__cstr, __size);
        }
    }
 
  template <class _CharT, class _Alloc>
    inline void
    _Rope_RopeRep<_CharT, _Alloc>::
    _S_free_string(_CharT* __s, std::size_t __n, allocator_type& __a)
    {
      if (!_S_is_basic_char_type((_CharT*)0))
        std::_Destroy(__s, __s + __n, __a);
      
      //  This has to be a static member, so this gets a bit messy
      __a.deallocate(__s,
                     _Rope_RopeLeaf<_CharT, _Alloc>::_S_rounded_up_size(__n));
    }
 
  //  There are several reasons for not doing this with virtual destructors
  //  and a class specific delete operator:
  //  - A class specific delete operator can't easily get access to
  //    allocator instances if we need them.
  //  - Any virtual function would need a 4 or byte vtable pointer;
  //    this only requires a one byte tag per object.
  template <class _CharT, class _Alloc>
    void
    _Rope_RopeRep<_CharT, _Alloc>::
    _M_free_tree()
    {
      switch(_M_tag)
        {
        case __detail::_S_leaf:
          {
            _Rope_RopeLeaf<_CharT, _Alloc>* __l
              = (_Rope_RopeLeaf<_CharT, _Alloc>*)this;
            __l->_Rope_RopeLeaf<_CharT, _Alloc>::~_Rope_RopeLeaf();
            this->_L_deallocate(__l, 1);
            break;
          }
        case __detail::_S_concat:
          {
            _Rope_RopeConcatenation<_CharT,_Alloc>* __c
              = (_Rope_RopeConcatenation<_CharT, _Alloc>*)this;
            __c->_Rope_RopeConcatenation<_CharT, _Alloc>::
              ~_Rope_RopeConcatenation();
            this->_C_deallocate(__c, 1);
            break;
          }
        case __detail::_S_function:
          {
            _Rope_RopeFunction<_CharT, _Alloc>* __f
              = (_Rope_RopeFunction<_CharT, _Alloc>*)this;
            __f->_Rope_RopeFunction<_CharT, _Alloc>::~_Rope_RopeFunction();
            this->_F_deallocate(__f, 1);
            break;
          }
        case __detail::_S_substringfn:
          {
            _Rope_RopeSubstring<_CharT, _Alloc>* __ss =
              (_Rope_RopeSubstring<_CharT, _Alloc>*)this;
            __ss->_Rope_RopeSubstring<_CharT, _Alloc>::
              ~_Rope_RopeSubstring();
            this->_S_deallocate(__ss, 1);
            break;
          }
        }
    }
#else
 
  template <class _CharT, class _Alloc>
    inline void
    _Rope_RopeRep<_CharT, _Alloc>::
    _S_free_string(const _CharT*, std::size_t, allocator_type)
    { }
 
#endif
 
  // Concatenate a C string onto a leaf rope by copying the rope data.
  // Used for short ropes.
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeLeaf*
    rope<_CharT, _Alloc>::
    _S_leaf_concat_char_iter(_RopeLeaf* __r, const _CharT* __iter,
                             std::size_t __len)
    {
      std::size_t __old_len = __r->_M_size;
      _CharT* __new_data = (_CharT*)
        rope::_Data_allocate(_S_rounded_up_size(__old_len + __len));
      _RopeLeaf* __result;
 
      uninitialized_copy_n(__r->_M_data, __old_len, __new_data);
      uninitialized_copy_n(__iter, __len, __new_data + __old_len);
      _S_cond_store_eos(__new_data[__old_len + __len]);
      __try
        {
          __result = _S_new_RopeLeaf(__new_data, __old_len + __len,
                                     __r->_M_get_allocator());
        }
      __catch(...)
        {
          _RopeRep::__STL_FREE_STRING(__new_data, __old_len + __len,
                                      __r->_M_get_allocator());
          __throw_exception_again;
        }
      return __result;
    }
 
#ifndef __GC
  // As above, but it's OK to clobber original if refcount is 1
  template <class _CharT, class _Alloc>
    typename rope<_CharT,_Alloc>::_RopeLeaf*
    rope<_CharT, _Alloc>::
    _S_destr_leaf_concat_char_iter(_RopeLeaf* __r, const _CharT* __iter,
                                   std::size_t __len)
    {
      if (__r->_M_ref_count > 1)
        return _S_leaf_concat_char_iter(__r, __iter, __len);
      std::size_t __old_len = __r->_M_size;
      if (_S_allocated_capacity(__old_len) >= __old_len + __len)
        {
          // The space has been partially initialized for the standard
          // character types.  But that doesn't matter for those types.
          uninitialized_copy_n(__iter, __len, __r->_M_data + __old_len);
          if (_S_is_basic_char_type((_CharT*)0))
            _S_cond_store_eos(__r->_M_data[__old_len + __len]);
          else if (__r->_M_c_string != __r->_M_data && 0 != __r->_M_c_string)
            {
              __r->_M_free_c_string();
              __r->_M_c_string = 0;
            }
          __r->_M_size = __old_len + __len;
          __r->_M_ref_count = 2;
          return __r;
        }
      else
        {
          _RopeLeaf* __result = _S_leaf_concat_char_iter(__r, __iter, __len);
          return __result;
        }
    }
#endif
 
  // Assumes left and right are not 0.
  // Does not increment (nor decrement on exception) child reference counts.
  // Result has ref count 1.
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_tree_concat(_RopeRep* __left, _RopeRep* __right)
    {
      using std::size_t;
      _RopeConcatenation* __result = _S_new_RopeConcatenation(__left, __right,
                                                              __left->
                                                              _M_get_allocator());
      size_t __depth = __result->_M_depth;
      
      if (__depth > 20
          && (__result->_M_size < 1000
              || __depth > size_t(__detail::_S_max_rope_depth)))
        {
          _RopeRep* __balanced;
 
