text: // SGI's rope class implementation -*- C++ -*-
  
  // Copyright (C) 2001-2016 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
  
    using std::size_t;
    using std::printf;
    using std::basic_ostream;
    using std::__throw_length_error;
    using std::_Destroy;
    using std::__uninitialized_fill_n_a;
  
    // 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)
      {
        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)
      {
        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)
      {
        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(size_t __n)
      {
        _M_current_pos += __n;
        if (0 != _M_buf_ptr)
  	{
  	  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(size_t __n)
      {
        if (0 != _M_buf_ptr)
  	{
  	  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, 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 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)
  	{
  	  size_t __size = this->_M_size + 1;
  	  _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, size_t __n, allocator_type& __a)
      {
        if (!_S_is_basic_char_type((_CharT*)0))
  	_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*, 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, size_t __len)
      {
        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,
  				   size_t __len)
      {
        if (__r->_M_ref_count > 1)
  	return _S_leaf_concat_char_iter(__r, __iter, __len);
        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)
      {
        _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, size_t __slen)
      {
        _RopeRep* __result;
        if (0 == __slen)
  	{
  	  _S_ref(__r);
  	  return __r;
  	}
        if (0 == __r)
  	return __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen,
  						__r->_M_get_allocator());
        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, __r->_M_get_allocator());
        __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, size_t __slen)
      {
        _RopeRep* __result;
        if (0 == __r)
  	return __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen,
  						__r->_M_get_allocator());
        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);
        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, __r->_M_get_allocator());
        __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)
      {
        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, size_t __start, size_t __endp1)
      {
        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, 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:
        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, size_t __n)
        {
  	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 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, size_t __n);
        // Returns true to continue traversal.
      };
  
    template<class _CharT, class _Traits>
      bool
      _Rope_insert_char_consumer<_CharT, _Traits>::
      operator()(const _CharT* __leaf, size_t __n)
      {
        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, size_t __begin, size_t __end)
      {
        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(basic_ostream<_CharT, _Traits>& __o, size_t __n)
      {
        char __f = __o.fill();
        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>
      basic_ostream<_CharT, _Traits>&
      operator<<(basic_ostream<_CharT, _Traits>& __o,
  	       const rope<_CharT, _Alloc>& __r)
      {
        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, size_t __start, 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>
      size_t
      rope<_CharT, _Alloc>::
      find(_CharT __pattern, 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)
      {
        for (int __i = 0; __i < __indent; __i++)
  	putchar(' ');
        if (0 == __r)
  	{
  	  printf("NULL\n");
  	  return;
  	}
        if (_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
  	{
  	  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
  		__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))
  	__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
        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;
  		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];
        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;
  		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)
      {
        size_t __left_len;
        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));
        _Self_destruct_ptr __result_left(_My_rope::
  				       _S_destr_concat_char_iter(__left,
  								 &__c, 1));
  
        _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(size_t __n, _CharT __c, const allocator_type& __a)
      : _Base(__a)
      {
        rope<_CharT,_Alloc> __result;
        const size_t __exponentiate_threshold = 32;
        size_t __exponent;
        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)
  	{
  	  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);
        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
  