          __try
            {
              __balanced = _S_balance(__result);
              __result->_M_unref_nonnil();
            }
          __catch(...)
            {
              rope::_C_deallocate(__result,1);
              __throw_exception_again;
            }
          // In case of exception, we need to deallocate
          // otherwise dangling result node.  But caller
          // still owns its children.  Thus unref is
          // inappropriate.
          return __balanced;
        }
      else
        return __result;
    }
 
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_concat_char_iter(_RopeRep* __r, const _CharT*__s, std::size_t __slen,
                        allocator_type& __a)
    {
      using std::size_t;
      _RopeRep* __result;
      if (0 == __slen)
        {
          _S_ref(__r);
          return __r;
        }
      if (0 == __r)
        return __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen, __a);
      if (__r->_M_tag == __detail::_S_leaf
          && __r->_M_size + __slen <= size_t(_S_copy_max))
        {
          __result = _S_leaf_concat_char_iter((_RopeLeaf*)__r, __s, __slen);
          return __result;
        }
      if (__detail::_S_concat == __r->_M_tag
          && __detail::_S_leaf == ((_RopeConcatenation*) __r)->_M_right->_M_tag)
        {
          _RopeLeaf* __right =
            (_RopeLeaf* )(((_RopeConcatenation* )__r)->_M_right);
          if (__right->_M_size + __slen <= size_t(_S_copy_max))
            {
              _RopeRep* __left = ((_RopeConcatenation*)__r)->_M_left;
              _RopeRep* __nright =
                _S_leaf_concat_char_iter((_RopeLeaf*)__right, __s, __slen);
              __left->_M_ref_nonnil();
              __try
                { __result = _S_tree_concat(__left, __nright); }
              __catch(...)
                {
                  _S_unref(__left);
                  _S_unref(__nright);
                  __throw_exception_again;
                }
              return __result;
            }
        }
      _RopeRep* __nright = __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen, __a);
      __try
        {
          __r->_M_ref_nonnil();
          __result = _S_tree_concat(__r, __nright);
        }
      __catch(...)
        {
          _S_unref(__r);
          _S_unref(__nright);
          __throw_exception_again;
        }
      return __result;
    }
 
#ifndef __GC
  template <class _CharT, class _Alloc>
    typename rope<_CharT,_Alloc>::_RopeRep*
    rope<_CharT,_Alloc>::
    _S_destr_concat_char_iter(_RopeRep* __r, const _CharT* __s,
                              std::size_t __slen, allocator_type& __a)
    {
      using std::size_t;
      _RopeRep* __result;
      if (0 == __r)
        return __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen, __a);
      size_t __count = __r->_M_ref_count;
      size_t __orig_size = __r->_M_size;
      if (__count > 1)
        return _S_concat_char_iter(__r, __s, __slen, __a);
      if (0 == __slen)
        {
          __r->_M_ref_count = 2;      // One more than before
          return __r;
        }
      if (__orig_size + __slen <= size_t(_S_copy_max)
          && __detail::_S_leaf == __r->_M_tag)
        {
          __result = _S_destr_leaf_concat_char_iter((_RopeLeaf*)__r, __s, 
                                                    __slen);
          return __result;
        }
      if (__detail::_S_concat == __r->_M_tag)
        {
          _RopeLeaf* __right = (_RopeLeaf*)(((_RopeConcatenation*)
                                             __r)->_M_right);
          if (__detail::_S_leaf == __right->_M_tag
              && __right->_M_size + __slen <= size_t(_S_copy_max))
            {
              _RopeRep* __new_right =
                _S_destr_leaf_concat_char_iter(__right, __s, __slen);
              if (__right == __new_right)
                __new_right->_M_ref_count = 1;
              else
                __right->_M_unref_nonnil();
              __r->_M_ref_count = 2;    // One more than before.
              ((_RopeConcatenation*)__r)->_M_right = __new_right;
              __r->_M_size = __orig_size + __slen;
              if (0 != __r->_M_c_string)
                {
                  __r->_M_free_c_string();
                  __r->_M_c_string = 0;
                }
              return __r;
            }
        }
      _RopeRep* __right = __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen, __a);
      __r->_M_ref_nonnil();
      __try
        { __result = _S_tree_concat(__r, __right); }
      __catch(...)
        {
          _S_unref(__r);
          _S_unref(__right);
          __throw_exception_again;
        }
      return __result;
    }
#endif /* !__GC */
  
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_concat(_RopeRep* __left, _RopeRep* __right)
    {
      using std::size_t;
      if (0 == __left)
        {
          _S_ref(__right);
          return __right;
        }
      if (0 == __right)
        {
          __left->_M_ref_nonnil();
          return __left;
        }
      if (__detail::_S_leaf == __right->_M_tag)
        {
          if (__detail::_S_leaf == __left->_M_tag)
            {
              if (__right->_M_size + __left->_M_size <= size_t(_S_copy_max))
                return _S_leaf_concat_char_iter((_RopeLeaf*)__left,
                                                ((_RopeLeaf*)__right)->_M_data,
                                                __right->_M_size);
            }
          else if (__detail::_S_concat == __left->_M_tag
                   && __detail::_S_leaf == ((_RopeConcatenation*)
                                                   __left)->_M_right->_M_tag)
            {
              _RopeLeaf* __leftright =
                (_RopeLeaf*)(((_RopeConcatenation*)__left)->_M_right);
              if (__leftright->_M_size
                  + __right->_M_size <= size_t(_S_copy_max))
                {
                  _RopeRep* __leftleft = ((_RopeConcatenation*)__left)->_M_left;
                  _RopeRep* __rest = _S_leaf_concat_char_iter(__leftright,
                                                              ((_RopeLeaf*)
                                                               __right)->
                                                              _M_data,
                                                              __right->_M_size);
                  __leftleft->_M_ref_nonnil();
                  __try
                    { return(_S_tree_concat(__leftleft, __rest)); }
                  __catch(...)
                    {
                      _S_unref(__leftleft);
                      _S_unref(__rest);
                      __throw_exception_again;
                    }
                }
            }
        }
      __left->_M_ref_nonnil();
      __right->_M_ref_nonnil();
      __try
        { return(_S_tree_concat(__left, __right)); }
      __catch(...)
        {
          _S_unref(__left);
          _S_unref(__right);
          __throw_exception_again;
        }
    }
 
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_substring(_RopeRep* __base, std::size_t __start, std::size_t __endp1)
    {
      using std::size_t;
      if (0 == __base)
        return 0;
      size_t __len = __base->_M_size;
      size_t __adj_endp1;
      const size_t __lazy_threshold = 128;
      
      if (__endp1 >= __len)
        {
          if (0 == __start)
            {
              __base->_M_ref_nonnil();
              return __base;
            }
          else
            __adj_endp1 = __len;
          
        }
      else
        __adj_endp1 = __endp1;
 
      switch(__base->_M_tag)
        {
        case __detail::_S_concat:
            {
              _RopeConcatenation* __c = (_RopeConcatenation*)__base;
              _RopeRep* __left = __c->_M_left;
              _RopeRep* __right = __c->_M_right;
              size_t __left_len = __left->_M_size;
              _RopeRep* __result;
              
              if (__adj_endp1 <= __left_len)
                return _S_substring(__left, __start, __endp1);
              else if (__start >= __left_len)
                return _S_substring(__right, __start - __left_len,
                                    __adj_endp1 - __left_len);
              _Self_destruct_ptr __left_result(_S_substring(__left,
                                                            __start,
                                                            __left_len));
              _Self_destruct_ptr __right_result(_S_substring(__right, 0,
                                                             __endp1 
                                                             - __left_len));
              __result = _S_concat(__left_result, __right_result);
              return __result;
            }
        case __detail::_S_leaf:
          {
            _RopeLeaf* __l = (_RopeLeaf*)__base;
            _RopeLeaf* __result;
            size_t __result_len;
            if (__start >= __adj_endp1)
              return 0;
            __result_len = __adj_endp1 - __start;
            if (__result_len > __lazy_threshold)
              goto lazy;
#ifdef __GC
            const _CharT* __section = __l->_M_data + __start;
            __result = _S_new_RopeLeaf(__section, __result_len,
                                       __base->_M_get_allocator());
            __result->_M_c_string = 0;  // Not eos terminated.
#else
            // We should sometimes create substring node instead.
            __result = __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__l->_M_data + __start,
                                                        __result_len,
                                                        __base->
                                                        _M_get_allocator());
#endif
            return __result;
          }
        case __detail::_S_substringfn:
          // Avoid introducing multiple layers of substring nodes.
          {
            _RopeSubstring* __old = (_RopeSubstring*)__base;
            size_t __result_len;
            if (__start >= __adj_endp1)
              return 0;
            __result_len = __adj_endp1 - __start;
            if (__result_len > __lazy_threshold)
              {
                _RopeSubstring* __result =
                  _S_new_RopeSubstring(__old->_M_base,
                                       __start + __old->_M_start,
                                       __adj_endp1 - __start,
                                       __base->_M_get_allocator());
                return __result;
                
              } // *** else fall through: ***
          }
        case __detail::_S_function:
          {
            _RopeFunction* __f = (_RopeFunction*)__base;
            _CharT* __section;
            size_t __result_len;
            if (__start >= __adj_endp1)
              return 0;
            __result_len = __adj_endp1 - __start;
            
            if (__result_len > __lazy_threshold)
              goto lazy;
            __section = (_CharT*)
              rope::_Data_allocate(_S_rounded_up_size(__result_len));
            __try
              { (*(__f->_M_fn))(__start, __result_len, __section); }
            __catch(...)
              {
                _RopeRep::__STL_FREE_STRING(__section, __result_len,
                                            __base->_M_get_allocator());
                __throw_exception_again;
              }
            _S_cond_store_eos(__section[__result_len]);
            return _S_new_RopeLeaf(__section, __result_len,
                                   __base->_M_get_allocator());
          }
        }
    lazy:
      {
        // Create substring node.
        return _S_new_RopeSubstring(__base, __start, __adj_endp1 - __start,
                                    __base->_M_get_allocator());
      }
    }
 
  template<class _CharT>
    class _Rope_flatten_char_consumer
    : public _Rope_char_consumer<_CharT>
    {
    private:
      _CharT* _M_buf_ptr;
    public:
      
      _Rope_flatten_char_consumer(_CharT* __buffer)
      { _M_buf_ptr = __buffer; }
 
      ~_Rope_flatten_char_consumer() {}
      
      bool
      operator()(const _CharT* __leaf, std::size_t __n)
      {
        uninitialized_copy_n(__leaf, __n, _M_buf_ptr);
        _M_buf_ptr += __n;
        return true;
      }
    };
 
  template<class _CharT>
    class _Rope_find_char_char_consumer
    : public _Rope_char_consumer<_CharT>
    {
    private:
      _CharT _M_pattern;
    public:
      std::size_t _M_count;  // Number of nonmatching characters
      
      _Rope_find_char_char_consumer(_CharT __p)
      : _M_pattern(__p), _M_count(0) {}
        
      ~_Rope_find_char_char_consumer() {}
      
      bool
      operator()(const _CharT* __leaf, std::size_t __n)
      {
        std::size_t __i;
        for (__i = 0; __i < __n; __i++)
          {
            if (__leaf[__i] == _M_pattern)
              {
                _M_count += __i;
                return false;
              }
          }
        _M_count += __n; return true;
      }
    };
 
  template<class _CharT, class _Traits>
  // Here _CharT is both the stream and rope character type.
    class _Rope_insert_char_consumer
    : public _Rope_char_consumer<_CharT>
    {
    private:
      typedef std::basic_ostream<_CharT,_Traits> _Insert_ostream;
      _Insert_ostream& _M_o;
    public:
      _Rope_insert_char_consumer(_Insert_ostream& __writer)
        : _M_o(__writer) {}
      ~_Rope_insert_char_consumer() { }
      // Caller is presumed to own the ostream
      bool operator() (const _CharT* __leaf, std::size_t __n);
      // Returns true to continue traversal.
    };
 
  template<class _CharT, class _Traits>
    bool
    _Rope_insert_char_consumer<_CharT, _Traits>::
    operator()(const _CharT* __leaf, std::size_t __n)
    {
      std::size_t __i;
      //  We assume that formatting is set up correctly for each element.
      for (__i = 0; __i < __n; __i++)
        _M_o.put(__leaf[__i]);
      return true;
    }
 
  template <class _CharT, class _Alloc>
    bool
    rope<_CharT, _Alloc>::
    _S_apply_to_pieces(_Rope_char_consumer<_CharT>& __c, const _RopeRep* __r,
                       std::size_t __begin, std::size_t __end)
    {
      using std::size_t;
      if (0 == __r)
        return true;
      switch(__r->_M_tag)
        {
        case __detail::_S_concat:
          {
            _RopeConcatenation* __conc = (_RopeConcatenation*)__r;
            _RopeRep* __left =  __conc->_M_left;
            size_t __left_len = __left->_M_size;
            if (__begin < __left_len)
              {
                size_t __left_end = std::min(__left_len, __end);
                if (!_S_apply_to_pieces(__c, __left, __begin, __left_end))
                  return false;
              }
            if (__end > __left_len)
              {
                _RopeRep* __right =  __conc->_M_right;
                size_t __right_start = std::max(__left_len, __begin);
                if (!_S_apply_to_pieces(__c, __right,
                                        __right_start - __left_len,
                                        __end - __left_len))
                  return false;
              }
          }
          return true;
        case __detail::_S_leaf:
          {
            _RopeLeaf* __l = (_RopeLeaf*)__r;
            return __c(__l->_M_data + __begin, __end - __begin);
          }
        case __detail::_S_function:
        case __detail::_S_substringfn:
            {
              _RopeFunction* __f = (_RopeFunction*)__r;
              size_t __len = __end - __begin;
              bool __result;
              _CharT* __buffer =
                (_CharT*)_Alloc().allocate(__len * sizeof(_CharT));
              __try
                {
                  (*(__f->_M_fn))(__begin, __len, __buffer);
                  __result = __c(__buffer, __len);
                  _Alloc().deallocate(__buffer, __len * sizeof(_CharT));
                }
              __catch(...)
                {
                  _Alloc().deallocate(__buffer, __len * sizeof(_CharT));
                  __throw_exception_again;
                }
              return __result;
            }
        default:
          return false;
        }
    }
 
  template<class _CharT, class _Traits>
    inline void
    _Rope_fill(std::basic_ostream<_CharT, _Traits>& __o, std::size_t __n)
    {
      char __f = __o.fill();
      std::size_t __i;
      
      for (__i = 0; __i < __n; __i++)
        __o.put(__f);
    }
 
 
  template <class _CharT>
    inline bool
    _Rope_is_simple(_CharT*)
    { return false; }
 
  inline bool
  _Rope_is_simple(char*)
  { return true; }
 
  inline bool
  _Rope_is_simple(wchar_t*)
  { return true; }
 
  template<class _CharT, class _Traits, class _Alloc>
    std::basic_ostream<_CharT, _Traits>&
    operator<<(std::basic_ostream<_CharT, _Traits>& __o,
               const rope<_CharT, _Alloc>& __r)
    {
      using std::size_t;
      size_t __w = __o.width();
      bool __left = bool(__o.flags() & std::ios::left);
      size_t __pad_len;
      size_t __rope_len = __r.size();
      _Rope_insert_char_consumer<_CharT, _Traits> __c(__o);
      bool __is_simple = _Rope_is_simple((_CharT*)0);
      
      if (__rope_len < __w)
        __pad_len = __w - __rope_len;
      else
        __pad_len = 0;
 
      if (!__is_simple)
        __o.width(__w / __rope_len);
      __try
        {
          if (__is_simple && !__left && __pad_len > 0)
            _Rope_fill(__o, __pad_len);
          __r.apply_to_pieces(0, __r.size(), __c);
          if (__is_simple && __left && __pad_len > 0)
            _Rope_fill(__o, __pad_len);
          if (!__is_simple)
            __o.width(__w);
        }
      __catch(...)
        {
          if (!__is_simple)
            __o.width(__w);
          __throw_exception_again;
        }
      return __o;
    }
 
  template <class _CharT, class _Alloc>
    _CharT*
    rope<_CharT, _Alloc>::
    _S_flatten(_RopeRep* __r, std::size_t __start, std::size_t __len,
               _CharT* __buffer)
    {
      _Rope_flatten_char_consumer<_CharT> __c(__buffer);
      _S_apply_to_pieces(__c, __r, __start, __start + __len);
      return(__buffer + __len);
    }
 
  template <class _CharT, class _Alloc>
    std::size_t
    rope<_CharT, _Alloc>::
    find(_CharT __pattern, std::size_t __start) const
    {
      _Rope_find_char_char_consumer<_CharT> __c(__pattern);
      _S_apply_to_pieces(__c, this->_M_tree_ptr, __start, size());
      size_type __result_pos = __start + __c._M_count;
#ifndef __STL_OLD_ROPE_SEMANTICS
      if (__result_pos == size())
        __result_pos = npos;
#endif
      return __result_pos;
    }
 
  template <class _CharT, class _Alloc>
    _CharT*
    rope<_CharT, _Alloc>::
    _S_flatten(_RopeRep* __r, _CharT* __buffer)
    {
      if (0 == __r)
        return __buffer;
      switch(__r->_M_tag)
        {
        case __detail::_S_concat:
          {
            _RopeConcatenation* __c = (_RopeConcatenation*)__r;
            _RopeRep* __left = __c->_M_left;
            _RopeRep* __right = __c->_M_right;
            _CharT* __rest = _S_flatten(__left, __buffer);
            return _S_flatten(__right, __rest);
          }
        case __detail::_S_leaf:
          {
            _RopeLeaf* __l = (_RopeLeaf*)__r;
            return copy_n(__l->_M_data, __l->_M_size, __buffer).second;
          }
        case __detail::_S_function:
        case __detail::_S_substringfn:
          // We don't yet do anything with substring nodes.
          // This needs to be fixed before ropefiles will work well.
          {
            _RopeFunction* __f = (_RopeFunction*)__r;
            (*(__f->_M_fn))(0, __f->_M_size, __buffer);
            return __buffer + __f->_M_size;
          }
        default:
          return 0;
        }
    }
 
  // This needs work for _CharT != char
  template <class _CharT, class _Alloc>
    void
    rope<_CharT, _Alloc>::
    _S_dump(_RopeRep* __r, int __indent)
    {
      using std::printf;
      for (int __i = 0; __i < __indent; __i++)
        putchar(' ');
      if (0 == __r)
        {
          printf("NULL\n");
          return;
        }
      if (__detail::_S_concat == __r->_M_tag)
        {
          _RopeConcatenation* __c = (_RopeConcatenation*)__r;
          _RopeRep* __left = __c->_M_left;
          _RopeRep* __right = __c->_M_right;
          
#ifdef __GC
          printf("Concatenation %p (depth = %d, len = %ld, %s balanced)\n",
                 __r, __r->_M_depth, __r->_M_size,
                 __r->_M_is_balanced? "" : "not");
#else
          printf("Concatenation %p (rc = %ld, depth = %d, "
                 "len = %ld, %s balanced)\n",
                 __r, __r->_M_ref_count, __r->_M_depth, __r->_M_size,
                 __r->_M_is_balanced? "" : "not");
#endif
          _S_dump(__left, __indent + 2);
          _S_dump(__right, __indent + 2);
          return;
        }
      else
        {
          const char* __kind;
          
          switch (__r->_M_tag)
            {
            case __detail::_S_leaf:
              __kind = "Leaf";
              break;
            case __detail::_S_function:
              __kind = "Function";
              break;
            case __detail::_S_substringfn:
              __kind = "Function representing substring";
              break;
            default:
              __kind = "(corrupted kind field!)";
            }
#ifdef __GC
          printf("%s %p (depth = %d, len = %ld) ",
                 __kind, __r, __r->_M_depth, __r->_M_size);
#else
          printf("%s %p (rc = %ld, depth = %d, len = %ld) ",
                 __kind, __r, __r->_M_ref_count, __r->_M_depth, __r->_M_size);
#endif
          if (_S_is_one_byte_char_type((_CharT*)0))
            {
              const int __max_len = 40;
              _Self_destruct_ptr __prefix(_S_substring(__r, 0, __max_len));
              _CharT __buffer[__max_len + 1];
              bool __too_big = __r->_M_size > __prefix->_M_size;
              
              _S_flatten(__prefix, __buffer);
              __buffer[__prefix->_M_size] = _S_eos((_CharT*)0);
              printf("%s%s\n", (char*)__buffer,
                     __too_big? "...\n" : "\n");
            }
          else
            printf("\n");
        }
    }
 
  template <class _CharT, class _Alloc>
    const unsigned long
    rope<_CharT, _Alloc>::
    _S_min_len[int(__detail::_S_max_rope_depth) + 1] = {
      /* 0 */1, /* 1 */2, /* 2 */3, /* 3 */5, /* 4 */8, /* 5 */13, /* 6 */21,
      /* 7 */34, /* 8 */55, /* 9 */89, /* 10 */144, /* 11 */233, /* 12 */377,
      /* 13 */610, /* 14 */987, /* 15 */1597, /* 16 */2584, /* 17 */4181,
      /* 18 */6765, /* 19 */10946, /* 20 */17711, /* 21 */28657, /* 22 */46368,
      /* 23 */75025, /* 24 */121393, /* 25 */196418, /* 26 */317811,
      /* 27 */514229, /* 28 */832040, /* 29 */1346269, /* 30 */2178309,
      /* 31 */3524578, /* 32 */5702887, /* 33 */9227465, /* 34 */14930352,
      /* 35 */24157817, /* 36 */39088169, /* 37 */63245986, /* 38 */102334155,
      /* 39 */165580141, /* 40 */267914296, /* 41 */433494437,
      /* 42 */701408733, /* 43 */1134903170, /* 44 */1836311903,
      /* 45 */2971215073u };
  // These are Fibonacci numbers < 2**32.
 
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_balance(_RopeRep* __r)
    {
      _RopeRep* __forest[int(__detail::_S_max_rope_depth) + 1];
      _RopeRep* __result = 0;
      int __i;
      // Invariant:
      // The concatenation of forest in descending order is equal to __r.
      // __forest[__i]._M_size >= _S_min_len[__i]
      // __forest[__i]._M_depth = __i
      // References from forest are included in refcount.
      
      for (__i = 0; __i <= int(__detail::_S_max_rope_depth); ++__i)
        __forest[__i] = 0;
      __try
        {
          _S_add_to_forest(__r, __forest);
          for (__i = 0; __i <= int(__detail::_S_max_rope_depth); ++__i)
            if (0 != __forest[__i])
              {
#ifndef __GC
                _Self_destruct_ptr __old(__result);
#endif
                __result = _S_concat(__forest[__i], __result);
                __forest[__i]->_M_unref_nonnil();
#if !defined(__GC) && __cpp_exceptions
 
#include <bits/requires_hosted.h> // GNU extensions are currently omitted
                __forest[__i] = 0;
#endif
              }
        }
      __catch(...)
        {
          for(__i = 0; __i <= int(__detail::_S_max_rope_depth); __i++)
            _S_unref(__forest[__i]);
          __throw_exception_again;
        }
      
      if (__result->_M_depth > int(__detail::_S_max_rope_depth))
        std::__throw_length_error(__N("rope::_S_balance"));
      return(__result);
    }
 
  template <class _CharT, class _Alloc>
    void
    rope<_CharT, _Alloc>::
    _S_add_to_forest(_RopeRep* __r, _RopeRep** __forest)
    {
      if (__r->_M_is_balanced)
        {
          _S_add_leaf_to_forest(__r, __forest);
          return;
        }
 
      {
        _RopeConcatenation* __c = (_RopeConcatenation*)__r;
        
        _S_add_to_forest(__c->_M_left, __forest);
        _S_add_to_forest(__c->_M_right, __forest);
      }
    }
 
 
  template <class _CharT, class _Alloc>
    void
    rope<_CharT, _Alloc>::
    _S_add_leaf_to_forest(_RopeRep* __r, _RopeRep** __forest)
    {
      _RopeRep* __insertee;             // included in refcount
      _RopeRep* __too_tiny = 0;         // included in refcount
      int __i;                          // forest[0..__i-1] is empty
      std::size_t __s = __r->_M_size;
      
      for (__i = 0; __s >= _S_min_len[__i+1]/* not this bucket */; ++__i)
        {
          if (0 != __forest[__i])
            {
#ifndef __GC
              _Self_destruct_ptr __old(__too_tiny);
#endif
              __too_tiny = _S_concat_and_set_balanced(__forest[__i],
                                                      __too_tiny);
              __forest[__i]->_M_unref_nonnil();
              __forest[__i] = 0;
            }
        }
      {
#ifndef __GC
        _Self_destruct_ptr __old(__too_tiny);
#endif
        __insertee = _S_concat_and_set_balanced(__too_tiny, __r);
      }
      // Too_tiny dead, and no longer included in refcount.
      // Insertee is live and included.
      for (;; ++__i)
        {
          if (0 != __forest[__i])
            {
#ifndef __GC
              _Self_destruct_ptr __old(__insertee);
#endif
              __insertee = _S_concat_and_set_balanced(__forest[__i],
                                                      __insertee);
              __forest[__i]->_M_unref_nonnil();
              __forest[__i] = 0;
            }
          if (__i == int(__detail::_S_max_rope_depth)
              || __insertee->_M_size < _S_min_len[__i+1])
            {
              __forest[__i] = __insertee;
              // refcount is OK since __insertee is now dead.
              return;
            }
        }
    }
 
  template <class _CharT, class _Alloc>
    _CharT
    rope<_CharT, _Alloc>::
    _S_fetch(_RopeRep* __r, size_type __i)
    {
      __GC_CONST _CharT* __cstr = __r->_M_c_string;
      
      if (0 != __cstr)
        return __cstr[__i];
      for(;;)
        {
          switch(__r->_M_tag)
            {
            case __detail::_S_concat:
              {
                _RopeConcatenation* __c = (_RopeConcatenation*)__r;
                _RopeRep* __left = __c->_M_left;
                std::size_t __left_len = __left->_M_size;
                
                if (__i >= __left_len)
                  {
                    __i -= __left_len;
                    __r = __c->_M_right;
                  } 
                else
                  __r = __left;
              }
              break;
            case __detail::_S_leaf:
              {
                _RopeLeaf* __l = (_RopeLeaf*)__r;
                return __l->_M_data[__i];
              }
            case __detail::_S_function:
            case __detail::_S_substringfn:
              {
                _RopeFunction* __f = (_RopeFunction*)__r;
                _CharT __result;
                
                (*(__f->_M_fn))(__i, 1, &__result);
                return __result;
              }
            }
        }
    }
  
#ifndef __GC
  // Return a uniquely referenced character slot for the given
  // position, or 0 if that's not possible.
  template <class _CharT, class _Alloc>
    _CharT*
    rope<_CharT, _Alloc>::
    _S_fetch_ptr(_RopeRep* __r, size_type __i)
    {
      _RopeRep* __clrstack[__detail::_S_max_rope_depth];
      std::size_t __csptr = 0;
      
      for(;;)
        {
          if (__r->_M_ref_count > 1)
            return 0;
          switch(__r->_M_tag)
            {
            case __detail::_S_concat:
              {
                _RopeConcatenation* __c = (_RopeConcatenation*)__r;
                _RopeRep* __left = __c->_M_left;
                std::size_t __left_len = __left->_M_size;
                
                if (__c->_M_c_string != 0)
                  __clrstack[__csptr++] = __c;
                if (__i >= __left_len)
                  {
                    __i -= __left_len;
                    __r = __c->_M_right;
                  } 
                else
                  __r = __left;
              }
              break;
            case __detail::_S_leaf:
              {
                _RopeLeaf* __l = (_RopeLeaf*)__r;
                if (__l->_M_c_string != __l->_M_data && __l->_M_c_string != 0)
                  __clrstack[__csptr++] = __l;
                while (__csptr > 0)
                  {
                    -- __csptr;
                    _RopeRep* __d = __clrstack[__csptr];
                    __d->_M_free_c_string();
                    __d->_M_c_string = 0;
                  }
                return __l->_M_data + __i;
              }
            case __detail::_S_function:
            case __detail::_S_substringfn:
              return 0;
            }
        }
    }
#endif /* __GC */
 
  // The following could be implemented trivially using
  // lexicographical_compare_3way.
  // We do a little more work to avoid dealing with rope iterators for
  // flat strings.
  template <class _CharT, class _Alloc>
    int
    rope<_CharT, _Alloc>::
    _S_compare (const _RopeRep* __left, const _RopeRep* __right)
    {
      std::size_t __left_len;
      std::size_t __right_len;
      
      if (0 == __right)
        return 0 != __left;
      if (0 == __left)
        return -1;
      __left_len = __left->_M_size;
      __right_len = __right->_M_size;
      if (__detail::_S_leaf == __left->_M_tag)
        {
          _RopeLeaf* __l = (_RopeLeaf*) __left;
          if (__detail::_S_leaf == __right->_M_tag)
            {
              _RopeLeaf* __r = (_RopeLeaf*) __right;
              return lexicographical_compare_3way(__l->_M_data,
                                                  __l->_M_data + __left_len,
                                                  __r->_M_data, __r->_M_data
                                                  + __right_len);
            }
          else
            {
              const_iterator __rstart(__right, 0);
              const_iterator __rend(__right, __right_len);
              return lexicographical_compare_3way(__l->_M_data, __l->_M_data
                                                  + __left_len,
                                                  __rstart, __rend);
            }
        }
      else
        {
          const_iterator __lstart(__left, 0);
          const_iterator __lend(__left, __left_len);
          if (__detail::_S_leaf == __right->_M_tag)
            {
              _RopeLeaf* __r = (_RopeLeaf*) __right;
              return lexicographical_compare_3way(__lstart, __lend,
                                                  __r->_M_data, __r->_M_data
                                                  + __right_len);
            }
          else
            {
              const_iterator __rstart(__right, 0);
              const_iterator __rend(__right, __right_len);
              return lexicographical_compare_3way(__lstart, __lend,
                                                  __rstart, __rend);
            }
        }
    }
 
  // Assignment to reference proxies.
  template <class _CharT, class _Alloc>
    _Rope_char_ref_proxy<_CharT, _Alloc>&
    _Rope_char_ref_proxy<_CharT, _Alloc>::
    operator=(_CharT __c)
    {
      _RopeRep* __old = _M_root->_M_tree_ptr;
#ifndef __GC
      // First check for the case in which everything is uniquely
      // referenced.  In that case we can do this destructively.
      _CharT* __ptr = _My_rope::_S_fetch_ptr(__old, _M_pos);
      if (0 != __ptr)
        {
          *__ptr = __c;
          return *this;
        }
#endif
      _Self_destruct_ptr __left(_My_rope::_S_substring(__old, 0, _M_pos));
      _Self_destruct_ptr __right(_My_rope::_S_substring(__old, _M_pos + 1,
                                                        __old->_M_size));
      typename _RopeRep::allocator_type __a = _M_root->_M_get_allocator();
      _Self_destruct_ptr __result_left(_My_rope::
                                       _S_destr_concat_char_iter(__left,
                                                                 &__c, 1,
                                                                 __a));
 
      _RopeRep* __result = _My_rope::_S_concat(__result_left, __right);
#ifndef __GC
      _RopeRep::_S_unref(__old);
#endif
      _M_root->_M_tree_ptr = __result;
      return *this;
    }
 
  template <class _CharT, class _Alloc>
    inline _Rope_char_ref_proxy<_CharT, _Alloc>::
    operator _CharT() const
    {
      if (_M_current_valid)
        return _M_current;
      else
        return _My_rope::_S_fetch(_M_root->_M_tree_ptr, _M_pos);
    }
 
  template <class _CharT, class _Alloc>
    _Rope_char_ptr_proxy<_CharT, _Alloc>
    _Rope_char_ref_proxy<_CharT, _Alloc>::
    operator&() const
    { return _Rope_char_ptr_proxy<_CharT, _Alloc>(*this); }
 
  template <class _CharT, class _Alloc>
    rope<_CharT, _Alloc>::
    rope(std::size_t __n, _CharT __c, const allocator_type& __a)
    : _Base(__a)
    {
      using std::__uninitialized_fill_n_a;
 
      rope<_CharT,_Alloc> __result;
      const std::size_t __exponentiate_threshold = 32;
      std::size_t __exponent;
      std::size_t __rest;
      _CharT* __rest_buffer;
      _RopeRep* __remainder;
      rope<_CharT, _Alloc> __remainder_rope;
 
      if (0 == __n)
        return;
 
      __exponent = __n / __exponentiate_threshold;
      __rest = __n % __exponentiate_threshold;
      if (0 == __rest)
        __remainder = 0;
      else
        {
          __rest_buffer = this->_Data_allocate(_S_rounded_up_size(__rest));
          __uninitialized_fill_n_a(__rest_buffer, __rest, __c,
                                   _M_get_allocator());
          _S_cond_store_eos(__rest_buffer[__rest]);
          __try
            { __remainder = _S_new_RopeLeaf(__rest_buffer, __rest,
                                            _M_get_allocator()); }
          __catch(...)
            {
              _RopeRep::__STL_FREE_STRING(__rest_buffer, __rest,
                                          _M_get_allocator());
              __throw_exception_again;
            }
        }
      __remainder_rope._M_tree_ptr = __remainder;
      if (__exponent != 0)
        {
          _CharT* __base_buffer =
            this->_Data_allocate(_S_rounded_up_size(__exponentiate_threshold));
          _RopeLeaf* __base_leaf;
          rope __base_rope;
          __uninitialized_fill_n_a(__base_buffer, __exponentiate_threshold, __c,
                                   _M_get_allocator());
          _S_cond_store_eos(__base_buffer[__exponentiate_threshold]);
          __try
            {
              __base_leaf = _S_new_RopeLeaf(__base_buffer,
                                            __exponentiate_threshold,
                                            _M_get_allocator());
            }
          __catch(...)
            {
              _RopeRep::__STL_FREE_STRING(__base_buffer,
                                          __exponentiate_threshold,
                                          _M_get_allocator());
              __throw_exception_again;
            }
          __base_rope._M_tree_ptr = __base_leaf;
          if (1 == __exponent)
            __result = __base_rope;
          else
            __result = power(__base_rope, __exponent,
                             _Rope_Concat_fn<_CharT, _Alloc>());
            
          if (0 != __remainder)
            __result += __remainder_rope;
        }
      else
        __result = __remainder_rope;
          
      this->_M_tree_ptr = __result._M_tree_ptr;
      this->_M_tree_ptr->_M_ref_nonnil();
    }
      
  template<class _CharT, class _Alloc>
    _CharT
    rope<_CharT, _Alloc>::_S_empty_c_str[1];
      
  template<class _CharT, class _Alloc>
    const _CharT*
    rope<_CharT, _Alloc>::
    c_str() const
    {
      if (0 == this->_M_tree_ptr)
        {
          _S_empty_c_str[0] = _S_eos((_CharT*)0);  // Possibly redundant,
                                                   // but probably fast.
          return _S_empty_c_str;
        }
      __gthread_mutex_lock (&this->_M_tree_ptr->_M_c_string_lock);
      __GC_CONST _CharT* __result = this->_M_tree_ptr->_M_c_string;
      if (0 == __result)
        {
          std::size_t __s = size();
          __result = this->_Data_allocate(__s + 1);
          _S_flatten(this->_M_tree_ptr, __result);
          __result[__s] = _S_eos((_CharT*)0);
          this->_M_tree_ptr->_M_c_string = __result;
        }
      __gthread_mutex_unlock (&this->_M_tree_ptr->_M_c_string_lock);
      return(__result);
    }
  
  template<class _CharT, class _Alloc>
    const _CharT* rope<_CharT, _Alloc>::
    replace_with_c_str()
    {
      if (0 == this->_M_tree_ptr)
        {
          _S_empty_c_str[0] = _S_eos((_CharT*)0);
          return _S_empty_c_str;
        }
      __GC_CONST _CharT* __old_c_string = this->_M_tree_ptr->_M_c_string;
      if (__detail::_S_leaf == this->_M_tree_ptr->_M_tag
          && 0 != __old_c_string)
        return(__old_c_string);
      std::size_t __s = size();
      _CharT* __result = this->_Data_allocate(_S_rounded_up_size(__s));
      _S_flatten(this->_M_tree_ptr, __result);
      __result[__s] = _S_eos((_CharT*)0);
      this->_M_tree_ptr->_M_unref_nonnil();
      this->_M_tree_ptr = _S_new_RopeLeaf(__result, __s,
                                          this->_M_get_allocator());
      return(__result);
    }
 
  // Algorithm specializations.  More should be added.
  
  template<class _Rope_iterator>  // was templated on CharT and Alloc
    void                          // VC++ workaround
    _Rope_rotate(_Rope_iterator __first,
                 _Rope_iterator __middle,
                 _Rope_iterator __last)
    {
      typedef typename _Rope_iterator::value_type _CharT;
      typedef typename _Rope_iterator::_allocator_type _Alloc;
      
      rope<_CharT, _Alloc>& __r(__first.container());
      rope<_CharT, _Alloc> __prefix = __r.substr(0, __first.index());
      rope<_CharT, _Alloc> __suffix =
        __r.substr(__last.index(), __r.size() - __last.index());
      rope<_CharT, _Alloc> __part1 =
        __r.substr(__middle.index(), __last.index() - __middle.index());
      rope<_CharT, _Alloc> __part2 =
        __r.substr(__first.index(), __middle.index() - __first.index());
      __r = __prefix;
      __r += __part1;
      __r += __part2;
      __r += __suffix;
    }
 
#if !defined(__GNUC__)
  // Appears to confuse g++
  inline void
  rotate(_Rope_iterator<char, __STL_DEFAULT_ALLOCATOR(char)> __first,
         _Rope_iterator<char, __STL_DEFAULT_ALLOCATOR(char)> __middle,
         _Rope_iterator<char, __STL_DEFAULT_ALLOCATOR(char)> __last)
  { _Rope_rotate(__first, __middle, __last); }
#endif
 
# if 0
  // Probably not useful for several reasons:
  // - for SGIs 7.1 compiler and probably some others,
  //   this forces lots of rope<wchar_t, ...> instantiations, creating a
  //   code bloat and compile time problem.  (Fixed in 7.2.)
  // - wchar_t is 4 bytes wide on most UNIX platforms, making it
  //   unattractive for unicode strings.  Unsigned short may be a better
  //   character type.
  inline void
  rotate(_Rope_iterator<wchar_t, __STL_DEFAULT_ALLOCATOR(char)> __first,
         _Rope_iterator<wchar_t, __STL_DEFAULT_ALLOCATOR(char)> __middle,
         _Rope_iterator<wchar_t, __STL_DEFAULT_ALLOCATOR(char)> __last)
  { _Rope_rotate(__first, __middle, __last); }
# endif
 
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace